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[80hinhiding]

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[ruffrecords]

What is the difference between trim, gain and level? Do you need all three on a line level mixer?

Cheers

Ian

 

[ruffrecords]

If you strip it down to the bare bones you could make each line input unbalanced and passive and do away with the gain control - see attached schematic. The compromises are the input impedance varies with the position of the controls (but most decent sources will cope with that) and you have to use VE mixing to maintain a decent cross-talk figure and there is just trim and fader controls.

Cheers

Ian

 

[CurtZHP]

My $0.02 (and you probably have change coming....)

If you're going to build a console, go for broke (or go broke, depending on how you look at it....) and add EQ and maybe compression for each channel, and maybe an aux buss or two.

 

[abbey road d enfer]

If one were to be having so much fun building a mixing console from scratch over the past year and a half that he is planning for the future already, thinking of a bare bones tube line console featuring a trim, gain, panning, level on each channel down to 2 bus output.. on an extreme budget - what could be accomplished from lessons learned already, I wonder?

You must have a good reason for wanting a tube mixer, and it has a cost. I think you should really define what you expect. There are plenty of tube gear where tubes are only decoration and plenty of people who buy tube gear just for the sake of saying it has tubes in it. Building a mixer takes a lot of dedication and always cost much more than expected at the end of the day, so you have to assess your motivation.

For line level, maybe we could get by without an input transformer. 

Are you ready to accept the risks associated with running unbalanced connections? Me, I don't care about "xfmr sound", but I care for signal integrity.

However if one was absolutely necessary, perhaps a Edcor WSM 10K:10K would suffice. 

Does "suffice" suffice? I believe you're expecting something special for this project, are you going to cut every corner of it?

Would budget tubes, military stock from Russia such as 61NP-EV work well instead of the ECC88?  Except for the high heater current.

They would need to be evaluated in view of your expectations; I can't answer this for you. They are quite different tubes; however, in the context of the REDD47's output stage's specifics (large load Z vs. inner resistance, under local NFB), the 61NP may provide satisfactory performance. Some values may need to be adjusted though.

Would OA2 voltage regulators be required?

Not necessarily, but a good understanding of grounding and decoupling is necessary anyway. You may have to use larger decoupling caps than the ones in the original. remember that lytic caps in the 60's were expensive and bulky; today they are much more cost-effective, smaller and more reliable.

What kind of vintage consumer gear might have some key components for a power supply, that could possible be scored for very little?  I've seen a Zenith tube radio for sale locally for $40, as one example. 

That is a possibility; I used to make guitar amps out of recuperated tube TV's when I was much younger. However, if all you end up salvaging is the PT, you're better off buying a new one; I wouldn't think you'll want to re-use 40 year old caps and rectifiers.

I was thinking of using a cheap 115V:24V 56VA transformer for plate voltage but by the time you triple that AC the B+ current capacity would be too small for 10 channels I think. 

Definitely a bad idea; in addition to the sag issue, you'll have to deal with large current spikes and the need for increased filtering.

The power transformers I see that have 220 mA and above are on the costly side for sure.. but might be the one thing to bite the bullet on..

A trick that is largely used consists in having a 115:6.3 capable of handling all the power and use another one (smaller) wired as 6.3:230 for HT. That gives about 290Vdc, which is enough for a mixer. Actually, the REDD47 takes 300V at 20mA for its operation, the rest is dissipated in the regulation (80V in the ballast resistor, 10mA in the OA2's). There is no reason why it wouldn't work at 280V.

 

[CurtZHP]

Does "suffice" suffice? I believe you're expecting something special for this project, are you going to cut every corner of it?

This.  If you were building a small gadget like a DI or a stomp box, by all means do it on the cheap.  But, for something this ambitious, go big or go home.  Otherwise, you'll never be happy with it, and you'll be stuck with it.

 

[Anthon]

10 tube channels for under 1000? 

If you ask me, there is no point in building a console, if you are not going to make it really good. So I wouldn't recommend cutting costs, just to end up with 'poor man's' tube console, just for the sake it being tube. Salvaging old equipment takes huge amount of time, it's not as cheap as it should be, and the parts you are getting are often of questionable quality. Buying new parts will save you so much potential headaches.

I think balanced in- and outputs are an absolute must for pro audio equipment.

Anyway, I also would like to construct a tube 8-12 channel recording console eventually.
The way I would do it, is to design a channel strip by experimenting with different circuit designs, features etc - once I have something that I like sound and functionality-wise, I would build a multi channel version of it.
I guess the challenge would be to make it relatively simple, yet good sounding and with useful feature set. 'Less is more'-approach.
There is always dedicated external gear, if more complexity is needed.

But it would be a long-term project, spread over several years.

 

[ruffrecords]

Sorry for starting a topic about this..

Adam

No need to apologise. It is interesting and has brought forth a good range of views.

Cheers

Ian

 

[Anthon]

If I was going to build a full on tube console, I'd go with the Redd circuit, and Ian's Redd EQ schematic on every channel.  Transformers everywhere.  I don't have that kind of money and as stated already went for broke on the transistor based console I'm already making.  I also stated I'm using a twin line amp that I built with tubes every day now, so it has a purpose and it is effective even to have line amps around.

Sorry for starting a topic about this..

Adam

Well you asked for opinions...
IMHO trying to cut costs on a project too much is a bad decision.Without a reasonable budget there is no point in doing it, so better to invest it in your solid state desk then.
Or go with quality over quantity: with 1000 bucks you could do 4 good quality channels. 10 is a bit unrealistic.

Perhaps you could make it so you can expand it with more channels in the future. That's what I would do, if I ever decided to start making a tube console - make a framework first, then expand it gradually over time.

Just my 2 cents.

 

[emrr]

Why the REDD circuit?  That's the first red flag to me, that I've no indication you've built and auditioned one (maybe you have), and there a SO MANY possible circuits to choose from.  You could build 10 of that, and hearing one of something else later could blow your whole perspective up. 

 

[CurtZHP]

I appreciate all the advice given, except I think Curt and Abbey you might be forgetting I've already gone big on a console that is still in progress now, and I have certainly learned a ton about the huge amount of work that goes into a mixer!

Certainly didn't intend to imply ignorance on your part, and I apologize if I did.  I'm looking forward to seeing (and maybe hearing) how it turns out.

 

[buildafriend]

Why the REDD circuit?  That's the first red flag to me, that I've no indication you've built and auditioned one (maybe you have), and there a SO MANY possible circuits to choose from.  You could build 10 of that, and hearing one of something else later could blow your whole perspective up.

The REDD47 is a nice circuit, but I agree that before building an array of valve amplifiers for mic and line level I would try experimenting with a bunch of other valve amps first.

Maybe build one channel of what you like currently and then see how it sounds at 2/3 gain with a 150 ohm resistors strapped between pins 2 and 3. Record that sound 12 times and layer those tracks in your DAW, how does the noise add up? It may be a let down, or not.

 

[Whoops]

There are plenty of tube gear where tubes are only decoration and plenty of people who buy tube gear just for the sake of saying it has tubes in it.

 

[abbey road d enfer]

I'm not going for decoration.

I understand that, still, you haven't answered the question; why do you want a tube mixer?

 

[efinque]

I understand that, still, you haven't answered the question; why do you want a tube mixer?

That's a good question.

 

[efinque]

I'd like to do it for fun, to carry on the tradition as well, and for the sound.  However, I know this isn't something to take lightly and I am still heavy into my solid state console production which I'm really enjoying, so it's just something to think about/discuss... for now.

Adam

Maybe a single channel strip for starters?

 

[efinque]

Yes, when the time comes. I think you might have missed my earlier post from Feb 05, 2018 in this thread, where I said I would prototype a single strip instead of rushing into the full thing (which is my instinct).  I changed my mind on doing one that is really stripped down, based on advice received here and from learning from my mistakes made already it's not a good idea to rush anything too much.  It's costly.. and so many factors influence the end result that things need to be tested out if we're to be happy with the product.  I do know though that trying things out naively is sort of working for me ha.

But thanks for the reminders everyone.

Adam

I've heard people using tubes in mic pres and channel strips (edit : and compressors, I think tube EQ's are somewhat rare) here and there in recording work, but I think a full tube console (esp. a DIY one, unless you're experienced and have good connections with suppliers) is expensive and is somewhat tricky to design.

But good luck anyway!

edit : edits..