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Any Quad Eight Q8 Experts Here??

 
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tonewoods
buyin' a studio


Joined: 17 Apr 2004
Posts: 884
Location: Orcas Island, WA

PostPosted: Fri Dec 30, 2016 2:09 pm    Post subject: Any Quad Eight Q8 Experts Here?? Reply with quote

Hey all...

I just got these Quad Eight mic pres, and had a few questions for someone who might know a bit about them....
(Yes, I've googled the hell out of them... Wink )

They are supposedly model MP-404 pres...can anyone confirm this?
(I'll post a pic of a model stamp that might refute this...)

Anyway, they sound great, but the gain seems to be very low, so I have them at my tech's place to make sure everything is wired up correctly...

OK, some pics:









...and here's the stamp that is onboard:



Any light that anyone can shed on these puppies would be greatly appreciated...
Thanks, and have a great '17 all...
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hogfish
steve albini likes it


Joined: 15 Dec 2003
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PostPosted: Sat Dec 31, 2016 9:02 am    Post subject: Re: Any Quad Eight Q8 Experts Here?? Reply with quote

Maybe Im missing something, but aren't those line amps?...
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tonewoods
buyin' a studio


Joined: 17 Apr 2004
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Location: Orcas Island, WA

PostPosted: Sat Dec 31, 2016 4:02 pm    Post subject: Re: Any Quad Eight Q8 Experts Here?? Reply with quote

hogfish wrote:
Maybe Im missing something, but aren't those line amps?...


I do not know...anyone??
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A.David.MacKinnon
mixes from purgatory


Joined: 07 May 2003
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PostPosted: Wed Jan 04, 2017 9:20 am    Post subject: Re: Any Quad Eight Q8 Experts Here?? Reply with quote

I don't know those pres or much about quad 8 but here's a thought. if it is a mic mixer and the gain is low maybe there's a missing output/summing section that adds the missing gain to the summed signal. Tapping off of the pre output might only give you part of the gain stage.
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tonewoods
buyin' a studio


Joined: 17 Apr 2004
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Location: Orcas Island, WA

PostPosted: Mon Jan 09, 2017 11:36 pm    Post subject: Re: Any Quad Eight Q8 Experts Here?? Reply with quote

...another shot:


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A.David.MacKinnon
mixes from purgatory


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PostPosted: Tue Jan 10, 2017 10:23 am    Post subject: Re: Any Quad Eight Q8 Experts Here?? Reply with quote

Are the outputs balanced?
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tonewoods
buyin' a studio


Joined: 17 Apr 2004
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Location: Orcas Island, WA

PostPosted: Wed Jan 11, 2017 6:18 pm    Post subject: Re: Any Quad Eight Q8 Experts Here?? Reply with quote

A.David.MacKinnon wrote:
Are the outputs balanced?


"No, they're not balanced."
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Scodiddly
ghost haunting audio students


Joined: 10 Dec 2003
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PostPosted: Wed Jan 11, 2017 8:22 pm    Post subject: Re: Any Quad Eight Q8 Experts Here?? Reply with quote

The only active parts seem to be those little 8-pin DIPs, unless I'm missing something. Can you post a closeup or give the numbers?
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emrr
re-cappin' neve


Joined: 07 Aug 2006
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PostPosted: Sat May 06, 2017 3:21 pm    Post subject: Re: Any Quad Eight Q8 Experts Here?? Reply with quote

Many similar mic mixers historically have low gain amounts as they are mean to feed another preamp for final level. I can't say for sure about these. At face value the IC gain 'could' be up to 40dB easily, but doesn't mean it is. Change of gain path structure could increase overall output. Loss may actually be in the 4->1 mixing system, whatever that is; passive maybe.
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Jim Williams
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PostPosted: Sun May 07, 2017 12:41 pm    Post subject: Re: Any Quad Eight Q8 Experts Here?? Reply with quote

Unlike the discrete versions I have here those are the later simple transformer in front of an opamp design. Gain is set by r shunt/r feedback +1.

Modern opamps like LME49710's will allow for the resistor swap to increase maximum gain, use that formula. Decrease the gain shunt resistor, 10k feedback + 200 ohm gain shunt from the inverting input to the gain set blocking cap will give you a +40 db max gain. Add the 20 db gain from the input transformer and you get +60db max

Swap the carbon film resistors to metal film for less noise.
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