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General Discussions => Studio A => Topic started by: ruffrecords on January 20, 2018, 04:50:27 AM

Title: All Tube Sidecar
Post by: ruffrecords on January 20, 2018, 04:50:27 AM
If you could have a 100% tube 8 channel sidecar, about the size of the Neve PSM shown below, that features and facilities would you want in it and why?

(https://www.gearslutz.com/board/attachments/high-end/4853d1102267564-ultimate-neve-sidecar-question-111038chne-v.jpg)

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: zamproject on January 20, 2018, 08:48:36 AM
that features and facilities would you want in it and why?

The 32/16/2 tube desk console that come with the sidecar  8)

I don't know if there is lot of "new" things that can be done for a small/sidecar console
I'm used to the studer 169, which more or less offer everything requested for this task, as certainly other console in this format.

So let say:

-mic/line pre with phase/rolloff/pad/P48
-mic/line selector based on relay you'll see below
-Direct out
-basic EQ with on/off switches (based on relay... you'll see below)
-2 aux at least (one stereo can be nice!) with pre/post routing option
-Insert (with in/out selector? based on relay...you'll see bellow)
-solo/mute
-PFL
-Pan (with in out selector ?)
-Fader (these day an option to bypass the fader and set unity can be nice option)

-At leas two basic stereo line IN (with fader ?) for aux return or extra input

-Standard stereo master/sum with basic comp/lim and insert

-Master metering with input selection following monitor selection if engaged

-General flip buttons that can switch on/off respectively all EQ, insert and mic/line
-Master global flip that set line in, insert and EQ out, to have instant unity line mixer, for instant multitrack playback.

-Monitor with descent input selection count, Master, PFL, AUX, as 2 or 3 stereo external input for DAW/recorder playback
-Monitor with at least two output (one can be combined with headphone), out select, dim, cut, mono sum
-Basic TB with dedicated output and/or via selected Aux (and monitor dim actuation)

Best
Zam

Title: Re: All Tube Sidecar
Post by: ruffrecords on January 20, 2018, 09:35:01 AM
Hi Zam,

Many thanks for your input. That is a lot of functionality to squeeze into a small tube mixer! Some of it is quite straightforward and other parts less so. First a few questions for clarification:

1. Whereabouts in the signal path is the direct out connected? Pre or post fader, pre or post EQ? Is i balanced or unbalanced

2. Ditto for the insert point.

3. I like the idea of the global relay switched EQ in/out and mic/line. etc  How does the logic work that decides if the module setting or the global setting prevails?

4. Do you really need talkback in a sidecar?

Cheers

Ian

Title: Re: All Tube Sidecar
Post by: zamproject on January 20, 2018, 10:43:25 AM
Hello Ian

1-let say DO post preamp by default, internal jumper to set post EQ/insert can be good...
DO post fader don't make sense to me but who know...
Balanced (trafo  ::) is better as you manly use this to go balanced multitrack IN

2-Insert post EQ by default, internal jumper pre EQ and/or post preamp (pre DO)
Unbalanced will certainly be enough as having send and return balanced might involve lot of extra circuit, connector and room...

3-Logical circuit:
-modules switches have hand when global off,
-global status overprint modules status when global engaged.
-master global overprint all global status (and modules).
this implies few signalling bus (one per function + supply)

4-I say when I use my side car for location recording (which is one of the purpose for side car IMHO),
 I'm always glad to have a talkback... , it happen also I just take it to have monitor and TB function...
Still that's just me, maybe there is no justification for TB.
The must will be to have tube TB mic pre  :P

An instant idea, if you add TB tube mic pre you can have it also like a small channel with only input gain and rotary fader to mix bus, so it can act as an extra input if requested.

Best
Zam
Title: Re: All Tube Sidecar
Post by: zamproject on January 20, 2018, 11:26:10 AM
Another idea, for simplification  ::)

DO and insert send share same symmetrical XLR out.
A simple switch (relay based or not) at back to set DO or insert function, basically just internal cut (or not) from DO/send to return
It give less routing capabilities right here, but with optional external wire like Y you mainly have all the same possibilities.

Best
Zam
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 20, 2018, 12:46:23 PM
Another idea, for simplification  ::)

DO and insert send share same symmetrical XLR out.
A simple switch (relay based or not) at back to set DO or insert function, basically just internal cut (or not) from DO/send to return
It give less routing capabilities right here, but with optional external wire like Y you mainly have all the same possibilities.

Best
Zam

Hi Zam,

I think I understand the global switches. EQ global cuts all EQ, mic/line global sets all inputs  to line and insert global switches out all inserts. Global global switch does all three at once to make instant line in mixer. Some simple diode logic should be OK for this.

For the mic/line this could be a PCB holding the two XLRs and a relay plus a couple of steering diodes.

For the insert I am not sure. Often the insert is unbalanced but we need the DO to be balanced. Also, because my tube pres use a 2:1 step down output transformer there is a 6dB drop in the balanced output. We had this question when Holger built his Krassemaschine. I think we decided to use a 1:1 transformer at the insert on the assumption it was never loaded with more less 10K. So if we go this way the levels are OK but the insert has a balanced send and an unbalanced return. Or we could just have a separate completely unbalanced insert on a TRS. What do you think?

EQ is no problem. It is passive and its bypass works by switching in a pad equal to the EQ insertion loss. Easy to replace the switch with a relay. The EQ will be in a separate module so the relay can be in there.

DO post EQ and post preamp but pre fader is a possible issue. All my designs tend to have the following signal chain:

mic pre -> fader -> EQ -> make up amp -> DO/Pan/Aux

To make it post EQ but pre fader means the fader needs to be moved:

mic pre -> trim -> EQ -> make up -> DO/fader/Pan/Aux

The make up amp now has the fader as an extra load (not a problem) but the fader has to drive the Pan and Aux. If I use good old fashioned voltage summing, the relatively high source impedance of the fader will cause an increase in cross talk on the stereo bus and it may become as low as -50dB. If I use virtual earth summing it will be OK but that needs two twin line amps for stereo when voltage summing only needs one. So that would mean losing the pre master fader bus insert; it would have to be post fader (after the second amp). This may not be a problem. What do you think?

Other than that it all looks basically OK. If only I could squeeze the three tubes of a TLA into a 35mm module......

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 20, 2018, 01:30:35 PM
@Zam,

One further question. Do the two AUX send need to be completely separate or could it be one AUX send control selected to one of two buses?

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: zamproject on January 20, 2018, 02:32:05 PM
hey

Yes signalling bus for global relay flip just need diodes.
But there is some under laying consequence for the line/mic flip, basically the line gain "have to" be fixed (studio line level unity)
to "truly" switch to line mixer/multitrack playback, don't now if your line input share the same gain sw as mic for adjust, but maybe to make it efficient and fast when flipping all, a fixed gain network have to be switched too when your line become a tape return.

Insert/DO, my first thinking is two different item XLR (sym) DO and TRS unbal send return.
Second idea is to combine DO/send sym, with cut or pass trough switch, but then it will be better to have return sym as well...
The better is both sym but then you need 3 trafo and 3 XLR at back per chanel, which could be to much space for small side car
(there is also Dsub option to gain space)
All option open, so it really depend at your side what is possible and not, with design constrain.

Regarding routing, I don't see the point to have DO post fader, because you then miss all the interest to have multitrack out AND stereo mixing and monitoring. But that's me and my workflow, let's ear what other says

Fader so soon in the chain is problematic if you want extended routing and option in "modules" position (EQ/insert)
I'm not used to tube design with load etc, so I understand they might be design limitation

But I think I get it, you need DO post makeup anyway and having fader post DO let the fader without buffer.
If the cost is just insert at master post fader (and not pre) I'll say it worth it...
VE summing have another advantage is that if you want a side car to your side car, you can link bus if you anticipate option at bus board  8)

regarding aux i'm not sure to undestand ? you mean one send only but switchable between two aux bus ?
I'll say if you have the space at FP, and layout room at modules pcb and buss board to have have 3 aux bus (meaning you can have 1 mono and one stereo or 3 mono) it will be just fine !

Best
Zam

Title: Re: All Tube Sidecar
Post by: ruffrecords on January 20, 2018, 05:10:16 PM
hey

Yes signalling bus for global relay flip just need diodes.
But there is some under laying consequence for the line/mic flip, basically the line gain "have to" be fixed (studio line level unity)
to "truly" switch to line mixer/multitrack playback, don't now if your line input share the same gain sw as mic for adjust, but maybe to make it efficient and fast when flipping all, a fixed gain network have to be switched too when your line become a tape return.
Depends on which of my designs I use. However at present the only design that will fit in the 35mm module is the Classic. The gain of that is set by a pad at the front and a trim half way down the gain chain. Engaging line input switches in the appropriate pad at the front so the only addition would be to bypass the trim control with a fixed pad to set overall unity gain
Quote
Insert/DO, my first thinking is two different item XLR (sym) DO and TRS unbal send return.
Second idea is to combine DO/send sym, with cut or pass trough switch, but then it will be better to have return sym as well...
The better is both sym but then you need 3 trafo and 3 XLR at back per chanel, which could be to much space for small side car
(there is also Dsub option to gain space)
All option open, so it really depend at your side what is possible and not, with design constrain.
The simplest option is balanced DO and unbalanced insert on a TRS. I have implemented this before.
Quote
Regarding routing, I don't see the point to have DO post fader, because you then miss all the interest to have multitrack out AND stereo mixing and monitoring. But that's me and my workflow, let's ear what other says
I agree. It is just this is awkward with the limited number of gain blocks you have in a tube mixer. If it was a semiconductor design you could just add another little op amp to buffer the fader but with a tube mixer that's at least one more tube per channel.
Quote
Fader so soon in the chain is problematic if you want extended routing and option in "modules" position (EQ/insert)
I'm not used to tube design with load etc, so I understand they might be design limitation

But I think I get it, you need DO post makeup anyway and having fader post DO let the fader without buffer.
If the cost is just insert at master post fader (and not pre) I'll say it worth it...
VE summing have another advantage is that if you want a side car to your side car, you can link bus if you anticipate option at bus board  8)
That is basically it and you are right about VE summing also giving expansions opportunities.
Quote
regarding aux i'm not sure to understand ? you mean one send only but switchable between two aux bus ?
That is exactly what I mean
Quote
I'll say if you have the space at FP, and layout room at modules pcb and buss board to have have 3 aux bus (meaning you can have 1 mono and one stereo or 3 mono) it will be just fine !

Best
Zam

FP space is very limited. Also there are only enough bus amps for four buses in total; two for the main stereo bus and two for AUXes. You could have one stereo AUX or two mono at the moment. I will look at squeezing extra amps in.

Regarding FP, there is a 3U by 35mm module for the mic pre (Basically 500 series size) and another one the same size for the three band EQ. So basically all the mic pre and routing controls have to fit in the 3U mic pre module; so that is 48V, phase, pad and mic/line switches, gain trim, pan and AUX pots and possibly solo, pfl and mute switches

Thank you for all your input.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: zamproject on January 20, 2018, 07:20:23 PM
Depends on which of my designs I use. However at present the only design that will fit in the 35mm module is the Classic. The gain of that is set by a pad at the front and a trim half way down the gain chain. Engaging line input switches in the appropriate pad at the front so the only addition would be to bypass the trim control with a fixed pad to set overall unity gain
Good.

The simplest option is balanced DO and unbalanced insert on a TRS. I have implemented this before.
If it's already implemented/approved this route is fine, keep it this way.

Also there are only enough bus amps for four buses in total; two for the main stereo bus and two for AUXes. You could have one stereo AUX or two mono at the moment. I will look at squeezing extra amps in.

Ok so let's think best possible routing option/workflow with two aux bus and room for one knob.
Switchable send is ok somehow but limited, if you have no room at FP i gess your send knob have a push/pull sw ?
Having only stereo send is the same, limited.
What about a dual concentric for send 1 and 2, BUT wired like a "dual pan" (acting like opposite balance)
meaning send 1 (gang 1) is 100% full CCW and send 2 ( gang 2) is 100% full CW, you'll then have visual feed back telling you if you are in stereo aux situation or two mono aux situation.
I'm sure it's sound strange right now , but as soon as you get it it will be quite ergonomic  :)
Pots pointers show individual level and differential level (stereo field) if you use the two aux as one stereo

You can also use a dual concentric gain and pan (aux 1/2) pot but then it's 2 shaft 3 gang.

...i'm thinking out loud  :-\
still finding a solution to have two aux available pre chanel (and not have to choice one or other) is a good target

Regarding FP, there is a 3U by 35mm module for the mic pre (Basically 500 series size) and another one the same size for the three band EQ. So basically all the mic pre and routing controls have to fit in the 3U mic pre module; so that is 48V, phase, pad and mic/line switches, gain trim, pan and AUX pots and possibly solo, pfl and mute switches

Yes, this is not unlimited space... to gain a little, is that complicated for you to have mute solo and pfl at fader bay ?
Because usually those switches better sir here for work flow.

Thank you for all your input.
your welcome Sir Ian, pleasure is mine  :)

Best
Zam
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 21, 2018, 04:52:05 AM
Hi Zam,

OK I will look at alternatives for providing two AUX knobs. I forgot to ask - do they need a pre/post fader switch??

Mute, solo and pfl in fader bay is a good idea - thanks!

Does mute button mute the AUXes?

In an early post you said Pan (with in/out switch?).  If pan is out how is channel routed to main buses??

I will start work on a block diagram to try to make this more clear.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: zamproject on January 21, 2018, 07:53:49 AM
Hello Ian

AUXes with pre-post select is good feature
still simpler routing option work to (if you have no room for lot of switches/pots)
-one fixed pre and  one fixed post
-one fixed and one switchable
-both fixed but jumper selectable at pcb
etc...
I'll say aux mute depend off place in the chain, like pre not affected by mute and post follow mute ?

Not sure PAN in/out sw is requested for a small desk ? But if PAN have a switch, PAN disengaged feed channel to mid

Yes a block diagram will be good  :)

Just something coming in mind, are you locked to a 3 bay design, (PRE/routing - EQ -Fader)
because if not you can add a bay for routing (like 2u)

Best
Zam
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 22, 2018, 05:16:07 AM
Hello Ian

AUXes with pre-post select is good feature
still simpler routing option work to (if you have no room for lot of switches/pots)
-one fixed pre and  one fixed post
-one fixed and one switchable
-both fixed but jumper selectable at pcb
etc...
I'll say aux mute depend off place in the chain, like pre not affected by mute and post follow mute ?
OK. lots of AUX options. One fixed pre and on fixed post is easy - a bit like the Studer?
Bottom line is you need two separate AUXes.
Mute after pre AUX and before post AUX seems sensible.
Quote
Not sure PAN in/out sw is requested for a small desk ? But if PAN have a switch, PAN disengaged feed channel to mid

OK, unusual. Front panel space will be the key.
Quote
Yes a block diagram will be good  :)
Working on it.
Quote
Just something coming in mind, are you locked to a 3 bay design, (PRE/routing - EQ -Fader)
because if not you can add a bay for routing (like 2u)

Best
Zam
[/quote

Not locked to it but for first project I want to use the Glensound frame I recently purchased:

(https://s26.postimg.org/sixmww361/frontscaledcropped.png)]

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 22, 2018, 11:44:23 AM
Here is my first stab at a block diagram.

I have also looked at the possibility of squeezing much of the functionality of a TLA into a 7HP module. I am pleased to say it looks like the two amplifiers can be fitted in, with a little space for some front panel controls (AUX send masters for example), but there is not room for input transformers. So it could not be used for mic pres but it could be used for bus amplification and perhaps as a talk back mic pre.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: zamproject on January 22, 2018, 01:51:00 PM
Hello

So far so good  :)

I don't know about insert post DO, but it should be the best option as is ?
If someone want to process the DO, you can chain the comp(or whatever) here.
If you have insert befor DO you don't need external chain to recorder, but then you process twice when playing back (except if insert off is handled with master flip)

Aux is fine like this, it's what do the studer I talk about with factory setting, but internally you have jumper between each bloc and you can custom set the send.
I say keep it this way, with maybe one design anticipation, put two connector/pin header before and after fader so if someone want to arrange pre/post send other way it's easy, also if one want use pot with push/pull sw, you can have a user selectable pre/post.

There is maybe some logic to clarify for line/mic flip with differentiation between the two relay and global flip
Because when mixing from line in (which is another thing that multitrack instant playback from line in for recording session)
We maybe need the trim active with line in and not the unity auto set.
Something like:
global mic/line flip the two relays (in select and gain unity)
local mic/line flip only input (and keep trim)

Best
Zam

ps: Your frame have little room/plate between fader bay and middle bay, you can maybe do something with this ? seems like each mm room will count for your build  ::)
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 22, 2018, 05:19:37 PM
HI Zam,

it is easy to move the insert to pre the DO.

Not sure about jumpers. My modules are not just a plug in PCB they are largely screened and they have high voltages inside so Access is deliberately discouraged!!. Maybe DIL switch?

I have been wondering about the global flip. For mixdown you may want both the trim, the EQ and the inserts available.  For a quick check of all recorded tracks you want unity gain and no EQ or inserts. At Neve back in the 70s we did a global tape/line in flip but left everything else untouched. What we do know is there can be a global switch for all mic/line, one for all trim, one for all EQ and one for all inserts.  Perhaps the Global Global switch could be thre interlocked switches. One selects unity gain, no EQ or inserts for playback checking; the second selects mixdown which just flips all inputs to line; the third could be a custom setting where four additional switches select which of mic/line, trim, EQ and insert are affected. It is only a bit of logic!!

The little space between faders and middle bay is a scribble strip but it would not be two hard to fit a couple of switches per channel in there instead.

Ihave not yet added Solo and PFL to the block diagram because these could work in several ways. For PFL I normally only switch the monitor section to the PFL but when a PFL bus is pressed so the DO and L/R groups are not affected. Monitor section allows sound to be heard and level to be set by meter.

Solo can be either destructive or not. What do you prefer? Do you wan solo in place??

Cheers

Ian

Title: Re: All Tube Sidecar
Post by: zamproject on January 23, 2018, 09:45:56 AM
Hello Ian

Not sure about jumpers. My modules are not just a plug in PCB they are largely screened and they have high voltages inside so Access is deliberately discouraged!!. Maybe DIL switch?

I Don't mean "user" selectable block/send point arrangement for daily change, more a factory/tech option. Some want two pre some want two post as a basic setup. Having to unmount screw/panel/screen sound not like an issue in this case ?
So make it as design allow.
Same for DO pre or post insert, if possible just add solder pad (for connector or wire) for both option
Or maybe it's just the trafo out directly soldered at back insert connector ? easy to hook tip or ring in this case...you can even have a switch at back panel connector...

Ihave not yet added Solo and PFL to the block diagram because these could work in several ways. For PFL I normally only switch the monitor section to the PFL but when a PFL bus is pressed so the DO and L/R groups are not affected. Monitor section allows sound to be heard and level to be set by meter.

Solo can be either destructive or not. What do you prefer? Do you wan solo in place??

I'll say if you have the PFL (non destructive, dedicated bus) you can have SIP at LR bus.
Otherwise it's an AFL which don't make much sense in a 8ch desk IMHO
Also with AFL you need another stereo bus !! having AFL pre pan (one bus) is completely useless too...and the PFL do 99% of the job then.

So, PFL and SIP ?
Still, SIP need signalling logic bus (to mute other) do you have room for the extra bus ?
In other hand It won't be a drama for a small 8/10 chn desk to only have PFL and Mute...

About monitoring, you mean monitor automatically flip to PFL input when local pfl is engaged ?

Best
Zam

Title: Re: All Tube Sidecar
Post by: ruffrecords on January 23, 2018, 11:44:52 AM
Hi Zam,

OK, tech adjustable jumpers are no problem. I just did not want to be responsible for a sound engineer electrocuting him/herself. Ditto for DO pre/post insert is OK too. Probably a separate PCB round the back anyway which also holds the relays.

PFL is usually non destructive and fed to monitor so you can set levels, check quality etc. Sometimes it has a DC bus that flips a relay in the monitor to automatically feed PFL audio bus to monitors/meters. Otherwise it can just be an audio bus and you have to select PFL in the monitor section to hear it/see it. Channel PFL button is normally a momentary type.

Destructive SIP means just muting all the other channels (another relay!!!)

Buses so far:

AUX1 & AUX 2
Master L/R
PFL (and maybe PFL dc)
SIP

That is a total of 6 or seven, Whether there are enough buses to cope with all these depends where the controls are. I think we already decided PFL, SIP and Mute buttons can be in fader bay. We could possibly place insert button there too. So any buses needed by these can be confined to this area.

One possibility for the little strip above the fader bay is to use it to hold the pan controls. We could then have the L/R bus running across this section. Then we only need AUX1 and AUX2 buses from the mic pres.

So I think I will be able to provide enough buses.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: G-Sun on January 23, 2018, 01:00:13 PM
For me it would be a 2x8ch summing-mixer,
2 channel with preamp/eq/comp
VU's are nice

Tracking through 1-2-channels, mixing mainly ITB, summing stems or stereo-channel on master.

Put short, a 2ch unit with summing-option.
So, could be much smaler.
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 23, 2018, 03:42:52 PM
For me it would be a 2x8ch summing-mixer,
2 channel with preamp/eq/comp
VU's are nice

Tracking through 1-2-channels, mixing mainly ITB, summing stems or stereo-channel on master.

Put short, a 2ch unit with summing-option.
So, could be much smaller.

That is a very interesting product idea. A bit like a cut down version of API The Box. What control, if any, would you want over the stems?

Cheers

ian
Title: Re: All Tube Sidecar
Post by: mrclunk on January 24, 2018, 06:49:08 AM
A stem RE:Mixer/summing box would be very cool.

Like G-sun said a couple of full channels for overdubs / vocals.
Maybe the eq's could be switched between the two full mic channels and the main LR outs for mix down?
Buffered inserts on the main LR.

For the summing part, 8 stereo channels would work, then you could do panning/solo ITB?

But on the summing channels i'd want auxiliaries for fx...
I generally re-apply verb/echo when remixing and that's normally real tapes/plates.  Mono fx sends would be ok.
Inserts switches on the summing inputs would be nice but this could be done on a patchbay.
Headphone out for the talent.
Sorry that's completely different to what you originally asked...
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 24, 2018, 08:47:00 AM
Sorry that's completely different to what you originally asked...

Doesn't matter, in fact it is good. I initially assumed nobody would want a small tube mixer for tracking because there was no way to include things like 8 AUXes per channel and all the other stuff you get in a mainstream mixer. So I thought the obvious application for it was as a sidecar. But is looks like there are other possible applications such a tracker/summer.

Tube summers with balanced inputs are easy to do. What is hard to do is FX sends. The 'obvious way to do them is to unbalanced each input, then its just like any line input and you can add AUX sends, pan, sole etc etc. But, in a tube mixer you need a transformer to unbalance each input so with 8 stereo stems that's 16 transformers which is potentially rather expensive. You  might be able to do one, perhaps two fully balanced AUXes without the need to unbalance the inputs but it will probably mean the DACs will need to be able to dive a load much lower than the regular 10K. I will look into it. In the past I have also looked at low cost 10K:10K line input transformers for just this sort of application so I will revisit that again as well.

Cheers

ian
Title: Re: All Tube Sidecar
Post by: mrclunk on January 24, 2018, 09:03:28 AM
I apologise unreservedly but dare I say...
Aux send /returns with solid state!!
Alot of extra power and heat, with valves on auxes, for minimal sonic gain.

Title: Re: All Tube Sidecar
Post by: ruffrecords on January 24, 2018, 09:59:36 AM
I apologise unreservedly but dare I say...
Aux send /returns with solid state!!
Alot of extra power and heat, with valves on auxes, for minimal sonic gain.

You may dare but you won't get it from me!!

Not really much extra heat; it is only one and a half extra tubes per AUX bus so with a couple that's three more tubes and maybe 10W of power/heat. The bigger problem is the cost/weight of all the input transformers.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: ombudsman on January 24, 2018, 01:01:38 PM
I think of a sidecar as being a bank of channel strips with direct outs. If it has a master section and auxes and can do monitor mixing or summing, I would call it a small console.

I would think a tube sidecar would be a more commercial idea.  There isn't a lot like that, and it provides consistency across tracks and a relatively compact rig (compared to outboard tube channels) like a console without duplicating functionality that most people in the market for it would already have in their daw.

If I were in the market I'd want a fairly simple eq, mic/line switch, input pad,  and linear output attenuator (rotary or fader)  to a direct transformer balanced out per channel, and individually switchable phantom power. Maybe a second output for each channel too.  If I was going to mix back through it - which I would only do sometimes if it was only 8 channels - I'd just send the individual outs to a separate summer.

It could have an empty 500 series slot instead of the channel EQ with an optional EQ module that could fill those slots.  That would attract some different users who could simplify transitioning to this type of gear.
Title: Re: All Tube Sidecar
Post by: bluebird on January 24, 2018, 04:43:34 PM
Might be advantageous to have a separate transformerless line input stage.
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 24, 2018, 05:19:47 PM
Might be advantageous to have a separate transformerless line input stage.

Maybe, but for 16 inputs it needs 16 extra tubes. Not quite as expensive or as heavy as 16 transformers but another 60W of heater power required. But definitely worth considering.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 25, 2018, 06:19:12 AM
I just found a very economical line inut transformer from OEP. It is 10K:10K and is housed in a mu-metal screened  can. Max input level is +22dBu. Part number is Z21807C and it costs Just £12.50 + VAT from Canford:

http://www.oep.co.uk/page-content/datasheets/1444119292Z21807C%20issue%205.pdf (http://www.oep.co.uk/page-content/datasheets/1444119292Z21807C%20issue%205.pdf)

RS lists it as discontinued but Canford still have it.

Cheers

ian
Title: Re: All Tube Sidecar
Post by: mrclunk on January 25, 2018, 06:28:05 AM
If they're anything like the OEP A262x series they won't handle low frequency signals well at all.
There's Edcor in the US that make reasonably priced open frame 10k:10Ks?
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 25, 2018, 10:39:20 AM
If they're anything like the OEP A262x series they won't handle low frequency signals well at all.
There's Edcor in the US that make reasonably priced open frame 10k:10Ks?

I already looked at the A262 series but discounted them for that very reason. The Z21807C seems much better specified at LF but it is about the same size so who knows.

The Edcors are indeed reasonably priced but their chipping costs to Europe effectively double the price. I have used the XSM series for outputs and found them to be very good but they would be very bulky and heavy for inputs. The WAM series might be OK for inputs as it will handle 10V rms (+22dBu) but they have no shielding and are still quite heavy. Each one weighs 0.4 lbs so 16 would be 6.4lbs.

This is not an easy question. Somewhere there must be a reasonably priced input transformer with a reasonable spec.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: mrclunk on January 25, 2018, 10:59:58 AM
As always, many steps ahead of me. :)
You've posted before about the OEP Z3003E.
Possible option and still made? £14 each.
http://docs-europe.electrocomponents.com/webdocs/0d6b/0900766b80d6b42f.pdf
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 25, 2018, 11:37:39 AM
As always, many steps ahead of me. :)
You've posted before about the OEP Z3003E.
Possible option and still made? £14 each.
http://docs-europe.electrocomponents.com/webdocs/0d6b/0900766b80d6b42f.pdf

I don't know about many steps ahead but I have looked at a few alternatives in the last couple of days. None of them seems perfect but each has its attractions:

A187A13C, 25H inductance (good) mu-metal core (good), £20.84 from RS (not bad), mu-metal shielding (good), no spec for maximum level (sigh), 20Hz distortion @0dBu is 0.09% but no info about higher levels.

K30A06C seems to be similar but more expensive (£33.33 @ RS) and distortion at 20Hz 0dBu is just 0.01%. Primary inductance of  119H is very good (Sowter territory).Definitely a larger core and the weight at 0.11Kg is as heavy as some of the smaller Edcors. Again no maximum level spec but it does have a mu-metal screen.

Z3002E and Z3003E appear to be the same transformer but the 03 has a spilt primary an is unaccountably cheaper (£14.44 plays £22.50) and I did test the 03 years ago. Both have a primary inductance of 61.2H (good), are inexpensive (good) and are quoted as having THD: 1% max at +20dB which sounds good but is more or less meaningless. No mu-metal screen (bad) but one is available as a separate part for £10.35. Not as big as the K30 but with a mu-metal screen it is about the same price.

Lastly the Z21807C, no spec for inductance (bad), but 40Hz 3% THD at +22dBu is the only one to specify a high level low frequency distortion (good). has a mu-metal case (good) and weighs only 45g.

I have already contacted OEP about pricing so I think I will ask for spec details on the others to fill in the obvious gaps, mainly core material, primary inductance, maximum operating level and 20Hz distortion at this level.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 25, 2018, 12:50:00 PM
For the summing part, 8 stereo channels would work, then you could do panning/solo ITB?

But on the summing channels i'd want auxiliaries for fx...
I generally re-apply verb/echo when remixing and that's normally real tapes/plates.  Mono fx sends would be ok.
Inserts switches on the summing inputs would be nice but this could be done on a patchbay.


Just going back to this point, if we  can get a decent input transformer, are your inputs all stereo? If so how does a mono FX send work from a stereo input - just a dual pot, one part per channel, fed to the same bus?

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: zamproject on January 25, 2018, 04:52:01 PM
Just going back to this point, if we  can get a decent input transformer, are your inputs all stereo? If so how does a mono FX send work from a stereo input - just a dual pot, one part per channel, fed to the same bus?

Cheers

Ian

Hello

Mono Aux send from stereo input can be L/R sum.
My current desk have this for stereo channel, not an issue as far as Aux return is stereo, (I feed all FX/Rev a mono signal)
This keep compatibilities between mono and stereo channel regarding Aux routing, and Aux bus count.
In your case with "only" two Aux send and bus, having mono channels that have two mono Aux and stereo with one stereo Aux on the same two bus will not be practical.

But now I have a doubt, you mean dual pot for L and R Aux 1 send (same for Aux 2) ?

Best
Zam
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 25, 2018, 07:29:06 PM

But now I have a doubt, you mean dual pot for L and R Aux 1 send (same for Aux 2) ?

Best
Zam

Half the dual pot is in the left signal path and the other half is in the R (just like it would be for a stereo level control. The wipers can each feed their own bus feed resistor which are then connected to the single (mono) AUX bus. And you would do the same for AUX2 .

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: peterc on January 26, 2018, 02:31:36 AM
HI Ian

Try searching RS for Z21807 (no 'C'), I get this return:
https://uk.rs-online.com/web/p/audio-transformers/6676038/?searchTerm=Z21807C&autocorrected=y&relevancy-data=636F3D3126696E3D4931384E53656172636847656E65726963266C753D656E266D6D3D6D61746368616C6C7061727469616C26706D3D5E2E2A2426706F3D31333326736E3D592673723D4175746F636F727265637465642673613D7A32313830372673743D43415443485F414C4C5F44454641554C542673633D592677633D4E4F4E45267573743D5A323138303743267374613D5A32313830374326

Hope this helps
Peter
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 26, 2018, 04:14:45 AM
HI Ian

Try searching RS for Z21807 (no 'C'),

Hope this helps
Peter

That is interesting. The spec is identical to the Z3003E and the Z21807C is the mu-metal encapsulated version. So it looks like the Z21807C is just a Z3003E in a mu-metal box..

Thanks for that.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: G-Sun on January 26, 2018, 09:01:50 AM
That is a very interesting product idea. A bit like a cut down version of API The Box. What control, if any, would you want over the stems?
Tracking and bus-work can be a little different.
Tracking: HPF, LoShelf, HiShelf, Comp fast/medium/slow attack, fast/medium release
 Then color midbands and/or versatile midbands
MasterBus: LoShelf, HiShelf, Transparrant option (like SS line In/Out), Comp fast/med at., auto/slow/very slow release. Solid metering and stereo-tracking.

It's very much about the color and versility, yet, to not too much for masterbus

Like, I got this Blue Robbie, very clean tube preamp, SS in/out,
thought it would be nice on master mid-channel,
but had to take if of.
Then again, for tracking it's pretty transparent.
So, could be hard to nail the all-in-one box :)

Some inspiration could be Warm Audio Tonebeast
and Lauder than Liftoff Silver Bullet.

From a technical point of view,
i guess passive summing in on DB25 is fairly easy to add.
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 26, 2018, 12:09:26 PM
Tracking and bus-work can be a little different.
Tracking: HPF, LoShelf, HiShelf, Comp fast/medium/slow attack, fast/medium release
 Then color midbands and/or versatile midbands
OK so you are talking about a compressor per channel for tracking as well as EQ. Is that right?
Quote
MasterBus: LoShelf, HiShelf, Transparrant option (like SS line In/Out), Comp fast/med at., auto/slow/very slow release. Solid metering and stereo-tracking.
So you would want simpler EQ on the master bus and different compressor options including (obviously) stereo tracking
Quote
It's very much about the color and versility, yet, to not too much for masterbus

So, could be hard to nail the all-in-one box :)
So inserts on channels and master bus would be good because you could then plug in anything?
Quote
From a technical point of view,
i guess passive summing in on DB25 is fairly easy to add.
Yes it easy as long as all you want is to sum them to the master bus.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: G-Sun on January 26, 2018, 03:33:36 PM
OK so you are talking about a compressor per channel for tracking as well as EQ. Is that right?So you would want simpler EQ on the master bus and different compressor options including (obviously) stereo trackingSo inserts on channels and master bus would be good because you could then plug in anything?Yes it easy as long as all you want is to sum them to the master bus.
These are just a few ideas based on my personal usage and workflow.
I wouldn't know every detail before putting the unit into actual usage.

Comp: Depends, just pre/eq is a nice thing as well.
Insert: Yes, but that's not mandatory. I could put a compressor after this unit as well.

I've tried a few tube-preamps now, the Robbie, DBX 676, Sound Sculptor 566. Very different units/flavors,
and they all falls short on masterbus due to not clean enough.
But with a design-goal of clean and transparent, combined with eg. Lundahls in/out it could be something.
And added distortion/saturation-stage with a type of wet/dry would be ideal,
yet, preserving a punchy low-end often seems hard.

I know many folks use 2ch Pultec on masterbus, but I've never tried it,
and often leave masterbus eq to the mastering-guy. But if it sounds good :)

Title: Re: All Tube Sidecar
Post by: pvision on January 26, 2018, 07:12:05 PM
I had lots of ideas.

1 - Recording
If the console is used for recording then likely you'd use each channel direct output straight to the DAW and setup a monitor mix & headphone mix at the DAW via the audio interface. In that case the stereo outs of the console are not used and the direct outs could be post-fader

If you wanted to mix mics you could use the console stereo bus and patch that to the DAW as above

In this mode I doubt you'd need effects sends

2 - Mixing / Summing
In this mode you might need effects sends but I can't see a need for them to be pre-fader. If you need a pre-fader send then you could use the direct out - but setup #1 suggests the DO would likely be post-fader

Rather than provide effects sends I'd provide additional buses. Four buses could be two stereos or one stereo and two mono sends. For a mono channel you could have a send pot plus a 1, 1+2, 2, 3, 3+4, 4 switch to select which bus it feeds

This then suggests you could have two channel outputs, fader & small fader, each with a routing switch as above. This would give LCR panning without a panpot. Add panpots to complicate as required

Add a global pre / post switch to each routing switch and you'd have two stereo bus outs per channel fed from two faders (or pots) each switchable pre / post fader

That would enable a monitor mix and a main output mix

I'll do a diagram to explain...

Nick Froome

Title: Re: All Tube Sidecar
Post by: ruffrecords on January 27, 2018, 03:58:50 AM
I'll do a diagram to explain...

Nick Froome

Diagrams are always good!

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: pvision on January 27, 2018, 07:36:26 AM
Diagram attached
Title: Re: All Tube Sidecar
Post by: pvision on January 27, 2018, 08:08:16 AM
This is the XML file for the diagram so anyone can edit it. To do so you'll have to remove the .pdf extension and rename it to .xml

It was created at www.draw.io

Nick Froome
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 27, 2018, 10:46:50 AM
HI Nick,

First question, why would you have the direct out after the fader?

Cheers

iam
Title: Re: All Tube Sidecar
Post by: pvision on January 27, 2018, 11:12:22 AM
why would you have the direct out after the fader?
So you can ride levels while recording

It's tied in with the question "Faders or pots?" If you have faders - and we all like faders - then logically you should be able to use them while recording

There is a permanent pre-fader output at the insert send

Nick Froome
Title: Re: All Tube Sidecar
Post by: pvision on January 27, 2018, 05:20:47 PM
Pan schematic
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 27, 2018, 05:34:20 PM
So you can ride levels while recording
OK. Is that common these days?

For a tube mixer this presents an extra difficulty; the fader needs to  be buffered. Its just another op amp in a semiconductor mixer but its an extra triode or two in a tube mixer. There would already be two or three triodes in the mic pre and the same in the EQ. The signal flow in my tube mixers is usually:

mic pre -> fader -> EQ -> EQ gain make up -> direct out

so you can still ride the faders.

You can add an optional unbalanced insert between the mic pre and the fader

Would you expect inserts to be balanced or unbalanced?

Cheers

Ian

Title: Re: All Tube Sidecar
Post by: Timjag on January 28, 2018, 03:26:37 PM
Direct outs are post fader on cheaper desks, on more expensive units you can switch it pre or post and it has a sperate control Pot. Again balanced inserts is all about price point, presumably that would be a lot of transformers for not a huge impact on sound,  but some folks insist on it

I would say a switch to shift the insert between pre and post eq is a great boon if you're going to go to that much detail.
Title: Re: All Tube Sidecar
Post by: ruffrecords on January 28, 2018, 03:36:55 PM
Direct outs are post fader on cheaper desks, on more expensive units you can switch it pre or post and it has a separate control Pot. Again balanced inserts is all about price point, presumably that would be a lot of transformers for not a huge impact on sound,  but some folks insist on it

I would say a switch to shift the insert between pre and post eq is a great boon if you're going to go to that much detail.

Some people seem to want it pre-fader so you can use the faders for a monitor mix, others want it post fade so you can ride the faders during tracking. In some ways it may be easier to leave the direct out where it is and switch the fader either before or after it.

Back in the very early days, mixers consisted of individual units, all balanced in/out, that you could plug together any way you wanted. Then along came the 'integrated' mixers that did away with all the interstage balancing and provided a fixed set of facilities. Nowadays, people seem to want an integrated mixer that has a bunch of switches that let you reconfigure its internal modules in several ways. How long before we come full circle??

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: Timjag on January 28, 2018, 05:17:21 PM
Ha! That's true. The thing is, we've all got very used to doing whatever we want.

Personally I'd give up all of that stuff for something that sounded excellent, otherwise it starts becoming like a 90s large format mixer like a soundcraft TS12 or Midas heritage 3000 live console which is probably the most routable console ever, where you can do just about anything but all done with handy cheap 5534s.

A tube console is a different proposition
Title: Re: All Tube Sidecar
Post by: Timjag on January 28, 2018, 05:35:17 PM
---Deleted ---

didn't mean to sidetrack the discussion
Title: Re: All Tube Sidecar
Post by: G-Sun on January 30, 2018, 03:23:00 AM
Personally, the only thing I'd use a fader for is tone -pushing prior stage less/more.
A  0/-10/-20 pad would be all I needed.
And then, only if it made a difference in tone.

I agree with Timjag, a Tube console should focus on basic excellence.
After that sonic flexibility, like saturation or a different transformer-option etc.
Then routing, auxes and the like.

SS mixers seems just so much better for do-it-all-routing, and even then,
who wants a SS 50ch monster these days?

That said, I'm no tube-purist, and see big benefits in some IC rails present :)

Mind you, I'm a home-studio user,
and speak from these perspectives.
Title: Re: All Tube Sidecar
Post by: bluebird on January 30, 2018, 08:33:43 PM
The market for a product like this is most likely going to be small studios or small mixing rooms. 90% of people will have pro tools/daw converters. I think you should put a good amount of work into the monitor section so people can throw out whatever they are using for a monitor box, Mackie big knob, Presonus monitor box, whatever.

Do your 8 tube channels simple like you first purposed. People will have 8 great tube recording channels and some cool eq's to mix selected tracks through.

The monitor section would be based around a nice Elma 4 deck 10K stepped pot. That way you could route auxiliary inputs directly to the pot and then to the monitor outputs. So a fully balanced monitor controller even when the whole console was not in use. Perhaps you could have a standby mode where the tube electronics were off but just the relay power would be on so the monitor section could be used without heating the whole room.

The Colman audio M3PHMKIII monitor controller uses a 4 deck Elma and is mainly passive with a headphone amp being the only active part. Simple mechanical push buttons for selection.
http://www.colemanaudio.com/cntrl.htm


So the monitor section would have:
Buss for the tube channels
Stereo monitor out with a selection for speaker set A or B.
Headphone out.
2 or 3 stereo auxiliary inputs for CD player or DAW main out, computer internal soundcard etc.

And if you want to go the extra mile...

16 channels via dsub connector of passive summing. You could feed it directly to the summing stage for the 8 tube channels. Or have a separate summing amp with a stereo output that could just be fed into two of the 8 tube channels. The only difficult (expensive) part is again the input transformers for unbalancing.

My 2 cents....



Title: Re: All Tube Sidecar
Post by: ruffrecords on January 31, 2018, 03:34:48 AM
@Bluebird

I like your sensible uncluttered reasoning.

I had not mentioned the monitor system simply because, for me, that is the relatively easy part. I would base it on the way we did them at Neve - a couple of 10K:600 transformers with the inputs switched to select almost any balanced source you like. The 600 side would go to a 4 bank ELMA 600 ohm stepped level control. There are four reasons for doing it this way. First the monitor becomes a light 10K bridging load so it does not affect the level of the signals being monitored, Secondly it is galvanically isolated so there is no danger of creating a hum loop.he nominal. Thirdly, the +4dBu output is dropped to about -8dBu. This level is ideal for powered monitors and regular power amps alike. Fourthlyy, the monitor output is 600 ohms which is less likely to lose any HF or pick up any interference on its way to the power amp.

At Neve we typically started the monitor section with a big three position rotary switch with a Marconi knob  to select master bus, 2 track playback or other inputs. This allowed rapid switching between source and recording and in the third position levels could be set up and individual sources heard. The two track playback selection often had another switch to select several sources and the master bus position often had another switches if there were groups as well as the master stereo bus. The third postilion usually had further switches to select direct outs, AUX sends and so on. Often this was implemented as a bank of interlocking push buttons.

8 or 16 channels of dsub passive summing is already on the cards. If it is straight passive summing with no trim controls, pan or AUX sends then you don't need the transformers (just the two on the summing amp inputs).

You mentioned cool EQ. For a while now I have been trying to tie down a neat three band EQ. The problem has been that none of my EQs so far manages to have bass boost and cut on a single pole 12 way rotary switch. They all need two pole switches which limits you to a small number of manufacturers. Mid and High are no problem but bass always has been. However, my new mastering EQ design overcomes this - all bands are implemented in the same way and use only a single pole switch for  boost/cut. On another thread here I came across NKK MRK switches which are tiny single pole 12 way switches that are not too expensive. Using thee I have designed a simple 3 band EQ, loosely based on my REDD EQ design. Each band has three frequencies selected by a three position toggle. It all fits neatly into a 3U high 35mm wide module. I got the PCBs back the other day s I will be building and testing it in the coming weeks.

Once again, many thanks for your input.

Cheers
Ian
Title: Re: All Tube Sidecar
Post by: ruairioflaherty on February 01, 2018, 11:23:46 PM
I had not mentioned the monitor system simply because, for me, that is the relatively easy part. I would base it on the way we did them at Neve - a couple of 10K:600 transformers with the inputs switched to select almost any balanced source you like. The 600 side would go to a 4 bank ELMA 600 ohm stepped level control. There are four reasons for doing it this way. First the monitor becomes a light 10K bridging load so it does not affect the level of the signals being monitored, Secondly it is galvanically isolated so there is no danger of creating a hum loop.he nominal. Thirdly, the +4dBu output is dropped to about -8dBu. This level is ideal for powered monitors and regular power amps alike. Fourthlyy, the monitor output is 600 ohms which is less likely to lose any HF or pick up any interference on its way to the power amp.

Hey Ian,

Before I offer any input let me say that I am not the target audience for this console, my tracking & mixing days are in the past.  That said a transformer in the monitor path is an instant deal breaker for me in any pro audio application.

In my work setting up high end speaker systems I've had the opportunity to set up large ($50 to $100k) speaker systems in several Neve rooms with transformers in the monitor path.  I have a standard procedure where I always start listening from a Prism Sound DAC and then after some time route through the console monitor path.  The difference is often astounding and while it can be a fun sound, it's not what the source actually sounds like....

I've never heard a transformer that I would want in a monitor path, a WE111C gets close but even then it does change things subtly, and those changes mean different engineering choices based on flawed information.

An opamp buffered attenuator is the way to go here, I know it doesn't fit the retro aesthetic but it is the right tool for the job. The last one I built from a kit measured 0.0004% THD+N, hard to beat that.

 
Title: Re: All Tube Sidecar
Post by: ruffrecords on February 02, 2018, 04:01:56 AM

I've never heard a transformer that I would want in a monitor path, a WE111C gets close but even then it does change things subtly, and those changes mean different engineering choices based on flawed information.

An opamp buffered attenuator is the way to go here, I know it doesn't fit the retro aesthetic but it is the right tool for the job. The last one I built from a kit measured 0.0004% THD+N, hard to beat that.

 

I agree that a transformer in the monitoring path inevitably colours the sound and that is the last thing you want in the monitor path (but I do wonder if it is significant in comparison the the colouration added by the monitor amp and speaker). Op amps are fine in this respect but unfortunately they do not provide galvanic isolation so tiny changes in noise/hum can and will take place and I think these are as important as colouration. In short, neither method is perfect.

The answer is probably to use a 10K balanced stepped pot for the monitor level and dispense with the transformer or op amp. In other words make it 100% passive. The downside with this approach is the output impedance can be as high as 2500 ohms which means that cable capacitance to the monitor amp can be an issue. For little or no phase shift at 2)Hz you want the 3dB down point to be about 10 times this frequency which gives a maximum cable capacitance of a little over 300pF. Using 40pF/metre cable means you can have over 7 metres of cable before you get that much capacitance

Thanks Ruairi, you just knocked couple of hundred bucks of the price of the mixer and improved its performance!

Cheers

Ian.
Title: Re: All Tube Sidecar
Post by: L´Andratté on February 02, 2018, 05:19:52 AM
The answer is probably to use a 10K balanced stepped pot for the monitor level and dispense with the transformer or op amp. In other words make it 100% passive. The downside with this approach is the output impedance can be as high as 2500 ohms which means that cable capacitance to the monitor amp can be an issue. For little or no phase shift at 2)Hz you want the 3dB down point to be about 10 times this frequency which gives a maximum cable capacitance of a little over 300pF. Using 40pF/metre cable means you can have over 7 metres of cable before you get that much capacitance

Hi!
I take it you mean 20kHz, great explanation, thanks!
Title: Re: All Tube Sidecar
Post by: ruffrecords on February 02, 2018, 06:46:54 AM
Hi!
I take it you mean 20kHz, great explanation, thanks!

Yes, sorry for the typo - my brain continues to outpace my fingers.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: Timjag on February 02, 2018, 10:22:12 AM
Hehe, Yeah with transformers in the monitor path you might end up making a terrible sounding album like Rubber Soul or Kind of Blue

 ;) :D
Title: Re: All Tube Sidecar
Post by: ruffrecords on February 02, 2018, 10:54:04 AM
Hehe, Yeah with transformers in the monitor path you might end up making a terrible sounding album like Rubber Soul or Kind of Blue

 ;) :D

If only it were that simple.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: Timjag on February 02, 2018, 11:32:32 AM
Personally (again) As someone that might use this kind of console I'd rather have some transformer colour, than farting about with cable capacitance, just for some type of purity that is subjective anyway. I know which ever transformers you select will be measured within an inch of their life anyway, I can't imagine anything I'd do particularly differently unless there was a huge discrepancy it bandwidth or at certain bands, and I don't think the transformers you'd choose would be like that.

Cost however is another issue, then I suppose there could be a choice between the two with a switch, but then you're getting into complications again.
Title: Re: All Tube Sidecar
Post by: pvision on February 02, 2018, 05:08:26 PM
I think if you created a tasty "tube" channel strip with mic / line, EQ, insert and a line out you'd find takers

How many takers you'd have for a full-featured monitor / speaker switching / output section I don't know, but it would be fewer

I think the addition of a channel compressor, or separate patchable compressor, would create a lot of interest and maybe attract more customers

Everyone has their own ideas about how best to setup routing, monitoring & etc so it might be hard to please everyone. However, with a "tube" channel strip you would definitely please everyone

Nick Froome
Title: Re: All Tube Sidecar
Post by: ruffrecords on February 02, 2018, 05:34:18 PM
Thanks for your input Nick. It is all too easy to get dragged the the road of creeping featurism so it is good to step back and look at the big, basic picture.

I am close to a basic tube channel strip design. Mic pre module with the usual pad, phase, phantom and mic/line switches plus a couple of AUX sends and a pan pot. This is followed by a three band EQ module with stepped boost/cut controls and three selectable frequencies per band. Lastly there is a fader module which includes mute and solo buttons. Monitor section can be considerably simplified because solo allows individual channels to be monitored so it can be little more than a master bus/2 track playback switch and a stepped level control and a couple of meters.

Anything else would be optional.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: Brian Roth on February 02, 2018, 09:03:29 PM
Thanks for your input Nick. It is all too easy to get dragged the the road of creeping featurism ....

.... Monitor section can be considerably simplified because solo allows individual channels to be monitored so it can be little more than a master bus/2 track playback switch and a stepped level control and a couple of meters.....



IMHO, at least two 2-track playbacks would be very useful.

Bri
Title: Re: All Tube Sidecar
Post by: bluebird on February 03, 2018, 01:15:11 AM
The passive 4 deck 10K monitor switch really does work well. There are a couple of the passive Colman units in the studio I work in. They are in some production rooms and get used for utility stuff here and there and there has never been a problem with them, hum, buzz, high end roll off wise. Most people will be driving powered monitors with standard high Z inputs.  Its a proven method of balanced/unbalanced attenuation for monitoring.

I think if you created a tasty "tube" channel strip with mic / line, EQ, insert and a line out you'd find takers

How many takers you'd have for a full-featured monitor / speaker switching / output section I don't know, but it would be fewer

Of course, no one was suggesting just a monitor controller. I'm saying in addition to the tube channels. And again it would be a bonus for someone who is looking for a small mixer and can sell whatever monitor controller they are using because the mixer will have all the monitor features they need included.


Personally (again) As someone that might use this kind of console I'd rather have some transformer colour, than farting about with cable capacitance, just for some type of purity that is subjective anyway.

Oh yea, there will be plenty of transformer/tube sound going on with the channel strips. But when you just want to hear the main out of your DAW your going to want to hear it as accurate as possible. If your A/B-ing a mix to an external source like a CD or media player you want the signal to be clean. And if you really want a transformer sound on your monitor feed, Just put some transformers in line with the output, your choice!
Title: Re: All Tube Sidecar
Post by: scott2000 on February 03, 2018, 11:08:52 AM
Would polarity flip on the  channels be useful and also maybe allow for some type of mid side experimenting??

I see it was already brought up...... :-[
Title: Re: All Tube Sidecar
Post by: ruffrecords on February 03, 2018, 12:42:30 PM
Would polarity flip on the  channels be useful and also maybe allow for some type of mid side experimenting??

I see it was already brought up...... :-[

Polarity flip per channel is fitted as standard  ;) There will be an insert point on the master bus so you can plug in a compressor, MS etc.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: ruffrecords on February 03, 2018, 04:30:34 PM
Here is my first stab at a block diagram for a channel. It is based on the Classic mic pre which is the only one I have right now in the new 35mm format. The only thing missing is an insert point. An unbalanced insert can be added just after either amplifier.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: pvision on February 03, 2018, 05:44:21 PM
In that diagram your pre-fader effects send & direct out are pre-EQ. This would limit their usefulness

Nick Froome
Title: Re: All Tube Sidecar
Post by: ruffrecords on February 03, 2018, 06:16:27 PM
Your pre-fader effects send & direct out are also pre-EQ in that diagram

Nick Froome

That is correct. It is a passive EQ so it needs a gain make up amplifier after it. You could change the fader to a 'gain' pot and put the 'proper' fader after the second amp but that means:

1. No post fader direct out
2. Fader has to drive the pan and post fader Auxes

A block diagram for this alternative is attached.

Edit: By the way, I forgot to mention the maximum mic pre gain of both version is about 55dB

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: pvision on February 03, 2018, 06:24:30 PM
With insert

(How do you insert attachments in a message?)
Title: Re: All Tube Sidecar
Post by: bluebird on February 03, 2018, 10:58:01 PM
Or you could have a female XLR under the direct out XLR labeled "Fader in (unbalanced)"
So the insert  would be the (direct out  --> fader in) XLR combo.
All you would need is a DPDT insert switch  (or relay) to break the signal between the last amp stage and the fader, while attaching the hot pin of the female XLR to the top of the fader..

The advantage over the standard normaling 1/4" jacks is a truly balanced output for the insert. And not having to use xlr to 1/4" adapter cables for your gear if you arn't using a patch bay. 

The disadvantage would be the extra switch. And if you do it that way, you should probably have an associated LED so one can see that the insert is engaged.

 
Title: Re: All Tube Sidecar
Post by: ruffrecords on February 04, 2018, 03:38:26 AM
@bluebird.

I like that idea. I is a bit like the arrangement we used at Neve between channel amps and routing modules excpet the input to the fader was unbalanced by a transformer.

Two Three things about this are not clear to me right now.

1. Where do you connect pin 3 in the return XLR? You cannot leave it floating because transformer balanced sources would not work. If you connect it to 0V analogue you run the risk of blowing up poorly designed electronically balanced outputs.

2. The level at the direct out is 6dB lower than at the fader because of the 2:1 output transformer. A fix for this would be to replace the 2:1 transformer with a 1:1 one. This would men the output could not longer drive a 600 ohm load (no Pultecs) but it would increase the overall available gain by 6dB. An alternative fix would be to pad the bypassed feed the fader by 6dB but this worsens the signal to noise by 6dB. A third possibility, for those with plenty of money, would be to fit a 1:2 step up transformer on the return which would drop the return input impedance to 5K but I think we can live with that,

3. I guess the fader return actually goes to the mute relay rather than direct to the fader so that solo still works the same.

Cheers

Ian

Edit: Just had a thought. I can see an insert PCB that fits in the back of the mixer. I has two XLRs and a relay on it. It also has provision for  output and input transformers. This means the same  board could be built three ways:

1. Unbalanced insert. Just the relay is fitted and the transformer connections are wire linked.

2. Balanced out unbalanced in. The relay and a  1:1 output transformer are fitted. The input transformer connections are wire linked. This is not capable of driving 600 ohm loads

3. Totally balanced  600 ohm drive capable insert with a 2:1 output transformer and a 1:2 input transformer

Ian
Title: Re: All Tube Sidecar
Post by: ruffrecords on February 04, 2018, 10:33:21 AM
I have updated the channel block diagram to V3 to reflect the changes discussed above.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: bluebird on February 05, 2018, 02:38:05 AM
You are right about the unbalanced input. Its not a robust (or responsible) solution. The extra PCB is a smart "compromise" but a lot of work just to allow for a less than optimal solution.

My three way rebuttal:
1. The balanced direct out is a must. So your half way there. I would just add the extra 1:2 transformer and do it right.
I think another balanced input post EQ is a nice bonus. I think it is worth the extra expenditure to make it stock.

2. If you decide you don't want to spend for the extra 8 transformers you can just put in two normaling 1/4" jacks at the insert point to be used at the risk of the operator. This would just be a convenience I/O that would be better than nothing.

3. Skip the insert all together because most people will probably be fine putting outboard gear between the DAW/converters and the channel strip anyhow.






Title: Re: All Tube Sidecar
Post by: ruffrecords on February 05, 2018, 03:39:00 AM
You are right about the unbalanced input. Its not a robust (or responsible) solution. The extra PCB is a smart "compromise" but a lot of work just to allow for a less than optimal solution.

My three way rebuttal:
1. The balanced direct out is a must. So your half way there. I would just add the extra 1:2 transformer and do it right.
I think another balanced input post EQ is a nice bonus. I think it is worth the extra expenditure to make it stock.

2. If you decide you don't want to spend for the extra 8 transformers you can just put in two normaling 1/4" jacks at the insert point to be used at the risk of the operator. This would just be a convenience I/O that would be better than nothing.

3. Skip the insert all together because most people will probably be fine putting outboard gear between the DAW/converters and the channel strip anyhow.

I do not disagree with what you said but....

My tube pre designs do not have room on board for the direct out output transformer. It needs to be fitted somewhere near the output connector and hooked up to the backplane. I know from bitter experience that hand mounting and wiring output transformers and XLRs  at the back of a mixer is no fun so I would design a PCB to hold the two of them anyway. I would enjoy designing the PCB far more. So you might as well make provisions for the alternatives while you are at it.

PS. A few posts ago I said the monitor would need only to switch between the master bus and 2TK playback for A/B comparison because the Solo feature would let you set levels/check quality of individual channels. However, I forgot about the AUX sends. So a third postion on the switch is needed to accommodate these.

Cheers

Ian

Title: Re: All Tube Sidecar
Post by: bluebird on February 06, 2018, 03:47:11 PM
I would enjoy designing the PCB far more. So you might as well make provisions for the alternatives while you are at it.

I shouldn't forget you are a seasoned designer so you know what it would take to make the extra pcb, and if its not that big a deal for you, I think it is a great idea to give the buyer a choice, or to make future upgrades.
Title: Re: All Tube Sidecar
Post by: ruffrecords on February 06, 2018, 03:50:32 PM
I shouldn't forget you are a seasoned designer so you know what it would take to make the extra pcb, and if its not that big a deal for you, I think it is a great idea to give the buyer a choice, or to make future upgrades.

You are right, it is not that big a deal for me and will certainly simplify assembly which is a surprisingly long task.

Which begs a question which PCB mount XLRs to use. I don't like the plastic ones at all. Can you get male/female right angle PCB mounting metal XLRs??



Cheers

ian
Title: Re: All Tube Sidecar
Post by: Brian Roth on February 06, 2018, 06:01:25 PM

Which begs a question which PCB mount XLRs to use. I don't like the plastic ones at all. Can you get male/female right angle PCB mounting metal XLRs??


http://www.neutrik.com/en/xlr/xlr-chassis-connectors/d-series/


Bri
Title: Re: All Tube Sidecar
Post by: ruffrecords on February 06, 2018, 06:31:45 PM
http://www.neutrik.com/en/xlr/xlr-chassis-connectors/d-series/


Bri

Thanks mate. So basically NC3FD-H* and NC3MD-H*. 

I'm spoilt for choice.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: Brian Roth on February 06, 2018, 06:36:42 PM

PS. A few posts ago I said the monitor would need only to switch between the master bus and 2TK playback for A/B comparison because the Solo feature would let you set levels/check quality of individual channels. However, I forgot about the AUX sends. So a third postion on the switch is needed to accommodate these.

Cheers

Ian

On various Neve and Amek desks the monitor had a switch for "internal" and "external" sources.  Then, two banks of switches selected stereo mix, auxes, etc for internal and several " 2 track" sources for external.

Bri

Title: Re: All Tube Sidecar
Post by: ruffrecords on February 06, 2018, 06:53:39 PM
On various Neve and Amek desks the monitor had a switch for "internal" and "external" sources.  Then, two banks of switches selected stereo mix, auxes, etc for internal and several " 2 track" sources for external.

Bri

Internal or external - that's a good way of thinking about it because it will actually mean something to the guy/gal operating the desk.  Good thought.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: pvision on February 07, 2018, 06:17:40 AM
To my way of thinking this is two units in one: a bunch of channel strips and a routing / monitoring module

When I think of channel strips I tend to think of the Focusrite channels you see racked up

(https://www.proaudioeurope.com/info/wp-content/uploads/2016/07/Focusrite-ISA110-8-way-rack-1.jpg)

In this case they are used just as channel amps. If you used the same approach, and created a channel amp with very little complexity, IMHO you'd open it up to a wider audience and more uses

A channel strip needs a mic / line amp, EQ and, ideally, an insert. Having the insert switchable pre/post EQ would be good. That saves all the complexity for a routing / sends / fader module

Going back to the Focusrite modules: they are racked up. If your modules are 35 wide then you'd get 12 in a 19" rack. You could use a 19" panel for the monitoring section. And a 19" rack power supply. Users who wanted to work mobile could have a rack of pres, with or without the monitoring section. Static users could have a sidecar setup

This is going away from your original concept. I don't throw the idea in to confuse, just as an idea to provoke thought & discussion. Also, separating the active parts from the switching & routing might help nail down what the proposition is, and what people want

Nick Froome
Title: Re: All Tube Sidecar
Post by: ruffrecords on February 07, 2018, 12:01:07 PM
Physically separating the functions of mic pre/EQ and routing is the classic Neve format. Perhaps that is one reason the channel amps are so popular racked on their own. And of course Focusrite is (now) a distant cousin of Neve.

The API 500 series approach is different. The mic pre and EQ are separate (smaller) modules which provides added flexibility.

Both methods allow different channel strips to be created (and used alone) by keeping routing separate.

The Mark III design started from the premise of trying to fit in twice functionality per unit width compared to the EzTubeMixer project to bring it in line with current products and avoid need for one metre of width for a 12 channel console as in Holger's wonderful Krassemaschine. As a first step I designed some 6U modules of the same width as the EzTubeMixer modules but each containing two channels. This saved me having to completely redesign all the PCBs and the mechanics but meant that these modules would be line in only because I had the same number of amplifiers but twice the channels to provide for. This was deliberate because current practice seems to be often to use outboard mic pres of various sorts fed directly to a DAW and possibly use a line level mixer (LILO) for monitoring and mixdown. I am sure this is the case because because I have sold several lunch boxes containing just tube mic pres and nothing else (not even EQ) and I have an order for a LILO mixer.

I then started experimenting with half width (35mm) modules which involved mounting the tubes vertically and completely redesigning the PCBs and mechanics. This allows not only twice the modules but twice the number of amplifiers (tubes) per unit width compared to the EzTubeMixer. The problems involved in doing this I believe I have now pretty much solved so the remaining question is simply one of how to package things. I can still supply mic pres alone in a 3U lunchbox but now I can get up to twelve in a lunchbox rather than the present six. The next step would be to add EQ, possibly in a 6U unit, which would be similar to the Focusrite modules you mentioned and could be racked similarly and I have begun the design of the first of these containing my REDD EQ design.

The first problem arises when you try to fit other EQ types, like the Helios 69 or my 3 band Pultec design into a 35mm wide module. The REDD fits because it has only 4 controls total. The Helios has 6 and the Pultec has 7. It is very hard to fit these into 35mm width without resorting to expensive dual concentric knobs and/or tiny unusable (in my view) knobs. The Focusrite illustrates this perfectly. I also think it is important for all EQ controls to be stepped (for accuracy, tracking and repeatability) which only the REDD achieves at the moment. So,based on the mastering EQ which I am also developing at the moment, I have devised a simplified three band version with stepped boost/cut controls and three selectable frequencies per band which fits neatly into a 35mm wide 3U module and does not need the fingers of a pixie to operate. This is the EQ I plan to use in the tube sidecar and also can be added to a 6U channel strip version (perhaps with added features like HPF and LPF). Either of these 6U modules could then be supplied in racks or used as channel strips in mixers.

The sidecar project is at least in part defined by my desire to fit it into the Glensound and EELA frames I have purchased. Both have a 3U section at the top in which I plan to house the mi pres. The Glensound has a second less deep 3U high section that the new EQ will fit in. It then has a fade section below which can also have Solo, Mute and Direct buttons. In this instance, the only available space to put the routing is in the mic pre module. This means the routing is relatively simple (pan plus two AUXes) but it does mean the overall mixer is really compact - it is only 500mm wide and it could be configured as an 8 into 2 or even a 10 into 2 which would make is smaller than a Neve Kelso.

So, to summarise, it is what it is right now because the Glensound provides me with a framework (literally) to work on and will actually produce something useful at the end. The 'final' version of the sidecar would undoubtedly have a custom frame that would allow the channel to be either two 3U units (mic pre and separate EQ) or a single 6U channel module, and routing would be a completely separate module. Any of thes modules can be use to make rack mounted pure mic pres or channel strips.

You can see I have a lot of work to do which s the main reason I am not taking any commissions at all  this year. I really want to get the Mark III sorted.

Many thanks for your input.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: Timjag on February 09, 2018, 03:26:34 PM
It's a great project Ian! Any photos yet?
Title: Re: All Tube Sidecar
Post by: ruffrecords on February 09, 2018, 05:44:34 PM
It's a great project Ian! Any photos yet?

It is all very much up in the air at the moment. I have got the PCBs for the little 3 band EQ which I will be building and testing in the near future. I also have a prototype front panel for that on the way so that will be the first tangible part I can take a picture of.  The mic pre is based on my Classic design which is currently in prototype as the UniVert (Universal Vertical Tube Preamp) (I think I posted a pic of that a while back in another thread). That PCB is being modified to comply with the new motherboard pin out that Holger and I devised to cater for the next generation of tube modules. The good old Twin Line Amp has been repackaged into a 35mm wide module. That PCB is ready to go and I am still working on the new 12 module motherboard. I expect to have all these ready for manufacture by the time the Chinese get back from their New Year celebrations.

I have spent a lot of time sorting out components. With such a narrow width module I wanted a scheme that a still allowed neat front panel layouts so I have standardised on MRK rotary switches and Alpha 9mm vertical mounting pots. These all mount on a PCB that sits parallel to the front panel which allow pots and switches to be lined up neatly. I wrote a post in my blog about this awhile back (and also about the Univert mic pre and the new module mechanics:

https://mark3vtm.blogspot.co.uk/ (https://mark3vtm.blogspot.co.uk/)

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: pvision on February 14, 2018, 10:33:22 AM
Just had a good read of your thoughts re the project, Ian, and have only one suggestion: put the HP filter on the mic amp module

This frees up panel space on the EQs (or allows more free space, depending whether an HPF was planned or not) and allows it to be put where it is most needed - on the mic pre

Nick Froome
Title: Re: All Tube Sidecar
Post by: ruffrecords on February 14, 2018, 12:41:04 PM
Just had a good read of your thoughts re the project, Ian, and have only one suggestion: put the HP filter on the mic amp module

This frees up panel space on the EQs (or allows more free space, depending whether an HPF was planned or not) and allows it to be put where it is most needed - on the mic pre

Nick Froome

Probably a good idea. The EQ module really has no room for this. To illustrate, here are a couple of pics of it (I just received the prototype front panel today and, after a little fettling, assembled the basic module. First pic shows the front panel:

(https://s26.postimg.org/wtmeqi40p/frontscaled.jpg)

As you can see there is little if any room to spare. I need to squeeze the EQ in/out switch in right at the top centre but there is certainly no room for an HPF as well.

Second  pic shows how the two boards fit together:

(https://s26.postimg.org/hkwhcr57d/sidescaled.jpg)

The EQ is based on the new mastering EQ topology scaled down to three bands. Its advantage is it gives peaking boost and cut in all three bands. I called it the REDDPLUS because the Q in all bands and the mid frequency selections are much the same as my original REDDEQ design.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: kambo on February 14, 2018, 02:20:44 PM
if i had to choose between shelving HF vs peaking HF EQ, i would pick shelving,
i dont remember using peaking eq at 9K-19K range, unless its surgical work!
Title: Re: All Tube Sidecar
Post by: pvision on February 14, 2018, 03:21:39 PM
I completely concur with your dislike for cramped panels. So maybe offset the switches on the EQ from the pots so there's more finger room?

The mechanical construction is very sweet

Nick Froome
Title: Re: All Tube Sidecar
Post by: ruffrecords on February 14, 2018, 05:19:11 PM
I completely concur with your dislike for cramped panels. So maybe offset the switches on the EQ from the pots so there's more finger room?
At the moment, the knobs (which are rather nice Sifam ones) are a lot taller than the toggle switches so they don't get in the way when you operate the knobs. However, they do look better when offset as in your illustration and what is more, that would make it easier the fit in the EQ in/out toggle above them. Nice idea, thanks. By the way, the knobs are 14.5mm diameter at the base so they are not the smallest available but the do nicely cover the switch nut. Now I have the panel I might try some 11mm diameter ones.

The vertical spacing is certainly fine - the rotaries are on 30mm centres.
Quote
The mechanical construction is very sweet

Nick Froome
I am mechanically challenged so it takes me absolutely ages to do this stuff. What you now see as 'sweet' is the result of several years plodding. Even then I cannot take much credit. The little die castings are the key to it and they are standard Eurorack parts made by all the sub-rack manufacturers like Schroff, Fischer and SRS and are designed specifically to connect Eurocards to front panels.

What I can claim credit for is extending this idea by making provision for two more such die casting one the right side of the front panel which allows you to attach a steel screening plate to the front panel. At the rear of the PCB you fit a pair of pillars to connect the back end of the PCB to the back end of the steel. The whole forms a very tough rigid structure. Top and bottom are open which allows free flow of air past any tubes.

The other thing I am proud of is finding a set of good quality vertical PCB mounting components (pots, rotary switches, toggles and push-buttons) that are almost exactly the same height above the PCB. This means you have great flexibility in positioning controls when designing front panel layouts.

Cheers

Ian
Title: Re: All Tube Sidecar
Post by: pvision on February 14, 2018, 06:41:34 PM
Those 14/5 mm Sifam knobs are excellent. There are some similar, cheaper ones at Rapid made by Cliff and some more expensive ones from OKW

Rapid also have some shaft joiners & flexible couplings which are esoteric but potentially useful for some projects

Have a look at this search
https://www.rapidonline.com/knobs?ra_source=tier-left-list&Attributes={%22Shaft%20Diameter%22:[%226mm%22],%22Fixing%22:[%22N%2FA%22,%22Push%20fit%22]}&Size=60&ResultsTotal=30

I've found it really difficult to find suppliers who carry a decent proportion of the Sifam range. Most have limited colours & sizes. There's a Eurorack synth module supplier close to me, Thonk, that has a good range

https://www.thonk.co.uk/product-category/parts/knobs/


Nick Froome
Title: Re: All Tube Sidecar
Post by: ruffrecords on February 14, 2018, 07:04:12 PM
I use Thonk quite a bit because they also do the vertical ALPHA pots. They do a great range of knobs but unfortunately no 1/8 inch types.

Your Rapid link gave an error. I'll try again later.

I agree it is incredibly difficult to find one supplier for all your knob requirements.

Cheers

Ian