Hi all-
I recently thought I'd give vinyl a try, so I just bought a Dual 1214 TT off of eBay and now need a phono preamp. I will be running this through my newer Onkyo receiver, which does not have phono inputs (only has CD and tape). From what I understand, the output from the TT will be too weak to work effectively... so I am in need of a preamp.
I could just use an opamp based circuit, but I'd really rather not, because my receiver doesn't have any opamps in the signal path (that I know of), and I'd rather not put any in there. I have a few 12xx7 tubes laying around, as well as two 6GM8's. Is there anything useful I can come up with using any of these? I would prefer it be as simple as possible, and not use very high voltage (I don't have any high-V transformers laying around unused... but I could use two transformers and get up to about 300V if I had to...). The TT will be here in a week, probably, so hopefully I could have the preamp done by then as well. Thanks all!
I recently thought I'd give vinyl a try, so I just bought a Dual 1214 TT off of eBay and now need a phono preamp. I will be running this through my newer Onkyo receiver, which does not have phono inputs (only has CD and tape). From what I understand, the output from the TT will be too weak to work effectively... so I am in need of a preamp.
I could just use an opamp based circuit, but I'd really rather not, because my receiver doesn't have any opamps in the signal path (that I know of), and I'd rather not put any in there. I have a few 12xx7 tubes laying around, as well as two 6GM8's. Is there anything useful I can come up with using any of these? I would prefer it be as simple as possible, and not use very high voltage (I don't have any high-V transformers laying around unused... but I could use two transformers and get up to about 300V if I had to...). The TT will be here in a week, probably, so hopefully I could have the preamp done by then as well. Thanks all!
sreten.
The "classic" RCA circuit is about as simple as it gets. It uses a pair of 12AX7s and passive (no NFB) RIAA EQ. You will have to add a voltage follower to the RIAA circuit, as it can't drive a substantial load, like your receiver's line stage.
You can get an adequate B+ rail from a 120 VAC winding by using a full wave voltage doubler to drive a voltage regulator circuit. SS will have to be used for rectification and regulation as Volts are at a premium. I suggest you use 1 A./600 PIV Cree Silicon Carbide (SiC) Schottky diodes for rectification. The SiC parts have a low forward voltage drop and zero switching noise. Ignoring the unavoidable real world losses, 120 VAC into a doubler yields a 339 V. B+ rail. That seems to be enough to drive a regulator. The 120 VAC winding powering the doubler will have to be rated for a minimum of 4X the DC current draw.
You can get an adequate B+ rail from a 120 VAC winding by using a full wave voltage doubler to drive a voltage regulator circuit. SS will have to be used for rectification and regulation as Volts are at a premium. I suggest you use 1 A./600 PIV Cree Silicon Carbide (SiC) Schottky diodes for rectification. The SiC parts have a low forward voltage drop and zero switching noise. Ignoring the unavoidable real world losses, 120 VAC into a doubler yields a 339 V. B+ rail. That seems to be enough to drive a regulator. The 120 VAC winding powering the doubler will have to be rated for a minimum of 4X the DC current draw.
Here is a modified RCA
This guy has an interesting variation that you might want to look at.
Bob's Phono Amp
This guy has an interesting variation that you might want to look at.
Bob's Phono Amp
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