Tube headaches with my Lynchbox

[TORMENT FAKTORY]

A couple years ago I bought an RM100 Lynchbox from a good friend of mine who used to visit these parts 'till he went traitor on us and bought a Peavey 5150 after selling me the Lynchbox. Shortly after purchasing this amp I replaced the EL-34's with a set of JJ 6L6's. I am no electronics expert by any means, so when I did this I had him talk me through it step by step. Well, yesterday I decided to upgrade to a matched set of JJ KT88's, but didn't have the benefit of having him talk me through it so I attempted to do it from memory. Again, I am no electronics expert, and because in my first attempt I didn't have the multimeter on the right setting I drastically over biased the tubes and proceeded to play through the amplifier for a couple hours. It sounded very good actually...for about two hours anyway, then I switched to my clean channel and immediately noticed that it sounded very "dirty", like it had a tube screamer in front of it or something. I immediately put the amplifier in standby and allowed the tubes to cool a bit, then finally was able to get ahold of the friend I mentioned earlier and had him talk me through setting the presets on the multimeter and re check the bias. When I checked the reading on the multimeter, each tube was showing well over 200ma, and as I mentioned earlier I had been playing for at least 2 hours with them on this bias level. I quickly re-adjusted the bias on each tube to around 50ma (a little high because the type of music I play usually requires very high gain levels), but now the amplifier sounds little better than when it had the 6L6's, and the gain seems to get a little bit weaker as time goes by while I play. While the amp is on, all four tubes still have the orange glow to them, and none of the tube fault lights in the back of the amp are illuminated, but it really seems like I ought to be hearing a significant increase in gain going from 6L6's to KT88's. Have I damaged my brand new tubes by running them at such a high bias setting for that long?
Also, I have never changed the three 12AX7's on this amplifier because I've heard that they really never go bad with normal use. Is this true, and can tonal differences as pronounced as a power tube change be heard by changing the 12AX7's? I also noticed when I removed the upper faceplate of the amplifier that there are two large black sort of cubical shaped things in there, (Transformers I think. I've attached a picture with the things circled. Anyone know exactly what they are and what their function is? ). After playing for quite a while I notice the larger of the two was quite warm and the other was stone cold. Is this normal?
I'm really trying to get a high quality tone from this amp, but I don't make a lot of money and definitely cannot afford to screw up what is for me a VERY expensive amplifier. I'd greatly appreciate any info and/or advise any of you might have for me on this. Thanks!

 

[eyeball987]

You won't notice a big increase in gain with a power tube change. If you are looking for more gain, boost the front of the amp.

 

[TORMENT FAKTORY]

Well, I noticed pretty significant gain increase when I switched the original EL34's out for the 6L6's that I had in there up till now. By boosting the front, do you mean change out the 12AX7's? If so, with what? You'll have to forgive my very limited of knowledge on this subject. trying to learn the basics still.

 

[drewiv]

Well, I noticed pretty significant gain increase when I switched the original EL34's out for the 6L6's that I had in there up till now. By boosting the front, do you mean change out the 12AX7's? If so, with what? You'll have to forgive my very limited of knowledge on this subject. trying to learn the basics still.

By "boosting in front" he means a drive or boost pedal in front of the amp. Guitar -> boost pedal (example: Tube Screamer) -> amp input.

You will notice difference in changing preamp tubes as well. Some people find a great difference, others find it to be subtle. Try it out preamp tubes can be rather inexpensive (or very expensive).

The best advice is try different things until you find something you like.

 

[drewiv]

FYI: if you are really new to tube amps, don't go tinkering too deep. They can (and do) hold deadly voltage. Even when off and unplugged.

 

[TORMENT FAKTORY]

Not really new to tube amps, and yes, I am aware of the voltage danger, just not real savy on all the ins and outs of tube amp modification, or what a lot of different components are or do for that matter. I'll definitely try the preamp tube switch to see what kind of difference it makes. Was I correct in assuming the two big black cube thingies I circled in the picture are transformers? If so, why after playing for hours was one warm and the other cold, and what is it that they actually do?

 

[TORMENT FAKTORY]

BTW, I have a tube screamer, it just isn't working very well because it has a short somewhere in the power input, but you are definitely right about them, when it was working properly there was a pretty significant gain increase :twisted:

 

[eyeball987]

BTW, I have a tube screamer, it just isn't working very well because it has a short somewhere in the power input, but you are definitely right about them, when it was working properly there was a pretty significant gain increase :twisted:

Yep. Set the pedal with the level all the way up and the gain below 9:00. That will get it done.

If you noticed more gain going from the 34's to 6L6's then I would guess that the 34's were on their last legs. 34's will usually have more mids and crunch than 6L6's which is often perceived as having more gain. 6L6's will have more bottom.

You can try other 12AX7's in the amp but the difference is usually not that great unless you have a bad tube in there now.

 

[TORMENT FAKTORY]

Cool, now that I have the whole tube issue hammered out, does anyone know what the story is with the two black "transformer" lookin' things is (Circled in the picture) and why one warms up after playing for a while, while the other stays cold as stone?

 

[seanh303]

I'm curious for input on OPs 2nd ? also. Bump.

 

[Zander]

Yeah - one of the transformers is a "power transformer". It powers the heaters to the tubes, the signal through your preamp stage and into your power tubes.

The other is an "output transformer" that takes the signal coming off the power tubes and with that signal, and some more juice, powers the speakers.

Presuming you're playing at non-concert volumes, the one getting warm is the power transformer. The output transformer would be getting warm if you were at concert volumes.

 

[m0jo]

About the gain and powertubes story:

When you have cleaner powertubes (6L6 or KT88) it will sound better and "higher gain" than with EL34's or overbiased ones of the former for the tone you're after. Preamp gain is tighter than overdriven powertubes (which won't actually produce that much gain untill you blow the windows out of the room you're in ). So that's probably more what you're looking for, so I think you're better off biasing your tubes normally and boosting the front of the amp.

On the other hand, I've never needed more gain than these mods produce by themselves. (Salvo's that is)
So depending on your mods, maybe you could try not boosting for more gain, but tweaking your EQ (tad more prescence, a *bit* less mids, boost the lows and density a bit). That way your tone will stay clearer and your riffs will sound brutal (actually more so because there's more definition).

Don't forget that while tweaking this you should really be playing with the full band, not alone. I've made that mistake a lot.... you find the perfect tone on your own, and it sounds completely wrong in the mix.

 

[Daryl]

So depending on your mods, maybe you could try not boosting for more gain, but tweaking your EQ (tad more prescence, a *bit* less mids, boost the lows and density a bit). That way your tone will stay clearer and your riffs will sound brutal (actually more so because there's more definition).
Don't forget that while tweaking this you should really be playing with the full band, not alone. I've made that mistake a lot.... you find the perfect tone on your own, and it sounds completely wrong in the mix.

Great advice!! +1 on that for sure. The gain knob can be fun, but there are sacrifices in other aspects of your signal that are made when you crank it too much. Too much gain will overcompress your signal and squash dynamics if you are not careful. I used to use a boost/OD before I ever heard of modded modules and the gain was never more than a sliver. I used the EQ on the pedal more as a pre-shaping tool before my guitar signal hit the input. Modded modules just don't need a boost IMO. They are ready to rock out of the box and that keeps tone sucking circuits out of your signal chain.

 

[m0jo]

So depending on your mods, maybe you could try not boosting for more gain, but tweaking your EQ (tad more prescence, a *bit* less mids, boost the lows and density a bit). That way your tone will stay clearer and your riffs will sound brutal (actually more so because there's more definition).
Don't forget that while tweaking this you should really be playing with the full band, not alone. I've made that mistake a lot.... you find the perfect tone on your own, and it sounds completely wrong in the mix.

Great advice!! +1 on that for sure. The gain knob can be fun, but there are sacrifices in other aspects of your signal that are made when you crank it too much. Too much gain will overcompress your signal and squash dynamics if you are not careful. I used to use a boost/OD before I ever heard of modded modules and the gain was never more than a sliver. I used the EQ on the pedal more as a pre-shaping tool before my guitar signal hit the input. Modded modules just don't need a boost IMO. They are ready to rock out of the box and that keeps tone sucking circuits out of your signal chain.

Yep! Although on full on leads a tubescreamer can be awesome for a little more smoothness and harmonic content!