Well, I was sick and tired of trying to find a phono preamp so I could listen to my vinyl, so I decided to give the very simple phono stage a try. I have to say I'm impressed with the results.
I decided to build it into my cheapie Rotel with AT133LP cartridge. It was built on Rat Shack protoboard with no "special" parts. The power supply is external. I took a few liberties on the supply. It has a 28VCT@1.1A transformer, 6A bridge pack, 6800uF per rail. On the preamp board I have a 22 ohm series resistor, 220uF, 12V regulator, and another 220uF per rail.
I used a single OPA2134 IC, and a 1K gain resistor.
My first impressions are that it's very good. Better than anything I've had before (built in to other receivers). The midrange is very liquid, with very good depth. The upper mid is too layed back, but I think it's my cartridge, because I've noticed that with everything I've played it through. The bass is EXCELLENT... very tight, resolved, punchy... it's just great. The upper treble is good. A little edgy at times, but I don't have a good setup on the cartridge right now. I had the tonearm all apart for rewiring. It had a connector on it, and one channel would occasionally cut out. I ohmed it out, and found one contact that wasn't making as well as the others, so I took it downstairs on the drill press and punched a hole through it and soldered wires directly to the cartridge! Sick of dealing with that nonsense. I went against good advice and rewired the tonearm with 26 ga silver plated OF copper wire, and then soldered pieces of the good wire left over from the old wiring onto the ends so it could pivot freely. Seems to be working very well so far.
Listed to "the lonesome jubilee" by Mellencamp, and it sounded very musical... especially the bass. I've been on a Yes kick lately, and have listened to the "fragile" cd all week. I put the vinyl on for comparison, and it really wasn't comparable. The vinyl sounded so much more musical! I was hearing details jumping out that I had missed in the cd. On some soft vocal / piano music, it had good clarity and focus, and soundstage depth was very good.
I really didn't expect much from an IC, but I am pretty happy overall with this. After I get the cartridge tweaked back in, I'll give a report back as to how it sounds.
Thanks, RJM, for the excellent project. I'm liking what I'm hearing!
Steve
I decided to build it into my cheapie Rotel with AT133LP cartridge. It was built on Rat Shack protoboard with no "special" parts. The power supply is external. I took a few liberties on the supply. It has a 28VCT@1.1A transformer, 6A bridge pack, 6800uF per rail. On the preamp board I have a 22 ohm series resistor, 220uF, 12V regulator, and another 220uF per rail.
I used a single OPA2134 IC, and a 1K gain resistor.
My first impressions are that it's very good. Better than anything I've had before (built in to other receivers). The midrange is very liquid, with very good depth. The upper mid is too layed back, but I think it's my cartridge, because I've noticed that with everything I've played it through. The bass is EXCELLENT... very tight, resolved, punchy... it's just great. The upper treble is good. A little edgy at times, but I don't have a good setup on the cartridge right now. I had the tonearm all apart for rewiring. It had a connector on it, and one channel would occasionally cut out. I ohmed it out, and found one contact that wasn't making as well as the others, so I took it downstairs on the drill press and punched a hole through it and soldered wires directly to the cartridge! Sick of dealing with that nonsense. I went against good advice and rewired the tonearm with 26 ga silver plated OF copper wire, and then soldered pieces of the good wire left over from the old wiring onto the ends so it could pivot freely. Seems to be working very well so far.
Listed to "the lonesome jubilee" by Mellencamp, and it sounded very musical... especially the bass. I've been on a Yes kick lately, and have listened to the "fragile" cd all week. I put the vinyl on for comparison, and it really wasn't comparable. The vinyl sounded so much more musical! I was hearing details jumping out that I had missed in the cd. On some soft vocal / piano music, it had good clarity and focus, and soundstage depth was very good.
I really didn't expect much from an IC, but I am pretty happy overall with this. After I get the cartridge tweaked back in, I'll give a report back as to how it sounds.
Thanks, RJM, for the excellent project. I'm liking what I'm hearing!
Steve
nobody special said:
I know what you mean.
Mine sounded a little edgy in upper high region to.
But over time it sounded much much better.
For me it was a run in problem.
After a week or two/three the upper treble sounded much better.
Sharpness was gone.
I use blackgate 4,7 non polar output caps by the way.
So...............
Maybe yours needs to run.
Greetings and enjoy.
Erwin
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