Studio 22+ mod

Does anyone have the mod for adding a seperate gain control to the lead channel to make the 2 channels more independant of each other? I tried a search but could not find it, Thanks in advance.

I wish I had known there was a mod for that. I tried all kinds of tube changes in mine to enable me to get the clean I wanted without the lead being over the top. I ended up selling it but if I could have balanced the two channels I would have kept it because I also liked the lead sound when it was dialed in right.

I read just today on the harmony central review page for this amp that mesa was doing them for a reasonable price a few years back, I have a message in to customer service to find out if they still are.

Product: Mesa/Boogie Studio .22+
Price Paid: N/A
Submitted 08/13/2003 at 04:12pm by Carl

Features : 9

Sound Quality : 9

Reliability : 6
It's broken at the moment but has been great otherwise

Customer Support : No Opinion

Overall Rating : 9
The reason for my submission is that I once had an issue with this amp years ago and at that time I sent it to MB in Cali.
I asked the tech, and for a small fee he also ADDED A LEAD GAIN KNOB to the back panel making the second channel usable. There was also an "upgrade" that he performed that made it sound even better. This thing sounds great. Anyone who has mentioned the problem with the second channel owes it to themselves to look into this!

My .22 already had the mod done to it so I can't say for sure what needs to be done, but I've heard there is an adjustable trim pot on the backside pcb board and you then put the volume knob where that is. It is between the powercord and the fuse I believe.

New to this board just want to say hey and I have a 22+ (and subway rocket). I think this amp is overlooked alot as it sounds great when its opened up abit (not bad at low volume) looking forward to hear boogies answer on the mod for this little beast!

I started another thread looking for a similar mod to the .50 caliber.
Frankly I'm surprised with all the Boogie freaks here nobody has come up with an answer....

I have a copy of the schematic for this mod. Let me know if anyone would like a copy. (please forward an email address and I can send it to you). I'm about to have this done to my .22+ so I can't vouch for it yet but it sounds like it's a worthwhile mod.

This adds a volume pot on the rear of the amp. It is supposed to let you blend the amount of lead channel drive to your rhythm channel tone when the lead channel is engaged.

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Just want to say as far as mods I have put all nos tubes in my preamp and it really made my amp come alive!! It sounds soooo much better!! The tubes that were in there was all boogie china stuff only a year old or so and if I can help it they will never see the inside of that amp again!!

Here is the schematic for this mod. The repair/service dept at Mesa/Boogie was kind enough to fax me a copy. I just had this done to my Studio .22+ by a local amp tech and it comes as advertised, it adds an extra volume pot on the rear of the amp. This lets you blend the amount of lead channel drive to your rhythm channel tone when the lead channel is engaged.

It works great. The lead and rhythm channels are still cascaded, dependent on each other for the total amount of gain. With some minor knob tweaking you can set it for two very usable tones. First jam with it last night I was able to set a nice clean rhythm, and slightly overdriven lead tone with a volume boost, new pot set at about 12 o'clock.


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This seams like a nice mod for more control over the gain. Thanks for posting!! Any info on changing the bias for nos power tubes in this model? I have not found any info of nos power tubes use in a 22+.

Thank you that looks like what I was looking for!

22+ said:

Any info on changing the bias for nos power tubes in this model? I have not found any info of nos power tubes use in a 22+.

Click to expand...

As far as I know, Mesa's EL-84 amps are cathode-biased (self-biasing), and do not need to be re-biased for new power tubes. They don't even sell EL-84s in matched pairs, only singles.
Try 7189s, they're the super-duper military heavy-duty high grade replacements.

Thanks for the schematics for the gain mod. I too would be interested in how to modify the Studio .22 for variable bias, I'm quite sure it's not cathode biased but fixed bias.

MrMarkIII said:

22+ said:

Any info on changing the bias for nos power tubes in this model? I have not found any info of nos power tubes use in a 22+.

Click to expand...

As far as I know, Mesa's EL-84 amps are cathode-biased (self-biasing), and do not need to be re-biased for new power tubes. They don't even sell EL-84s in matched pairs, only singles.
Try 7189s, they're the super-duper military heavy-duty high grade replacements.

Click to expand...

No. The EL84 power tubes are definitely not cathode biased. They are fixed bias. You either need to use tubes that have been measured to be within the correct bias range, or you need to mod the amp to change the bias.

The last set of JJ tubes I bought were specified to be used in a Boogie DC-3. I was sent a matched set of tubes that were measured to be corrrect for use in that amp (without modification).

Just bought a Studio 22+ off eBay, should arrive today - my first Boogie. Can anyone provide me details and a schematic of the lead gain mod please? Thanks

I moved the reverb pot to the back on mine and put the lead drive pot where the reverb was.

I put the reverb control in a small box screwed to the side panel at the back to avoid drilling the chassis. The lead mod makes the amp way more flexible.

I didn't need to drill my chassis to move the reverb pot to the rear. My amp does not have GEQ so I pulled the plastic hole plug out of the hole where the GEQ footswitch would be and mounted the pot there.

Could someone send me the studio 22+ lead drive mod from MB at Boogie. I need to tame the over the top lead channel.
Thanks