I wonder if Hugh can chime in and comment on the ‘slam and impact’ part with regards to the Darlington in this circuit? I am wondering what technically is happening and if it has to do with changes in transconductance or if it is because it’s a BJT characteristic?
https://www.digikey.com/en/products/detail/sanken-electric-usa-inc/2SD2560/3661819
https://www.semicon.sanken-ele.co.jp/sk_content/2sd2560_ds_en.pdf
I’ll be playing with the power JFET discussed earlier in this thread and can add this BJT Darlington into the comparison mix
Best,
Anand.
https://www.digikey.com/en/products/detail/sanken-electric-usa-inc/2SD2560/3661819
https://www.semicon.sanken-ele.co.jp/sk_content/2sd2560_ds_en.pdf
I’ll be playing with the power JFET discussed earlier in this thread and can add this BJT Darlington into the comparison mix
Best,
Anand.
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Have just done a 'clipping' measurement with a 4 ohm load.
p-t-p voltage at just before clipping is 38v (with +/-21v rails) so - if my calculations are correct - this gives 45w into 4 ohms:
* 38v p-t-p ==> 19v peak
* ==> 13.4v rms
* power = Vrms^2 / load
* which is 180 / 4
* ==> 45w.
This is the same for my other AN4R - which hasn't yet had its Source resistors changed from 0.12R to 0.15R.
Which shows that the bias current doesn't affect the power output - so I guess it only affects:
* how well the amp drives low loads
* and of course ... the heat output into the room!
p-t-p voltage at just before clipping is 38v (with +/-21v rails) so - if my calculations are correct - this gives 45w into 4 ohms:
* 38v p-t-p ==> 19v peak
* ==> 13.4v rms
* power = Vrms^2 / load
* which is 180 / 4
* ==> 45w.
This is the same for my other AN4R - which hasn't yet had its Source resistors changed from 0.12R to 0.15R.
Which shows that the bias current doesn't affect the power output - so I guess it only affects:
* how well the amp drives low loads
* and of course ... the heat output into the room!
Τhanks Andy for your measurements.
The difference of bias has impact to quality of sound? Do you heard any changes?
Haven't listened to them yet, Nikos. (I need to wait until I have changed over R141/142 in my 2nd AN4R, to be able to do a proper listen.)
But I suspect I won't be able to make a valid comparison ... as it's so long since I listened to the amps in their initial state!
But we do know that higher bias current enables the AN circuit to drive lower spkr loads, well. Somewhere in these 154 pages of posts is a report from someone who tried to drive 4 ohm spkrs with his AN8R (1.7a of bias current) ... he said it didn't sound good.
Whereas my AN4R circuit - with 3.2a bias - drives 4 ohm spkrs very well.I have to wait and see whether reducing the bias current to 2.5a (by increasing R141/142 from 0.12ohm to 0.15ohm) has degraded the sound with my 4ohm spkrs.
It has certainly reduced the heat output into the room - down from 500w to 420w, for 4 channels.So I'm hoping I get another couple of months in the year when I am able to run them.