Pre-amp tube make over...Recommendations for high gain....

bsideexperiment · Dec 22, 2006

Ok, so i think i need some help. I've been using the diode setting because for some reason to me, it sounds better than using the power tubes. I play metal and i;ve talked to a few people and some agree, i guess becuase its slightly clearer and punchier. Oh yea, i could be wrong but it sounds like it gives it more gain. Anyway, i've decided that i was going to get a new set of pre amp tubes. I've been looking at Eurotubes and Doug's tubes. My question for all you experienced tube switchers, what is the best preamp tubes to buy. I'm open to try anything and i know a lot of people will say there's more than enough, but my one request is i'd like to mess around with some higher gain (how much more gain should i expect?). Also i'm interested in getting a hot plate. Can anyone share their experience with one. THANKS!!!

OH yea, one more thing, Am i right by thinking that using the diode setting has no corralation with the rectifier tubes. Because if so, perhaps i should just retube everything.

eliot323 · Dec 26, 2006

I think you'll find that with a valve amplifier input and output stage, you're always using the power valves in the output stage: the diode/tube tracking option simply refers to the rectification process (how the amp converts incoming AC electricity to DC).

This can be done using a transistor/diode (also known as solid state rectification) or by using valve rectification, which tends to give a more loose vintage feel, with some sag. The received wisdom is that changing the rectifier tube (check your Mesa manual for the circuit diagrams) has little effect on the sound of the amp.

However, you can increase the gain by changing the pre-amp tubes and/or the power amp tubes - you can get various higher output 6L6s EL34s etc from most of the main manufacturers - Mesa, JJs, Electro-Harmonix etc. The Harma brand of tubes are well worth pursuing (from the UK based Watford Valves) - I use their cryo tubes and they are excellent in both my Mesas. The stock Mesa tubes aren't necessarily the best available and are mainly re-branded Sovteks but they are tested by Mesa for reliability etc.

Pre-amp valves (tubes) can be more tricky to select, but the higher gain ones tend to be the JJs 12AX7s or the Electro-Harmonix 12AX7s. The thing about them is that they are generally relatively cheap and easy to change. I've tried the JJs in mine but they were a little too dark for me. I use a combination of the Groove Tubes Mullard reissues and the Harma cryogenic 12AX7s (which have a number of gain-rated options).

As far as I know, the Groove Tubes 12AX7s are re-branded (but graded and tested) JJs (note that the JJs branded tubes are cheaper). However , given the less than stellar modern day valve manufacturing and quality control methods, most valves can be a bit unpredictable and unreliable, so it may be worth getting them from somewhere that has their own pre-sale QC and testing procedures. That is unless you can stretch to afford some of the NOS (new old stock) tubes made by the great manufacturers in the heyday of valve manufacture - these are good but not readily available and the best ones do cost...

If you want distortion earlier in the gain cycle, you can use lower gain pre-amp tubes instead, which will break up earlier than other types. You do get less clean headroom this way though.

Check out some of the threads in the "Tubes" section of the forum for more received wisdom on the re-tubing options.

Elpelotero · Dec 27, 2006

This can be done using a transistor/diode (also known as solid state rectification) or by using valve rectification, which tends to give a more loose vintage feel, with some sag. The received wisdom is that changing the rectifier tube (check your Mesa manual for the circuit diagrams) has little effect on the sound of the amp.

great post, but this is the only piece i'll have to disagree with. I've tried both the stock 5u4gb and the older 5u4g rectifier tubes. the latter produce a much tighter and clearer sound. more attack. the former have lots of sag and can be mushy. so the rectifier tubes affect the tightness mostly.

eaeolian · Dec 27, 2006

I'll throw in my usual plug for the TungSol 12AX7 "reissues", which are generally as highly rated as the GT 12AX7-M. I use one in V1 in a high-gain environment, and they're very smooth and musical.

I haven't heard the Harmas. Hmm...