WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
I'm reviving this thread to see what new information we can squeeze out about the best OPTs for our beloved 300b SETs.
Interested particularly in actual comparative listening data, rather than word of mouth recommendations.
I just compared these:
a) O-netics OPT. This was flat out my favourite - in another class for tone and detail
b) Lundahl LL1620/60mA. Lacks the refinement of the O-netics on strings and voices, but it does have quite good tone to instruments. A loss of micro-detail compared to the O-netics. Bass was strong but less defined in tone
c) Audio Note Trans-300/IE. About the same level as the Lundahl above - smoother and more rounded but a further slight loss of micro detail. Bass again strong but less defined in tone than the O-netics
I further have been using the Lundahl LL1623/50mA in another amp. I haven't compared this directly but my other listening gives me the impression it's better than the LL1620. I've loaned it out so can't compare right now.
All parts in an amp need to be balanced in order to get a good result. Especially if you are looking for the best sound/cost ratio. If a poor driver and mediocre power supply are chosen the amp will not sound good even with a sophisticated output transformer.
For no compromise amps with the best possible driver, PSU and filament supply:
I have not tried the Tango X3.5S yet, that one is probably even better
I also have a permalloy core 3.5k Tangot OPT which I have not tested yet.
Ambitious amp, but somewhat restricted budget:
If on a budget:
Oh, and the tube makes a big difference too. For me chinese or russian 300Bs do not cut it.
Personally, I use, and recommend, the Sowter SA08s.
They may not get much of a mention elsewhere, but what I can say for certain is that they allow me to develop 300B driver and filament circuits by listening. In listening tests, the SA08 allows very easy selection among tiny circuit changes in any other part of the amplifier. And I am able to enjoy big symphonies in the same way as I do live concerts, and often the pleasure is greater, because the orchestral parts are better and more clearly presented.
Thanks for the ETF shootout info. Clearly the AN Trans-300 is better than the Trans-152 which is pretty average really and didn't do too well in the Silk shootout. Lundahls don't seem to be at the top of the tree - there's a lot of windings in most of them. I was disappointed with the LL1620.
The transformers I had Bud wind are for GM70 tubes. With an impedance of 6K they could be swapped into my DRD 300B amp easily. If you would like I will give that a try, as I have been wondering how they would sound. Not that the standard copper Electraprint iron is any slouch.
I also have some solid silver secondary Electra-print iron for 2A3 finals. They are nice. And Gery at Transcendar makes some great iron. Back when he was still taking custom orders he wound 6pr of custom 10Y/801A transformers that I still listen to daily. Great synergy with those little 10+ Transcendars.
The most detail can be heard from the silver secondary Electraprint iron, the best tone from the Onetics, but we are talking many different amps, so its not apple to apple because of my limited experience.