Hey guys,
I also finished my amp
But I have a short question to you. I use a transformer with 2* 25V and instead of
2SD2081/2SB1259 I use 2SD2014/2SB1257. There seems to be too much voltage drop on the darlingtons - I only get +/- 22,7V on the rails.
Bias is at 100mA
Is a mod needed using the 2SD2014/2SB1257?
Thanks in advance!
P.S. It sounds very nice so far!
I also finished my amp
But I have a short question to you. I use a transformer with 2* 25V and instead of
2SD2081/2SB1259 I use 2SD2014/2SB1257. There seems to be too much voltage drop on the darlingtons - I only get +/- 22,7V on the rails.
Bias is at 100mA
Is a mod needed using the 2SD2014/2SB1257?
Thanks in advance!
P.S. It sounds very nice so far!
Last edited:
Audiophonics might get the OPA2604 in a month or so, which is the dual channel, if that is of interest.
https://www.audiophonics.fr/en/opa/burr-brown-opa2604ap-dual-opa-dip8-unit-p-6229.html
https://www.audiophonics.fr/en/opa/burr-brown-opa2604ap-dual-opa-dip8-unit-p-6229.html
Burr Brown / TI has discontinued the 2604. Check their official website, it's no longer listed as a product.
The unconfirmed scuttlebutt was: customers found that when you ran it at absolute max permitted supply voltage and drove absolute max permitted output current, it got warm enough that it failed to meet its input offset voltage spec and its input bias current spec. TI found that the dual-604 had this problem but the single-604 did not. Then TI decided to discontinue the dual product rather than attempt to fix the issue. UNCONFIRMED.
The unconfirmed scuttlebutt was: customers found that when you ran it at absolute max permitted supply voltage and drove absolute max permitted output current, it got warm enough that it failed to meet its input offset voltage spec and its input bias current spec. TI found that the dual-604 had this problem but the single-604 did not. Then TI decided to discontinue the dual product rather than attempt to fix the issue. UNCONFIRMED.
Hello,
A quick update on my progress:
As for the operation, the OFFSET is less than 1mV, and the BIAS is at 330mV. The amplifier sounds wonderful.
Have a great day!
Jérôme
A quick update on my progress:
- Due to a small issue with the toroidy, I changed the voltage to a 2x26V transformer.
- There is a 0.5V offset on the -24V rail, which is strange because there is only a 0.1V offset on the zener. I replaced the zener on the -24V rail, and now it's perfect with only 0.08V offset.
- However, I'm only getting 23.4V on the rail with 35V at the input of the 2SD2014/2SB1257 transistors. Can someone who has 24V on their rails let me know the measurement at this point?
As for the operation, the OFFSET is less than 1mV, and the BIAS is at 330mV. The amplifier sounds wonderful.
Have a great day!
Jérôme