PP OPT in a SE Amp

[Trevor_Long]

Hey guy's...

No luck finding this info in the search function, so I have to ask:

Some time ago, I built a standard, unmodified 5f2a circuit with the exception of using a 15W push-pull OT with a 8000 ohm primary.  The OT was wired as if it were a single-ended OT.  The sound is fantasic as the guy I built the amp for continually raves about it.

But I have to ask...  Are there any potential issues with using this ungapped OT in a single ended circuit?  I have been asked to build two additional units identical to the original and I'm trying to avoid any potential issues.

Thanks in advance!

[phsyconoodler]

It may be a problem,but lots of guys have done that using an OT that has at least twice the wattage output of the single ended amp you are installing it into.
  However,if you think it sounds good now,try getting an Allen Amps single ended OT.I did just what you are doing and got an OT from Allen Amps and the already 'great' sound was even better with the proper OT.

[PRR]

> any potential issues

Flubby or weak bass, possibly excess weight.

It matters more in Hi-Fi than in a small guitar amp. A little bass-shave often helps guitar "sound", and an extra pound just adds "beef".

No, it won't turn into a pumpkin at midnight. If it is happy the way it is, do it again.

[Trevor_Long]

Thanks for the input!  Much appreciated!

[bigdaddy]

Didn't Leo use PP OTs in his tweed 5F2s? Of course to save money.

If I were you for the heck of I would try one of David Allen's SE OTs.

[Trevor_Long]

If I were you for the heck of I would try one of David Allen's SE OTs.

You guy's have really noticed a difference with these transformers?  Anything done differently from, say a Hammond?

[HotBluePlates]

Some time ago, I built a standard, unmodified 5f2a circuit with the exception of using a 15W push-pull OT...

4w SE amp and 15w P-P transformer.

That might all even out, or maybe you have a little extra low end with the 15w OT.

A 5w Hammond SE transformer weighs 1.1 lbs (for response down to 100Hz, for full power; 125BSE $63), while a 15w Hammond P-P transformer weighs 1.5 lbs (with response down to 150Hz, at full power; 125E $51).

So you could save $12 buying the 15w PP part. It may or may not shave bass as much as the rating suggests, but a guess is hard becuase it isn't being used as intended. But even the 5w Hammond is probably overbuying; the original Fender OT for a Princeton could well be smaller than Hammond's 3w SE OT. I never really looked hard at or weighed the OT in the '55 Princeton I once owned.

[bigdaddy]

I did a test between a Hammond 125 and a similar Allen and yes the Allen sounded better to me. With bigger Allen OT you can use either a small bottle 6V6 or big bottle 6L6/EL34, it has a 4K primary for the bigger bottle, with the 6V6 just use the 4 ohm for an 8 ohm load. I use a pair of Jensen 8 ohm speakers in series for 16 ohms and use the 8 ohm tap with a 6V6.

With the 125 it's either 2.5K/5K/10K, plus they cost more. David's cost cost $39 and sound great, much bigger than their size.