I recently purchased a C32 preamp at a reasonable price, but it does have a few issues. Surprisingly, there is not much here in Audiokarma about troubleshooting and rebuilding these units (at least compared to other units). I thank you in advance for the help you can give.
Overall I like the sound very much. Even in original condition, I like the sound a little better than my fully rebuilt MAC 1900. I can’t wait to hear it after it is fully rebuilt. There is definitely a lot more hiss than the 1900 though, but I’ve read that a rebuild will mostly take care of this. Now to the issues:
1. Expander issue. The expander needs to be on for both channels to work. When turned off, only the right channel works. There is no audio in the left channel, only the hiss. I’ve read several posts about the audio connectors between the boards going out and that reflowing the solder takes care of many of these types of issues. I’ll give that a try once I tear into the unit. Let me know if you have any other suggestions.
2. EQ issue. When I first bought it, both channels worked with the EQ on but after about a week the left channel went out. Both channels work if I bypass the EQ though. Same symptoms as the expander issue, no audio in the left channel, only hiss. I suppose it could be an audio channel connection problem but I noticed that the left channel has a different set of OP Amps than the right. The ones on the right look stock and the ones on the left don’t. The Op Amp is sandwiched between a couple of capacitors and I don’t have the right tool to pull it out yet. I’ll order one from Mouser along with the rebuild parts.
There are a couple of posts about rebuilding C33’s C34v’s that suggest swapping out the EQ OP Amps to a low noise NE5534AN, or an NOPA132P. Would these also work for a C32? If not, what would be the proper Op Amp to replace it with?
As far as the rebuild goes, I also have several questions:
1. A couple of posts talk about replacing the harsh sounding tantalum caps used in the phono section. I looked for them but could not find anything that looked like what I’m used to seeing. I found some caps that look a lot like ceramic. Are these actually tantalums?
2. There are some non polar electrolytic caps on the AUX, Tape, and Tuner inputs (C256 – C265). Are those worth replacing with WIMA Film MKS2 caps? Would the difference be noticeable?
3. There is a lot of debate about ½ watt resistors being less noisy than ¼ watt ones. Any suggestions on whether to replace the signal path resistors with ½ watt ones?
4. Luckily my ribbon cables look to be in great shape. Should I expect them to disintegrate if I pull them out of the boards several times during the rebuild? Do most of you replace components while the ribbons are still connected?
Thanks so much reading the post.
Mike
Overall I like the sound very much. Even in original condition, I like the sound a little better than my fully rebuilt MAC 1900. I can’t wait to hear it after it is fully rebuilt. There is definitely a lot more hiss than the 1900 though, but I’ve read that a rebuild will mostly take care of this. Now to the issues:
1. Expander issue. The expander needs to be on for both channels to work. When turned off, only the right channel works. There is no audio in the left channel, only the hiss. I’ve read several posts about the audio connectors between the boards going out and that reflowing the solder takes care of many of these types of issues. I’ll give that a try once I tear into the unit. Let me know if you have any other suggestions.
2. EQ issue. When I first bought it, both channels worked with the EQ on but after about a week the left channel went out. Both channels work if I bypass the EQ though. Same symptoms as the expander issue, no audio in the left channel, only hiss. I suppose it could be an audio channel connection problem but I noticed that the left channel has a different set of OP Amps than the right. The ones on the right look stock and the ones on the left don’t. The Op Amp is sandwiched between a couple of capacitors and I don’t have the right tool to pull it out yet. I’ll order one from Mouser along with the rebuild parts.
There are a couple of posts about rebuilding C33’s C34v’s that suggest swapping out the EQ OP Amps to a low noise NE5534AN, or an NOPA132P. Would these also work for a C32? If not, what would be the proper Op Amp to replace it with?
As far as the rebuild goes, I also have several questions:
1. A couple of posts talk about replacing the harsh sounding tantalum caps used in the phono section. I looked for them but could not find anything that looked like what I’m used to seeing. I found some caps that look a lot like ceramic. Are these actually tantalums?
2. There are some non polar electrolytic caps on the AUX, Tape, and Tuner inputs (C256 – C265). Are those worth replacing with WIMA Film MKS2 caps? Would the difference be noticeable?
3. There is a lot of debate about ½ watt resistors being less noisy than ¼ watt ones. Any suggestions on whether to replace the signal path resistors with ½ watt ones?
4. Luckily my ribbon cables look to be in great shape. Should I expect them to disintegrate if I pull them out of the boards several times during the rebuild? Do most of you replace components while the ribbons are still connected?
Thanks so much reading the post.
Mike