Cheap way of making SS sound like a tube amp...

[chris661]

Hi all, just wanted to post my findings...

Quote from wiki to begin

"Tube instrument amplifiers are often equipped with lower-grade transformers and simpler power regulation circuits than those of hi-fi amplifiers."

Based on this, I got my (old, but still quite nice) amp, and put a mains transformer across the output (used one of the 12V legs) and put the speaker across the other 12V leg. I mean, you can't get much lower grade than a cheap mains transformer, right?

I played through it for a while, and I really like the sound, so I thought it might be worth letting you guys know, so you can (if you so wish) give it a try.

Dad mentioned that, a long time ago, there were discussions about the differences between tube and SS amps, and one person pointed out that it's only the transformer that adds much difference.

I don't have an opinion of this theory, but, after trying it with my amp, it seems to have some merit.

I've probably gone a little OT, so, anyway...
I know most of you will have a mains transformer lying around somewhere, so give it a try. You'll be as surprised as I was.

Chris

[chris661]

Should've mentioned - insulate the mains primary winding connections - 230V (or whatever you happen to use) hurts a lot, and won't do the amp much good if it shorts.

[Ola]

The laws of physics say that any inductor is a device that slows down the changes in the passing flow of electrones.

[Cornelis Spronk]

You might like the sound, but it is hard to argue that the quality and clarity of the sound is improved. The magnetic core of an iron transformer does not increase in a linear fashion with the input current in the primary. An elementary physics experiment in electricity and magnetism demonstrates that.

[chris661]

I should've made it more clear - it's a guitar amp. Hence it's posting under musical instruments.
Adding a high quality transformer may give a more high-end tube sound to SS hifi equipment.

[mjf]

..........iirc mcintosh use opt in their solid state power amps.
greetings

[chris661]

I was a little surprised more people aren't doing so.
The sound it gives isn't really distorted or anything, but it sounds different. Not unclean, but certainly more flowy (I'm not making much sense, am I?)
Sounded good when I plugged a distortion effects pedal in.

I just wanted to let you guys know, so someone else could give it a go.

[gain-wire]

Hello Chris661,

I actually have done this before, and somehow, I think that even I was not the first one, even given my advanced intelligence. As mjf pointed out, McIntosh id use output transformers in some of their amplifiers. Anyway, my goal was more to build a push-pull MOSFET version of a typical tube amplifier. So the source of each mosfet went to one side of a center-tap transformer (also a step down transformer, like you used) and the output went to a little speaker. The distortion I got (OK, I was using an op-amp front-end to overdrive the MOSFETs) was not too shabby either, but all in all it failed to really produce a nice, "not-so-buzzy" tone.

Actually the earliest solid-state power amplifiers had to use transformers. I don't know if it was because the current limitation of transistors at the time was very low or because of impedance mismatch, but I've seem many an amp schematic with an output tranny, although most of those schematics, if not all, were Class-A topology.

Anyhow, an interesting experiment.

[chris661]

Certainly.
The amp I'm using is a class AB thing, designed to be clean, with bass, mid and treble controls.
As I said - it doesn't give a huge load of distortion, just makes things sound smoother. The SS harshness has gone (it's a late 70s amp), replaced with something nicer.
As stated above, adding the transformer introduces new and interesting non-linearities (checked this using a scope, set to sum, connected to before and after the transformer) - more difference at the lower frequency strings.
I didn't want to experiment on my little Fender amp, so I bought something faulty off ebay - that way, I don't mind if it explodes.
I like it so much it's now my main amplifier. Shame it doesn't go so loud - you run into all sorts of nasties at 7/10 on the volume control. I expect it's the power supply, but for what I paid for the amp, it's probably not worth upgrading much.

Chris

[Mooly]

Have you tried a low value resistor around 0.22 to 0.68 ohms in series with the speakers when using solid state amps.
It mimics the non linear output impedance of an output transformer to some degree... and interacts with the impedance curve of the speaker. Subtle but good