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Toroidal transformer on tube amp
Toroidal transformer on tube amp
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Old 13th February 2012, 12:22 PM   #11
ratbagp is offline ratbagp  United States
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Join Date: Mar 2008
Location: North East, MD
Our local group had a competition to build a 6V6 amp for under $200. Here is my entry that used toroids as the output transformers in a parafeed design. It was a fun build.

Audio ratbag: Lumiere

ray
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Old 28th May 2018, 12:08 PM   #12
Alexandru is offline Alexandru  United States
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Who one?
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Old 28th May 2018, 12:13 PM   #13
ratbagp is offline ratbagp  United States
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I do have a web page with pictures and some schematics but it needs some repair. I will fix it and let you know. Mine did not win because a screw had loosened on the drive down to our meeting place and a channel was not working. At a subsequent meet, it sounded better and more powerful than another of the contestants.

ray
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Old 18th June 2019, 09:46 AM   #14
OldHector is offline OldHector
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Location: Täby, Sweden
Default Primary 230v, secondary 33-0-33 v, 200VA

I have bought a couple of these transformers, and they appear to be good quality.

I have been considering if they are sufficiently flexible in the way they could be used, if it was worth getting a couple more for the 'parts bin'.
  1. They could be linked back to back, to get 230v isolated, and piggy back of the linked 33-0-33 secondaries to feed heaters.
    (Question: How best to link the secondaries? Treat them as 0-66V, and do not attach the CT?)
  2. I could try and use one with a voltage doubler. That should get me to 180V, I was hoping. Would this be enough for a PP EL86 amplifier? (A = G2 = 170v)
  3. I could use them in series, primaries connected in parallel, so I'd get 66-33-0-33-66 400VA.
  4. I like the idea of using power supply toroids as output transformers, but I don't think these voltages are much use. If I had 8ohm speakers, and a PP output stage (centre tap to B+), then I am looking at (230*230)/(33*33) * 8, which is just 388 ohm raa, and not useful, as far as I know.

The original idea was to try and build the simple valve tester on the Valve Wizard site ...
The Valve Wizard
... and I think with my mains (235v) and basic bridge rectifier with a 100uf cap, the 100v should be OK.

How useful are they?
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Old 18th June 2019, 11:58 AM   #15
OldHector is offline OldHector
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Just realised the error of (4.) above. The centre tap is on the secondary, so that rules out a PP OPT.
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Old 20th June 2019, 12:16 PM   #16
Dinolobe is offline Dinolobe  Canada
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Antek makes toroidal transformer for tube amps. I think that the reason we are not seeing more toroids in tube amps is due to the fact that not many are available on the market. Besides Antek, the other brands that I have seen were a lot more expansive than hammond or edcor, so that might be keeping people from diving into this. On the other hand, antek transformer are affordable and available in many different power ratings and secondary voltages. All of their high voltage transformers have 6.3V secondaries with good current ratings. I seriously considered them for my tubelab sse, but found a good deal on used allied 6k7vg...

AnTek Products Corp
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Old 20th June 2019, 04:25 PM   #17
kodabmx is offline kodabmx  Canada
Affordable triode connected sweep tube amps.
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Toroidal transformer on tube amp
AnTek only make power transformers tube amps. None of them would be suitable for use as an OPT though.
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Old 20th June 2019, 04:28 PM   #18
Dinolobe is offline Dinolobe  Canada
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Quote:
Originally Posted by kodabmx View Post
AnTek only make power transformers tube amps. None of them would be suitable for use as an OPT though.
In a regular circuit, I totally agree with you. But mains transformers have been successfully used as output transformers. Have a look at this design :

Return of the Darling
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Old 20th June 2019, 04:33 PM   #19
randytsuch is offline randytsuch
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I remember Plitron making toroid OPTs, but that they were expensive.
I can't reach their website right now, so can't check.

In Europe, these guys make:
Tube output transformers - Shop Toroidy.pl
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Old 20th June 2019, 04:38 PM   #20
kodabmx is offline kodabmx  Canada
Affordable triode connected sweep tube amps.
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Join Date: Oct 2011
Location: Toronto
Toroidal transformer on tube amp
Quote:
Originally Posted by Dinolobe View Post
In a regular circuit, I totally agree with you. But mains transformers have been successfully used as output transformers. Have a look at this design :

Return of the Darling
Let me specify: None of the power transformer they make for tube amps are suitable.

They make other power transformers that will work though. Personally, I use Triad since I'm in Canada, and AnTek want's a fortune for shipping.

I'm using a pair in series connection for my monoblocs. I get full power (112W) at 30 Hz this way.

Quote:
Originally Posted by randytsuch View Post
I remember Plitron making toroid OPTs, but that they were expensive.
I can't reach their website right now, so can't check.

In Europe, these guys make:
Tube output transformers - Shop Toroidy.pl
Plitron was in Toronto, and I think they have ceased production.
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