Transformer choice for 6V6 Express

[beasleybodyshop]

Progress continues on my Express build! However I do have a question:

I remember reading a few posts on the forum about using lower powered iron to fully capitalize the tone of 6V6 tubes. I can't for the life of me find the posts, can anyone educate me? Thanks.

[wsaraceni]

isnt the express already lower powered?

[2tone]

the Express voltage of 390-400 is fine for 6v6's...

[Firestorm]

I think it's the OT you might want to "underpower." If the OT is only rated for 15-20W or so, it will have a harder time coupling low frequencies. I've always found that using "stock" Express iron with 6V6s makes it bassy, which is not what the Express is about.

[2tone]

Been running 6v6's in my old transformer express for years with great balance of frequencies, bass is never too much or too loose. I think the new transformers are the same(Pacific) in that the bottom is not over represented. Maybe some other problem or circuit deviation exists in your Express?

[Firestorm]

Been running 6v6's in my old transformer express for years with great balance of frequencies, bass is never too much or too loose. I think the new transformers are the same(Pacific) in that the bottom is not over represented. Maybe some other problem or circuit deviation exists in your Express?

I also "quieted" the lead dress on the tone leads, so there's that. But I didn't do anything crazy and it sounds bright as heck with Els. Tubes maybe.

[RJ Guitars]

The Express and the Liverpool both use a slightly higher input impedance from the published "ideal", although nothing extreme. Gerald Weber in his book shares the thought that you can match (or mismatch) transformer impedance to +/- ~100% of the "ideal" match with no risk of transformer damage. I don't necessarily think that is gospel but overall from my experience it's worked out to be true for me.

As mentioned previously, the result of slight mismatches gives you various flavors of power and tone... For myself I am planning to use an 8K primary Edcor for my next 6V6 Express transformers.

YMMV

rj

[beasleybodyshop]

RJ, I sent you a PM. Thanks for the info.

[Firestorm]

The Express and the Liverpool both use a slightly higher input impedance from the published "ideal", although nothing extreme. Gerald Weber in his book shares the thought that you can match (or mismatch) transformer impedance to +/- ~100% of the "ideal" match with no risk of transformer damage. I don't necessarily think that is gospel but overall from my experience it's worked out to be true for me.

As mentioned previously, the result of slight mismatches gives you various flavors of power and tone... For myself I am planning to use an 8K primary Edcor for my next 6V6 Express transformers.

YMMV

rj

Kevin O'Connor says the same thing (and makes merciless fun of Weber in the process). KO'C basically holds that impedance matching is a "tone control" and you can, within reason, play with it to your heart's content. The exception that everyone notes is old Marshall transformers, which were, evidently, not quite up to the task of running at "correct" impedances.

IMO, output transformers can color the tone more than anything else you can play with: pushing a big signal into underrated iron can strip some low frequencies; mismatching the load shifts the tubes into a different part of their curve.

Weber says he did a blind taste test with several guitarists and found they all preferred the sound of double the stock impedance. I generally concur. You may lose an imperceptible amount of output power, but if it sounds right...

[rp]

Matchless, a real company and not a tweak boutique shop, runs the Lighting 100% off spec, it's been in there catalog for 20 years. It does sound a bit different as I tried mis-matching my very proper clone to the correct 2 EL84 8K value and I have to agree it sounds best at 4K. Makes you wonder how they got there, I'd guess they wired it up wrong at some point and preferred it.

I never built an Express, but if I were going to build a 6V6 one I'd be tempted to use a BF Deluxe 6.6K OT. Can't say why technically but it just feels like it should work out well. Maybe one of the Allen Heyboers.

[Firestorm]

Many years ago, I talked with Doug Hoffman about trannies he had at the time. I asked about the impedance and he said he picked the ones that sounded best. No numbers, just ears. But

[gingertube]

8K Raa is the book spec and I have built a few guitar amps with various output trannies (with an Raa of 8K) ranging from Hammond 1608 to cheap chinese jobs (see link below), all sounded fine.

The 6K6 (see rp's post above) would also be OK, I haven't built an amp with a 6K6 Raa output tranny BUT I have built one with a quad of 6V6. In that case I used a JTM45 Output Tranny with an Raa of 3K4, that was gorgeous (3K4 for a quad is same as 6K8 for a pair).

Latest 6V6 PP Amp I used one of these:
http://www.mableaudio.com/en/productvie ... ormer.html
It is a 8K Raa HiFi Tranny with a rating of 12 Watts RMS intended for a pair of EL84 in Ultralinear Mode. Since we are not trying to get much bass out of it for the guitar amp you can use it at more than the rated 12 watts. It worked fine at 15 Watts from a pair of 6V6 in Pentode mode. Just tape and stow the unused Ultralinear taps. One of the guys who has tried out this amp was so impressed he has asked me to build him an identical amp with the identical output tranny (luckily I have 2 of these trannies, I pulled them from a EL84 HiFi Amp and replaced them with Hammond 1608, the Hammond was superior for HiFi, the Chinese jobbies are just fine for guitar since we don't need extended tops or bottoms).

Cheers,
Ian

[M Fowler]

I'm going to be building an Express 6V6 using small Fender Deluxe sized iron because I want to see what effect lower wattage has compared to the higher wattage Express. Besides the Express is too loud.

[rp]

I'm going to be building an Express 6V6 using small Fender Deluxe sized iron because I want to see what effect lower wattage has compared to the higher wattage Express. Besides the Express is too loud.

Mark, I suggested the BFDR OT only cause the Tweed style OTs saturate very early and I think are not interleaved. Glorious in a 5E3 but maybe too dinky, too much dirt too soon in a TW and seeing how KF always sought out high quality OTs to voice his amps. But you can't know till you try, the Tweed OT might let you hit the hair/dirt sweet spot sooner and help with the loudness that way. IIRC Allen also has an overbuilt BFDR OT - so now you have "3 Degrees Of Saturation".

Latest 6V6 PP Amp I used one of these:
http://www.mableaudio.com/en/productvie ... ormer.html

That Mabel Audio link has terrific prices. Check out the Fender Necks and body prices, and the cabs - is that bulk or @? Chinese junk? Chinese wonder products? Too bad they are on the other side of the globe, for $34 for a finished neck I'd go for one right now.

[Richie]

Kevin O'Connor says the same thing (and makes merciless fun of Weber in the process). KO'C basically holds that impedance matching is a "tone control" and you can, within reason, play with it to your heart's content. The exception that everyone notes is old Marshall transformers, which were, evidently, not quite up to the task of running at "correct" impedances.

I think The Marshall note was about output impedance mismatch.