trinityamps.com

Hi,

I'm just curious - has anyone tried different tubes in different positions in the TC15 preamp? Or any preamp, for that matter. Not brands, I'm wondering if anyone can characterize what would be different about a 12AU7 in the phase inverter, say, or a 5751 in the first or second position, sonically speaking. Has anyone done any listening tests?

Thanks

I've done some experimentation with the preamp tubes in my TC-15, both with a TT Alnico 12 and also a vintage Altec 417-8H in a combo cab. I have an Amperex Bugle Boy for the EF86, which sounds very rich and full to me. I see no point in searching further for anything better there (channel 1). Though the NOS Amperex, and other EF86s, are very pricey. I think I paid about $60. Don't want to do that again anytime soon.

I have an RCA 12AX7A in V3, which likewise made the sound a bit rounder to my ears than the JJ I first had there - though pretty subtle difference, not a huge change. I believe both channels have V3 in their circuit path, but channel 1 (EF86) bypasses V1 and V2. In V2 I have the Mullard 12AX7 remake, but didn't make any subs in that position, so don't have any comparisons to make.

The biggest sound difference (understandably) came from using a 5751 in V1. It is an RCA triple mica blackplate, and it really sounds rich with a full palette of frequencies. I tried that one because I wanted to reduce the fizziness I hear with all three 12AX7s being pushed - a little too much gain (distortion) for me when the preamp volume is turned past about 12:00. The 5751 is about 70% of the power of a 12AX7 (though different brands and even individual tubes can vary somewhat, I've read). Now, channel 2 has a more pleasant overdrive with its (preamp) volume maxed, and even up at about 3:00 there is plenty of cleaner headroom - though not sterile clean, it's a very rich and complex clean with just a hint of distortion. Very nice I think.

I also tried a 12AY7 in V1, yielding sounds reminiscent of my Trinity Deluxe - very nice, but at about 40% of the power of the called-for 12AX7, I found that I lost too much overall volume. Fine for the living room and definitely worth the experimentation, but for my tastes the 5751 works best of all I've tried in V1. Give it a try, you may like it!

BTW, I'm using JJs in the other positions: EL84s and rectifier. I tried RCA EL84s, but couldn't hear an appreciable difference. I don't want to spend the big bucks on a NOS 5AR4 - especially since I generally have liked the sounds of tubes running on the hot side, and JJ rectifiers put out a healthy voltage. I've been very pleased with JJs in three guitar amps - never found a bad sounding one or a microphonic one.

Happy experimenting! Amp research definitely beats spending time doing the old chemistry labs (and I was a chem major). Though maybe sometime I'll mix up some visual fireworks to go with the Trinity sonic pyrotechnics.

Thanks again to Coco for making such great sounding amps available to us at huge savings! Not to mention the fun of building.

Regards to all,
Jim

Thanks Jim, that's very interesting. I do have a couple of used GE 5751s, so once I get the amp up and running I'll do some switching around. I turned loose for a NOS Mullard EF86. I figure I deserve a treat every now and then, but I'm not making a habit of it.

Hmm.. I'd like to hear your thoughts on the 5751 after you give it a whirl. I've tries 2 different 5751's in my marshallized Traynor and although I do like the slight gain reduction ..both seemed rather microphonic compared to the ax7s.
Congrats on the new amp BTW!!
Stew

Has anyone tried Electro Harmonix (EHX) tubes in their TC-15? Specifically the EF86. Just wondering how it compares to other EF86's. I have limited choice at the tubestore.com. I can either get EHX or the new Tungsol gold pin for twice as much. Any thoughts??