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Hi all, I personally had the same symptom in a Studio Preamp : In this Studio Preamp, the preamp stage's power supply filtering electrolytic capacitor was too old (dried out => very high ESR, it's internal resistance). I found that it produced an unexpected "alternate", frequency dependant...

Hi sotosprince, thanks for your feedback. It's interesting that you used a parametric EQ to supplement/complement the graphics EQ Since my first tests, I've found some nice tones, too (good old 295 Simul Class amp, the later model with the front knobs). Finally tested it with an Altec ER12L...

I just got a Studio Preamp, with a set of almost new Mesa tubes (used 1 month). I was really surprised that the lead channel is really "fizzy". The high end is reminiscent of fuzz box (still with some tube elegance...). I tried very possible knobs settings, tube swapping, Effects Send...

I've just added a Studio Preamp to the collection. The rack is dated 12/19/1989 . The Graphic EQ background color is blue/gray. I've a Quad Preamp, dated 11/10/1990. The Graphic EQ(s) background color is black. I've seen picture of Mark III with both color schemes. Was this blue/gray color...

Hi IronSean, thanks for the comments and all the info. Finally, I've found some nice Rythm 2 tones with volume in the 8 to 10 range. Heavy, but singing, blues tone w/ a Les Paul (if this makes sense).

I have some Carvin amps. A XV-112 combo, second generation (with EL34). The first generation was voiced slightly differently, and used 6L6. This is a very capable amp, the combo version of the X100B (they share the same schematics). This is a dual channel (+ boost) tube preamp followed by...

As I have no access to another Quad preamp (or a MkIII), I have no way to know if the bassy tone of Rythm 2 is normal. I made some measurements, and compared to a circuit simulation (quite accurate) of the Quad preamp, in order to see if there is any discrepancies. If there is no hudge...

While analyzing the bass response of my Quad Preamp, I found a few differences with the schematics available here : http://tubefreak.com/fschema.htm Here are the corrections :

Thanks a lot ! 8) I think that a frequency sweep with a reamping setup would work nicely. But based on your tests, I'll probably have to check my Quad's Rythm 2 mode in depth.

The difference I'm talking about is much more than the usual tubes variations : with all knobs at 5, Rythm 1 is crisp, and Rythm 2 is really bassy. Now, Rythm 2 can be dialed in to be very bright ! I've simulated the whole Rythm 1 and 2 preamps (3 tube sections), with all knobs set at 5, and...

Some info, I didn't find elsewhere : One part of the currently available Quad Preamps schematics is missing. This is the all important "post lead" frequency shaping (and the corresponding LDR switches). AFAIK, this important network of 2 resistors and two capacitors accounts for a large part...

Some more infos regarding the version of my Quad Pre, if this helps. I've checked my Quad circuit against the available schematics. So far, values on these schematics seem accurate. My Quad, dated 1990 : 1/10/90 (on reverb pan) and 1/10/91 ("export" 240V power transformer), is likely revision...

Thanks alot ! You're right,the manual says : Channel 1 is very similar to the Mark IIC, while Channel 2 is very much like the Mark III.

Hi all, this is my first post, although I have a Triaxis, a 295 Simul Class power amp, and a D180 since long... BTW, this means that my only contact with the venerable Mk series is through the Triaxis... I just got a Quad Preamp this week. I compared Rythm 1 and Rythm 2 tones with all knobs...