I have cloned the entry Croft Acoustics phono stage with two 12AX7 and a simpel mosfet series regulator. PSU is in seperate box. I was dissapointed with the sound It was very muffled and unclear.
Then I reused the psu, and build the phono stage L2 from AudioNotes preamp kit with a 12AX7/12AU7:
Audio Asylum Thread Printer
Same story It also sounds very muffled, undynamic and unclear. I have not used audiofile grad components, but those in the croft was also standard components.
I see that It is very high impedance circuits, the first tube have to drive the RIAA filter and also the grid of the next tube through many hundreds of Kohm is´nt that a problem?
Tubes are new EH types. 12V heater supply is simple with LM7812 regulator.
Riaa curve of the Croft clone was meassured by a friend with a setup for that. It was not very precise but quite ok I belive.
I have tried to drive It with step transformer and an active stepup with same result.
I have been through the circuits severel times and belive it is build correctly.
I would like to have som input from more experinced builders?
Then I reused the psu, and build the phono stage L2 from AudioNotes preamp kit with a 12AX7/12AU7:
Audio Asylum Thread Printer
Same story It also sounds very muffled, undynamic and unclear. I have not used audiofile grad components, but those in the croft was also standard components.
I see that It is very high impedance circuits, the first tube have to drive the RIAA filter and also the grid of the next tube through many hundreds of Kohm is´nt that a problem?
Tubes are new EH types. 12V heater supply is simple with LM7812 regulator.
Riaa curve of the Croft clone was meassured by a friend with a setup for that. It was not very precise but quite ok I belive.
I have tried to drive It with step transformer and an active stepup with same result.
I have been through the circuits severel times and belive it is build correctly.
I would like to have som input from more experinced builders?
I skipped using 12axx tubes in phono and went straight for frame grid type tubes. E88cc and/or 5842. And a sneaky mosfet on the input.
I just don’t think a 12ax7 is a good audio tube.
5687 in linestage.
Basically built Allen Wrights SVP, but used KandK audio shunt regs and CCS in one.
I also used One of Allen’s philosophy’s. “If some is good more is better“ I use 4 shunt regs. (I think my pre uses as much power as a medium sized power amp)
Can easily drive a denon dl103r MC cart.
Note I use shunt regs, but based on Allen’s advice, never tried a series reg. So I cannot comment on them.
I am considering experimenting with ec86 and ec88. Ec8010, d3a and that 6S45p
I just don’t think a 12ax7 is a good audio tube.
5687 in linestage.
Basically built Allen Wrights SVP, but used KandK audio shunt regs and CCS in one.
I also used One of Allen’s philosophy’s. “If some is good more is better“ I use 4 shunt regs. (I think my pre uses as much power as a medium sized power amp)
Can easily drive a denon dl103r MC cart.
Note I use shunt regs, but based on Allen’s advice, never tried a series reg. So I cannot comment on them.
I am considering experimenting with ec86 and ec88. Ec8010, d3a and that 6S45p
Which line stage youh ave connected to the phono?
The L2 has a anode output with a high impedance Z
Walter
The L2 has a anode output with a high impedance Z
Walter
Which cable do you use to connect RIAA and your integrated amplifier? Could be that the capacitance in the cable with the high output impedance of the RIAA stage attenuates high frequencies. BTW 12AX7 is an excellent audio tube if you know how to use it, (hint, the high miller capacitance and the high output impedance has to be considered and taken care of)
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