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 3rd October 2019, 06:25 PM #41 syrbinche   diyAudio Member   Join Date: Jun 2018 Great circuit! I have just tested it and it's really good! Very very loud, so i have to lower that otherwise gonna burn my headphones I took 10ohm resistor in the R4 position and have like 90mA thru 2xBD139 I have +/-24V power in my setup and i wonder if this could be modified for 48V? Does it make sense to do that?
 3rd October 2019, 07:25 PM #42 Osvaldo de Banfield   diyAudio Member     Join Date: Dec 2011 Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina What warranty that both hemicycles receive equal amplifying factor (or gain)? The input transistor has a gain of about 10 (1200Ω collector/120Ω emitter). The upper final transistor is a follower, so gain ≈1. The lower final transistor ??? __________________ Osvaldo F. Zappacosta. Electronic Engineer UTN FRA from 2001. Argentine Ham Radio LW1DSE since 1987.
 3rd October 2019, 07:47 PM #43 Mark Johnson   diyAudio Member     Join Date: May 2011 Location: Silicon Valley Sounds like a question that motivated hobbyists might attack very quickly using circuit simulation software.
 3rd October 2019, 08:07 PM #44 Osvaldo de Banfield   diyAudio Member     Join Date: Dec 2011 Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina Yeah, but over any simulation, is good to know what one is doing, because if not, you can't understand what the simulation is saying to you. This is like an example, a professor told us in the university. Suppose you have a tester (VOM) that is malfuctioning. Suppose also that with this VOM you read 50V, for example, in the 220V power line. Do you touch the wires under those conditions? __________________ Osvaldo F. Zappacosta. Electronic Engineer UTN FRA from 2001. Argentine Ham Radio LW1DSE since 1987.
 3rd October 2019, 08:36 PM #45 Mark Johnson   diyAudio Member     Join Date: May 2011 Location: Silicon Valley Fantastic! Good luck and best wishes.
 12th November 2019, 03:40 PM #46 gasboss775   diyAudio Member     Join Date: Feb 2015 Location: Stirling, Central Scotland, UK In LT spice I tried replacing the 1K2 resistor with a current source using a jfet and resistor. The THD was reduced to around 0.09% ( mostly 2nd order ) image.png __________________ offense is the collateral damage of free speech - Ricky Gervais
 21st November 2019, 05:36 PM #47 gasboss775   diyAudio Member     Join Date: Feb 2015 Location: Stirling, Central Scotland, UK I have built the original circuit using both TIP41 and 2SC3852A transistors and would say it definitely sounds better with the TIP41s. __________________ offense is the collateral damage of free speech - Ricky Gervais
 21st November 2019, 10:53 PM #48 avtech23   Certifiably addicted to DIY. diyAudio Member     Join Date: Dec 2017 Location: South 'straya Have you tried it with the jfet current source to compare with the original design? __________________ The ever growing project list.. :NAP140 Clone, NAD 3020i & 3225PE, JLH1969, TDA2050, Fender 5F2A Princeton, NE5532 Pre, SHPA, B1 Korg, T2. : VSQC Phunk Style, Retro 50W, Filmosound 601, LM4780. : Apex AX-14, TGM-10, TDA7265 (Last in line)...maybe
gasboss775
diyAudio Member

Join Date: Feb 2015
Location: Stirling, Central Scotland, UK
Quote:
 Originally Posted by avtech23 Have you tried it with the jfet current source to compare with the original design?
Yes, but not thoroughly tested. First impression was there was greater clarity at the high end.
The open loop gain was much higher as expected.

Note these comments pertain to using TIP41s as the output transistors, with the 2sc3852a's it sounded bad! Very muddy and distorted.

I used a J112 and a 180 ohm as the current source the current was around 10.5mA. I will probably try again with other jfets.
__________________
offense is the collateral damage of free speech - Ricky Gervais

Mark Tillotson
diyAudio Member

Join Date: May 2018
Location: Cambridge UK
Quote:
 Originally Posted by Osvaldo de Banfield What warranty that both hemicycles receive equal amplifying factor (or gain)? The input transistor has a gain of about 10 (1200Ω collector/120Ω emitter). The upper final transistor is a follower, so gain ≈1. The lower final transistor ???
The 2SC3852 is extremely high current gain (guaranteed > 500), so there's a lot of feedback available. The circuit is dominated by feedback, and that transistor enables it to perform very well. The gain is stabilized by the feedback (masking imperfections of the output stage).

Give it a more linear output stage it will perform even better I suspect. The lower transistor is the obvious low-hanging fruit.

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