Any Quad Eight Q8 Experts Here??

Recording Techniques, People Skills, Gear, Recording Spaces, Computers, and DIY

Moderators: drumsound, tomb

Post Reply
User avatar
tonewoods
buyin' a studio
Posts: 885
Joined: Sat Apr 17, 2004 2:48 pm
Location: Orcas Island, WA
Contact:

Any Quad Eight Q8 Experts Here??

Post by tonewoods » Fri Dec 30, 2016 10:09 am

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... ;-) )

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:

Image

Image

Image

Image

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

Image

Any light that anyone can shed on these puppies would be greatly appreciated...
Thanks, and have a great '17 all...
"You see, the whole thing about recording is the attempt at verisimilitude--not truth, but the appearance of truth."
Jerry Wexler

hogfish
steve albini likes it
Posts: 301
Joined: Mon Dec 15, 2003 9:26 am

Post by hogfish » Sat Dec 31, 2016 5:02 am

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

User avatar
tonewoods
buyin' a studio
Posts: 885
Joined: Sat Apr 17, 2004 2:48 pm
Location: Orcas Island, WA
Contact:

Post by tonewoods » Sat Dec 31, 2016 12:02 pm

hogfish wrote:Maybe Im missing something, but aren't those line amps?...
I do not know...anyone??
"You see, the whole thing about recording is the attempt at verisimilitude--not truth, but the appearance of truth."
Jerry Wexler

User avatar
A.David.MacKinnon
ghost haunting audio students
Posts: 3238
Joined: Wed May 07, 2003 5:57 am
Location: Toronto
Contact:

Post by A.David.MacKinnon » Wed Jan 04, 2017 5:20 am

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.

User avatar
tonewoods
buyin' a studio
Posts: 885
Joined: Sat Apr 17, 2004 2:48 pm
Location: Orcas Island, WA
Contact:

Post by tonewoods » Mon Jan 09, 2017 7:36 pm

...another shot:

Image
"You see, the whole thing about recording is the attempt at verisimilitude--not truth, but the appearance of truth."
Jerry Wexler

User avatar
A.David.MacKinnon
ghost haunting audio students
Posts: 3238
Joined: Wed May 07, 2003 5:57 am
Location: Toronto
Contact:

Post by A.David.MacKinnon » Tue Jan 10, 2017 6:23 am

Are the outputs balanced?

User avatar
tonewoods
buyin' a studio
Posts: 885
Joined: Sat Apr 17, 2004 2:48 pm
Location: Orcas Island, WA
Contact:

Post by tonewoods » Wed Jan 11, 2017 2:18 pm

A.David.MacKinnon wrote:Are the outputs balanced?
"No, they're not balanced."
"You see, the whole thing about recording is the attempt at verisimilitude--not truth, but the appearance of truth."
Jerry Wexler

User avatar
Scodiddly
ghost haunting audio students
Posts: 3415
Joined: Wed Dec 10, 2003 6:38 am
Location: Mundelein, IL, USA
Contact:

Post by Scodiddly » Wed Jan 11, 2017 4:22 pm

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?

User avatar
emrr
buyin' a studio
Posts: 806
Joined: Mon Aug 07, 2006 10:21 am
Location: NC
Contact:

Post by emrr » Sat May 06, 2017 12:21 pm

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.
Doug Williams
ElectroMagnetic Radiation Recorders
Tape Op issue 73

Jim Williams
tinnitus
Posts: 1135
Joined: Sat Jun 03, 2006 8:19 am
Location: beautiful Carlsbad, CA
Contact:

Post by Jim Williams » Sun May 07, 2017 9:41 am

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.
Jim Williams
Audio Upgrades

Post Reply

Who is online

Users browsing this forum: No registered users and 15 guests