DataMix mic pres racked

[TAVD]

Nice. I'd love to see a pic of the inside if you have a chance. As you might remember, I have a few of these too. Looks like some JLM go betweens were used. I'm curious about what output transformers were used and of course, how it sounds.

[Bill@WelcomeHome]

Originally Posted by TAVD

Nice. I'd love to see a pic of the inside if you have a chance. As you might remember, I have a few of these too. Looks like some JLM go betweens were used. I'm curious about what output transformers were used and of course, how it sounds.

Yes, I had bought the JLM power supply and the DI etc before I realized the complexity of the project and passed it off to Michael. Whatever other pieces/parts were used to make them work, I wouldn't know. Michael makes a lot of custom audio electronics and designs (for Korby Audio among others...) so I would expect the quality to at least fit industry standards.

What do you want to see that i didn't show? There is nothing behind the switches but wiring harnesses and the JLM boards; and the I/O connectors.

[TAVD]

Originally Posted by Bill@WelcomeHome

What do you want to see that i didn't show? There is nothing behind the switches but wiring harnesses and the JLM boards; and the I/O connectors.

So no output transformers? Is it unbalanced or did Michael use the cue/echo send amps as a line driver? Mine are a bit different but similar enough. I used old API output transformers in mine, taking the output signal from the EQ amp.

[Bill@WelcomeHome]

Originally Posted by TAVD

So no output transformers? Is it unbalanced or did Michael use the cue/echo send amps as a line driver? Mine are a bit different but similar enough. I used old API output transformers in mine, taking the output signal from the EQ amp.

I remember him telling me that he would have to chose output transformers, but that he already had some on hand. I know that Michael winds his own, I don't know if these are his or someone else's that he had sitting around. With Michael you never know, he's got a building filled with stuff that he has picked up over the years including a small collection of Hammond organs and cabs. He's got a couple of Sony 38s just in a pile somewhere, and stacks of live reel to reel tapes from the 70s.

There is a separate TRS for echo and one for insert as well as the standard output.

"Mine are a bit different but similar enough."

There is a number on the corner of the circuit card which corresponds to the date in some way. (like n68 or whatever the format is would be a card from 1968.) Have you gotten yours working?

" did Michael use the cue/echo send amps as a line driver?"

When we first started the project I asked him to try to keep the original design as much as possible. Where it came down to 'we can make it better..' we did not do that. For good or ill I wanted to try to retain the original sound as much as possible, understanding that the following stages of the console would have had an affect on the final sound. I wanted the phase, phantom, and DI added, but we did not do any re-purposing or re-designing.

[TAVD]

Have you gotten yours working?

I had one passing audio on the bench but have yet to finish any. A few years ago, I decided to copy the amp section onto a 2520/990 footprint and drop it into a CAPI VP26. It sounds looser and less aggressive so it's a nice contrast to a 2520. I've considered making them available but I'm not 100% pleased with my board layout. I'll get back on finishing the originals when time permits.

[Bill@WelcomeHome]

I spoke with Michael a little while ago.

He left the unit unbalanced as per our 'leave it alone' plan. No transformer.

He also wasn't too happy with the output level from the Cue/Echo circuit, but again, he left it alone as requested.

He says that the pres are quiet, no hum, a little hiss. But they are susceptible to RF, so I should pay attention when I rack them with other gear.

[chrisso]

Interesting.
I missed this thread a few weeks ago.
I had a pair of Datamix (look identical to Bill's) racked by John Vrtacic in Vancouver about 7 years ago.
I then loaned them to a friend in Canada until recently.
A few months ago I installed the unit in my home studio in Australia.
I'm mostly ITB, and only really record analogue synths at home, sometimes electronic drums.
The Datamix sound punchy, and not in a bad way. The eq is obviously quite radical (again, not bad).
I've read Michael Brauer interviews and emailed back and forth with Ken Hirsch at Orphan Audio, both say the key to getting the best out of these is to restore them with original spec transformers, a correct output amp and proper gain staging.
Ken says they are a unique module and should be restored, racked and used.
It's so long ago, and I've lost the emails, so I can't remember what decisions John Vrtacic made. Sadly he's no longer with us.
I have a couple more raw modules and would love to get the best out of them.

[TAVD]

I cleared some old projects from my bench recently and decided to finally tackle these old modules. I have one earlier S/N similar to those posted by Bill. This one is a later version, S/N 247. Some differences are: slightly taller front panel, fully discrete amps (using 7 transistors), stepped gain + input pad. I'm still sorting out the EQ section but it's mostly there. Both are basket cases so it's slow going, reverse engineering mods and making sense of the conflicting schematics that I've collected over the years.



Also, for anyone interested, here's a copy of the [partial] schematic that used to be on the old Purple Audio site.

Datamix

[Bill@WelcomeHome]

Originally Posted by chrisso

Interesting.
... both say the key to getting the best out of these is to restore them with original spec transformers, a correct output amp and proper gain staging....
.

If anyone has the data to accomplish this, I hope they will share.

Bill

[EisenAudio]

If they haven't already been recapped, you'll want to use the same formula Sprague TE series, which are still available at newark.com and a few other catalogs. This is a very unique sounding cap, with heavy tonal footprint, when compared to modern alternatives.

[chrisso]

Originally Posted by TAVD

This faceplate and controls look exactly like mine.
I've been using it a lot just for fun. I'm mostly recording electronics like analog synths. Curious if mine could be improved, but as we all know, details are scarce.

[EisenAudio]

Originally Posted by chrisso

Curious if mine could be improved, but as we all know, details are scarce.

You can make sure there's an adequate external line amp driving the post-fader output, that all of the electrolytic caps have been replaced with similar types (e.g. new stock Sprague), and that the power and grounding are solid. Beyond this, there is little "improvement" to be had with the Datamix circuits. For instance, I have studied some of the design notes and schematics which Gordon Clark (RIP) left behind, and can tell you with some certainty the fact that all of its amplifiers are so slow is the only thing keeping them stable with those EQ networks so precariously wrapped around the same loops. Upgrade the amps, and then you've got to the re-design the loops, which would destroy the Datamix character... because, like a number of other channel amplifiers from this era, the tone we love is inseparable from the electronic shortcomings which enabled it.

[chrisso]

By "improved" I meant using the most authentic replacement components to preserve the character you talk about.
All my raw Datamix modules have issues. Not being a tech myself, I'm not certain they are being respectfully restored, or not.