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[danieldempsey]

Hi All,

I have an 8ch Spectra Sonics sidecar that was custom built, neglected, and apparently rebuilt. It was quite a mess when I got it but is now passing signal. It uses 101 cards for mic amps and EQ and has the two-band 501 EQs. However, it has little gain and low headroom and tends to distort with nasty clipping well before healthy line level gain.

Power supply is good, cards are recapped and in good shape. I'm wondering if it's a block diagram issue?

Here's how the channels are currently configured:

Polarity switch>Input transformer (Triad A-67J)>Pads>101 amp card, (with resisters in feedback loop for gain)>10k pot for attenuation>101 card with 501 EQ in feedback loop>unbalanced output

I'm wondering if the mic amps should come after the cards with EQ? If I use enough gain on the mic amps it seems to clip the EQ cards, and they have no makeup gain. Also, I get the sense that that 10k pot in the middle of the two cards is not ideal.

I've scoured the web for this issue but haven't seen it addressed directly. Any suggestions?

Thanks!

Daniel Dempsey

[Jim Williams]

Ray Kimber has the most complete collection of Spectrasonics documents. He has a wall full of them in his office in Ogden, Utah.
www.kimberkable.com

[danieldempsey]

Maybe I could put it another way:

Does anyone know how Spectra Sonics channel strips with two 101 amp cards and 501 EQ are typically configured?

 

[Jim Williams]

If you call Ray and if he can't help you, the original Spectrasonics guy is over at the Ogden Utah airport, he has his own hanger with Spectrasonics writen across it. Ray will put you in touch with him, if you call.

[danieldempsey]

Thank you Jim!

I spoke with Bill Cheney at Spectra Sonics and he was incredibly helpful. He's rounded up some schematics and is going to send them over.

Looking like the cards are indeed configured backwards right now (mic amp>EQ, rather than EQ>mic amp), so hopefully it won't take much to get it sorted.

Also, turns out my EQs are model 500, not 501. They're the inductor units with selectable frequencies.

[danieldempsey]

Here's a pic for reference: 

[RB]

Hi,

My console schematics show:

Line/Mic switch -> transformer ->  pads -> 101 with 500 in the feedback loop -> 2.5K eab fader -> 101 as the output amp to the busses. If you need schematics I can scan the ones I have for my console. Hope all is well,

Ryland