Much tone benefit from pre-tube swap??

[Jouni]

Hi again folks!

Another dilemma and a problem!... well, what do ya expect, I'm a struggling artist!

From the beginning:
I've played through a Koch Pedaltone-->Sovtek mig-30 head, and liked the sound very much!.. So, I figured that getting a Mig-50H head would give me the tone with the crunch without the awkward preamp. ...yeah, right.

Haha....

The sound of the amp is fine when played with plain ear, but record it, or using earplugs with the drummer, and lift volume, the "overdrive" becomes a fuzzy mush with no clarity of any sort in the mids, top nor bottom. Like an amp through a dozen bigmuff-pedals!
Running the preamp through the cleaner amp settings gives a similar good tone as the mig-30, so, I think it's related to the amps preamp. ..??..

Shortly:
Could the harsh, fuzz-like, mushy distortion be turned into a usable overdrive with preamp-tube swap???

I have a small collection of tubes handed to me, of different gains, any suggestions?:
http://serif.pp.fi/images/Etuset.jpg

Should I try to ask some specialized place like Tubedepot etc.?

Thanks for reading.

 

[Dogbreath]

I'm kinda tryin this stuff myself. If you've already got some 12AX7's layin around (which I'm assuming is in the pre socket) then swap em and see if ya like it.

Like was pointed out to me in another thread, swappin speakers will make more diff than swappin tubes. And, in my case, swappin the power amp tube as well. I'm still gettin a handle on it but the tubes are makin a more subtle difference than I expected. Except for going from a 12AX7 to...say a 12AT7. That was pretty noticeable. But I still liked the sound of the AX in my head compared to the AT.

Luck man...
Kel

 

[ocnor]

the "overdrive" becomes a fuzzy mush with no clarity of any sort in the mids, top nor bottom. Like an amp through a dozen bigmuff-pedals!

That pretty much describes the tone of the Sovtek Mig 50 no matter which tubes are used. You should have bought a Marshall instead.

 

[daav]

I'm kinda tryin this stuff myself. If you've already got some 12AX7's layin around (which I'm assuming is in the pre socket) then swap em and see if ya like it.

Like was pointed out to me in another thread, swappin speakers will make more diff than swappin tubes. And, in my case, swappin the power amp tube as well. I'm still gettin a handle on it but the tubes are makin a more subtle difference than I expected. Except for going from a 12AX7 to...say a 12AT7. That was pretty noticeable. But I still liked the sound of the AX in my head compared to the AT.

Luck man...
Kel

To add to this, from what i understand, the 12AT7 should be a significantly lower gain tub for your preamp stage, this page is handy: http://thetubestore.com/gainfactor.html

I recently ordered a set of 12AT7s for my fender blues deluxe to try to tighten up my tone as well, but i haven't gotten them yet to try them out.

Definitely take some time to play around with the diff options for gain staging, guitar-> pedal-> preamp-> poweramp has lots of options, but you seem to say you have the right tone to your ear so far.

It sounds like the big problem is when you then try to take the signal and record or squashg it through headphones, so you have a whole new set of issues. Most distortion will get much muddier when recorded.

Daav

 

[Jouni]

Yes, I'll try some 12at7, 12au7 and 5751 tubes in the front, all are of lesser gain than the 12ax7.

Then another thing, I e-mailed one reputable amp-tech in U.S, and he said that there are things going on with the Sovtek output transformer. (recommended a mercury magnetics or a marshall plexi transformer) From that I remembered that when switching off stanby, there's a clearly audible "trrrannn..."-sound from the tranny, and it keeps humming quite a bit. Consulted a local technician who said that that would surely cause some interference to the signal. If memory serves, it's one of those you can tighten up with screwes, so I'll try that too.

To the Blatant "get a Marshall"- comment I can say that I just don't want one. I'd rather go Orange.

 

[Tadpui]

The sound of the amp is fine when played with plain ear, but record it, or using earplugs with the drummer, and lift volume, the "overdrive" becomes a fuzzy mush with no clarity of any sort in the mids, top nor bottom. Like an amp through a dozen bigmuff-pedals!
Running the preamp through the cleaner amp settings gives a similar good tone as the mig-30, so, I think it's related to the amps preamp. ..??..

If the amp sounds fine at moderate volumes but starts to turn to mush when turned up loud, I'd suspect either the power amp/power tubes or the speakers/cabinet. Really I wouldn't suspect the preamp tubes at all judging by your description of the problem.

I'd suspect the speakers above all. So it sounds like you've played both a 30-watt head and a 50-watt head through the same cabinet (just a guess since you didn't say). But maybe the cabinet isn't rated to handle the power or the Ohms put out by your new head.

I can't find any info on the Mig series of amps to save my life. Are they discontinued? If not, where the hell do they sell them? I can't find any info on whether they expect a 4 Ohm load, an 8 Ohm load, or what.

 

[ocnor]

To the Blatant "get a Marshall"- comment I can say that I just don't want one. I'd rather go Orange.

Now I finally have a shot for a Sovtek mig-50H, from France, But the price is high, could get a JCM800 for the money.

You were the one that brought up Marshall before as if you had it narrowed down to one or the other.

 

[Jouni]

If the amp sounds fine at moderate volumes but starts to turn to mush when turned up loud, I'd suspect either the power amp/power tubes or the speakers/cabinet. Really I wouldn't suspect the preamp tubes at all judging by your description of the problem.

I'd suspect the speakers above all. So it sounds like you've played both a 30-watt head and a 50-watt head through the same cabinet (just a guess since you didn't say). But maybe the cabinet isn't rated to handle the power or the Ohms put out by your new head.

I can't find any info on the Mig series of amps to save my life. Are they discontinued? If not, where the hell do they sell them? I can't find any info on whether they expect a 4 Ohm load, an 8 Ohm load, or what.

The speakers are rated to 70watts and 8ohms, a 2x12" cabinet. all my heads have 4,8 and 16 ohm outputs. The cab plays fine with mig-30 and my 100watt Spetel head. (not cranked, ofcourse)
I think you were right on the power-section, though. I e-mailed a dude called Lee Jackson about his DVD on Sovtek maintenance, described the problem, and he replied saying that the culprit is probably the output transformer, which he said to be rubbish to begin with. Tube swaps didn't cure the problem, though on lesser volume, the tone got very nice with 6l6gc:s on power- and a 5751 as V1-tube. But come cranking time, buzz/fuzz allover.

(Sovtek amps were manufactured in Russia by electro-harmonics in the 90's)

To Mercury magnetics I roam.... I'm determined to make that cute little devil as my tonefull gigging amp, no matter if I have to replace every damn component along the way.
It's kinda like getting an old vintage automobile, or a bike... therapy of sorts.

Sorry Ocnor, I didn't mean to come out that offensive, yes, I compared to Marshall as a price comparison for a used 50W head. And frankly, Marshall would have got me closer to dreamtone to start with, but I kinda enjoy the battle.

 

[Jouni]

The situation would be all too clear but for one thing that throws me off..:
How come I can get a decent tone out of it on high volumes, if using a separate preamp before the head??....
That I can't wrap my head around, if the culprit is the output transformer.