One-Bottle Preamp

[Kingston]

Nice, since the circuit is small which uses one tube only so the heater current is reduced so it is possible to place side by side 4-6 channels in a single 2U chassis, with the PSU inside. 
What do you think a version with an output stage with a solid state buffer with the advantage to have a trasformerless out too? It could reduce price and space.

12AV7 heater current is somewhat on the high side, 0.45A/6.3V or 0.225/12.6V.

A solid state buffer would be strange. You would have to drop from the high voltage 12AV7 plate to a sensible output voltage via attenuator, and also provide a separate PSU for it. If you were to do this, you could pick a better tube since you would no longer need the semi-low output impedance of 12AV7 (needed to drive a transformer). You could even use a 12AX7 with some optimisations and then you would have very low heater requirements also.

Or maybe you were thinking of some unique (high voltage?) solid state buffer instead?

Since 12AV7 is happy to drive a 4:1 transformer, take full advantage of it and pick some cheap but good performance Edcor for example (read: WSM10K/600, which is also quite small). If you invest in decent input transformer it's a winner combo.

I can certainly picture 4-6 channels and a PSU in a 2U chassis, like a small scale vintage broadcast mixer. But I hope you can shield the PSU extremely well!

 

[ppa]

12AV7 heater current is somewhat on the high side, 0.45A/6.3V or 0.225/12.6V.

yes, a different tube is needed.

A solid state buffer would be strange. You would have to drop from the high voltage 12AV7 plate to a sensible output voltage via attenuator, and also provide a separate PSU for it.

No, it is not, because I can add a diodes protection to avoud DC spikes into buffer.
Separate PSU is not a problem because, in any case, I need the 48V for the phanthom so I could use this +48V also for the buffer. BTW a power supply trasformer costs less than 4-5 good out trasformers.

If you were to do this, you could pick a better tube since you would no longer need the semi-low output impedance of 12AV7 (needed to drive a transformer). You could even use a 12AX7 with some optimisations and then you would have very low heater requirements also.

yes, 12AX7 should be fine.

Since 12AV7 is happy to drive a 4:1 transformer, take full advantage of it and pick some cheap but good performance Edcor for example (read: WSM10K/600, which is also quite small). If you invest in decent input transformer it's a winner combo.

Yes, it is fine, very fine  8)

I can certainly picture 4-6 channels and a PSU in a 2U chassis, like a small scale vintage broadcast mixer. But I hope you can shield the PSU extremely well!

Yes, it is a must.

 

[ppa]

has anyone designed a PCB for this preamp?

 

[Kingston]

has anyone designed a PCB for this preamp?

I think several people have, some have posted it on the forum but I'm lazy to search for the links. I also made a generic PCB of a one-bottle two-stage building block that I have used as a make up gain amp for passive EQ and as line level amp. It only takes a few resistor changes to mod this into many tasks with different tubes.

[edit]

ppa, here are two examples of the direction you're going for:

http://groupdiy.com/index.php?topic=45990.0
http://groupdiy.com/index.php?topic=31148.0

I know there was at least one another PCB released somewhere on this forum.

 

[mus1k_freak]

i just got my pcbs in today for this preamp and it sounds awesome!!! only bug is my volume control isnt working right, hunting down that issue, otherwise im gonna make some corrections to the silk screen and order a new revision, i have 6 pcbs now, ide be willing to part with 2

has anyone designed a PCB for this preamp?

 

[ppa]

i just got my pcbs in today for this preamp and it sounds awesome!!! only bug is my volume control isnt working right, hunting down that issue, otherwise im gonna make some corrections to the silk screen and order a new revision, i have 6 pcbs now, ide be willing to part with 2

has anyone designed a PCB for this preamp?

thanks for replay

but a month ago I have designed a PCB for one bottle preamp.
BTW I have designed the one bottle preamp with an E88CC/6DJ8 tube.
This version has only 150V of VCC reducing costs for preamp and PSU, since one bottle
preamp is cheap preamp, this version is more cheap too.

 

[ppa]

However, I have designed the 6DJ8/ECC88/E88CC version because many preamps in the market don't use this tube (but Avalon yes) so I would want to add a new sound look for this preamp.
Moreover, with 150V of Vcc safety is increased for diyers.

 

[mitsos]

I'm doing a 2 channel of this P2P, but also a few other tube circuits and would like to try regulated PSUs, something like Kingston's IRF840 PSU but only one stage.  I'm curious if this preamp might see some benefit from B+ regulation?  Also, is there still benefit from regulating just once to 300V and feeding that to the B+ input and using the resistors to bring it down to whatever the valves need (does that makes sense?)?

thanks!

 

[mus1k_freak]

The tube needs to see a load on the plate,  so  you'd need a resistor for that,  part of of the mojo of tube gear is voltage sag (hence using tube rectifier and not ss) so you probably wouldn't want a regulated one unless you  want super clean

 

[mitsos]

Well, rereading that post, I don't think I explained that very well. I am wondering if there is any benefit to feeding the NYD1B a regulated 300V to R13. I didn't mean removing the anode R's if that's what it sounded like.

I've never directly compared tube vs SS rectification. I'm open to recommendations, though.  I'm using Kingston's PSU as a reference because it seems to be working for a few people.  Schematic is in the first post of the M670 thread (nice read if you have parts for, or plan to build a PM660/ 670)

http://groupdiy.com/index.php?topic=51478.0

thanks!

 

[mus1k_freak]

It would definitely work but for something like a one bottle it's a bit if overkill,  for mine I used 3 47uf caps with resistors between them and have almost no hum,  very low parts count and super easy to build.  But there's no reason you couldn't use the one you posted.

 

[Max51]

Hi everybody,

First, thanks to Dave for this project !
I have a question for diyers who built that project : I've got a neutrik NTM1 input transformer in stock  and I asked me : why don't build a mono tube preamp ?

So, the neutrik NTM1 has a 1:1 ratio and the following specifications :
Typical source impedance : 200ohms
Typical load impedance : 2kohms

If I use it in the NYD one bottle preamp could I have honnest gain ? ( I would use an edcor WSM 600/10k as an output transformer)

Thanks for you help and sorry for my terrible english.

 

[alexc]

Lucky enough to score (thanks Greg!)  a quad  channels pcb of  NY Dave's TM 'One Bottle' mic pre.

A serious pcb indeed - don't know the pcb designer but yep. A really nice job.

This build will feature off board psu, AV7 tubes all round.

Two channels Lundahl input, two channels Cinemag input. They are 1:4 and 1:5 or so.

On the output side, I'm using output traffos as well.

Two are Cinemag outputs 6.3:1 and two Carnhill 4:1 outputs.

Should be very nice indeed.

I'm considering one small enhancement to my build - a simple passive sum buss with level and L/R assign switch. Gain will be provided by a pair of  additional amp stages - could be ss or tube, not sure yet.

Coolio !  This is intended as a remote 4ch preamp for drums recording with the stereo send for monitor mix. It may be that I'll also add a couple of stereo input-to-sum-bus connectors to do a local effects mix to monitor.

Should be very nice and it will be a  module in a modular setup - one PSU feeding 3 or 4 modules.

My other module is one channel of federal limiter. Also adding a mic psu module and a low power tube amp.

 

[Freddy G]

Lucky enough to score (thanks Greg!)  a quad  channels pcb of  NY Dave's TM 'One Bottle' mic pre.

A serious pcb indeed - don't know the pcb designer but yep. A really nice job.

This build will feature off board psu, AV7 tubes all round.

Two channels Lundahl input, two channels Cinemag input. They are 1:4 and 1:5 or so.

On the output side, I'm using output traffos as well.

Two are Cinemag outputs 6.3:1 and two Carnhill 4:1 outputs.

Should be very nice indeed.

I'm considering one small enhancement to my build - a simple passive sum buss with level and L/R assign switch. Gain will be provided by a pair of  additional amp stages - could be ss or tube, not sure yet.

Coolio !  This is intended as a remote 4ch preamp for drums recording with the stereo send for monitor mix. It may be that I'll also add a couple of stereo input-to-sum-bus connectors to do a local effects mix to monitor.

Should be very nice and it will be a  module in a modular setup - one PSU feeding 3 or 4 modules.

My other module is one channel of federal limiter. Also adding a mic psu module and a low power tube amp.

Hey! That's my PCB design! Cool....did you get her going? My 8 channel NYD pre (2 of those PCBs in a 2 rack space chassis) is still going strong with almost daily use.

Freddy

 

[My3gger]

Well, rereading that post, I don't think I explained that very well. I am wondering if there is any benefit to feeding the NYD1B a regulated 300V to R13. I didn't mean removing the anode R's if that's what it sounded like.

I've never directly compared tube vs SS rectification. I'm open to recommendations, though.  I'm using Kingston's PSU as a reference because it seems to be working for a few people.  Schematic is in the first post of the M670 thread (nice read if you have parts for, or plan to build a PM660/ 670)

http://groupdiy.com/index.php?topic=51478.0

thanks!

Preamps in class a like this one won't really sag even when psu isn't regulated. This is explained here:
http://www.aikenamps.com/index.php/what-is-sag
Advantage of regulated psu is ease of dialing correct voltage, lower ripple, etc. In case of One Bottle you still need R13. Downside is heating of pass transistor or regulator, there are more parts too.
You could use voltage multiplier with zeners into base of pass transistor. If designed properly transistor stays cool and whole psu doesn't need much capacitance at typical preamp's current (base cap's value is multiplied by tr. beta).
I'm using multipliers lately with great results, typical schematic has like 4 caps, TIP50 tr., 2 5W resistors (they don't heat either up to ~25mA/300V) and some 5W zeners for needed voltage. None failed in years and probably won't for long time because they don't heat. I tested one by shorting it for a few minutes, it survived. Ripple is much lower compared to simple RC filters, lack of heatsinks is nice thing compared to regulator, it can also be built fast and well on veroboard. Can't really say how their sound compares to tube rectifiers and simple RC filters, difference is mostly in cleaner voltage with cap multipliers or real regulators. I would only use tube rectifier, chokes and things like this for restoring old gear.
Can't find schematic for one at the moment because i'm moving to another apartment. If you pm me i can send it to you later. PM670 seems like a good plan too.

 

[alexc]

Hey! That's my PCB design! Cool....did you get her going? My 8 channel NYD pre (2 of those PCBs in a 2 rack space chassis) is still going strong with almost daily use.

Freddy

Cool - it is a very nice pcb design. Just enough features and not too much. 

I'm yet to get it going but will be not too distant  (maybe a year or so    I have some nice old stock AV7s to use with it and some nice lundahl and cinemag input traffos.

My additions will be to add haufe active traffo balancing modules for the 4 channels and a stereo sum bus with active traffo.

Will be a nice blend of tube front and sand state + traffo back end.

I like the compact nature of the pcb layout for use with an external psu.

In short Freddy, you nailed the pcb design!

Alex

 

[mhelin]

This is old thread but there was some discussion on using SS output stage. I think it could be best done using LND150 depletion mode MOSFET like in this FX loop circuit:
http://music-electronics-forum.com/attachments/36235d1445867855-mojotone-loop1.gif

That circuit biases the gate of LND 150 to B+/2 using 1M resistors.

 

[alexc]

Or you could use some That Corp DRV balanced line driver chips ...  they are super great quality, cheap and easy to implement, even with vero-board.

I'm using Haufe/AKM  balancing modules on my quad-OneBottle build - they are an integrated ne5534+transformer combo in a mu-metal can.

Performance is pretty good, but the That DRV chip is better with respect to THD.

 

[Pief]

NYD one bottle build. The housing is a steel box from an old car battery charger.


Comming from europe we don.t really have 12AV7's so i just swapped it for a 12AT7(ECC81) and it sound just fine with the rest of the cirquit the way it is. Lots of gain...and dead quit, certainly given my unconventional layout.

I uses a 1:10 dynacord 3553 step-up from an old Dynacord Eminent. It measure 7.5k on the secondary.
No output transformer is used.
ow...Ac heated with a hummingpot installed.
Overall, transparent, nice and punchy, but maybe a tad too bright. but not sure yet.

I wanted to install a variable attenuation at the end of the cirquit instead of at the input as Dave had  drawn it up.
But i can,t figure out what the best variant would be. Any suggestions? H-Pad, T-pad?  would this work with an unbalanced output?

I.ll post some samples i made later this week.

 

[ruffrecords]

Nice compact build. Excellent re-use of an old charger. Well done.

Cheers

Ian