Author Topic: Locally available Audio Output Transformers  (Read 430 times)

Offline Mars

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Locally available Audio Output Transformers
« on: June 26, 2018, 12:19:28 PM »
Hi All

I have regular requests from people looking for parts for their DIY tube amp projects. Output transformers seems to the hardest to find at a decent price. While scanning the web, I found this item at RS

 5.6kΩ: 4 Ω/8 Ω/16 Ω, 25W Output Transformer for EL34

    RS stock no. 123-7237 Mfr. Part No. V78A01F Manufacturer OEP



The specs are as follows:

 V78A01F 25W valve output transformers are constructed with a grain orientated steel core. The core construction reduces distortion and reduces the stray magnetic field. Featuring 24.5% UL taps on the primary output these push-pull transformers have outputs for 4 Ω, 8 Ω and 16 Ω. V78A01F push pull transformers are suitable for use with amplifiers with EL34 valves.

UL94-HB (minimum)
Temperature class B (+130°C) minimum
19 H total primary inductance at 1 kHz
85.7 mH total secondary inductance at 1 kHz
Isolation of primary to secondary is 1 kVrms for 2 seconds

Do you know of any similar products available in SA?
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Offline El Sid

Re: Locally available Audio Output Transformers
« Reply #1 on: June 26, 2018, 12:27:02 PM »
There's a chap called Karel down in Paarl who winds a mean OPT...   ;) ;D

Offline bushtech37

Re: Locally available Audio Output Transformers
« Reply #2 on: June 26, 2018, 12:46:05 PM »
What about SJ Andrews in Marlboro Jhb? Got good service from them.

Offline Qualityten

Re: Locally available Audio Output Transformers
« Reply #3 on: June 26, 2018, 10:56:15 PM »
Is getting RS to ship to SA not viable? Sorry if that's a dumb question.

Offline wonderbob

Re: Locally available Audio Output Transformers
« Reply #4 on: June 27, 2018, 08:43:48 AM »
Is getting RS to ship to SA not viable? Sorry if that's a dumb question.

RS has a big local operation, but I do not know whether their full catalog is available for local orders. I have bought lots of components of https://za.rs-online.com/web/ through the years

Offline Hi-Phibian

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Re: Locally available Audio Output Transformers
« Reply #5 on: June 27, 2018, 08:57:15 AM »
Full catalog.  If not in stock it takes 6 working days. 

That said they cater for repair and maintenance and proto typing more than manufacturing.  Meaning good consistent availability of small quantities but at a price. 







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Offline Mars

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Re: Locally available Audio Output Transformers
« Reply #7 on: June 28, 2018, 11:28:30 AM »
Thanks for that, Thomas

I searched "audio transformers" and missed this gem:



 D29A09F 10W push-pull audio transformers from OEP are constructed with a grain orientated silicon steel core. This core enables reduced distortion and stray magnetic field. These audio output transformers are suitable for use with EL84 valves in push-pull amplifiers and guitar amplifiers with 20% UL taps.

10 W maximum load at 40 Hz
Primary inductance of 20.7 H at 1 kHz, 0.1 V
Typical primary leakage inductance of 8 mH at 1 kHz, 0.1 V
1.6 nF interwinding capacitance at 20 kHz

This should work nicely with a Mullard 5-10? I like the 20% UL taps.

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Power and Integrated Amplifiers
Phono Pre-amplifiers
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Offline Qualityten

Re: Locally available Audio Output Transformers
« Reply #8 on: June 29, 2018, 12:49:24 AM »
Yes, that 6k6 primary inductance is just right for matching with the 20% taps. A very competitive price compared with some of the Dynaco clones for sale in the US. And the shroud is a bonus.