I am looking for some opinion/experience with One Electron output transformers from Antique Electronics Supply. They are twice the price of a similar sized Edcor but without the 2 month wait.
Excellent
They are also shielded, which helps reduce mains noise. They will not be rigorous with reducing rectifier switching noise if you heat with the same transformer aux windings, so either use dedicated transformers for sensitive heaters or take care in rectifier selection and transformer snubbing. Its not enough to toss a cap or RC across the diodes; you will want a RC across any rectified windings.
But in short, the transformers are good quality; I used one in a 300B SET which was convenient having needed heater voltages right there. If I recall they also have a gauss band for reduced mag field strays.
They are also shielded, which helps reduce mains noise. They will not be rigorous with reducing rectifier switching noise if you heat with the same transformer aux windings, so either use dedicated transformers for sensitive heaters or take care in rectifier selection and transformer snubbing. Its not enough to toss a cap or RC across the diodes; you will want a RC across any rectified windings.
But in short, the transformers are good quality; I used one in a 300B SET which was convenient having needed heater voltages right there. If I recall they also have a gauss band for reduced mag field strays.
Some thoughts from Tubelab on the UBT-3 here:
Budget Output Transformers | Tubelab
I'm also interested in more 3rd party experience with these. They fill a price gap between the Hammond 125XSE series and the 1600SE series and they're immediately available.
They are about twice the weight of the Edcor 15W rated GXSE and bigger in both height and depth.
Budget Output Transformers | Tubelab
I'm also interested in more 3rd party experience with these. They fill a price gap between the Hammond 125XSE series and the 1600SE series and they're immediately available.
They are about twice the weight of the Edcor 15W rated GXSE and bigger in both height and depth.
I just wish One Electron made a few Push-Pull transformers... I've heard nothing but good things about their single-end ones, but the only stocked PP transformers suitable for a 6L6 are Hammond... And everything I've heard about One Electron is that their transformers are quite a bit nicer than Hammond.
In terms of single ended transformers, I think they're very hard to beat for how little they cost.
In terms of single ended transformers, I think they're very hard to beat for how little they cost.
The UBT-1 and UBT-3 are good units, nice build quality, excellent bandwidth, esp for the first watt. A pair of UBT-3s are playing in a "crash test dummy" amp of triode-strapped 6AV5s in SE with MOSFET follower drivers - thanks George (Tubelab_com). The 1600ohm UBT-1 pair are in a somewhat experimental 6336 SE amp - it sounds pretty good but needs a new chassis and driver electronics. One day.
I have used the UBT-1, UBT-2, and UBT-3. They worked well for me. They are good for the price you pay. You do need to use them properly (drive with appropriate plate impedance, and appropriate quiescent current).
I have used (and am still using) both the 3K primary and the 4.8K versions. The 3K is in a stereo 2a3 amp, the 4.8K is in a stereo 300B WE91 knockoff. I find them to be excellent performers. The 3K unit represented an audible improvement over a Hammond 1627SE in the upper mid-treble range. In a pair of mono block 300B amps, a comparison was made between 4.8K and a lundahl 1623 configured for 5.6K, and I was unable to hear any difference. The only down side to them is the finish isn't as nice as some of the others, but sound wise you can't go wrong.
Going have some down time and have put together makin's for a *em7 spud and might test them there. UBT-3 will be used on some el34 se monoblocks afterwords.
Has anyone tried the One Electron UBT-2 with global feedback around the secondary? I've tried Edcor CXSE-25-5K with global feedback and I am not happy with the result--a real bear to stabilize with any significant amount of global feedback applied.
Hoping the One Electron might offer better performance in this regard.
Hoping the One Electron might offer better performance in this regard.
kward,
Edcore:
What tube type are you using to drive the Edcor CXSE-25-5k?
If it is a pentode or beam power tube, are you using it in triode-wired mode?
UBT-2:
I would expect you need to use a triode, or a triode-wired pentode, or a triode-wired beam power tube if you are going to use global feedback and the UBT2.
If you do not want to use triode-wired mode on a pentode or beam power tube:
You might use Schade feedback output tube plate to driver tube plate, or you might use output plate to driver cathode feedback.
Take a look at the UBT2 data sheet and the phase and frequency response graphs.
You will see that the test is run with a 2400 Ohm driving impedance.
There are some phase and frequency anomalies as early as 35kHz, depending on whether you are using the 4 Ohm, 8 Ohm, or 16 Ohm taps.
Using pentode or beam power wired tubes, the plate impedance is far greater than 2400 Ohms. Maybe not the best way to use global feedback.
With triode-wired pentode and triode-wired beam power tubes, you may have better luck with global feedback.
I have a pair of UBT-2 transformers.
I would be interested in trying one of your Edcor CXSE-25-5k, if you want to try one of my
UBT-2 transformers.
Then we could decide if we want to swap a second set of them (if you have two).
Edcore:
What tube type are you using to drive the Edcor CXSE-25-5k?
If it is a pentode or beam power tube, are you using it in triode-wired mode?
UBT-2:
I would expect you need to use a triode, or a triode-wired pentode, or a triode-wired beam power tube if you are going to use global feedback and the UBT2.
If you do not want to use triode-wired mode on a pentode or beam power tube:
You might use Schade feedback output tube plate to driver tube plate, or you might use output plate to driver cathode feedback.
Take a look at the UBT2 data sheet and the phase and frequency response graphs.
You will see that the test is run with a 2400 Ohm driving impedance.
There are some phase and frequency anomalies as early as 35kHz, depending on whether you are using the 4 Ohm, 8 Ohm, or 16 Ohm taps.
Using pentode or beam power wired tubes, the plate impedance is far greater than 2400 Ohms. Maybe not the best way to use global feedback.
With triode-wired pentode and triode-wired beam power tubes, you may have better luck with global feedback.
I have a pair of UBT-2 transformers.
I would be interested in trying one of your Edcor CXSE-25-5k, if you want to try one of my
UBT-2 transformers.
Then we could decide if we want to swap a second set of them (if you have two).
6A3sUMMER,
Yes I would consider swapping OPTs Edcor for One-Electron. I have only the one pair that are bolted and wired into the amp, but I don't mind removing them. Might not be a fair trade? One Electron OPTs seem to be more expensive, but we could work out a swap deal with cash on the side maybe.
My full response to your other questions would totally derail this thread. Let me start a new thread and provide a full response.
Yes I would consider swapping OPTs Edcor for One-Electron. I have only the one pair that are bolted and wired into the amp, but I don't mind removing them. Might not be a fair trade? One Electron OPTs seem to be more expensive, but we could work out a swap deal with cash on the side maybe.
My full response to your other questions would totally derail this thread. Let me start a new thread and provide a full response.
Many years ago I used the UBT-2 for a pentode driven 300B amplifier, ala Thorsten Loesch. One of the more impressive SET amps I've heard; just not enough power with rock 'n' roll music for my-then speakers. But - subjective impression alert - very "fast" and detailed with a lot of transparency.
They are very good. I have a pair of UBT-3 and made a couple of tests with them and the frequency response is excellent and they have no ringing.
Paper bobbin is by far less reliable than plastic ones, when they catch a minimum quantity of moisture, the form conductive via destroying isolation to the core. Never saw it in plastic bobbins.