Mains toroids appear to be great for audio

[bigwill]

I just performed a small experiment with results far better than expected. I got two 6v mains toroids, and wired them back to back, and drove the two secondary 6v windings in series with one channel of a NAD amplifier and connected a speaker to the other two (in series)

The transformers were only small at 50VA.

Surprisingly, they let the full spectrum though seemingly with no problems at all! The bass wasn't distorted and sounded just as extended as the channel without toroids! The treble sounded equally un-harmed. There wasn't any distortion on bass notes and everything sounded "proper". The toriods probably DID colour the sound, but even if they did, they did in a very benign way. It was impressive considering the audio was going through two small MAINS transformers! If anything, I would seriously consider using them if I needed a temporary long cable run to my speakers. (Like 100v line transformers but probably better)

I know this is the tube forum but obviously this forum has the most use for audio transformers so I thought I'd post it here. I'd bet these would make great output transformers! (ensuring no overall dc bias) They cost nothing

[jacco vermeulen]

Mmm Will,

did you enjoy the 20 year stay on an isolated tropical island ?

[bigwill]

Originally posted by jacco vermeulen
Mmm Will,

did you enjoy the 20 year stay on an isolated tropical island ?

Yes it was very nice

[bigwill]

Further experimentation reveals that the transformers roll off the treble slightly

but I will cut them some slack because of what they are

[Gold_xyz]

Also I Think the toroid is better.
All Vellemann Tubes Kits have a toroid output tansformer.
In my experience the toroid can have a worse isolation.
In factorys production they are sometimes found with shorted windings.

[ray_moth]

I read somewhere that toroid power trannies had been used successfully as OPTs in PP headphone amps.

[Kent Smith]

I have played a little with power transformers at audio.... I have found that some worked quite well while others did not. I have no idea what was different between them. I have not tried toroids yet. Any ideas here??....

[Shoog]

If you keep DC out of them they work excellently. They need to be sized 4-6 x their rated load to prevent bass saturation. I have used them in a parafeed SE and my current PP. Both work really well. Its a matter of sucking it and seeing, you have very little to lose as if you don't like them they can always serve as "power Transformers".

Shoog

[Kashmire]

While testing prototype amplifiers, I commonly connect my speakers through transformers. This helps mitigate DC offsets and other nasties that can burn out speakers with prototype amps.

Mine don't sound bad, in fact, I've left them in my system for weeks at a time without being bothered by them. I built a Linkwitz dipole with a tri-amp active crossover. The tweeter needed to be connected directly to the amp! Yipes. It was really easy to fry. In practice now, I use a coupling capacitor tuned a decade under the tweeter's lowest frequency. This helps a lot.

They are old 117 : 6.3 : 6.3 filament transformers for really big tubes. Each 6.3V winding is good for 10 amps. I hook the amp to one of the 6V taps and the speaker to the other. I don't mess with the 117V winding. So basically, it is a 1:1 (6.3 : 6.3) coupling transformer that works rather well for testing stuff. The windings are beefy enough not to fry if my test amplifier belches a big DC ...

Nowadays, I've been building lots of Pass and Valve amplifiers. These don't have a tendency to DC.

[bigwill]

Originally posted by Shoog
If you keep DC out of them they work excellently. They need to be sized 4-6 x their rated load to prevent bass saturation. I have used them in a parafeed SE and my current PP. Both work really well. Its a matter of sucking it and seeing, you have very little to lose as if you don't like them they can always serve as "power Transformers".

Shoog

While I agree with the logic of this, the 50VA trannies I had didn't seem to have a problem when driven by a 25W amp up to near clipping, the bass was tight even with the ported speakers (although to be fair they only extend down to about 50Hz so any deficiencies may've been hidden

Another interesting thing I noticed that they made the amp sound a lot "nicer", they took off the harsh transistor sound that the amp had. Probably due to the rolled off treble or possibly something else? Either way it sounded good.