Transboost - anyone?

[pinkjimiphoton]

If you are going to use a "good" transformer, you may as well throw out T1 and U2b and wire it through.

The only point of the transformer here is to be "bad". Use a small bad transformer. I suspect the circuit values are deliberately scaled to the TY-250B.

i'd bet damn near any smallish transformer could be adapted to work.
transformer overdrive can be very nice.... used to put i think it was a 470r resistor between two "tips" on a pair of rca jacks and intentionally misuse the reverb circuit in my fender to get "overdrive". very warm, very brown.

but i preferred the reverb. 
cool concept!

[PRR]

> foreseen from their specifications?

No.

I am suspecting it depends on details of lamination lap/butt joints, and relative permeability of the iron and the effective gap. Some of this stuff is more art than science. (And sometimes just what is easy for the factory.)

[PRR]

> Looks like a doorbell factory.

Looks like 200KHz.

So not a big audio problem.

It is very unlikely that three fairly different parts ALL ring at 200KHz. You expect their top-rings to be 10KHz-50KHz. Setup artifact?

[lion]

80 Hz, 2VRMS in:

Oh my, poor Bourns... gross saturation. Given how soon the Xicon started distorting, it's notable that it holds up far better here... Old Hammond is steady as a rock.

Looks ugly on the scope, but if we want xf saturation maybe this is actually "good" - what would it sound like?
Or put another way, if there is such a thing as "good" saturation, what would it look like, and is it any different from the usual squashed/bended curves from the usual OD/distortion devices?

The above example is down at 80Hz - almost out of the guitar range - I notice not even the cheap xformers seems
to bend much at the more interesting freqs for guitar, 240 and 1000Hz, with 2-3V input. Can we deduct (or estimate) from the available specs how much it'll take to get into saturation at 240/1000Hz.

I'm trying to get my head around this. In the Transboost thread one of the designers said that he couldn't say (and wondered) if there was any saturation of the TY-250P happening at all.

> foreseen from their specifications?

No.

I am suspecting it depends on details of lamination lap/butt joints, and relative permeability of the iron and the effective gap. Some of this stuff is more art than science. (And sometimes just what is easy for the factory.)

So we're down to (mostly) trial and error in choosing the "best" xformer I guess.

Erik

[Vitrolin]

> foreseen from their specifications?

No.

I am suspecting it depends on details of lamination lap/butt joints, and relative permeability of the iron and the effective gap. Some of this stuff is more art than science. (And sometimes just what is easy for the factory.)

some of this can be foreseen in data sheets, ofcourse it is some times very little information given:
Hammond:
http://www.hammondmfg.com/pdf/5c0045-46.pdf
Xicon, check that frequency range:
http://www.minikits.com.au/doc/42TL-Series-Transformers.pdf
Bourns gives a lot of data:
http://www.bourns.com/docs/Product-Datasheets/LMNPLP.pdf

here it is obvious why bourns and hammond does farbetter than xicon on low frequencies.

some manufactors at times also gives max DC current, that way you might be able to clip earlier if you bias the trnsformer at or close to current limit.

[PRR]

> some of this can be foreseen

I meant how "abruptly" the iron gives-up and falls-down. Whether large bass is bent gradually or abruptly.

A "hard" tape-wound core will saturate very abruptly.

Certain types of E-I lap cores saturate very gradually. First a small bit at the point of maximum flux, effectively making gap a little bigger and reducing inductance but not a lot. Gradually the saturated zone gets larger. At an extreme, imagine 8 E-cores facing east then 8 E-cores facing west. First the two middle cores saturate and permeability falls off. With more input, the other lams fade-out one by one. Such stacking details are in the Build Sheet but almost never in the sales literature.