New member and some info for upcoming projects

Hi People,
What a nice forum!

I`m a sound engineer from Spain, I was building modular synths and modules for years and then I`ve found this group...
I just ordered some pcbs for my first audio DIY projects: G9, SSL, PeQ1 and calrec.
ITOH, I got some old neumann/siemens/Telefunken modules and I`m building some racks now:

-Neumann rack with 2 x467B pres, 2x 491A Eq and 1x472-2B meter
-Telefunken rack·1 with 2x V376s
-Telefunken rack·2 with 2x V620s
-Siemens active summing buss: For summing from my DAW out the box, I wanted a very high quality summing so the rack will be 16x2 (8 stereo chanels actually) all balanced XLRs using 2x siemens V275s, Eckmiller MR90 stereo for master control, 2x TAB V74s for amp and a neumann 472-2b for metering.
I`ve got Power one and Sola linear 24V PSUs for mounting inside the racks, what do you think about those PSus?
Also any advice is very apreciated!

Thanks a lot and sorry for my poor English...

Howdy synthi & welcome..

That's a bunch of nice modules you got there :green: and your idea for a mixer sounds just about right :thumb:

I have no experience with Power One or Sola PSUs. I do know that Power Ones are often recommended though. As long as they're linear, not switchmode and can pump enough current (at least 2x the needed amperage) you should do allright. Watch out if the PSUs have sensing terminals.

All the discrete TFK/TAB/Siemens modules I've seen all have internal filtering with at least a cap/emitter follower. Some even have more elaborate stuff going on.

Good luck!

Be sure to take a pic when you're done :grin:

Are you using both PSUs for the mixer/summer or do you plan to use one for your micpre rack? It would not be a god idea to use two different PSUs for the V275 modules, imo.

I would use one for the mixer and the other for the rack. If the ground is connected to the PSU's enclosure you may need to lift that if you fit the PSU in the same frame as the modules...

And don't excuse for your exellent english. I learned spanish ten years ago, and all I can remember is like, "Que tal?" & "Esta loco!" :razz:

Note, that the V275 have 1kOhm summing resistors. Be sure that your DAW or whatever can drive that. The V275 are really exellent summing boards, imo :grin: You probably also need to trim the gain, R15, if you're using two modules so you won't have a difference in the left/right output. A scope would be neat, but you can invert one channel, sum and trim the other until you get maximum cancellation, I did that in a pinch :green: :thumb:

Here's kubi's selection of TFK/TAB/Siemens schematics in case you haven't seen them;

www.kubarth.de/diy/german/index.html

Ohh, you must also check for DC leaky caps! Those ol' Frakos weren't meant to live +40 years... :evil:

Ola Synthi!

welcome at The Lab.

Where in Spain are you located?

Cheers,
Tony dB

I have several Powerone and Sola PSUs but I`ll use one PSU for each rack
Those neumann, telefunken 1&2 and Siemens summing are different projects, each with one PSU.

My DAW outpus are balanced 500 Ohms. Dod I need to change the 1K input resistors for the 275s?
Also thanks for the advice about tweaking R14 for same L-R gain!
The modules are checked and recapping when needed, I got them from a electronics dealer and are tested, hmm... I`m thinking the 275s must be trimmed since I specified I need matched pairs for stereo use...
I`ll post pictures for all projects, don`t worry.
I`m designing the pront panels using schaeffer, I can send you the fpd files if you whant them.
Tony, I`m Located in Madrid (in a town at the mountains near Madrid actually)


Thanks alot lot for the info,

Synthi

Great! Use as many PSUs as possible..

The sum inputs on the V275s are not balanced and you may get a slight level drop when feed from your DAW outputs. Maybe even distortion. I don't see why you couldn't increase the 1kOhm resistors to something like 5kOhm.

Better ask the seller just how closely he matched the gain..

I have family in Madrid. It's been some years since I was there last time though.. great place!

Welcome!

I know the 275 inputs are unbalanced but the seller told me a mod for this: adding another 1 k resistor foe each input to pin "2" of the transformer and cutting the conection of pin "2" to 0V, and also conecting pin"5" to 0V., do you think i need to replace the 1K input resistors with 5k and also use 5K for the modification?

I have some schematics and information:
Tele/ELA V620, Siemens V270 and Neumann U472-2B the 275 are already in the www.
I don`t have a webpage at the moment but if some of you (kubi??) can store them I`ll scan and mai you the docs. Just contact me:
synthi(at)audio24bit(dot)com
Also I have the complete manual for the EMT 261 Compressor/Limiter and the best part is that comes with full schematics and a PC traces and layout!
May be we can clone this!??
Anyone interested ?

Best regards,

Josue Arias AKA Synthi

Kubi, I not received your email, please resend it or leave a message.

I just scaned the EMT261 PCBs and schemos.

Kubi, I just sent you the PCbs and Schemos, can you put them in your website?
Also, I think we would open a new topic about the posibility for a 261 clone.

Best regards,

synthi.

I'm new here, also, Gus sent me over. There is some serious work taking place.
[quote author="sismofyt"]
I have no experience with Power One or Sola PSUs. I do know that Power Ones are often recommended though. As long as they're linear, not switchmode and can pump enough current (at least 2x the needed amperage) you should do allright. Watch out if the PSUs have sensing terminals.

[/quote]
I have a big (15v-0-15v -3 amp) Power One PS I was planning to use for powering some hybrid preamps. What is the issue with sense terminals?

apologies for the semi-hijack --it seemed like this was on-topic though.

--Eric

The sensing terminals are connected to the regulator part. If you have long powersupply cables, you connect the sensing terminals at the circuit and they compensate for cable. If you don't have long PSU cables you can just connect them at the PSU... They must be connected somewhere though. Dunno if explained that good enough

[quote author="sismofyt"]The sensing terminals are connected to the regulator part. If you have long powersupply cables, you connect the sensing terminals at the circuit and they compensate for cable. If you don't have long PSU cables you can just connect them at the PSU... They must be connected somewhere though. Dunno if explained that good enough [/quote]

That was fine.
I knew what they were for, but didn't know they must be connected, so thanks.

-Eric

my PSus have +V, -V +S and -S, I toticed the Vs and Ss have the same voltage so are they the sensing terminals?
I`ll use short cables, but do you think is better using the sensing terminals anyway?
Thanks!

Synthi.

I'd just strap 'em on at the PSU :green:

Thanks Kubi, I`ll try to email you the complete manual today or tomorrow.
Also, does anyone checked the files? Do you think would be a reliable project for DIY??

Thanks,

Synthi.

[quote author="synthi"]Do you think would be a reliable project for DIY??[/quote]

probably not.

A lot of the circuits in the EMT compressor is there in order to compensate for the lousy opamps available at the time it was built. And many of the components would be hard to find.

But it's a very interesting circuit nonetheless..

Jakob E.