I agree about the S-240's. I have a pair from Magnequest that were built with M3 cores and I think they sound really nice across the board. I'm waiting/hoping to get a pair of 6.6k outputs from O-netics some time this year. He's backed up with orders right now so not sure when.
If you are referring to the Lundahl LL1663, that's not going to happen!
$500 CAD for 2 OTs.....nah....
But thanks for the thoughts!
Out of my price bracket, I think.....$290 USD for a pair plus shipping plus taxes.
But thanks for the info.
Since it's the high-frequencies that are usually 'lost' first in hearing loss, I would have thought that 'more tweeters!!; turn up that treble control!!' would be the demand from us oldsters!
I think all audio 'gurus' should be required to post a recent hearing test by a registered audiologist before making pronouncements...start with the 'reviewers' for the audiophile magazines.....
It's not always just sine frequencies. Transients can have high frequency content above 20kHz and we still hear them as clean crisp transients even though our sine wave sensitivities have diminished. I think there have been tests that show that humans can distinguish higher frequencies than 20kHz when they are part of the leading edge of transients.
Good luck with your project,
John
Good luck with your project,
John
I use a 300 VA output transformer on a 10 W PP amplifier. My arguments:
- I could use thicker wire, the resistive loss is lower, output impedance is lower (This is a no feedback design)
- No risk of saturation and magnetic nonlinearity
- I suppose the stray magnetic field is also less
- I suppose it is more linear at the bottom end of the B-H curve
- I suppose the hysteresis loop has also less area
- I could use thicker wire, the resistive loss is lower, output impedance is lower (This is a no feedback design)
- No risk of saturation and magnetic nonlinearity
- I suppose the stray magnetic field is also less
- I suppose it is more linear at the bottom end of the B-H curve
- I suppose the hysteresis loop has also less area
I'm 68 and I've just spent about that building a type 26 DHT pre. And added supertweeters! I CAN hear the difference!That idea - 300B, Lundahl iron, etc. is in the 'way too expensive' category for me.
It will be 'a frosty day in hell' when I spend $2000 CAD on parts for an amp
Thanks for the suggestion, though.
OT specifications
Hi there all.
With this discussion on OT power rating vs fidelity and response, how important is it to match the p-p impedance to the tubes?
I am starting to build a revised Williamson design, but using 2 x 2, 807s in the driver stage, which'll give me 5kOhm p-p impedance.
But I am having problems finding a 5kOhm p-p OT, in the 50Watt range.
I have found a 60Watt OT, but its a 6kOhm p-p?
Hi there all.
With this discussion on OT power rating vs fidelity and response, how important is it to match the p-p impedance to the tubes?
I am starting to build a revised Williamson design, but using 2 x 2, 807s in the driver stage, which'll give me 5kOhm p-p impedance.
But I am having problems finding a 5kOhm p-p OT, in the 50Watt range.
I have found a 60Watt OT, but its a 6kOhm p-p?
He was talking nonsense. (lots of people selling books do).
The size of OPT is usually related to simple physical questions such as winding wire gauge and the turns ratio needed to get linear response over a wide range of frequencies.
It's also very largely related to OPV quiescent current.
If you use a QUAD (PPP) the QC is relatively high, and the magnetisation characteristics correspondingly different.
There's no point in reinventing the wheel, small powers, high or low gain OPVs (?) (2 x 6V6/EL84), low QC = small cores. Look what some of the best did in the 50s-60s.
7591? One of the best, because it has high gain and higher current capability.
Look at what Scott did with it.
Says it all really.
Larger powers, higher QC, linear frequency reponse without saturation and with linear waveform reponse at 20-40hz needs a larger core.
The highest energy is concentrated in the 30-80hz range, fine if you want to make it less linear and introduce a filter on the bass, use an undersized OPT.
If you want stuff to work properly at LF without compromises use a larger core.
So long as not TOO large it won't scale badly at 10-18khz.
Did you know you can successfully use 70V/100V/140V line distribution transformers as OPT?
Dirt cheap usually and often outperforming lots of the silly price stuff you see on the market today.
Just saying.
Depends if you are doing AB1 or AB2.
807s are improved 6L6 designed for high voltages, hence a bit silly to use them as strapped triodes, cos it defeats the whole point of them unless you use 5bxx5M loctal variants which have no top cap and are tiny.
(I think they are truly wonderful at 500-600V like that).
My AB2 amps run 3K A-A load at 600V. This is the right way to do it.
AB1 6L6 will be fine at 6k6, if you go PPP, you can halve this, so easy use a 4K5-5K OPT.
There's loads of suitable OPT out there, eg, Transcendar which are not so expensive and SUPERB.
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A comment about hearing high frequencies that are higher than your ear's ability (top frequency ability to hear sine waves):
1. If you look at some early and middle year production CD players, you will find some tests that show intermodulation.
One test is 19kHz and 20kHz. If you listen to this test instead of measuring it, you may hear the 1kHz 2nd order Intermodulation product (20kHz - 19 kHz = 1kHz)
Also, there are other tests show high frequency tests of sine waves that beats with the 44.1 sampling rate. The resulting 2nd order intermodulation frequency is in the audio range of sine waves that you can hear.
That is because, those high frequency tones, which are beyond the CD's correct upper range, are exceeding the Nyquist frequency (i.e. a tone of 44.1kHz/2 = 22.05kHz is at Nyquist frequency).
A tone higher than 22.05 kHz will beat down (2nd order intermodulation) into the audio range which is in your ear's ability to hear sine waves.
2. It is not only the CD player that can have that problem, it is your pre amp and your power amp (they have frequency ranges that exceed your ear's ability to hear sine waves).
The preamp and power amp have 2nd order intermodulation distortion too. And those extremely high frequencies can beat down (intermodulate) into the audible sine wave frequency range of your ear.
3. Your tweeter may have frequencies sent to it that are above your ear's sine wave frequency abilities. But tweeters also have 2nd order intermodulation. Those high frequencies can intermodulate right into your audible frequency range.
4. There may be other reasons that cause you to hear high frequencies that are above your ear's maximum sine wave frequency range.
The question is: are you hearing the frequencies that are above 20kHz, or are you hearing the intermodulation beat tones that are in your ear's sine wave frequency range.
That will take a little more research and testing than this thread will solve.
1. If you look at some early and middle year production CD players, you will find some tests that show intermodulation.
One test is 19kHz and 20kHz. If you listen to this test instead of measuring it, you may hear the 1kHz 2nd order Intermodulation product (20kHz - 19 kHz = 1kHz)
Also, there are other tests show high frequency tests of sine waves that beats with the 44.1 sampling rate. The resulting 2nd order intermodulation frequency is in the audio range of sine waves that you can hear.
That is because, those high frequency tones, which are beyond the CD's correct upper range, are exceeding the Nyquist frequency (i.e. a tone of 44.1kHz/2 = 22.05kHz is at Nyquist frequency).
A tone higher than 22.05 kHz will beat down (2nd order intermodulation) into the audio range which is in your ear's ability to hear sine waves.
2. It is not only the CD player that can have that problem, it is your pre amp and your power amp (they have frequency ranges that exceed your ear's ability to hear sine waves).
The preamp and power amp have 2nd order intermodulation distortion too. And those extremely high frequencies can beat down (intermodulate) into the audible sine wave frequency range of your ear.
3. Your tweeter may have frequencies sent to it that are above your ear's sine wave frequency abilities. But tweeters also have 2nd order intermodulation. Those high frequencies can intermodulate right into your audible frequency range.
4. There may be other reasons that cause you to hear high frequencies that are above your ear's maximum sine wave frequency range.
The question is: are you hearing the frequencies that are above 20kHz, or are you hearing the intermodulation beat tones that are in your ear's sine wave frequency range.
That will take a little more research and testing than this thread will solve.
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