Mesa TA-15 tube replacement

alie123 · Mar 10, 2013

I think it's time to change the tubes of my Mesa TA-15. Still running the stock tubes.
I'm planning to replace the complete set.

My experience with my Mesa Stiletto amp is that I got much better results replacing the tubes with other brand tubes than Mesa.
(running Tung-sol and JJ tubes, mixed in preamp, and SED el34 in power amp.) My stiletto can be biassed.

This TA-15 is fixed bias, so .. can I just throw in any other branded EL84 tube (matched pair) ?
I've heard something that EL84 tubes has smaller margins between tubes than el34's has.

Someone good results when switching between specific power or preamp tubes?

Any advice is welcome!

thanks

dml13 · Mar 11, 2013

I had the TA-15 initially - ended up trading it back for the Express Plus - but thinking I had a tube malfuntion I threw a Tung-Sol in V2 that I had lying around and thought it def made a difference - for the better!

shimmilou · Mar 20, 2013

alie123 said:
...This TA-15 is fixed bias, so .. can I just throw in any other branded EL84 tube (matched pair) ?...

Hi alie123,

Fixed bias isn't the same as Cathode biased. Cathode biased means pretty much plug-and-play (like most all preamp and PI tubes), while fixed bias just means that the tube's grids have a negative voltage applied to set the idle current through the tubes. In fixed bias amps, some have an adjustment pot for the bias adjust, and some do not. The fixed bias amps that do not have an adjustment pot can still have the bias changed, it usually just means changing a resistor value, or adding a pot. The TA-15 does not have a bias adjustment pot (AFAIK), so you either should follow MB advice and use the recommended tubes (MB, or GT 4 to 7 rated), or get a tech to change the bias resistor value if the new tubes require it for the proper bias. If I understand correctly, changing components, such as the bias resistor, or using tubes that aren't approved can void the warranty. :idea: It is possible to get other brands of tubes that will be biased properly in this amp without any changes, if the seller is very familiar with this amp and it's tubes' ratings, warranty considerations still worth mentioning.

shimmilou · Mar 30, 2013

Even though I really like the sound of the stock tubes, I like to try new ones just to experiment. I just tried some new Tung Sols in the preamp and PI, and the sound was too warm and lost the crispness and highs that the stock tubes had. The clean channel wasn't quite as clean, and the distortion wasn't as crisp and crunchy with the Tung Sol. But if you want a smoother, less edgy sound for your distortion, and a warmer cleans with a little more breakup, the Tung Sol might work well. The stock tubes have much shorter Plates than the Tung Sol. I put the stock tubes back in, and I'm ordering some spare Mesa tubes, as they sound great for my taste.

alie123 · Apr 3, 2013

Thanks for your replies!

Also changed the preamp tubes. V1+V2 are Tung-sol, V3 JJ, and V4 balanced LPS.
I must say, I do like the sound of it. But that's also personal taste. I think the Tung-sols give a clear inyourface sound with enough highs. Maybe the JJs are also a good or even better option because I like the midrange of them. (And the TA have no mid knob ) But I like the tungsols of their open and clear sound.

But, the power tubes: I was so curious and I ordered a matched pair of JJ powertubes which I discussed / adviced together with my tube reseller. Installed them and the're safe to use. Maybe he ordered a specific grade of it. Don't know exactly. My TA is killer sounding now, (but it was already killer with the stock. But I'm a bit of a tone freak I guess, and want to get the best out of that little blue devil) And offcourse I Always take my old mesa el84's with me as a spare set.

I'll stick with these for a few gigs. Maybe later change the tungsols for the JJ preamp tubes to hear what's happening..! Great amp.

I'm curious to everyones experiences.
Maybe I will record a sound clip with these tube set installed.