# Peavey Rockmaster questions...



## mrmatt1972 (Apr 3, 2008)

Hi everyone,

I just picked up a Peavey Rockmaster preamp at the local pawn shop for cheap. I figured it would be a good (read: cheap :smile way to make my Blackheart into a channel switching amp. It works pretty well, however, I have some questions and issues that I can't seem to figure out.

Issue #1, Footswitch: The footswitch jack is a stereo plug. The preamp defaults to the "Ultra" channel without a switch in the jack. I used a Roland single button footswitch that I had and had no problems switching from clean to ultra with it. I pulled the jack out part way and could use the same switch to change from "Crunch" to "Ultra" so I thought the switch relay was working fine. The only two button footswitch I have is a Traynor footswitch from a YCV40. I hooked it up, the lights work, I can switch from clean to bypass, but not crunch/ultra. What's going on here?

Issue #2, what tubes control what functions?: Looking at the block diagram is of no help at all... I'd like to switch the "Ultra" channel tube to something with less gain (12at7 or 12au7) to calm it down a bit, but I don't know which one to swap. Can anyone help me here?

:rockon:

Thanks,
Matt


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## Guest (Jul 20, 2008)

You'll have to get a schematic first. I owned one of these when rack stuff was in and it was excellent once modded. The first thing you'll want to do is lower the plate resistors pertinent to the ultra path or pull the bypass caps on the cathode resistors on those same stages. Be careful, because many of those stages, the first ones, are shared if I remember right. Changing tubes is going to be very subtle. I had actually ended up beefing the crunch channel up by doing the opposite. I used to run this preamp into my Peavey 60/60 power amp into a Marshall JCM900 cab, rave reviews to say the least. I miss my Rockmaster.


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## mrmatt1972 (Apr 3, 2008)

Thanks for the reply. I don't want to start monkeying around with the components just yet though. Overall I like the sound (love the clean channel!), there's just a little bit too much "sizzle"/highend when the gain gets high on the ultra channel. This could be because I'm running into the front end of a Blackheart which is runs an el84 in class A - nature of the beast kind of thing. But, subtle change is all I'm after, so if anyone can tell me which tubes do which functions I'd REALLY appreciate it. I'm a little weak in the schematic reading dept. but here is a link:

http://www.jimkim.de/files/rockmaster/peavey_rockmaster.jpg

What really makes me shake my head is that there are only 4 12ax7 tubes in the unit and the schem shows 8!? 


I'm pretty sure the crunch channel is going to end up being my bread and butter once I can get a footswitch that works. Any suggestions?

Matt


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## Hamm Guitars (Jan 12, 2007)

I owned a Rockmaster and I have only ever owned one footswitch that works with all of my amps. It is a Marshall two button controller with a stereo 1/4" jack.

There are 8 tubes shown in the schematic because each 12ax7 contains two individual units (like a stereo pair).


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## mrmatt1972 (Apr 3, 2008)

Hamm Guitars said:


> There are 8 tubes shown in the schematic because each 12ax7 contains two individual units (like a stereo pair).


I thought that was the case, but I'm a noob wrt electronics. I got and read the London Power "elecronics for dummies" book a while ago, but that's as far as I've gone so far. Can you tell from the schem and this pic which tubes control the gain for the Ultra channel?

http://spinoo.free.fr/projetG5/Images Amplis/Peavey Rockmaster.jpg

thanks

P.S. I've dropped my wife and kids at church, I'm going to go swap tubes randomly and play aroud for a while...

Matt


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## greco (Jul 15, 2007)

mrmatt1972 said:


> I'm a noob wrt electronics. I got and read the London Power "elecronics for dummies" book a while ago, but that's as far as I've gone so far. I'm going to go swap tubes randomly and play aroud for a while...
> 
> Matt


Matt...did Kevin O'C's book discuss the dangers of caps discharging (into you) if you touch their leads ...there are some big caps in that circuit !!

*Be careful brother!*

Good luck with getting the tone you are looking for.

Dave


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## mrmatt1972 (Apr 3, 2008)

greco said:


> Matt...did Kevin O'C's book discuss the dangers of caps discharging (into you) if you touch their leads ...there are some big caps in that circuit !!


Yup, I'm not going near them, and changing tubes with the unit unplugged is pretty safe, I think.


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## Guest (Jul 20, 2008)

There are four tubes but two stages in each tube thus the schematic shows eight stages. I'll study the schematic for you later this evening and I'll tell you what I'd do to cut the sizzle back.


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## Guest (Jul 21, 2008)

For starters, put a short (or jumper if you prefer) across CR1 or CR2. They are in parallel so a jumper shorts them both out. That'll take some fizz off the ultra. Let's start with that. Tell me what you think. Watch the high voltages. Discharge your big supply caps and never work plugged in.


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## mrmatt1972 (Apr 3, 2008)

Thanks for your time and effort Konasexone. I'm not going to add or subtract anything from the circuit board just yet. I'm pretty much in love with it as is now. I just needed some time to tweak the gain and eq. I can't seem to get a footswitch at either of the music stores in town (!), so I'm ordering one online. Once I have all 3 channels I'll be set I think. I ended up putting a 12au7 in my Blackheart to make it a (much) cleaner amp and it worked very well.

:rockon:
matt


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## wozzer (May 13, 2011)

mrmatt1972 said:


> Hi everyone,
> 
> I just picked up a Peavey Rockmaster preamp at the local pawn shop for cheap. I figured it would be a good (read: cheap :smile way to make my Blackheart into a channel switching amp. It works pretty well, however, I have some questions and issues that I can't seem to figure out.
> 
> ...



I just had this same situation - the Traynor footswitch doesn't work with Peavey Rockmaster correctly. This is because the Traynor footswitch has current limiting resistors in series with the LEDs and therefore not enough current is available to switch the relays in the Rockmaster. If you short the resistors (or remove and replace with wire) in the footswitch then the RM should function correctly.


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## Budda (May 29, 2007)

this thread is 5 years old...


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## JamesPeters (Feb 2, 2006)

7 actually. The original poster probably doesn't own the preamp anymore, and even if so it's probably turned into a pile of dust by now... :congratulatory:


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