Output transformers ? sound quality ?

[t-head]

Onetics

Bud Purvine, of EnABL thread, makes transformers to order. I have his OTs in a set of 300B Mono 7s from Wright Sound. George Wright used to use Sowters but recently switched to Onetics. Some Canadians are using Onetics as well and like them. For reference, 300B transformers are USD $100...mine are linear, clear, detailed and sweet - YMMV

 

[planet10]

Re: Onetics

Bud Purvine...Onetics

We have a set of Bud's cheap SE OPTs... but i find very intriguing his push-pull transformers are kinkless (i haven't since the measures he says he has). This would make them pretty special,

Onetics transformers are available at a number of quality levels.

dave

 

[Tubes4e4]

Hi Rich,

I'm on the hunt for good quality p-p makes.

For example Gerd Reinhöfer of Röhrentechnik. For his PP OPTs see here..

And BTW, he is one of the very few OPT manufacturers I know who has nothing to hide and hence cares to publish some real data of his PP OPTs. IOW, you don´t have to rely on subjective hearsay of other buyers and the usual marketing mumbo jumbo of other vendors 🙂

Regards,

Tom

 

[EC8010]

Some time ago I made a square wave measurement on a friend's Onetics 6k6 "Level 1" PP transformer driven by a pair of 2A3. This was without feedback, but there was still a slight resonance at 26kHz (hinted at by the square wave).

 

[BudP]

EC8010,

Do you have any more test data you would care to share, on this particular OPT or others? This was designed for use with the 300 B set up in the Karna.

Bud

 

[kevinkr]

Re: Re: Output transformers ? sound quality ?

Hi Rich,



For example Gerd Reinhöfer of Röhrentechnik. For his PP OPTs see here..

And BTW, he is one of the very few OPT manufacturers I know who has nothing to hide and hence cares to publish some real data of his PP OPTs. IOW, you don´t have to rely on subjective hearsay of other buyers and the usual marketing mumbo jumbo of other vendors 🙂

Regards,

Tom

Hi Tom,
For those of us who don't speak German a quick guide to the terms in the tables would be helpful, some are obvious and others aren't..
How are his prices?

Kevin

 

[soundbrigade]

I have got a mains transformer from German company Welter Electronic. They also sell various OP-transformers as well in different classes (quality). Have anyone tried those?

 

[EC8010]

Do you have any more test data you would care to share, on this particular OPT or others? This was designed for use with the 300 B set up in the Karna.

I only had a very short time to look at that transformer so the only other thing I had time to measure was distortion vs frequency at 10W. Essentially, everything was fine down to 25Hz, but distortion rose (due to transformer saturation) as frequency fell; 1.4% at 20Hz, then 3% at 17Hz.

Here's a mains toroid (240V CT to 9V) as an output transformer...

 

[BudP]

EC8010,

Is there a chance we could get you to comment on what the square wave data shows, as a comparison between these two. I am of course interested in what the various differences might mean in character or subjective results, but I am more interested in what the data shows us about in circuit performance in an objective sense.

Taking these two examples, are there benefits to performance in the rest of the amplifier, since these things are essentially the final arbiter of amplifier performance.

Bud

 

[andyjevans]

I have used this O-netics 6K6 OPT with a 2a3 amp - very pleased. It's a clear and sweet sound with no nasties. Pretty much no sonic signature - not heavy or trebly or anything.

 

[Tubes4e4]

Re: Re: Re: Output transformers ? sound quality ?

Hi Kevin,

Hi Tom,
For those of us who don't speak German a quick guide to the terms in the tables would be helpful, some are obvious and others aren't..
How are his prices?
Kevin

For PP OPT prices, look here.

Some quick & dirty translations of the terms in the tables:

Hauptinduktivität bei 1Veff = Primary inductivity at 1 Vrms
Hauptinduktivität bei 230V / 50Hz = Primary inductivity at 230V / 50Hz
Streuinduktivität Primär-Sekundär = Leakage inductivity, primary to secondary
Resonanzfrequenz = primary resonance frequency
Streuresonanz Ausgang erdfrei = Leakage resonance with secondary floating (not tied to ground)
Wirkungsgrad = efficiency
Leistung für 20 Hz bei 1,1/1,6 T = Allowed power at 20 Hz for 1,1 and 1,6 Tesla
(Same for 30 Hz and 50 Hz)

Hope it helps,

Tom

 

[EC8010]

EC8010,

Is there a chance we could get you to comment on what the square wave data shows, as a comparison between these two.

A clean 10kHz square wave indicates good HF response with little phase distortion and implies that global feedback can be applied with little danger of instability, Obviously, it's not the whole story, and the other end of the spectrum is important too. Mains toroids might pass an excellent 10kHz square wave but they can't cope with power at low frequencies and are easily saturated by out of balance anode currents. That mains toroid I tested needed anode currents to be within 1mA of one another. In the end, audio transformers are about octaves. The trick is to maximise the number of octaves that can be passed and to position them in the right place. Of course, mains toroids work well as tweeter amplifiers.

 

[316a]

Of course, mains toroids work well as tweeter amplifiers.

I'm using mine full range , single ended and not parafeed either 😉 It's a 30VA unit 230:9+9 Multicomp , £9 each from Farnell -3dB @ 18Hz and 35kHz (-0.4dB down at 20kHz) . The primary is wired as per a standard SE transformer , one secondary is used for the speaker , the other is run in series with the (high impedence) DC filament supply . 1A of filament current offsets 40mA of anode current . I'm really hoping the James 6123 I've ordered up are an improvement 😉

cheers

316A

 

[EC8010]

1A of filament current offsets 40mA of anode current.

Nice trick. 😉

 

[richwalters]

Although a famous name, it took me a mighty amount of midnight oil squinting with a waveform shown in pic and correcting it and if not for experience I would have thrown the towel in. Beginners eager to get in the power game take note what one is up against ! It Pays to keep to easier LP and known designs.
10Khz at 100W isn't quite all gloves off.
Thanks to all comments, I'll now hunt down the german types and sus'em out.


richj

 

[Tyimo]

Hi!

Could somebody post this article?:

Theory and Practice Of Widebandwidth Toroidal OPT, Menno Van der Veen

I cann't find anywhere.....

Greets:

Tyimo

 

[Tyimo]

Heureka!

I found it on the Plitron's site!😀

Tyimo

 

[soulmerchant]

Although a famous name, it took me a mighty amount of midnight oil squinting with a waveform shown in pic and correcting it and if not for experience I would have thrown the towel in. Beginners eager to get in the power game take note what one is up against ! It Pays to keep to easier LP and known designs.
10Khz at 100W isn't quite all gloves off.
Thanks to all comments, I'll now hunt down the german types and sus'em out.


richj

That looks quite impressive...

 

[EC8010]

That looks quite impressive...

Quite impressive? I'd say it's amazing!