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Replacement OPT for Rogers E20A

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Freyr_Gud

Member
Joined 2022
#1
Hi there
I'm looking for a replacement output transformers for a Rogers E20A amplifier, the first one.
The amplifier is build by Audio Note in England, 6L6 PP Cathode Follower and Self Biased
Got this amp in non working condition with one of the opt. blowned. The transformers used in this amp are Trans-187 6.6K 20W from AN.
They don't have this transformer anymore and recommended the Audio Note Trans-185-6K 20W. Can't find any more info on either of those transformers.

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But I was thinking I could as well use Lundahl, maybe the LL2766? if it will fit the circuit or some other brands.

Anyone here who has some toughts on that? Which other opt would fit the circuit? I don't mind if I have to make some adjustments to the chassis if the size is bigger.

regards
Freyr
 
#2
Do you have the schematic? I searched and haven’t found it yet, but I did find this - give it a try: https://www.diyaudio.com/community/threads/rogers-e20a-audio-note-transformer.280788/#post-5257514

Without a schematic it is guesswork. Is it an Ultra Linear output transformer? In general, the circuit should accept any number of decent 6.6k primary transformers without problem. A bigger problem will be physical fit in die space available. Then the issue will be tweaking of the feedback circuit values to suit whatever new transformer you get (unless it is identical to the original).

The Lundahl LL2766 appears to be intended in PP for 6V6 amplifiers. It might work with your Rogers E20A amplifier, but I see the E20A is specified for 20-20k Hz +/- 0.5 db. I doubt that this model Lundahl will reproduce bass that low at 18 watts.
 
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#4
In order to help more information will be useful. Do you know how to check the wiring to determine if it is UL connected or not? (If not who will be doing the transformers swap and other work?) To buy the right replacements you need to know what you have, because, for example, the Lundahl LL2766 does not provide UL connections. What speakers do you use, i.e. what output impedances do you require on the transformer outputs. It would also be useful to have photographs of the amplifier to see the design of the current output transformers. Measure the space available so that you can easily determine of a given transformer will fit. It may also help you to trace out the schematic before you start working, as well as photographs to guide you in putting everything together again.

You do not show where you are physically located. That would help in providing local sources of transformers, or it there might be winders nearby that could rewind your blown transformer, instead of replacing both. If you must replace and are in the UK, I hear good feedback about Primary Windings. They have a transformer which will probably work well in the your circuit, based on specs, at a reasonable price. However, at 2kg they seem fairly light and primary inductance relatively low, so these will need further investigation. (What is the weight of your blown transformer?)

See: https://primarywindings.com/product/25w-6600-ohms-ultra-linear-push-pull-output-transformer/

I assume you have looked at the AN recommended replacement at: https://www.hificollective.co.uk/catalog/trans185-p-373.html
It is twice the weight and more than twice the cost of the primary windings offering, but sparce on specs.
 
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#6
Francois G said:
In order to help more information will be useful. Do you know how to check the wiring to determine if it is UL connected or not? (If not who will be doing the transformers swap and other work?) To buy the right replacements you need to know what you have, because, for example, the Lundahl LL2766 does not provide UL connections. What speakers do you use, i.e. what output impedances do you require on the transformer outputs. It would also be useful to have photographs of the amplifier to see the design of the current output transformers. Measure the space available so that you can easily determine of a given transformer will fit. It may also help you to trace out the schematic before you start working, as well as photographs to guide you in putting everything together again.

You do not show where you are physically located. That would help in providing local sources of transformers, or it there might be winders nearby that could rewind your blown transformer, instead of replacing both. If you must replace and are in the UK, I hear good feedback about Primary Windings. They have a transformer which will probably work well in the your circuit, based on specs, at a reasonable price. However, at 2kg they seem fairly light and primary inductance relatively low, so these will need further investigation. (What is the weight of your blown transformer?)

See: https://primarywindings.com/product/25w-6600-ohms-ultra-linear-push-pull-output-transformer/

I assume you have looked at the AN recommended replacement at: https://www.hificollective.co.uk/catalog/trans185-p-373.html
It is twice the weight and more than twice the cost of the primary windings offering, but sparce on specs.
Click to expand...
Thank's for your reply Francois and thank you very much to take the time and look into this with me. I'm located in Norway by the way.
I've been away from audio for ages, looking forward to get into it again.
I had to look it up about the difference output stage topology in tube amps 🙂 I think I have to dive into it more, going to do some more reading, check the screen connection and try to find my way around the circuit.
 
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