Transformers: Classictone, Hammond, Mercury?

[Enzo]

Oh, I am fine with repurposing things.

But to assume something made for 120v meets all safety specs is not good. Does it carry a UL sticker? Nothing says it has to. If the maker is in China, there is no way a liability problem could ever reach them.

[bob p]

olddawg was discussing PTs.

oops. somehow i read OT when i was reading that post. nevermind.

.

[olddawg]

Oh, I am fine with repurposing things.

But to assume something made for 120v meets all safety specs is not good. Does it carry a UL sticker? Nothing says it has to. If the maker is in China, there is no way a liability problem could ever reach them.

Well... the VHT amps in the same pallet pile that used the same parts did. They don't get warm or smell and there is no leakage to the bells or chassis. I see stuff from other brands too from time to time without really looking. Bugera, Blackstar, and others. I'm getting into your age territory Enzo, trying to finish my projects and downsize. It's hard to walk away.

[cjenrick]

the Tweed DeLuxe used a gapped core.

this means that they did not stack the core with, say, 3 lams going this a way and 3 lams going that a way like most push-pull transformers are laced these days.

it is laced just like a choke or SE Champ xfmr. why? maybe Triad wanted a universal xfmr that could be used with balanced DC of the P-P amps, or unbalanced DC like the Champ. kind of a "one size fits all" approach to marketing.

what does this air gap do? in addition to preventing DC saturation (B= 1.25 X AMP-TURNS) it stabalizes the permeabillity of the core which stabalizes the primary inductance.

the gapped xfmr changes the sound. don't ask me why. maybe a rolloff thing, maybe the speaker-transformer-tube transfer function changes,

the gapped core for the Tweed DeLuxe will need more turns of wire to make up for the loss in permeabillity, so you might have 3000 turns instead of 1000. and even with the additional turns, your Henries will still be lower than the Lap 3 stack. this is because gapping a core will bring the perm down to around 500, instead of your typical 10,000 for GOSS core. that is a factor of 20 to 1, but inductance is quadratic in turns, in other words going from 10 turns to 20 will increase your inductance by 2^2 = 4. so 3000 turns instead of 1000 will increase the pri ind. by 3^2 = 9.

so you get 9 times the inductance which gets divided by 20 for the gapped core so figure 1/2 the pri. ind. for the Tweed DeLuxe. that will translate into less bass which might save those old Jensen speakers,

there is also more DC resistance in the 3000 turn wind which will shift the phase angle at the bottom end (arc tan DCR/XL) and add compression.

with the addition of more wire, capacitance will go up, especially with the lack of layer insulation on that scatter wound coil. this will roll off the top end.

so decreased hi and lo end are the result of the gap in the 75 EI lams.

[Mick Bailey]

Some amps sound best with cheap iron because that's what they were built with to begin with, and our ears are trained to love that tone. Look at the Tweed Deluxe. The original transformers for that amp were very cheaply made, spiral wound, and they sound great. To properly reproduce the tone of those amps, an expensive boutique transformer is not required. You can get great tone out of a cheap transformer. I think it was Bruce Collins who was the first on this site 15-20 years ago to tell people not to go spending huge sums of money on a boutique 5e3 OT because something like the Hammond 125E was commonly available, dirt cheap and sounded great.

+1.

My last 5E3 build has Hammond iron and does the rounds with pro players, including Bill Kirchen who loves it. If he can't tell a good 'Tweed' then no-one can.

[mikepukmel]

Thanks everyone for the great advice. I just ordered a hammond set 1760H OT, 291BX PT, and 194A choke from Mouser along with the resistor set and a few caps. Can't wait to hear how it sounds.

[scottosan]

I like mercury, but do not like the price of them. I just used Classic Tone in a 100 watt build and they are great for the price.