Patrick, is an Agilent 34401A good enough? Eventually even 4 wire probe.
Not calibrated every year anyway.
As you were kind enough to offer your nice design to the forum, can you briefly descibe the power supply you are using? A custom 650 VA xfrm (12+12V I guess) and then?
Thank you!
Not calibrated every year anyway.
As you were kind enough to offer your nice design to the forum, can you briefly descibe the power supply you are using? A custom 650 VA xfrm (12+12V I guess) and then?
Thank you!
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@ ashaw
amplifier's active electronic doesn't know how you made that symmetrical PSU ;
and probably doesn't care
so - 36Vct or 2x18V - irrelevant , energy wise
2x18V is better - noise and hum wise
amplifier's active electronic doesn't know how you made that symmetrical PSU ;
and probably doesn't care
so - 36Vct or 2x18V - irrelevant , energy wise
2x18V is better - noise and hum wise
I am referring to the fact that his circuit requires a 16V supply where all FW amps use about a 24V supply
too much dissipation
you need greater bias through halves than original F5 , because each half see just half of load
so - you must decrease PSU voltage because of excessive dissipation
anyway - it's doable , but with doubling outputs and enormous heatsinks
Ashaw,
This amp will produce about 64w class A into 8ohms
4A*4A*8ohms=128W peak which is 64w average.
Is that not enough for you?
(It can also continue untill 72w into class Ab)
This amp will produce about 64w class A into 8ohms
4A*4A*8ohms=128W peak which is 64w average.
Is that not enough for you?
(It can also continue untill 72w into class Ab)
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Does the power supply have enough voltage to swing 4A into 8 ohms? Correct me if I'm wrong, but I think you would need 20VDC rectified to get 64W into 8ohms.
I'm in. I keep building amps, and buying into various group buys, collecting parts, organizing them, first one with everything gets built, more boards and parts get bought. Rouns and round it goes......thank goodness! Thanks to all for making this possible!
Russellc
Russellc
Nice power increase! Does this increase gain, or does that remain at 15 db? (Of course I mean with the standard feedback resistors)
Russellc
I suppose i just need a new transformer...
also can you propose a balanced preamp that would suit a balanced f5, I mean one with supersymmetry, wide bandwidth and no caps?
also can you propose a balanced preamp that would suit a balanced f5, I mean one with supersymmetry, wide bandwidth and no caps?
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I'm building a DCB1 buffer (2) boards to feed my balanced F5's. I don't think its super-symmetric, but it's simple and cap free along the signal path. There is a group buy in the works that ends on Sunday.
It's time for me to go to sleep:
Swing will be 24v each way, that is 36w/8ohms class A .
My mistake...
Though Half load is seen
4A*4A*4ohms= 64w peak= 32w average ,if biased 2 amps
Hope it's correct.
Good night guys.
Swing will be 24v each way, that is 36w/8ohms class A .
My mistake...
Though Half load is seen
4A*4A*4ohms= 64w peak= 32w average ,if biased 2 amps
Hope it's correct.
Good night guys.
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Meaurement of a Vishay Dale CPF3 0.47 Ohm resistor, with Fluke meter
Here are the results of 10 readings taken of a single resistor
0.467, 0.467, 0.467, 0.466, 0.466, 0.465, 0.466, 0.465, 0.466, 0.465
Average 0.466
Standard Deviation 0.000816
It’s not better than 0.1% but it’s not bad either.
I would be interested to see how it compares to your method.
If you can elaborate I will do it just to satisfy my curiosity.
Here are the results of 10 readings taken of a single resistor
0.467, 0.467, 0.467, 0.466, 0.466, 0.465, 0.466, 0.465, 0.466, 0.465
Average 0.466
Standard Deviation 0.000816
It’s not better than 0.1% but it’s not bad either.
I would be interested to see how it compares to your method.
If you can elaborate I will do it just to satisfy my curiosity.
thanh,
Zen Mod & I are simply trying to tell you a professional way of measuring small value resistors reliably.
If you think your method is good enough for you, that's fine with me. There is no challenge, as there is no price for me to win.
If you want to compare the 2 methods, send me a email and I tell you how. You are welcome to publish the results. It is just much more reliable by principle and less subjected to errors. Check out what a 4-lead resistor does, like those from Isabellehuette, e.g.
As to power supply, as said I design for 6 ohm. Dissipation per FET max 32V. That gives 16Vx2A bias per FET. Max output to load is theoretically 32V (rail to rail for balance circuits), 4A (2x bias), or 64W 8ohm (sine). But I (and Nelson) normally leave 4V Vds minimum to avoid excessive nonlinear behaviours of the FETs, which reduce to 24V 4A, or 48W 6ohm (sine).
4 FETs 32W makes 128W. Factor of 3 for toroidal means 384VA min. I said I use 650VA, because it fits the housing. You can use 400VA or 500VA as you like. No real issue, but also not much price difference.
You can change voltage / current according to your own needs (at your own risk). Just make sure you don't cook the FETs.
Am still looking for EU-based volunteer to organise GB for source resistors. If all fails then thanh gets the job, and I only do the buying. Only helping me with matching and distributing (one anonymous offer) is still too much burden for me. But thank you very much for the offer anyway, JB.
Patrick
Zen Mod & I are simply trying to tell you a professional way of measuring small value resistors reliably.
If you think your method is good enough for you, that's fine with me. There is no challenge, as there is no price for me to win.
If you want to compare the 2 methods, send me a email and I tell you how. You are welcome to publish the results. It is just much more reliable by principle and less subjected to errors. Check out what a 4-lead resistor does, like those from Isabellehuette, e.g.
As to power supply, as said I design for 6 ohm. Dissipation per FET max 32V. That gives 16Vx2A bias per FET. Max output to load is theoretically 32V (rail to rail for balance circuits), 4A (2x bias), or 64W 8ohm (sine). But I (and Nelson) normally leave 4V Vds minimum to avoid excessive nonlinear behaviours of the FETs, which reduce to 24V 4A, or 48W 6ohm (sine).
4 FETs 32W makes 128W. Factor of 3 for toroidal means 384VA min. I said I use 650VA, because it fits the housing. You can use 400VA or 500VA as you like. No real issue, but also not much price difference.
You can change voltage / current according to your own needs (at your own risk). Just make sure you don't cook the FETs.
Am still looking for EU-based volunteer to organise GB for source resistors. If all fails then thanh gets the job, and I only do the buying. Only helping me with matching and distributing (one anonymous offer) is still too much burden for me. But thank you very much for the offer anyway, JB.
Patrick
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I got interested to see how good these Dale CPF3 resistors are.
I increased the temperature to 60 degrees (RT=20 degress) and I got immeasurable temperature change. That is if there was any change it was below the resolution of the meter (<1 mOhm)
So TCR is better than (or less than) (1x1000000)/(466x40) = 53.6ppm
This is much better than the manufacturers spec sheet.
I will do these measurement again with better instrumentation and at higher temperatures to get more accurate results.
I increased the temperature to 60 degrees (RT=20 degress) and I got immeasurable temperature change. That is if there was any change it was below the resolution of the meter (<1 mOhm)
So TCR is better than (or less than) (1x1000000)/(466x40) = 53.6ppm
This is much better than the manufacturers spec sheet.
I will do these measurement again with better instrumentation and at higher temperatures to get more accurate results.
😱
Mpc74 are +/- 10% resistors.
A huge batch and a lot of work will be needed to match them at 1/1000.
Mpc74 are +/- 10% resistors.
A huge batch and a lot of work will be needed to match them at 1/1000.
I have found the manufacturers specs are very conservative.
If they say 10% tolerance then usually something like 90% of the batch is better than 2%
If they say 10% tolerance then usually something like 90% of the batch is better than 2%
I have 4 each of 2sk1530 and 2sj201 that are not matched, is it really that important to match or could I use these?
Matching is compulsary for a balanced amp.
Or it is not balanced.
Rather to build a regular F5 with them.
Or it is not balanced.
Rather to build a regular F5 with them.
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