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
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
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
Shoog
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.
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.
Shoog said:
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.
well look at the physical properties of toroids...
they have much lower B field and EM emmissions, which are contained within the windings. The need for shielding other devices from the toroids is greatly reduced. Many commercial SS amps have no shielding of the toroids at all.
And yup, they've been used for ever (almost) in power supplies. Not sure of their use as outputs in tube amps.
they have much lower B field and EM emmissions, which are contained within the windings. The need for shielding other devices from the toroids is greatly reduced. Many commercial SS amps have no shielding of the toroids at all.
And yup, they've been used for ever (almost) in power supplies. Not sure of their use as outputs in tube amps.
The physics of it dictates that the core is only designed to handle power down to 50hz so by the time you are down to 20hz the core will be heavily into saturation. The ones I have used are at least 10 times the power rating and they cope well down to about 10hz. This is probably over the top - but the treble doesn't suffer so I am happy to carry the extra weight.
The bass reflex impedence hump was probably helping a good deal in stopping the core from saturate.
Shoog
The bandwidth of a toroidal is so huge that if it is reducing the treble - its way out of audable range.
The real issue to watch for is ultrasonic ringing, which can sound like treble extension.
I have also found that response can be effected by the direction in which the secondaries are connected. I observed this on my scope.
Shoog
The real issue to watch for is ultrasonic ringing, which can sound like treble extension.
I have also found that response can be effected by the direction in which the secondaries are connected. I observed this on my scope.
Shoog
Shoog said:
Hmm, that's odd, how come my toroids sounded like they were rolling off the treble? Could it be they were somehow just changing the signal in some way that SOUNDED a bit like they were?
When I say rolling off the treble I mean a slight reduction, not full on removal. It still sounded balanced and natural, just "warmer" than without the toroids..
If anything, more natural.
Nanook said:
About two decades ago a bunch of cheese people did the UL40 or the 100 watt ultra linear design by Vanderveen, that was published in Radio Bulletin.
ILP, nowadays Amplimo, manufactured the toroidal output transformers for both designs.
Now and then i see a couple of these, by now old, toroids flash by on the driv-ebay.
There's probably more than just a single relic who constructed the mid '80s UL designs present on this club.
The UL40 received an update around the turn of the millenium, the output toroids were better than the amp design itself.
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