Ah, I see what you mean. That's something I hadn't really thought of. Maybe I can find curve charts for James and Toroidy.
Yikes, yeah that looks a bit complex. Another point for Toroidy, James or Edcor. Hoping one of those pans out (especially Toroidy).
I'm going to give high marks to Electra-Print. Get them while you can. The number of people who can successfully build this kind of product are going away very quickly as the skillset ages out. There was a Golden Age in the early 1990s when Transformer Winders re-emerged out of the depths to satisfy the new demand - i.e. the era of Sound Practices, Harvey Rosenberg, Nobu Shishido, etc. Those people are rapidly going into retirement now.
Two things to say about Jack's product. He knows how to build product that can sustain high voltages - he's well aware of materials and manufacture to meet the reliability. I bought a pair of output for an 845 and they have been in service for nearly two decades. Second, a bought a pair of Interstage Transformers for him, both tested to spec. No ringing, no frequency response fall-off, properly gapped for full 60mA idle current, etc.
If there is a transformer that you need for a specific application - either Interstage or for a 211/845/etc - now is the time to lay your hands on one while you can.
Two things to say about Jack's product. He knows how to build product that can sustain high voltages - he's well aware of materials and manufacture to meet the reliability. I bought a pair of output for an 845 and they have been in service for nearly two decades. Second, a bought a pair of Interstage Transformers for him, both tested to spec. No ringing, no frequency response fall-off, properly gapped for full 60mA idle current, etc.
If there is a transformer that you need for a specific application - either Interstage or for a 211/845/etc - now is the time to lay your hands on one while you can.
Jack E. must be getting up in years - extremely cool and easy to deal with when I had some custom inductors wound.
I hope Hammond's SE are better than their old 1650 PP series. Those had a lot of funky resonances, and open loop, some subjective HF rolloff vs good iron such as whatever EICO made for their ST70 integrated amplifier. That rolloff may have not been a bad thing as made CD of Beethoven cello & piano sonatas sound "lush"
If Edcor measure and listen well and one isn't old and running out of time then a wait might be OK.
- wish in the day I would have bought E-P rather than UBT-1 - I think the low end would have been a bit better but my SE parallel 2A3 amp also had LF (and HF) limitations with its interstage.
How does that toroid fare vs gapped EI on the low end?
I hope Hammond's SE are better than their old 1650 PP series. Those had a lot of funky resonances, and open loop, some subjective HF rolloff vs good iron such as whatever EICO made for their ST70 integrated amplifier. That rolloff may have not been a bad thing as made CD of Beethoven cello & piano sonatas sound "lush"
If Edcor measure and listen well and one isn't old and running out of time then a wait might be OK.- wish in the day I would have bought E-P rather than UBT-1 - I think the low end would have been a bit better but my SE parallel 2A3 amp also had LF (and HF) limitations with its interstage.
How does that toroid fare vs gapped EI on the low end?
I'm so pleased to have gotten so many helpful and interesting responses on this thread. Thanks to everyone who has contributed.
As of now, I have requests for quotes out for James, Toroidy and Electra-Print. If none of those pan out, or if they're too expensive, Edcor CXSE25 is my backup plan.
I'm sort of hoping that the Toroidy price is right, because I love the look of their potted transformers.
But based on all the many responses here, I'm sure that whatever option I get in the end will be quality.
As of now, I have requests for quotes out for James, Toroidy and Electra-Print. If none of those pan out, or if they're too expensive, Edcor CXSE25 is my backup plan.
I'm sort of hoping that the Toroidy price is right, because I love the look of their potted transformers.
But based on all the many responses here, I'm sure that whatever option I get in the end will be quality.
Its very hard to make a toroidal transformer withstand dc current without saturating..
Therefore a single ended output transformer is quite difficult to make succesfully.
They have apperantly some kind of special core and winding method that makes that possible.
As i said, i was skeptical but they have proven themselves to sound good and actually measure good as well.
For the price I was blown away...
Therefore a single ended output transformer is quite difficult to make succesfully.
They have apperantly some kind of special core and winding method that makes that possible.
As i said, i was skeptical but they have proven themselves to sound good and actually measure good as well.
For the price I was blown away...
I did find them at tme.com, but not the potted version, which is what I'm after. Toroidy emailed me to ask for my specific shipping address so they can send me a quote, so I'm now waiting to hear back from them.
There is a long thread here about SE output transformers. I don't know if it will help, or just add to the confusion.
SE Output xfmrs....who are the current suppliers for not many $$$
It should be noted that every transformer maker has their own way of specifying power handling capability (wattage rating). A transformer built with sufficient insulation to handle voltages in the kilovolt range may do a good job passing over 100 watts at 1 KHz, but may only pass 15 watts or so at 20Hz. In the bass case, size matters. You can't beat physics. Getting solid bass out of a single ended amp at the 10 watt power range needs a 3 to 5 pound transformer minimum. Bigger is almost always better.
The "60VA" transformers that I got from Toroidy will not pass 60 watts at 20 Hz, 10 watts, maybe. None of the speaker systems that I will use them with could do anything with 20 Hz, so in this case it does not matter.
On the other extreme it takes power to constantly flip the magnetic domains back and forth in that massive lump of iron. The bigger the iron, the bigger the losses. Since you are flipping them faster at HF, there will be more treble loss in that big transformer. The Hammond 1628SEA gives up about 10% more power than the Edcor CXSE 25 in the same amp. In order to preserve the most power and HF response I would limit the transformer to less than 10 pounds at the 10 watt level.
These are generalizations, and the driving impedance of the amp that is feeding the transformer makes a big difference. Most of my testing was done with an SSE running KT88's.
The new UNSET design can possibly move the limits at both ends. I have tested the Hammond VS Edcor in the UNSET and the frequency response plots look almost identical. The 10% power penalty for the Hammond is still there though. The Toroidy's will meet the UNSET soon, but they are much lower impedance, so no direct comparisons can be made.
SE Output xfmrs....who are the current suppliers for not many $$$
It should be noted that every transformer maker has their own way of specifying power handling capability (wattage rating). A transformer built with sufficient insulation to handle voltages in the kilovolt range may do a good job passing over 100 watts at 1 KHz, but may only pass 15 watts or so at 20Hz. In the bass case, size matters. You can't beat physics. Getting solid bass out of a single ended amp at the 10 watt power range needs a 3 to 5 pound transformer minimum. Bigger is almost always better.
The "60VA" transformers that I got from Toroidy will not pass 60 watts at 20 Hz, 10 watts, maybe. None of the speaker systems that I will use them with could do anything with 20 Hz, so in this case it does not matter.
On the other extreme it takes power to constantly flip the magnetic domains back and forth in that massive lump of iron. The bigger the iron, the bigger the losses. Since you are flipping them faster at HF, there will be more treble loss in that big transformer. The Hammond 1628SEA gives up about 10% more power than the Edcor CXSE 25 in the same amp. In order to preserve the most power and HF response I would limit the transformer to less than 10 pounds at the 10 watt level.
These are generalizations, and the driving impedance of the amp that is feeding the transformer makes a big difference. Most of my testing was done with an SSE running KT88's.
The new UNSET design can possibly move the limits at both ends. I have tested the Hammond VS Edcor in the UNSET and the frequency response plots look almost identical. The 10% power penalty for the Hammond is still there though. The Toroidy's will meet the UNSET soon, but they are much lower impedance, so no direct comparisons can be made.
There was an earlier version of the Hammond 1628SE about 20 years ago that had a "bug" in the design. There was a profound dip around 13kHz - almost notch like, but only on the 8 ohm tap. This was reported in various forums and I measured it myself on a Bode plot. Nonetheless, I hauled a low-voltage 845 design across New England where it was auditioned in several group meets and several private listening rooms and people loved my amp - despite the measured notch-filter-like effect in the response!
That same transformer, 1628SE, I turned into a big-*** plate choke (unloaded secondary) and then used secret legendary Radio Shack NOS Nickel Cored 70V Matching Transformer as a Parafeed Transformer. That was spectacular! Tried the same trick using the 811A in A2 - equally spectacular. If you Big *** transformer is suffering HF issues because of leakage inductances or interwinding capacitances - you can turn it into a Plate Choke and go fetch yourself a Tiny Parafeed transformer.
This article covers how to use the Taps on the plentiful and diverse 70V System Matchers to do the Parafeed deed. Note - to choose the value of the Parafeed Capacitor needed - you need to know the L of your Plate Choke the the plate resistance of your tube.... Its often in the 4uF-8uF range...
This is a cheap, but fun, Parafeed experiment!
Audio Transformer Substitutes
That same transformer, 1628SE, I turned into a big-*** plate choke (unloaded secondary) and then used secret legendary Radio Shack NOS Nickel Cored 70V Matching Transformer as a Parafeed Transformer. That was spectacular! Tried the same trick using the 811A in A2 - equally spectacular. If you Big *** transformer is suffering HF issues because of leakage inductances or interwinding capacitances - you can turn it into a Plate Choke and go fetch yourself a Tiny Parafeed transformer.
This article covers how to use the Taps on the plentiful and diverse 70V System Matchers to do the Parafeed deed. Note - to choose the value of the Parafeed Capacitor needed - you need to know the L of your Plate Choke the the plate resistance of your tube.... Its often in the 4uF-8uF range...
This is a cheap, but fun, Parafeed experiment!
Audio Transformer Substitutes
So, I heard back from Electra-Print Jack.
In an expletive-laden email, he said that the 140mA is far too much for the EL84 tubes, and that such a thing would likely destroy them. He says 45mA is the max for those tubes, and any higher will "cause the plate to turn red". He... shall we say... suggests a 50mA transformer.
Now, because of his generally unfriendly and cantankerous demeanor, I'm not particularly inclined to order anything from him. His products may be good, as some in this forum have claimed, but his mannerism does not seem deserving of my money.
But, his latest email has sewn the seeds of doubt in my mind.
Most of the transformers I've been looking at have a higher Max Current rating: The Edcor CXSE25 is 200mA, the Toroidy TTG-EL84SE is 150mA, even the no-longer-available Transcendar was 140mA. The one exception to this was this Edcor GXSE10 I had considered due to the price, which is rated at 80mA.
Knowing what we do about the SSE design, and the EL84 tubes, are this current ratings over 100mA fine? This is what everyone here has told me.
Or, is Electra-Print Jack on to something with his claim?
In an expletive-laden email, he said that the 140mA is far too much for the EL84 tubes, and that such a thing would likely destroy them. He says 45mA is the max for those tubes, and any higher will "cause the plate to turn red". He... shall we say... suggests a 50mA transformer.
Now, because of his generally unfriendly and cantankerous demeanor, I'm not particularly inclined to order anything from him. His products may be good, as some in this forum have claimed, but his mannerism does not seem deserving of my money.
But, his latest email has sewn the seeds of doubt in my mind.
Most of the transformers I've been looking at have a higher Max Current rating: The Edcor CXSE25 is 200mA, the Toroidy TTG-EL84SE is 150mA, even the no-longer-available Transcendar was 140mA. The one exception to this was this Edcor GXSE10 I had considered due to the price, which is rated at 80mA.
Knowing what we do about the SSE design, and the EL84 tubes, are this current ratings over 100mA fine? This is what everyone here has told me.
Or, is Electra-Print Jack on to something with his claim?
Higher current means you need a larger core area to prevent the transformer from saturating. Higher core area -> more iron -> more expensive -> higher losses. So Jack is onto something. If you're paying good money for a custom transformer, it makes sense to get something that's optimized for your use case.
If you're using a generic transformer, you have to make do with what's available. But still try to find something that's reasonably close to your actual use case.
Tom
Tom
Unfortunately two different tubes with similar numbers are being confused here. The EL84 is a small 9 pin tube commonly found in guitar and HiFi amps, and yes 140 mA, or even 100 mA will melt them. 40 to 50 ma is about right for an EL84. The SSE amp does not use EL84's, the SPP does.
The SSE amp uses EL34's which are a much bigger octal tube. They will run at 100 mA, but that is really too much. They are best used in the 60 to 80 mA range, so a transformer with a 100 mA or more MAXIMUM current is appropriate.
The Edcor CXSE25-5K is a good choice for an EL34 amp. I have not tried the Toroidy TTG-EL84SE, but it was intended for the smaller EL84 tube, so you might not be happy with it at EL34 power levels, especially in the bass department.
If I was to pick a transformer from Toroidy to use in an SSE, I would use the TTG-KT88SE. It is made for the KT88 or 6550 tube and thus has a 3K ohm primary. The EL34 will work with a 3K ohm load, but it can do very well with a transformer like this.
My own SSE uses a pair of the Transcendars that were designed for a 300B amp with a 3K ohm primary and a 4 and 8 ohm secondary tap, just like the TTG-KT88SE. I put speaker jacks on the back for both outputs. For use with EL34's in triode mode, I simply plug my 8 ohm speakers into the 4 ohm jacks giving the EL34's a comfortable 6K ohm load. When it's time to rattle the walls with some Pink Floyd, I plug in some KT88 tubes engage the Cathode Feedback and UL modes, and connect the big speakers to the 8 ohm tap. The only place where this might not work is if your speakers have impedance's that go below 4 ohms. Consult the chart for all the speaker systems that you might be considering.
That SSE amp was my main listening amp from it's build in about 2007 until it was dropped during a move in 2014. It's been sitting on a shelf here calling my name every so often saying fix me.....fix me.....
I agree Jack is trying to sell you the best product for your application.
As small a transformer as possible to accomodate your power transfer - while minimizing losses.
The 11 Pound Hammond 1628SE spec sheet says you can use it with anything from a 7-pinner 6AQ5 to the might 572B DHT - which will happily run 100-100mA idle current, and everything in between. You don't need a transformer that big for 6AQ5! But you do for the 811A/572B !
As small a transformer as possible to accomodate your power transfer - while minimizing losses.
The 11 Pound Hammond 1628SE spec sheet says you can use it with anything from a 7-pinner 6AQ5 to the might 572B DHT - which will happily run 100-100mA idle current, and everything in between. You don't need a transformer that big for 6AQ5! But you do for the 811A/572B !