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I was just browsing Triode Electronics and came across these OPTs for $39.95, I wondered if anyone had any knowledge of them or is brave enough to try a pair. They're at

http://store.yahoo.com/triodeel/10outr.html

Here's the description:

A generic 100W output transformer for use with 4 6L6-GC, EL34, 6550 or KT88 tubes. 1800 ohm primary with 4, 8 and 16 ohm taps. DC resistance across whole primary is 60 ohms.
4 1/8 inches (105mm) high X 3 3/8 inches (85mm) wide X 3 3/4 inches (95 mm) deep over the end bells, weighs about 9 pounds. Mounting centers are 2 5/8 inches (65mm) by 2 5/8 inces (65mm). Judging from the size should be good down to 40 Hz at 100W, about 75W @ 30 Hz, and about 45W @ 20 Hz.
Yes, these transformers are a bit cosmetically challenged, (some rust on the lams) , but for only $39.95 it's still a heck of a deal for a 100W output transformer..



NSC01200$39.95

Hi All,

Jeez, Geez, that sounds kind of small to be pumping 100 watts through. The output transformers I make for my 50 watt amp are either emulations or clones of the original HF-89 OPT, and they get noticibly warm (not hot) after a period of high output. But, as you point out, 40 bucks is a damn good price. You could buy a lot of fans and steel wool with the money saved.

Frequency response, transient response, and damping are another matter, though. My educated guess is that this tranny would make for a great 100 watt P.A. amplifier.

These look like guitar amp OPTss, which tend to be small for their power ratings, as compared to "hi fi" OPTs. I have a PT and OPT from a Carvin
axe amp, the PT is plenty hefty, but the "60W" PP POT is relatively small, I've seen 10W OPTs that were larger and heavier. Typical guitar amps have a narrower frequency response, and some pretty "weird" power rating methods, so I'd figure these OPTs for 35W/Ch or less. Still a pretty good deal to at least try one out sometime...

I used to figure that guitar amps were rated at 2.828 X the real RMS output power, just for a safe margin. (twice the sqrt of 2).

The primary impedance seem s a bit odd, fairly low for this application, if I read it right... If it is indeed 1800 ohms CT, that would make it 450 ohms each side of the CT, might be a good match for those strange and wonderful 6C33C Russian "pineapple" tubes if the primary can handle the rather high DC currents. A pair of those in PP could really scream! :twisted:

/ed B in NH

erichayes wrote:Hi All,
Jeez, Geez, that sounds kind of small to be pumping 100 watts through. The output transformers I make for my 50 watt amp are either emulations or clones of the original HF-89 OPT, and they get noticibly warm (not hot) after a period of high output.

A general (albeit rather rough) rule of thumb is that as you double
the minimum frequency that the transformer is expected to pass, the
mass of the transformer goes down by about half.
Example: The Dynaco A470 used on the ST70 was claimed good for 70 watts,
but only down to 30 Hz, rather than 20 Hz. At 20 Hz it's good for 35W.

My guesses re the frequency vs wattage rating are based on the size,
it's a bit bigger than an A470, and about the same as what was on an
Altec 1569...which was rated 80 watts @ 40 Hz, and about the same
as what's on a Marshall 100W head.

Any rate, I'm having someone check them out to get a better idea
of the frequency response, distortion & bandwidth. I do know it's
an OEM part for a 100W guitar amp.

I used to figure that guitar amps were rated at 2.828 X the real RMS output power, just for a safe margin. (twice the sqrt of 2).

That may be true of claims made for transistor guitar amps, but
output wattage claims made for tube guitar amps generally are RMS,
but at a narrower bandwith (usually 40 Hz & up for bass, 50 to 80 Hz
and up for lead) and higher distortion (usually 10%), than
what's usually used re claims made for tube hifi amplifiers.

Hi All,

A Fender Twin '94 came across my bench today and Ned, you're right on. The OPT is about the same size as a Fisher 500C's, and it's handling Four 6L6s. Spec says 100W@5% distortion. I remember in my youth having to be careful not to touch the iron in Fender amps (particularly the Twin and Dual Showman) after they'd been played for a while, as they ran so hot you'd leave skin behind if you did.

If I get a chance, I'll throw the Z bridge on it and see what the primary impedance is

erichayes wrote:Hi All,A Fender Twin '94 came across my bench today and Ned, you're right on. The OPT is about the same size as a Fisher 500C's, and it's handling Four 6L6s. Spec says 100W@5% distortion.
If I get a chance, I'll throw the Z bridge on it and see what the primary impedance is

I'd guess somewhere between 1.8 to 2.2K. Guitar amps typically overload the tubes
a bit to encourage a higher proportion of low order distortion..heck, Dynaco
did, too, sometimes ;-)

70's Fender Twins used to claim 135W, but I guarantee you, you couldn't
see anything on a scope resembling a sine wave at 135W....