I think that it means that the transformers will perform quite well in their intended application which is a parallel pair of 300B's or a parallel pair of KT88's per transformer. They should work well in other applications that make a similar amount of power and draw a similar amount of current through the transformer.
The 300 mA and 60 watts are obviously a 1 KHz spec. I have not run 60 watts or 300 mA through these yet as it would take three BIG (26LW6) sweep tubes to get there without a meltdown event. I have seen 45 watts and 250 mA with good performance at 1KHz. The test was only for a few seconds as my 40 watt tubes were dissipating over 60 watts each.
I plan on using these in an SE amp build, but I'm not sure of the exact power level or tube count yet.
The 300 mA and 60 watts are obviously a 1 KHz spec. I have not run 60 watts or 300 mA through these yet as it would take three BIG (26LW6) sweep tubes to get there without a meltdown event. I have seen 45 watts and 250 mA with good performance at 1KHz. The test was only for a few seconds as my 40 watt tubes were dissipating over 60 watts each.
I plan on using these in an SE amp build, but I'm not sure of the exact power level or tube count yet.
Sure, but I'm assuming they didn't specify 1kHz (maybe they did?). Obviously, a transformer will be capable of way more power at 1kHz than at the low end of audio.
Industry standard seems to be 30Hz power spec or sometimes 20Hz.
But as you say, stick to something close to the suggested application and you'll be fine.
Industry standard seems to be 30Hz power spec or sometimes 20Hz.
But as you say, stick to something close to the suggested application and you'll be fine.
As I have always said about OPT's.......size matters.
The Transcendar OPT's that I have weigh 2.2 Kg. They are a custom design created for a commercial 300B amp. They were sold as surplus when the amp company ceased production. When I got them the only specs were "300B, 3000 ohms, 75 mA, 10 watts max."
The Toroidys weigh 2.5 Kg which puts them in the same weight class, so their use for twice the number of 300B's is probably a bit of a stretch compared to the Transcendars, but they are probably conservatively rated.
I have a pair of Eastern Audio (Chinese) SE OPT's in the same size and weight class, and they are rated at "50 watts," Again, I can get 50 watts through them at 1 KHz, but far less at 30 Hz.
It is not even a fair game to compare The big 4 to 6 Kg OPT's like the Edcors and Hammonds to a 2 to 2.5 KG OPT's.
Years ago Plitron and Amplimo made OPT's with the "Vanderveen Design." He now markets his own OPT's. Rumor says that Toroidy is making something very similar, if not a direct copy.
The Toroidy's cost me $208 USD for the pair delivered to my address in the USA. ($176 for the transformers and $32 for shipping). For the delivered price, they are not a bad deal. If I had the budget I would order a pair of the 1250 ohm Edcors for a comparison, but that's not an option right now.
The Transcendar OPT's that I have weigh 2.2 Kg. They are a custom design created for a commercial 300B amp. They were sold as surplus when the amp company ceased production. When I got them the only specs were "300B, 3000 ohms, 75 mA, 10 watts max."
The Toroidys weigh 2.5 Kg which puts them in the same weight class, so their use for twice the number of 300B's is probably a bit of a stretch compared to the Transcendars, but they are probably conservatively rated.
I have a pair of Eastern Audio (Chinese) SE OPT's in the same size and weight class, and they are rated at "50 watts," Again, I can get 50 watts through them at 1 KHz, but far less at 30 Hz.
It is not even a fair game to compare The big 4 to 6 Kg OPT's like the Edcors and Hammonds to a 2 to 2.5 KG OPT's.
Years ago Plitron and Amplimo made OPT's with the "Vanderveen Design." He now markets his own OPT's. Rumor says that Toroidy is making something very similar, if not a direct copy.
The Toroidy's cost me $208 USD for the pair delivered to my address in the USA. ($176 for the transformers and $32 for shipping). For the delivered price, they are not a bad deal. If I had the budget I would order a pair of the 1250 ohm Edcors for a comparison, but that's not an option right now.
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I've heard that the Vanderveen transformers are quite a bit cheaper than the ones that were sold from Plitron. I corresponded with someone who built a Unity-Coupled amp with the ones from Vanderveen and he paid significantly less than I paid for my transformers from Plitron.
I'm sure they're not as cheap as Toroidy but they seem much more reasonable now.
I'm sure they're not as cheap as Toroidy but they seem much more reasonable now.
That was the UC amp I documented on AudioKarma.
Torusni transformatori - Uvod
AFAICT they are made with the same 11 herbs and spices as the ones that were made by plitron and amplimo...
Many of Toroidy's offerings are stocked by Electronic components. Distributor, online shop – Transfer Multisort Elektronik. On some USA holidays (memorial, july 4th...), they have a 15% off sale. Their standard shipping used to be $9.95 that allowed one transformer to be ordered and stay under the weight limit. Make two orders and save a few more bucks...
Torusni transformatori - Uvod
AFAICT they are made with the same 11 herbs and spices as the ones that were made by plitron and amplimo...
Many of Toroidy's offerings are stocked by Electronic components. Distributor, online shop – Transfer Multisort Elektronik. On some USA holidays (memorial, july 4th...), they have a 15% off sale. Their standard shipping used to be $9.95 that allowed one transformer to be ordered and stay under the weight limit. Make two orders and save a few more bucks...
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zintolo,
Good question, I am not sure, but . . .
Let's put this in perspective.
How low of a frequency are you talking about?
A 32Hz organ pipe?
20Hz?
The world's biggest orchestral Thunder drum?
The 6Hz of the canon of the definitive 1812 Overture recorded by Telarc?
Oh, did I forget to mention the broken windows at the college where the canon was recorded?
If they do not saturate with 420mA peak at those low frequencies, go to church and thank God.
After that, get new speakers, not too many can handle all of that.
(During the late 1950s RCA recording of the 1812 Overture, they used a real canon. They had the recording monitor speakers turned up too high, and the woofer cones jumped out of the speaker baskets . . . live and learn).
Remember, do not use negative feedback that comes from the output secondary.
It will only make the saturation worse, because the feedback correction will pump even more current into the primary.
The quickest solution, turn the volume down a little bit.
Good question, I am not sure, but . . .
Let's put this in perspective.
How low of a frequency are you talking about?
A 32Hz organ pipe?
20Hz?
The world's biggest orchestral Thunder drum?
The 6Hz of the canon of the definitive 1812 Overture recorded by Telarc?
Oh, did I forget to mention the broken windows at the college where the canon was recorded?
If they do not saturate with 420mA peak at those low frequencies, go to church and thank God.
After that, get new speakers, not too many can handle all of that.
(During the late 1950s RCA recording of the 1812 Overture, they used a real canon. They had the recording monitor speakers turned up too high, and the woofer cones jumped out of the speaker baskets . . . live and learn).
Remember, do not use negative feedback that comes from the output secondary.
It will only make the saturation worse, because the feedback correction will pump even more current into the primary.
The quickest solution, turn the volume down a little bit.
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I've tested Toroidy TTG-KT88PP (4K Ohm 80 Watt P-P ) and TTG EL34PP (6.6K Ohm 50/60 Watt P-P ) OTs for low freq. performance using a Variac source (across the 8 Ohm sec), current probe and scope. The TTG-KT88PP shows significant current spiking at 46.6V and loud buzzing at 55V 60 Hz.
47V at 60 Hz would work out to 80 Watts at 32.3 Hz.
The TTG-EL34PP shows the same significant current spiking at 37V ( 8 Ohm 60 Hz ) and loud buzzing at 44V.
37V would work out to 28 Hz at 50 Watts, or 30.5 Hz at 60 Watts. (the datasheet calls it 50 Watt but the actual OT has 60 W marked on it )
I tested an Edcor CXPP60-MS-4.2K OT also, to compare with. It shows the same level of current spiking at 53V 60 HZ ( on the 8 Ohm sec ), which would be 60 Watt at 24.8 Hz.
I plan to buy a Toroidy TTG-CFB4000PP ( 80 Watt 4000 Ohm CFB P-P OT ) soon, so I will test that too. These three Toroidy OT's all have the same core size, so you can compute the relative turns used on them from the primary inductance data. TTG-KT88 says 427H, TTG-EL34PP says 591H, and TTG-CFB4000P says 580H. The 1st two do check out with the measurements, so that would work out to 54.77 V at 60 Hz for similar current spiking on the CFB model. So 27.7 Hz at 80 Watt.
This all goes to show than one should get maybe a 20% bigger OT (Watts) if you don't want noticeable magnetizing current (spikes) distortion at the low freq. end at full power.
The other higher Zpri CFB models show the same primary inductance, which concerns me, since the secondary would have to have fewer turns to get the higher stated impedance ratios to 8 Ohms. That would mean lower secondary voltage tolerance and Watts than they are spec'd at, at least for a 30 Hz bottom end..
47V at 60 Hz would work out to 80 Watts at 32.3 Hz.
The TTG-EL34PP shows the same significant current spiking at 37V ( 8 Ohm 60 Hz ) and loud buzzing at 44V.
37V would work out to 28 Hz at 50 Watts, or 30.5 Hz at 60 Watts. (the datasheet calls it 50 Watt but the actual OT has 60 W marked on it )
I tested an Edcor CXPP60-MS-4.2K OT also, to compare with. It shows the same level of current spiking at 53V 60 HZ ( on the 8 Ohm sec ), which would be 60 Watt at 24.8 Hz.
I plan to buy a Toroidy TTG-CFB4000PP ( 80 Watt 4000 Ohm CFB P-P OT ) soon, so I will test that too. These three Toroidy OT's all have the same core size, so you can compute the relative turns used on them from the primary inductance data. TTG-KT88 says 427H, TTG-EL34PP says 591H, and TTG-CFB4000P says 580H. The 1st two do check out with the measurements, so that would work out to 54.77 V at 60 Hz for similar current spiking on the CFB model. So 27.7 Hz at 80 Watt.
This all goes to show than one should get maybe a 20% bigger OT (Watts) if you don't want noticeable magnetizing current (spikes) distortion at the low freq. end at full power.
The other higher Zpri CFB models show the same primary inductance, which concerns me, since the secondary would have to have fewer turns to get the higher stated impedance ratios to 8 Ohms. That would mean lower secondary voltage tolerance and Watts than they are spec'd at, at least for a 30 Hz bottom end..
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After I first bought from Gery (what10 -12 years ago?) I was impressed with his transformers. When I later needed another pair he'd stopped. A few years ago I read he was making again and I immediately bought a pair of 7 watt OPT. When Covid hit I put in an order for a pair of 10 Watt 3K/100mA SE UL with a 23% UL tap with the intention to use it for aPP SE L84 (6BQ5). (23% UL is optimum for EL84 / EL34.)
Unfortunately I ended up with the wrong Hammond mains transformer and then stumbled acorss a pair of NOS EL506 which were the first power tubes I ever used and who fitted the mains transformer perfectly.
Ended up designing a SE amplifier with the EL506 after discovering they are the latest iteration of the 7868 / 7591 / 6GM5.
Came across a quad of 7868 with known prvenance locally at a reasosable price so bought those too.
In the intervening time my health deteriorated and it was likely that this would be the last amplifier I would physically be able to build, had some brilliant idea (NOT!) of wanting CFB+ UL + GNFB and the Transcendars could not do it (4,8 & 16 Ohm secondary). Discovered that the ISO (Tango) FC-20S was capable, hummed and ahh'd about it and ordered a pair. The amplifier is up and running and I'm rather happy although the CFB+UL+GNFB did not work as expected: E81CC in SRPP and the 7868 in CFB works better than anything else when the screen is dropped about 20V below the plate. (< 0.15% distortion at 1 Watt measured on a HP 339A).
Have not yet decided what to do with either the EL506 (if I use them then the contacts in the sockets get widened and the 7868 won't fit any longer) or the Transcendars. I've a German PCB for a SE amplifier that can use octal based tubes like the 5881 / EL34 / KTxx but it did not model as nice as my own concoction. Gery's OPT are conservatively rated - his 10 Watt OPT are 1.8Kg whereas the 20W shielded ISO (double C core) is 2.1Kg.
Regarding Hammond: Measuring the DC resistance of the HT windings both cold and heated up for six hours show after calculation an increase of 40C - 42C which is totally acceptable since the Hammonds insulation is rated class A (= 105C)
Deduct 10C for hot spots and 10C for tolerance and you'll get to 85C. 85C - 42C = 43C maximum ambient temperature, hmmm... we do not get that temperature in our home here.
The Hammonds can be noisy - first thing to do is to remove the bell cover and take out that wire that is for earthing the faraday shield - it sits between the bell cover and the laminations and the result is that the bell cover is not sitting flush. Bring to the outside of the bell cover.
Or go one step further: Buy some new bell covers and reroute the mains to the other side and mount the transformer flat on the chassis using some silicon grommets. Don't forget to seperately earth the transformer and you'll need some longer bolts with some nylocks. Cannot hear that Hammond now even in the middle of the night without any noise around.
Unfortunately I ended up with the wrong Hammond mains transformer and then stumbled acorss a pair of NOS EL506 which were the first power tubes I ever used and who fitted the mains transformer perfectly.
Ended up designing a SE amplifier with the EL506 after discovering they are the latest iteration of the 7868 / 7591 / 6GM5.
Came across a quad of 7868 with known prvenance locally at a reasosable price so bought those too.
In the intervening time my health deteriorated and it was likely that this would be the last amplifier I would physically be able to build, had some brilliant idea (NOT!) of wanting CFB+ UL + GNFB and the Transcendars could not do it (4,8 & 16 Ohm secondary). Discovered that the ISO (Tango) FC-20S was capable, hummed and ahh'd about it and ordered a pair. The amplifier is up and running and I'm rather happy although the CFB+UL+GNFB did not work as expected: E81CC in SRPP and the 7868 in CFB works better than anything else when the screen is dropped about 20V below the plate. (< 0.15% distortion at 1 Watt measured on a HP 339A).
Have not yet decided what to do with either the EL506 (if I use them then the contacts in the sockets get widened and the 7868 won't fit any longer) or the Transcendars. I've a German PCB for a SE amplifier that can use octal based tubes like the 5881 / EL34 / KTxx but it did not model as nice as my own concoction. Gery's OPT are conservatively rated - his 10 Watt OPT are 1.8Kg whereas the 20W shielded ISO (double C core) is 2.1Kg.
Regarding Hammond: Measuring the DC resistance of the HT windings both cold and heated up for six hours show after calculation an increase of 40C - 42C which is totally acceptable since the Hammonds insulation is rated class A (= 105C)
Deduct 10C for hot spots and 10C for tolerance and you'll get to 85C. 85C - 42C = 43C maximum ambient temperature, hmmm... we do not get that temperature in our home here.
The Hammonds can be noisy - first thing to do is to remove the bell cover and take out that wire that is for earthing the faraday shield - it sits between the bell cover and the laminations and the result is that the bell cover is not sitting flush. Bring to the outside of the bell cover.
Or go one step further: Buy some new bell covers and reroute the mains to the other side and mount the transformer flat on the chassis using some silicon grommets. Don't forget to seperately earth the transformer and you'll need some longer bolts with some nylocks. Cannot hear that Hammond now even in the middle of the night without any noise around.
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