A few notes on re-capping and modifying an A-720....
First of all, attached is a spreadsheet with a list of the electrolyic caps for an A-720, along with a few notes. They are bunched by function, and should be complete, but if I missed anything please feel free to update it.
I've made a few modest mods to the amp which I would like to share with anyone who's interested.
First off, I replaced the op-amps in the phono section. The original op-amps are 8-pin SIP's. To adapt the new DIPs I bought some Brown Dog adapters. Due to my ignorance of what good subs would be, I relied as usual upon the kindness of strangers and came up with these:
M5218 (or NJM4558): replaced by an NJM4580DD. See this thread for a discussion -- http://www.audiokarma.org/forums/showthread.php?p=6563913
M5219L: replaced with an LME49860 - Decision was based on this thread: http://www.audiokarma.org/forums/archive/index.php/t-330811.html
I wish I had some way to measure the before and after, but I don't, so the post-mod evaluation is totally subjective. I like to use a pair of decent Grado headphones for first-pass listening, this I think keeps comparisons on somewhat of a level playing field. So, after the op-amp update, my report is: yes, records did (subjectively) sound better ;-) I tested with both MM and MC cartridges.
The second mod was shortening the audio path by excising out the run to the adapter jacks -- about 24" of wire is removed. I have a couple photos showing the before and after, highlighting the areas to look for. It's a simple matter to desolder the connector pins and tie wrap the wires out of the way, and just as simple to put them back into place if desired.
I wasn't expecting much, if any difference, but to my surprise taking the accessory jack wire run out of the audio path made a (subjective) difference in improvement, too. Not night and day, but it was there. Or at least I thought so.
Any improvement quickly establishes itself as the new threshold, so the perceived difference is washed out fairly quickly, but I am overall very pleased with the A-720. The cost of both op-amps is just a shade over $4, so the investment is modest, and as hobbyist, it's a fun little thing to do. If anyone else tries these out, or has other recommended tweaks or advice, I'd be interested in hearing about it.
First of all, attached is a spreadsheet with a list of the electrolyic caps for an A-720, along with a few notes. They are bunched by function, and should be complete, but if I missed anything please feel free to update it.
I've made a few modest mods to the amp which I would like to share with anyone who's interested.
First off, I replaced the op-amps in the phono section. The original op-amps are 8-pin SIP's. To adapt the new DIPs I bought some Brown Dog adapters. Due to my ignorance of what good subs would be, I relied as usual upon the kindness of strangers and came up with these:
M5218 (or NJM4558): replaced by an NJM4580DD. See this thread for a discussion -- http://www.audiokarma.org/forums/showthread.php?p=6563913
M5219L: replaced with an LME49860 - Decision was based on this thread: http://www.audiokarma.org/forums/archive/index.php/t-330811.html
I wish I had some way to measure the before and after, but I don't, so the post-mod evaluation is totally subjective. I like to use a pair of decent Grado headphones for first-pass listening, this I think keeps comparisons on somewhat of a level playing field. So, after the op-amp update, my report is: yes, records did (subjectively) sound better ;-) I tested with both MM and MC cartridges.
The second mod was shortening the audio path by excising out the run to the adapter jacks -- about 24" of wire is removed. I have a couple photos showing the before and after, highlighting the areas to look for. It's a simple matter to desolder the connector pins and tie wrap the wires out of the way, and just as simple to put them back into place if desired.
I wasn't expecting much, if any difference, but to my surprise taking the accessory jack wire run out of the audio path made a (subjective) difference in improvement, too. Not night and day, but it was there. Or at least I thought so.
Any improvement quickly establishes itself as the new threshold, so the perceived difference is washed out fairly quickly, but I am overall very pleased with the A-720. The cost of both op-amps is just a shade over $4, so the investment is modest, and as hobbyist, it's a fun little thing to do. If anyone else tries these out, or has other recommended tweaks or advice, I'd be interested in hearing about it.