[sdiy] DIY Mixer - please help!

[Jerry Gray-Eskue]

This is all just for Info, Personally I think a pure op amp setup would work
great, and If you want Tube distortion, just run the output through a Tube
preamp, or power amp.

The hybrid thing sounds excellent too, the extra headroom would be nice.

<< whether they can replace the vintage parts
they are meant to be compatible with, due to their subjective
performance in the circuits they would be in (what is sparsely and
incorrectly called 'sonic quality').>>

I have seen a lot of "subjective" reviews that say they are good, If you
care to look at a few you can check these out.

My point is Nothing can give you "Tube sound and distortion" like a tube
can. There are a lot of active discussion groups on this very subject, and
it gets down to which current production tube they like best and think is
the Same or Better than the original tubes.

http://www.guitarcenter.com/Accessories,Page-1.gc?src=tube&o=6&ipp=15

http://www.tubedepot.com/12ax7reviews.html

http://www.tubedepot.com/6l6reviews.html

http://www.tubedepot.com/el84reviews.html


<<And I presume tube circuits are
going to be just amazingly difficult to manufacture on a scale larger
than two units every five years.>>

Not really, its just another type of electronic device, Look how many Tube
devices are available in large quantity here:

http://www.guitarcenter.com/Guitar-Amplifiers-Guitar-Amplifiers-and-Effects.
gc


- Jerry

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of cheater cheater
Sent: Thursday, September 03, 2009 10:26 AM
To: synth-diy
Subject: Re: [sdiy] DIY Mixer - please help!


Jerry,
tube production is of course going on, but it's nowhere near the
output that existed 'back in the day'. There are also questions on the
quality of those tubes and whether they can replace the vintage parts
they are meant to be compatible with, due to their subjective
performance in the circuits they would be in (what is sparsely and
incorrectly called 'sonic quality'). And I presume tube circuits are
going to be just amazingly difficult to manufacture on a scale larger
than two units every five years.

Ken stone's tube vca is indeed interesting but I'm not sure if it's
the same kind of thing that would go in the summing bus of a mixer. It
is, however, a start of *some* sort, definitely.

D.

On Thu, Sep 3, 2009 at 3:21 PM, Jerry Gray-Eskue<jerryge at cableone.net>
wrote:
>  <<The tube manufacture
> market has mostly folded. And then he won't give you the best ones
> anyways :)
> - if this design is to be used by a lot of people, you can easily see
> how resource problems would start happening with the insufficient
> (negative) worldwide supply of tubes that we are experiencing>>
>
>
> The Boutique guitar amplifier market has keep tube production going, Tubes
> are far from obsolete discontinued museum pieces.
>
> There are a lot of tubes in current production in
> Russia (Sovtek http://www.tubedepot.com/sovtek.html ) and
> China (Sino http://www.tubedepot.com/sino.html) and several other
> manufactures, some of these are just re labeling the China/Russia tubes,
> some are not - some nice stuff and a good selection of tubes for audio
use.
>
> http://thetubestore.com/
>
> http://www.vacuumtubes.net/?source=google&gclid=COnhmc3EhpwCFRmbnAod8GqW_g
>
> http://www.tubedepot.com/?gclid=CKLamfnGhpwCFRaenAod2Svd-g
>
> <<- tubes seem to require impedance matching transformers, unless I'm
> wrong.>>
>
> Hammond makes these transformers and are still in business, you can buy
them
> from Mouser and other distributors.
>
>
>
>
> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl
> [mailto:synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of cheater cheater
> Sent: Thursday, September 03, 2009 8:58 AM
> To: synth-diy
> Subject: Re: [sdiy] DIY Mixer - please help!
>
>
> Jerry,
> there are several problems with this:
> - tubes are not as easy to predict. You can't get new, 'great' tubes
> nowadays unless you buy them from someone who regularly pulls them off
> ebay and has a warehouse of ten thousand of them. The tube manufacture
> market has mostly folded. And then he won't give you the best ones
> anyways :)
> - if this design is to be used by a lot of people, you can easily see
> how resource problems would start happening with the insufficient
> (negative) worldwide supply of tubes that we are experiencing
> - solid state is, I guess, easier for people to DIY.. and I guess we
> have more experts for this here!
> - tubes seem to require impedance matching transformers, unless I'm wrong.
>
> However a tube-based design could be very interesting sometime in the
> future. There is no denying that this would be the next step after a
> 'clean and nice' solid state design is finished - a tube-based summing
> bus would be the obvious choice for something that complements a
> solid-state summer.
>
> Thanks
>
> D.
>
> On Thu, Sep 3, 2009 at 2:39 PM, Jerry Gray-Eskue<jerryge at cableone.net>
> wrote:
>>
>>
>> Given that, and assuming you would like the "tube" type distortion I
would
>> say that you should go ahead and use a tube(s) for the summing buss, this
>> does leave you with the issues of scaling the output down for recording,
>> headphones, or other lower voltage applications, but it is all easily
>> "doable" and could make a very nice setup. The other advantage is this
>> system could drive speakers directly and would be a cool setup for live
>> performances.
>>
>> If you want to max out the tube effects, you could use standard tube
> preamp
>> designs for your inputs and dump use of op amps altogether.
>>
>> - Jerry
>>
>>
>>
>> -----Original Message-----
>> From: synth-diy-bounces at dropmix.xs4all.nl
>> [mailto:synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of cheater cheater
>> Sent: Thursday, September 03, 2009 8:29 AM
>> To: synth-diy
>> Subject: Re: [sdiy] DIY Mixer - please help!
>>
>>
>> I think Seb has mentioned a good point here, Jerry.
>>
>> What seems to be a very important thing in analogue electronics
>> (especially mixers) is not *whether* they distort. There will always
>> be distortion and you can't escape it. You might even want to
>> introduce it by overloading channels - that happens quite often.
>>
>> I think the important thing is *how* they distort.
>>
>> So when designing the amplifier in the summing stage, it could be very
>> useful to have a lot of headroom, but to be able to dial in a little
>> bit of distortion by going higher.. and then the higher you go the
>> more distortion you get. I guess this requires some sort of
>> information on what sort of circuits distort the best.
>>
>> Also I'm not very happy with using divide-down/resistors/whatevers in
>> the summing bus input. The first problem is that it changes the way
>> the mixer works depending on how many channels are in use (and the
>> additional complexity of added switches/relays/etc is not worth it).
>> The other problem is, as I understand it, that such approaches either
>> require an active element (which adds distortion) or a passive network
>> (which can easily create problems in impedance matching)
>>
>> For example Manley seem to be using solid-state strips, but the
>> summing bus is a tube based circuit, which can easily run on high rail
>> voltage, since tubes like high voltages, and also distorts nicely,
>> since tubes, well, distort nicely. But I think that a similar approach
>> can be had with a discrete design based on solid state circuits, I
>> might be wrong of course (probably am).
>>
>> So the question is - how do you make a summing stage that can work on
>> high voltages that reach, say up to 75V without distortion, and then
>> progressively starts being less and less linear, behaving like a nice
>> soft clipper? I think it would be nice if the behavior when you're
>> near the rails were similar to what I described.
>>
>> I think it would also be nice to be able to dial in the symmetry
>> yourself by inputting a DC bias - instead of the circuit changing
>> symmetry in itself. For example I sometimes see this used for clipping
>> off 'spikes' on just one side of a signal. I understand that one trick
>> is that if you leave the spikes only in the 'negative' part of the
>> signal, they would happen when the tweeter 'pulls' and not when it
>> 'pushes', giving you a mellower high-end.
>>
>>
>>>> I believe this is to achieve high headroom. Unconfirmed information
>>>> tells me that most op amp designs will distort more the closer you get
>>>> to the maximum output voltage.
>>>
>>> I doubt this is the case except when you're almost at the rails. A more
>>> important limitation is simply the maximum supply voltages audio opamps
>> will
>>> tolerate, which for the NE5532 (very low distortion opamp if the pcb is
>>> designed correctly) is +- 22V max. Not that having "only" 27 dBu max
> level
>>> is a problem IMO.
>>
>> Thanks for your comment Antti. The NE5532 sounds interesting... how
>> does it behave near rail voltage?
>>
>> Not that I expect it not to distort.. but does it distort in a nice way?
>>
>>>> Do you think that a 741 will handle this sort of use?
>>>
>>> No. The comment about 741 was meant to show how poor some of the
>> electronics
>>> were in some respects.
>>
>> - this just shows what sort of rube I am when it comes to real-life
>> parts and choices like that. :^)
>>
>> Thanks
>> Damian
>>
>> On Thu, Sep 3, 2009 at 2:07 PM, Seb Francis<seb at burnit.co.uk> wrote:
>>> Antti Huovilainen wrote:
>>>>
>>>> On Thu, 3 Sep 2009, Seb Francis wrote:
>>>>
>>>>> I guess it's a question of whether you consider a mixing desk to be
>> 'part
>>>>> of the sound' or you simply want to mix your instruments, insert/send
> to
>>>>> effects, etc. and choose what colouration to add when desired.
>>>>
>>>> Sadly, these two options will rarely produce the same result. It's hard
>> or
>>>> impossible to reproduce the effect of dozens of small nonlinearities
and
>>>> phase shifts in a single effect box.
>>>>
>>>> Whether you want "warm" or "clean" sound is a different question of
>>>> course. Both are valid choices.
>>>>
>>>
>>> I think I like "warm" & "clean" :)
>>> i.e. Some warm sound sources, but with an overall clean mix so that any
>>> 'clean' sounds can really come through.
>>>
>>> And even with a 'clean' signal path, judicious use of EQ (both analog
and
>>> digital) can go a long way towards a 'warm' sound.
>>>
>>> Seb
>>>
>>>
>>>
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