Studio Pre clean mod

[ytse_jam]

hi partyofone... i listened to your clip and your problem with the clean channel is way worse than i thought! With volume set on 5-6 i still get nearly crystal clean tones even with my 2 whole step down tuned guitar with humbuckers. Have you ever tried the main outputs? i can get decent clean tones even with those (using them direct to tape as they were the recording ones)... if your main outs work well, yours could be a problem concerning the built-in poweramp+cab simulator circuitry. I'm not sure, but i think the mod you were talking about may influence also the lead channel, so be careful if you like your overdriven tone... so i definitely think there's something wrong or damaged in your preamp. Personally, i would have it checked by a technician before doing any mod.
maybe this afternoon (now it is 11.40 am for me here in italy!) i'll record a clean channel clip.

 

[ytse_jam]

here's the first clip with these settings:

rhythm bright switch on
volume 5
master 5
treble 8
bass 5
middle 5
reverb 3
output level 8

actually it isn't the cleanest tone ever heard, however it has a lot to do with my soundcard. When playing through the mixing console in studio the sound is even cleaner.
Guitar is an old Cimar by Ibanez tuned 2 whole steps down.

www.freewebs.com/ytse_jam/StudioClean.mp3

and here's another clip with volume at 10:

www.freewebs.com/ytse_jam/StudioClean2.mp3

since it always happens to me (don't know why) to create "circular links" please copy/past the addresses!

 

[partyofone]

wow the clip was very helpful. I guess a sound clip is worth a thousand words! Hmmm, well, maybe it has come to the point where I should take it in because it does seem kinda crazy how much distortion I'm getting. And yes, I did try the main outs yesterday and got the same result. Also note that this is after I've JUST replaced all the tubes with what is supposedly Sovtek's highest grade 12AX7, so that rules out old tubes.

p.s. the "circular link" thing is happening again! don't know why, but I just copied and pasted it. good tone by the way, I have to find out what pre you're using. (ha,ha)

 

[Luijo]

Ytse's clips are right on line with what I get with my SP, so there's must be a little problem with yours.
Try performing the clean mod, but as already noted, it might impact your lead sound. Maybe you'll have to run your lead drive lower, but that's it, no change in tone is my guess. After all, you'll be changing gain structure, no tone-modifying components.

 

[Blueracer]

I have taken a look at the schematic for the studio pre. It is tube V3 which is switched in for the lead to get extra gain. There are other posts I have seen that refer to the led resistive switches bleeding. To test for this put your studio in the rhythm mode then turn the lead drive all the way off. The lead drive is on the input to V3 which should be switched off in the clean mode. You will probably have to increase the volume to get something out of the preamp. See if this cleans things up. If it does you may have faulty switches. Another possibility is this fix that Mesa gave you. There is the possibility that the leds are being biased on slightly by the zener Z2 set voltage. If this is the case it is something of a design flaw. A test for this is to see if the lead master has any affect on volume when in the rhythm mode. If it does it might be a global switching problem pointing back to this zener diode. Note that the zener diode is not in the signal path of the amplifier. It has no direct affect on tone other than to aid in switching between lead and rhythm. Hope this helps.

Recommend test settings as follows:

Volume 7
Master 7
Treble 7
Bass 2
Middle 4
Lead Drive 0 <- The important setting
Lead Master 10

 

[partyofone]

thanks for the informative post. I have heard of what are saying about the lead channel, and tried it some, and although I didn't notice a difference I will check again to make sure. basically, you're saying that the mod shouldn't affect tone though?

 

[Blueracer]

No the addition of the zener should not directly affect the tone. There will be some difference in tone only because the switching rather than being left on slightly is completely on or off. It will operate the way it was intended to operate. The best analogy I can think of is the power fuse. If the fuse blows it does affect tone but I don't think anyone would think a properly operating fuse would affect tone.

BTW I have tried turning the lead drive to zero and lead master to 10 and switched between lead and rhythm on my studio pre. There is only a very slight difference in the tone. Setting these two controls in this manner is a very close approximation to what happens when the unit is set to rhythm. Note that these controls are really at absolute minimum and maximum respectively. Think in terms of -1 and 11 as if you were the lead guitarist for Spinal Tap. Even a little bit of lead drive will dirty the tone up. Again I hope this is helpful.

 

[partyofone]

I tried switching channels with settings as you reccomended but I didn't hear any difference. does this rule out a particular problem?

 

[Blueracer]

Yes if the pre does not sound different with these settings and switching between rhythm and lead it eliminates a large number of possibilities such as some other stage going into saturation. This is assuming that this did clean the pre up. If you are still distorting back off on the volume and master. If it is still dirty at lower volume/master settings it would indicate that the switching is not the problem but it is somewhere else.

The idea behind the settings was to simulate the clean/rhythm channel regardless of whether lead or rhythm is selected. It should give you an idea of how the rhythm channel will sound. Now what you should try is to put the pre in rhythm with these settings and then start turning up the lead drive. In a properly operating unit there should be no affect. If there is then the led switches are either completely on or partially on. Next try decreasing the lead master while in the rhythm channel. Again in a properly operating pre this should not affect volume. If it does then the led switch associated with this control is either completely or partially on. If both controls affect the pre while in the rhythm channel then this would point to a global problem with the swithching circuit and would very likely be the zener that Mesa indicated. If only one of the controls has affect then it would indicate it is the specific led switch associated with that control.

BTW if you want to use the pre in a clean mode before getting the thing serviced then put the lead drive to zero the lead master to 10 and adjust all the other controls for the tone you want.

 

[Mongo1]

Can someone send me the PDF from Mesa for the Studio Pre.
The ones I find online are barely legible.
Please PM me if you have one.

Thanks,

 

[Stilettouser]

Definitely turn the clean channel's volume down while leaving the master volume cranked! It's like a single channel amp with the way the volume works. The more volume you have, the more gain. The same applies with the gain channel.

-Sam

 

[japster]

Hi,

I'd also like the schematic if you it's still available. I'd love to know some more about this awesome bit of kit.

Also would love to mod it :-

Please send schematic to : [email protected]

Thanks,