Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Colas LeGrippa on June 07, 2012, 12:20:14 pm

Title: S/E and P/P transformer all in one ?
Post by: Colas LeGrippa on June 07, 2012, 12:20:14 pm

Here's how ANGELA describes her 125 series transformers on her site:

Hammond Universal Single Ended or Push-Pull Output Transformers Open style with minimum 5" long primary leads, secondary solder lugs for convenient secondary connections. Tables provided with each transformer listing 90 precalculated impedance ratios. Primary impedances from 1,200 to 25,000 ohms, so you can use virtually any output tube, single-ended or push-pull. The three primary wires obey the standard color code for push-pull output tranformers; the blue and brown wires are plate leads, the red wire is the center tap. For SINGLE-ENDED use of the output transformers in the 125 Series, simply use the two blue and brown plate lead wires; just tape off the red center tap wire. We have recently confirmed this hookup information with the technical staff at Hammond. Secondary impedances from 1.5 to 15 ohms. See this page for 125 Series Impedance Table. For more information on using this table check out the commentary on the Simple 6V6 Guitar Amp Project under the How To Section of this website.

Hammond suggests to use PP trannies  for SE purpose,,,strange, no ? They're out of 125SE series ?

Title: Re: S/E and P/P transformer all in one ?
Post by: PRR on June 07, 2012, 10:00:48 pm

For applications where quality is not important. Fixing old radios so they "play".

Depending on size and connections, you are likely to have bass distortion at high levels. This may be quite acceptable in an old table-radio. It may not (or may be) acceptable for high-level guitar bass.

The SE series is specifically engineered for medium-quality SE operation.

There's another high-price series for "excellent" SE operation. This may be a little flavor-less for e-guitar; anyway very heavy price and weight.

Title: Re: S/E and P/P transformer all in one ?
Post by: Colas LeGrippa on June 08, 2012, 07:11:39 am

This is exactly what I am experiencing with my PP OT : bass distortion at high level. The guitar notes are less defined.  The overall tone is better with my small SE tranny, but not so much better.

Thanks

Colas

Title: Re: S/E and P/P transformer all in one ?
Post by: PRR on June 08, 2012, 08:10:40 pm

> cabin ...that was fed one 120v leg

You drew power on both half-cycles. There was no one-way DC component of current.

An SE amp pulls DC. This energy must be stored in the core to kick-up the half cycle where the tube is going "off".

Title: Re: S/E and P/P transformer all in one ?
Post by: Colas LeGrippa on June 08, 2012, 08:15:26 pm

Bad idea, my friend. The two push pull leads must be used, with the red ( center tap ) taped off. I experienced it. The tone is at its maximum that way. But the air gap in a SE OT makes all the difference and for the max. tone in a SE configuration amp, we MUST use a SE transformer. My recent tests confirmed that.


Colas

Title: Re: S/E and P/P transformer all in one ?
Post by: Colas LeGrippa on June 09, 2012, 04:57:08 pm

the patients learn too from the doctor don't forget that !