GE 6L6 GC for a Mark 1?

[Central Scrutinizer]

I'm thinking about picking up 2 matched NOS GE 6L6GC for my Boogie Mk 1. I'll be replacing a couple of JJ's. Any recommendations or comments on the possible tonal variations?

*I'm rather new to the tubes and am looking for a bit warmer tone.

 

[stokes]

My opinion of the GE's over the JJ's is that they will be warmer,more balanced in general.I find the JJ's to be very harsh,with a shrill,metalic high end,but if you've read any of my posts I would talk up almost any NOS 6L6 over the JJ's.Mavguy or T.Wolf could give you a much more detailed critique of the differences.Be sure the GE's are in the right bias range for your amp,better yet,do an adjustable bias mod so you can find the "sweet spot" for those tubes,you're paying premo $$ they should sound and perform their best.

 

[Central Scrutinizer]

I'm not sure how to determine the bias on my amp. I just picked it up. It's a '77 Mark 1. The shrill sound is what I dislike about the amp. I was attibuting it to the Altec, but it may very well be the tubes. Would I have to take it to a tech?

 

[212Mavguy]

Altec speakers can be pretty bright. I have a 15 inch Altec 418b that has a wonderfully detailed top end, but I run the treble knob turned down a bit for the dirty channel if I play through it. An amp as old as yours is has a strong probability that some of the resistors and caps in it have drifted from original values. I would definitely take it to a tech and have the bias checked, and at least change out the bias resistor if bias does not fall into the 60% max plate dissipation range +- 5% for those GE's when installed. But putting in the adjustable bias mod would most definitely be the way I'd want to go if I owned one. I'd also pimp the pre with some vintage tubes from the era that it was made, like some shortplate Sylvania, Mullard, Amperex, or especially Siemens 12ax7's. If you have the opportunity to purchase some decent vintage 6l6gc, by all means do it, why cheat a masterpiece out of the opportunity to be its best? They will sound warmer and better overall than any modern 6l6gc in that amp. The preamp tubes will have an even greater effect on the tone than the power tubes. The speaker has more effect than tubes, though.

 

[stokes]

sounds like the new tubes will be an improvement,even when using the JJ's and the Mesa tubes simply adjusting the bias will improve the tone and minimalize that shrillness.Dont overlook the preamp tubes as well,they can make an even bigger difference in many cases.Again the two guys I mentioned in my first response can give better descriptions of different pre tubes.A nice tube to try in the V1 position is a good NOS 5751,it will go a long way to "smoothing" the overall break-up.Pre amp tubes can be changed with no assistance from a tech,but for the power tubes,unless you use tubes rated to match the bias setting of your amp,it is best to consult a tech.If you do a search here for preamp tubes you will find a lot of good info,pay close attention to posts by Mavguy212 and Timber Wolf,they are probably the most knowledgeable guys here when it comes to the nuances of tube tone.

 

[stokes]

Just to add to what Mav said about the component values drifting,some times that can be a good thing,sometimes not.There are many vintage amps that definately get their particular "mojo" because of that drift.I would also change the filter caps and all the electros in any amp that old,even before messing with the tubes too much.When electrolytics get old they do not add any magic as some other components may.They deteriorate and weaken your power supply and degrade the response of the amp.I dont let any of my own amps go ten years without a re-cap.

 

[Central Scrutinizer]

Great info. Thanks.

I just had the amp serviced and re-capped just after it arrived. It sounds great. Having some "crackling" on the low E and A strings at high volume. I think it is possible that either I have a loose socket on one of the power tubes, or its the speaker. It doesn't "crackle" when I plug into my Marshall 4 x 12 extension cabinet only.

I'm really looking for a nice warm tone and I think some money well spent on vintage tubes will help. I may replace the speaker if the "crackling" continues. I've had a Weber Michigan with a paper cone recommended on the speaker. I'm having a maple cabinet and extension built (the cab is on the way right now) and I need a speaker for the 1 x 12 anyway.

Thanks again. Any advice is well appreciated!

 

[stokes]

Weber makes some of the best speakers today,in my experience.I have a Michigan 15" as well as a few other 10's and 12's and every one is on the money.He's a great guy to deal with too.Every speaker I ordered I did so by telling him what I was looking for tone wise and what the circuit I built to use it was,and he was dead on with every recommendation.