[ruffrecords]

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?



Cheers

Ian

[zamproject]

that features and facilities would you want in it and why?

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

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

[ruffrecords]

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

[zamproject]

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 

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

[zamproject]

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

[ruffrecords]

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

[ruffrecords]

@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

[zamproject]

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 

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

[ruffrecords]

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

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.

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.

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 

That is basically it and you are right about VE summing also giving expansions opportunities.

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

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

[zamproject]

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

[ruffrecords]

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

[zamproject]

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

[ruffrecords]

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.

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.

Yes a block diagram will be good 

Working on it.

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:

]

Cheers

Ian

[ruffrecords]

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

[zamproject]

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 

[ruffrecords]

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

[zamproject]

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

[ruffrecords]

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

[G-Sun]

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.

[ruffrecords]

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