McCurdy At-305 Preamp schematic?
- Thread starter shuchoco
- Start date
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bananamoon
Member
I have it (with 305A modifications as well), I'm getting back home tomorrow, I'll sent then.
Nicolas
Nicolas
bananamoon
Member
Hello,
here it is. It seems most AT305 got modified to AT305A. So I added the modifications in red (the original output transistors are 2S721, I didn't keep that there). The RPY13 is an opto tube for remote volume control (it would be nice to use it as a compressor but I'm not sure it can be done), it is usualy optional and pretty much impossible to find. I have the data sheet somewhere but I found it on the web... I salvaged a few from a scrap yard and I'm rebuilding them from scratch. Once recapped and replaced faulty transistors (with NOS) they sound similar to my Yamaha PM1000 (more bass but more noise at high gain). A bit slow and muddy.... But then I changed to more recent transistors, changed a few resistors, bypassed the electrolytics and the noise when way down and there is a little more highs. The output is realy hot, you'll probably need a pad after the transformer. I have a few 24 pin connectors if you need any. I looking for some MRI 2001 transformers if ever you have some extras. Have fun!
regards
Nicolas
(sorry if my english gets a little weird I'm mostly francophone...)
here it is. It seems most AT305 got modified to AT305A. So I added the modifications in red (the original output transistors are 2S721, I didn't keep that there). The RPY13 is an opto tube for remote volume control (it would be nice to use it as a compressor but I'm not sure it can be done), it is usualy optional and pretty much impossible to find. I have the data sheet somewhere but I found it on the web... I salvaged a few from a scrap yard and I'm rebuilding them from scratch. Once recapped and replaced faulty transistors (with NOS) they sound similar to my Yamaha PM1000 (more bass but more noise at high gain). A bit slow and muddy.... But then I changed to more recent transistors, changed a few resistors, bypassed the electrolytics and the noise when way down and there is a little more highs. The output is realy hot, you'll probably need a pad after the transformer. I have a few 24 pin connectors if you need any. I looking for some MRI 2001 transformers if ever you have some extras. Have fun!
regards
Nicolas
(sorry if my english gets a little weird I'm mostly francophone...)
bananamoon
Member
The image didn't post.... here is a link to the album... that should work
Nicolas
http://twin-x.com/groupdiy/displayimage.php?pos=-3399
Nicolas
http://twin-x.com/groupdiy/displayimage.php?pos=-3399
Thanks a milion Nicolas!! You RULE!
Sounds like you're not very impressed with the performance you've gotten out of your AT-305. That's a bummer. I had heard such great things about them. One guy told me he thought the AT-305 sounded like the AU-300 only cleaner... then again, he was trying to sell me some modules, so I guess I should have taken his comment with a healthy dose of salt. ;D I'm still excited to rack this thing up and give it a listen.
If i ever run into any MRI 2001 xformers I'll be sure to let you know! Let me know if you are looking for any other McCurdy Schematics. I don't have a big collection, but I'm happy to share whatever I have.
Thanks again!
Brad
Sounds like you're not very impressed with the performance you've gotten out of your AT-305. That's a bummer. I had heard such great things about them. One guy told me he thought the AT-305 sounded like the AU-300 only cleaner... then again, he was trying to sell me some modules, so I guess I should have taken his comment with a healthy dose of salt. ;D I'm still excited to rack this thing up and give it a listen.
If i ever run into any MRI 2001 xformers I'll be sure to let you know! Let me know if you are looking for any other McCurdy Schematics. I don't have a big collection, but I'm happy to share whatever I have.
Thanks again!
Brad
bananamoon
Member
Hi Brad,
the one I "upgraded" opened up and sounds much better but I still haven't tested it properly. There is that low pass filter (C2 and R4) that I haven't tweaked yet. If I'm satisfied with it I plan to make a 8 to 10 channel mixer with the others I have. I believe these came between the AU300 and the AT242. You might want to read the AT242 data/service sheets (if you have them), it explains "how it works" and helped me a lot (I'm a total newbie) since they are similar in some aspects. Let me know how it goes,
Nicolas
the one I "upgraded" opened up and sounds much better but I still haven't tested it properly. There is that low pass filter (C2 and R4) that I haven't tweaked yet. If I'm satisfied with it I plan to make a 8 to 10 channel mixer with the others I have. I believe these came between the AU300 and the AT242. You might want to read the AT242 data/service sheets (if you have them), it explains "how it works" and helped me a lot (I'm a total newbie) since they are similar in some aspects. Let me know how it goes,
Nicolas
EvLoutonian
Well-known member
- Joined
- Jul 8, 2010
- Messages
- 197
Hi guys,
I know this is an old thread, but I've been looking at a few of these AT305 modules (with a PS874 power supply module, in a rack unit) and just wondering how you guys went with your modules, and it'd be great if you could post some audio files of work you've done on them?
Thanks!
Evan.
I know this is an old thread, but I've been looking at a few of these AT305 modules (with a PS874 power supply module, in a rack unit) and just wondering how you guys went with your modules, and it'd be great if you could post some audio files of work you've done on them?
Thanks!
Evan.
