Hi guys,
After completing rod elliot's bass guitar preamp, and with the satisfaction of the crispiness of its output, i tought its time to make another project from one of his designs.
So i started building his project88 preamp. It uses OPA2134 opamp. But instead of using OPA2134 i used TL072,
After finishing the board, i tested it and it sounds good. Experimented with/tried NE5532,JRC4558.
Well the output is quite acceptable.
But i made some mods, i designed an adaptor board for the opamp, instead of using a dual opamp TL072, i used 2 single opamp OPA627 for one chanel.
So i need to make 2 adaptor boards for stereo. And used 4 OPA627s.
The outcome is very good, esp the hi and lows.
I checked each chanel with the balance control and its working well.
But when i removed the rca jack of the left channel. I noticed that there is still an output on both channel eventhough with mono input. I reinserted the left rca jack and removed the right channel rca,
There, the problem started.
No output on both channels when the left rca jack is inserted. And the right channel rca is unplugged.
Its like it is feeding the amp with stereo signal but with mono input in the preamp's input rca.
Help guys!!
Thank you in advance.

 

Can you link to the schematic? Better yet, show the exact schematic of your project.

 

Hello,

ESP has moved. Here is the link to project 88:
http://sound.whsites.net/project88.htm

Bertus

 

Oh thank you sir bertus.

 

There you go sir. Single channel only.
Input stage, balance and second stage.