One of the builders uses step up transformers for MC. I heard it, sounds pretty good.
No doubt, but I hope you aren't trying to limit me to just one phono pre-amp!
Of course not, I thought you wanted to use this one for MC.
Not now, sorry. I hope to get more time for production and distribution in future.
some thoughts
Having worked with similar circuits - derived from the Cello Palette preamplifier - and used in both low and high-gain applications;
1. Add an OPA633 to the "buffer list".
2. the 627 can oscillate under certain conditions. C3 may be necessary - start with 100pf and work up or down.
3. Since the output offset of the 627 can be trimmed, the servo might be unnecessary. Some folks don't like servos.
Charles
Having worked with similar circuits - derived from the Cello Palette preamplifier - and used in both low and high-gain applications;
1. Add an OPA633 to the "buffer list".
2. the 627 can oscillate under certain conditions. C3 may be necessary - start with 100pf and work up or down.
3. Since the output offset of the 627 can be trimmed, the servo might be unnecessary. Some folks don't like servos.
Charles
This has dragged on quite a while now. The case work took longer than I expected, partly because I ordered a chassis that is too small to fit everything. I had to offset the boards vertically so they could overlap horizontally.
I mounted the raw DC supply in a separate chassis:
The Salas shunt regulators powered up nicely:
External view:
This weekend I will double-check for output offset, and hopefully start to listen!
I mounted the raw DC supply in a separate chassis:
The Salas shunt regulators powered up nicely:
External view:
This weekend I will double-check for output offset, and hopefully start to listen!
Superb!
So today I powered it up again and checked the offset on the outputs. I measured 0.0 mV on both channels, so I guess that servo works OK!
Until now my old Thorens TD160 with Signet TK-7e cart was hooked up to the phono section of my old Arcam Delta-290 integrated amp, which in turn was connected to my DCB1 preamp. I replaced the Arcam with the OpenAmp1 today. Cranked up the volume on the DCB1, heard no hum or noise. Next I put on "Tales of a Courtesan" by the Toshiko Akiyoshi – Lew Tabackin Big Band. Fantastic! I think the OpenAmp1 has a little more gain and less noise (not that the Arcam was noisy). I don't generally spend a lot of time comparing amplifiers, and the Arcam sounded great, but I found dynamics were excellent, low frequencies a little better. Trombones and saxes had a nice "raw" sound. The only drawback is that my phono stage and preamp are both DC coupled, so the phono system is a little more sensitive to footfalls (I think I need to tune the suspension of the Thorens a little better). I can see the woofers of my Pluto 2's dancing if I walk near the TT! I think the Arcam had a subsonic roll-off.
Anyway, thanks Pavel, it sounds great, and now I am DIY from phono input to speakers (and even the Thorens has some mods).
So today I powered it up again and checked the offset on the outputs. I measured 0.0 mV on both channels, so I guess that servo works OK!
Until now my old Thorens TD160 with Signet TK-7e cart was hooked up to the phono section of my old Arcam Delta-290 integrated amp, which in turn was connected to my DCB1 preamp. I replaced the Arcam with the OpenAmp1 today. Cranked up the volume on the DCB1, heard no hum or noise. Next I put on "Tales of a Courtesan" by the Toshiko Akiyoshi – Lew Tabackin Big Band. Fantastic! I think the OpenAmp1 has a little more gain and less noise (not that the Arcam was noisy). I don't generally spend a lot of time comparing amplifiers, and the Arcam sounded great, but I found dynamics were excellent, low frequencies a little better. Trombones and saxes had a nice "raw" sound. The only drawback is that my phono stage and preamp are both DC coupled, so the phono system is a little more sensitive to footfalls (I think I need to tune the suspension of the Thorens a little better). I can see the woofers of my Pluto 2's dancing if I walk near the TT! I think the Arcam had a subsonic roll-off.
Anyway, thanks Pavel, it sounds great, and now I am DIY from phono input to speakers (and even the Thorens has some mods).
I assume this should be solvable. I have Technics SL-1200MkII, and it is perfectly resistant against steps or mechanical impacts. My system is all DC coupled as well. Maybe to place some shock absorbing pad under the turntable?
Everyone who is interested in PCBs please send me an e-mail. I will announce when the boards are produced (expected date is August 20). I have a PP account, so I can send PP requests when to boards are finished. I do not plan to open web shop etc., as this is a one-time action and the time I can spend with audio is limited.