Studio 22+, Hiss and Speaker question

[Daevid]

Despite the fact that the poweramp tubes are mounted on the PCB this is one very portable and nice sounding amp...

One thing i would like to know is how to sort it so there is less hiss out of the Studio 22+. With the Master on 5 there is hiss on the Preamp signal from 1 1/2 til it reaches 9, then no more hiss :?

Would changing the Caps help, or changing the preamp tubes, or is it possibly an issue with the transformer?

I'm also considering replacing the stock Black Shadow speaker for something else... possibly an EVM12L or a Celestion V-30... what do you think? which would go best in this little amp?

 

[Daevid]

Can anybody help with either of these questions :?

 

[stomper]

Are you getting hiss in the clean channel or overdrive channel?
If it is the drive channel, a look at the schematic will give ideas on what may be the cause. Try swapping in a known good 12ax7 tube in each location. The dirty channel is pretty lame in this amp if you are trying to channel switch. Best bet is use it clean or use it dirty and skip the channel switching. The online bible for tube amps.... http://geofex.com/ampdbug/ampdebug.htm

 

[Daevid]

Hmm... seeing as the hiss does change in volume then decrease on the pre volume then this may be the cause...

"A good way to divide and conquer is to turn the volume control(s). If the hiss changes levels as you do this, then the source of the hiss is something that affects the stages of the amp before the volume control. A faulty, hissing preamp tube will be turned up this way very quickly. Conversely, if the volume control does not affect the hiss, the cause is somewhere after the volume control. In general, the volume level of the hiss is an indicator of where the hiss is occuring - the louder the hiss, the more likely its source is near the input of the amp where the gain applied to it will be the greatest"

But i have changed the pre-amp tubes repeatedly... could it be a faulty resistor?

 

[stomper]

Are you getting hiss in the clean channel or overdrive channel?
:roll:

 

[Daevid]

Are you getting hiss in the clean channel or overdrive channel?
:roll:

In both...

 

[stomper]

Okay, that helps. Try pulling the first and second 12ax7 tubes out of the amp and powering it up. You won't be able to play through it, but you will be able to tell if there is less hiss. There should be. If there isn't a lot less hiss, then the problem (or part of it) is between the power section and tube 3. Switch between both channels and use the volume controls as they are located around tube 3 and will work somewhat.
There are only a handful of resistors that feed the preamp tubes and especially since they are near the preamp tubes and about 20 years old they may have drifted in value and become noisy. Here is a link to the schematic in case you don't have one.
http://www.freeinfosociety.com/electronics/schematics/audio/mesaboogie22caliberplus.pdf

You asked about speakers also. I have my original speaker in a box in a closet. I've been running a celestion Greenback in the amp for about 5 years. I like it.