Sorry for OT, but it fits in the context of discussing power ratings which may apply to the OP situation..
What would you use for 71A/45 at (0.5/2W) 20/35mA?. The H507S and XE(FC)-20S iron is expensive to end up with somewhat compromised 5k?.
I see these:
PRODUCT PAGE
and refer to:
Noguchi Finemet: FM-3WS-H + FM-6WS output transformers
What would you use for 71A/45 at (0.5/2W) 20/35mA?. The H507S and XE(FC)-20S iron is expensive to end up with somewhat compromised 5k?.
I see these:
PRODUCT PAGE
and refer to:
Noguchi Finemet: FM-3WS-H + FM-6WS output transformers
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FM-3WS
"Pri. Inductance ... 15H(5k) DC18mA"
It's 5k .... at 53Hz.
See my #7 post.
It's not -large- problem if you drive it with appropriate tube, which has enough low (lower than 1k) output impedance.
Also has secondary impedance on the higher side (too thin wire), so loss is higher than usual.
"Pri. Inductance ... 15H(5k) DC18mA"
It's 5k .... at 53Hz.
See my #7 post.
It's not -large- problem if you drive it with appropriate tube, which has enough low (lower than 1k) output impedance.
Also has secondary impedance on the higher side (too thin wire), so loss is higher than usual.
Thanks, amp is for >150Hz so LF is not so important and loading is still sufficient for low distortion and to avoid LF phase issues. Parafeed is option and small cap required is appealing.
I understand about inductance for LF vs winding capacitance which limit HF, and oversized air gap affect on inductance etc. But, there is a quite some overlap where full range is possible with both oversized or smaller traffo, trying to get an idea as to which is least compromised approach .. better oversized to begin with, ie 8W build for 2W amplifier, or much closer to what is actually required?.
Thanks.
I understand about inductance for LF vs winding capacitance which limit HF, and oversized air gap affect on inductance etc. But, there is a quite some overlap where full range is possible with both oversized or smaller traffo, trying to get an idea as to which is least compromised approach .. better oversized to begin with, ie 8W build for 2W amplifier, or much closer to what is actually required?.
Thanks.
Parallel feed is very convenient since you can use the parallel feed cap to keep the loading on the tube nice and high and roll off the low end for your specific application. This is far more preferable to just getting a junky transformer that is 5K at 1kHz and 1K at 20Hz.
Parallel feed either requires a very High Voltage Current Source,
Or
A Very good Choke. Inductance, Saturation at low frequencies, distributed capacitance are still factors to deal with.
But there are many who have very successfully done one, or the other, or both.
Do not loose heart.
Or
A Very good Choke. Inductance, Saturation at low frequencies, distributed capacitance are still factors to deal with.
But there are many who have very successfully done one, or the other, or both.
Do not loose heart.
A couple days ago, I posted some speculations about the frequency response of Hammond 125xSE single-ended output transformers (post #16). 6A3sUMMER pointed out that magnetic saturation was an additional issue; this post is a belated response.
I looked for a way to estimate saturation limitations of a Hammond 125xSE output transformers depending on the primary impedance selected. I concluded that if the transformer handles its full rated power at 100Hz and 10kOhms, it will equally well handle half the rated power at 50Hz and 5kOhms, and a quarter of the rated power at 25Hz and 2.5kOhms.
The reasoning assumes that their rated power represents the saturation limit at the rated low frequency limit. Saturation is a function of voltage rather than power, so the worst case is at the highest impedance. If it handles full rated power at 100Hz wired as a 10kOhm transformer, it will actually handle twice as much at 5kOhms, and four times as much at 2.5kOhms, all at 100Hz.
However, power varies as the square of the frequency, so at 5K you can get half the rated power at 50Hz, and at 2.5K you can get a quarter of the rated power at 25Hz.
I think this helps explain and validate the successful use of these transformers in some Hi-Fi applications specifically SETs operating at 2.5kOhms.
I looked for a way to estimate saturation limitations of a Hammond 125xSE output transformers depending on the primary impedance selected. I concluded that if the transformer handles its full rated power at 100Hz and 10kOhms, it will equally well handle half the rated power at 50Hz and 5kOhms, and a quarter of the rated power at 25Hz and 2.5kOhms.
The reasoning assumes that their rated power represents the saturation limit at the rated low frequency limit. Saturation is a function of voltage rather than power, so the worst case is at the highest impedance. If it handles full rated power at 100Hz wired as a 10kOhm transformer, it will actually handle twice as much at 5kOhms, and four times as much at 2.5kOhms, all at 100Hz.
However, power varies as the square of the frequency, so at 5K you can get half the rated power at 50Hz, and at 2.5K you can get a quarter of the rated power at 25Hz.
I think this helps explain and validate the successful use of these transformers in some Hi-Fi applications specifically SETs operating at 2.5kOhms.
Paul,
Thanks!
And good to hear you posting again.
I have often wondered what the performance of a 125xSE would be,
if it is used in a Parallel feed application.
Yes, it may be a waste to have the Air Gap, because there is no DC current in the transformer.
But saturation would be less of an issue.
Still, I am curious about the overall performance of using it that way.
Decades ago I took a push pull transformer, pulled out the E's and I's and stacked them
E's, Air Gap, I's. I then used the OPT as a conventional SE transformer, with the complete primary connected between B+ and Plate.
Now I am curious of Parallel feed using an Air Gap transformer, just the inverse of the above.
Oh, for those of you who do not know, Paul did the consummate Parallel feed studies, and presented them at VSAC in Silverdale Washington all those years ago.
Paul, Thanks to you.
Thanks!
And good to hear you posting again.
I have often wondered what the performance of a 125xSE would be,
if it is used in a Parallel feed application.
Yes, it may be a waste to have the Air Gap, because there is no DC current in the transformer.
But saturation would be less of an issue.
Still, I am curious about the overall performance of using it that way.
Decades ago I took a push pull transformer, pulled out the E's and I's and stacked them
E's, Air Gap, I's. I then used the OPT as a conventional SE transformer, with the complete primary connected between B+ and Plate.
Now I am curious of Parallel feed using an Air Gap transformer, just the inverse of the above.
Oh, for those of you who do not know, Paul did the consummate Parallel feed studies, and presented them at VSAC in Silverdale Washington all those years ago.
Paul, Thanks to you.
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I recall looking at gapped output transformers in parafeed, and concluding it was not worth further exploration. But that was a very long time ago, so naturally I don't remember what my reasoning was. I might come to a different conclusion these days. I'll look through my scattered notes and see if I can find something useful.