More show and tell (Mixer)

[jamesfei]

In the spirit of the recent project displays, here are a couple of mine.

This came to me as an unfinished project by Steve Hogan (formerly Jensen Transformers, now The Sound Steward). It was completed as only two mic preamps (Steve's implementation of the Twin Servo). Those cards were removed and racked (I do mostly location work), and the remaining card was kept as make-up gain for passive summing (servo'd Jensen 990's driving Jensen output transformers).

The mixer is very simple: unbalanced inputs to P&G faders, fader buffer (OPA627), pan pot, summing resistors, 990, master volume (this section can be bypassed to keep the number of gain stages to 2). The summing network is mounted right on the card, to keep wiring short. Power and ground are tied to single points. The PPM meters are Innovonics Gordon Headroom Meters. There is also a monitor/headphone output.

Steve Hogan was more than kind in taking time to talk to me about his designs and the 990.


Here's a lunchbox of Auditronics 110 modules. Not quite as exciting.

There are some more pictures of various projects on my website, but this may be of interest to some of you: RCA Synthesizer Mk II.

Best,

James

 

[laitue5]

http://www.organizedsound.com/gear3-rca.html => :shock:

That?s serious vintage!

 

[Flatpicker]

Cool enough for me! :thumb:

 

[mnats]

Looks like Roederstein caps in there:

Been racking my brain every once in a while trying to figure out where I got them. Thanks for reminding me!

Nice mixer you've got there - smells vintage even from here.

 

[jamesfei]

Thanks. Yes, Jensen typically used (and sold back then, with their DI kit and others) Roederstein caps and resistors. I recapped the power supply bypass caps on Steve Hogan's suggestion. I have another custom mic pre built from Jensen parts (again, using Hogan's 990 op amp) years ago, also all Roederstein. The rest of the mixer uses Vishay/Dale resistors and Panasonic FC's (for PS only, the mixer is entirely DC coupled). Power supply is external: an Acopian (for IC's and meter driver) and Power One (990).

[quote author="mnats"]Looks like Roederstein caps in there: Been racking my brain every once in a while trying to figure out where I got them. Thanks for reminding me!

Nice mixer you've got there - smells vintage even from here.[/quote]

 

[jamesfei]

Here are a few more:

My monitoring attenuator, a Daven switch with Holco resistors:

Steve Hogan's Jensen Twin Servo cards racked (w/JLM power supply board). I've since replaced the Bourns pots with new Clarostats and moved the power supply transformer to an external box: