I recently acquired a pair of old Ampex 620 amps. 6AX5 Rect, 2x6V6, 12AU7 PI and a 5789 preamp tube. I've recapped the amp, new tubes, etc. The input level is very low as they are line level inputs. Is there a reasonably simple mod or anything I can do to get more volume out of this amp? I'd like to use these for a stereo pair in the studio. If anyone could give me some specific directions or suggestions, it would be much appreciated. I'm not finding much on the internet about these.
http://recordist.com/ampex/schematics/620man/620-2.pdf
Thanks
http://recordist.com/ampex/schematics/620man/620-2.pdf
Thanks
moved to correct forum....
A friend of mine was given two of these units and he only took them with the intention to use for guitar. I took a look at them for him but unfortunately both units had fried power supply capacitors, output transformers and power tubes. He had no money and didn't want to put any money into them. The drivers were fine they were just not hooked up. I cringed when he told me that when he first got the units he tried for a while to play his guitar and ipod through them but he was plugging into the 1/4" extension speaker jack for the input. I can't be sure that he damaged the units but I told him it was a bad idea to have tried to turn them on and even worse to try to play music through them without a speaker connected as a load.......remember we grew up with solid state gear where no load is fine.
He told me I could keep one if I fixed the other up for him and I had so much other stuff going on I declined......I think I offered to buy both of them because I would want to use them in stereo so one was useless to me (remember he only wanted one for use with guitar). I told him to hold on to them and when he gets some efficient speakers and some dough to fix them up he should use them as a stereo.
They were cool looking
now that I think about it I wish I took him up on his offer and kept one to fix the other. I have since lost touch with him and hope he hasn't ditched them or left them somewhere.
He told me I could keep one if I fixed the other up for him and I had so much other stuff going on I declined......I think I offered to buy both of them because I would want to use them in stereo so one was useless to me (remember he only wanted one for use with guitar). I told him to hold on to them and when he gets some efficient speakers and some dough to fix them up he should use them as a stereo.
They were cool looking
now that I think about it I wish I took him up on his offer and kept one to fix the other. I have since lost touch with him and hope he hasn't ditched them or left them somewhere.
I did..
My 620 had been painted black, and most of the resistors and caps were missing, so I didn't ruin anything a collector would want.
But I just read your original post, and it wasn't a simple mod (removed everything and rebuilt from scratch), and you mentioned a stereo pair.. This amp is only a guitar amp now. Doesn't have the frequency response for everything else.. And it been designed (if you can call it that) to distort.
It's still a work in progress, but I'll post a schematic soon, when it's mostly finalized.
(I posted one in another thread a few days ago, but it's changed a lot since then)
The problem now is... The original chassis is no good for a guitar amp.. at least not mine. It's not closed on all sides. And doesn't have room for knobs and switches.
So yeah, you can build a guitar amp w/ those tubes and transformers, but it wouldn't have much to do w/ the ampex620.
My 620 had been painted black, and most of the resistors and caps were missing, so I didn't ruin anything a collector would want.
But I just read your original post, and it wasn't a simple mod (removed everything and rebuilt from scratch), and you mentioned a stereo pair.. This amp is only a guitar amp now. Doesn't have the frequency response for everything else.. And it been designed (if you can call it that) to distort.
It's still a work in progress, but I'll post a schematic soon, when it's mostly finalized.
(I posted one in another thread a few days ago, but it's changed a lot since then)
The problem now is... The original chassis is no good for a guitar amp.. at least not mine. It's not closed on all sides. And doesn't have room for knobs and switches.
So yeah, you can build a guitar amp w/ those tubes and transformers, but it wouldn't have much to do w/ the ampex620.
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