Nice looking work, well done.
Are those Wima MKS capacitors on the in and out?
Anything polypropylene and good quality should be well an upgrade.
Another option would be to switch the OPamps to the LME49720. It has some fancy skullduggery inside that is beyond my comprehension but prevents any DC, meaning you can omit the coupling caps all together. As the saying goes, the best capacitor is no capacitor.
I have done this in the post above yours and it works great and sounds fantastic.
Are those Wima MKS capacitors on the in and out?
Anything polypropylene and good quality should be well an upgrade.
Another option would be to switch the OPamps to the LME49720. It has some fancy skullduggery inside that is beyond my comprehension but prevents any DC, meaning you can omit the coupling caps all together. As the saying goes, the best capacitor is no capacitor.
I have done this in the post above yours and it works great and sounds fantastic.
Thanks Sadface for your quick reply and suggestion. The caps I used on the inputs and outputs are Vishay Metalized Polyester film, 1uF, 63V, 5%. As I understand it, they take a while to break in. I’ll check out the LME49720. Thanks!
The LM4562 is the dual version of the LME49720, BTW - it got dual numbered for silly reasons.
Huh? Its just an opamp. A high spec one.
Hello,
I finished hicoco's p88 pcb finally and unfortunately i don't have any dip switches to use at the moment.
Can anyone tell me which switch positions should i bridge for 14.5dB gain?
thanks,
I finished hicoco's p88 pcb finally and unfortunately i don't have any dip switches to use at the moment.
Can anyone tell me which switch positions should i bridge for 14.5dB gain?
thanks,
Thanks Hicoco.
If I increase r7ar and r7al to 4.3k should i use any dip switch? or simply omit them?
If I increase r7ar and r7al to 4.3k should i use any dip switch? or simply omit them?
Thanks.
But I'm confused! Which ones should i wire for 14.5db gain?
Unfortunately i couldn't understand this dip switch chart printed on pcb.
But I'm confused! Which ones should i wire for 14.5db gain?
Unfortunately i couldn't understand this dip switch chart printed on pcb.
Yes, unfortunately there is a mistake printed PCB.
the left chart is for DIP1 & DIP2 and the right chart DIP3 & DIP4. If you keep the DIP switches with R7AR and R7AL 4k3, 1OFF &2ON you will have 14.5db
the left chart is for DIP1 & DIP2 and the right chart DIP3 & DIP4. If you keep the DIP switches with R7AR and R7AL 4k3, 1OFF &2ON you will have 14.5db
Any opamp recommendations for this preamp?
So far I tried AD712, NJM4565, NJM4580, NE5532, LM833. Bipolar opamps sounds somewhat dull, AD712 little bit more open but not perfect.
Btw, I didn't replaced R7AR and R7AL to 4.3K. Both of them 2.2K. I don't know how much gain I have with this resistors.. All dip switches are set to 1off & 2on.
So far I tried AD712, NJM4565, NJM4580, NE5532, LM833. Bipolar opamps sounds somewhat dull, AD712 little bit more open but not perfect.
Btw, I didn't replaced R7AR and R7AL to 4.3K. Both of them 2.2K. I don't know how much gain I have with this resistors.. All dip switches are set to 1off & 2on.
Just a quick update on my ESP88 equipped Conrad Johnson PF-R. Shortly after the June 2023 posting, I switched the IC's in the P88 to LME49720's and was pleased with the results. However, I recently replaced the output 49720 with a Burnson V5i hybrid, and I think it's an improvement in clarity, separation and placement of instruments in the sound stage. I considered going with one of the Burnson V7 models, but since they operate in a class A mode, get very hot, and the PF-R chassis has not ventilated, I elected to stay put. I think the preamp sounds great for the hack that it is! As an aside, I use this preamp to check out power amp projects, most recent of which is my my old Hafler DH-220 which I upgraded to the "C" version by Cordell/Savas. I will post something on this upgrade in a separate thread.