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zintolo 27th September 2012 06:43 PM

Guitar Amps Output Transformer specs
Hi all,
I would like to resume some informations about output transformers (I will open another thread on power transformers too), because I've found someone near me that can build it way cheaper than usual, so I can try different solutions for the same bucks.

Here is something I've found by now:

Dagnall C1998 38x38mm EI M6 core:
- 16-0 ohm secondary (parallel): 120 turns x 0.76mm
- primary: 2 x 620 turns x 0.45mm
- 8-16 ohm secondary: 35 turns x 1.18mm
- 4-8 ohm secondary: 25 turns x 1.18mm
- 0-4 ohm secondary: 60 turns x 1.60mm
All lead diameters are measured including the insulation on it.

Dagnall C2668 on 38x40mm EI M6 core:
- 0-4 ohm secondary: 60 turns x 1.76mm AWG13
- 1/2 primary: 620 turns on four layers x 0.45mm AWG26
- 4-8-16 ohm secondary: 25+35 turns x 1.18mm AWG18
- 1/2 primary: 620 turns on four layers x 0.45mm AWG26
- 0-16 ohm parallel secondary: 120 turns on two layers x 0.75mm AWG21

Dagnall C3070 32x60mm EI M6 core:
- 1/4 primary: 310 turns on two layers x 0.45mm AWG26 (B+ to half A2)
- 0-2 ohm secondary: 40 turns x 1.76mm AWG13
- 1/2 primary: 620 turns on four layers x 0.45mm AWG26 (B+ to A1)
- 2-4 ohm secondary: 20 turns x 1.76mm AWG13
- 4-8 ohm secondary: 25 turns x 1.76mm AWG13
- 8-16 ohm secondary: 35 turns x 1.76mm AWG13
- 1/4 primary: 310 turns on two layers x 0.45mm AWG26 (half A2 to A2)
(not sure about that one)

Soldano SLO100 OT
is similar to C3070, except is 32x50mm and has an higher primary impedance.

Some uningegneristic impressions that need to be confirmed:
- M6 works like 6L6GC, stays cleaner up to a point where it starts to add more harmonics (like more NFB)
- M27 works like EL34, more vintage oriented, cruncier, better on saturation (like less NFB)
- M19 and M26 works like EL84, smoother and adds a bit more of a bassy (nice for EL84 too)

Then some very useful links:
Index of ../Transfos/Papers/

Some useful links:
EDCOR - M-6 Steel Lamination

Some useful links that need translation:
Transformator wyj?ciowy

Does anyone has some more info on Guitar Amps' OTs and on iron effect on sound?

Thank you all!

zintolo 27th September 2012 08:55 PM

An internal link to a BudP post:


Originally Posted by BudP
The difference in sonic’s is interesting. An amorphous core OPT for PP will be very clear, have great transient response and excellent tonality. However, they are somewhat one dimensional in that most of the fine gradient detail that provides internal note structure and makes transient noises into musical events, has been stripped away by the lack of E Field coupling and the higher dielectric constant materials used in the coils, essentially half of the information must be lost to avoid frequency response peaks.

An M3 commercial core, properly constructed for audio purposes, will sound slightly softer than an Amorphous core transformer. There is after all more distortion, and when comparing 99.997% correct signals (Amorphous) with 99.993% correct signals (M3), this is what you should expect. However, there can be a great deal more internal information made available, for all musical signals, because you do not have to throw away half of the signal and the antenna event is actually encouraged during it's E Field portion.

In addition the M3 and M6 core are basically only providing a ferrous bounding box for the coil antenna event above 400 Hz. The material still responds but the losses are so high, with extended frequencies, that it neither adds nor subtracts to the signal passing from coil to coil, so long as that core construction issue has been dealt with. Neither amorphous core not M3 core is "better", they have differing strengths, and when both are used properly either will provide superb audio, within the limitations found above, and their pricing will be about the same too. An M6 core unit, with more distortion and only slightly less information, without quite the refinement of either of the other materials, is a much less expensive alternative, with very few drawbacks.

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