DSJR
07-05-2010, 16:58
My penny-pinching quest continues....
I put the Croft preamp back into service this week and once again it's working its magic up to a point...
I use three amps with a 25K input impedance with the Croft, two in bridged-mono form for the speakers driven from the preamp outputs. The third is used as a headphone amp and this is a problem when driven from the record-outs on the Croft, which use one resistor in series to "load" the output...
The problem is this, the phono stage in the Croft seems to have a high ouput impedance (the reason why my preamp has 500K pots fitted) and if all three amps are connected, the bass all but disappears on the phono input - something I've commented on before. remove the "headphone" amp from the tape outs and all the bass comes back on vinyl and the Croft "magic" is restored in abundance. The line sources are simply routed straight through to the record outs with no buffering other than the resistor in series.
Musical Fidelity X10-D units now sell for their brand new price of £120 nigh on12 years ago :( and the V3 tends to go for nearly £200 as it's been discontinued. Is there anything else out there cheaper, or do any of you have such a thing, home made or not, that you'd sell for less than a ton?
The idea of this buffer is that its input impedance is around half a meg (500K) and the output impedance low enough for a 10K - 25K amp load. If I asked anyone to custom-make one, I suspect the price would be through the roof and I just can't do this at the moment.
Cab anyone help? I've asked an Ebay seller who tried to sell an X10D (it dodn't reach reserve) if he's going to re-list it, but haven't yet had a reply..
[edit] P.S. Glenn has kindly offered to modify the phono stage output to enable more available pots to be used and this may all but cure the problem, although I'd still like an active (valve/FET?) style buffer in circuit if possible.
I put the Croft preamp back into service this week and once again it's working its magic up to a point...
I use three amps with a 25K input impedance with the Croft, two in bridged-mono form for the speakers driven from the preamp outputs. The third is used as a headphone amp and this is a problem when driven from the record-outs on the Croft, which use one resistor in series to "load" the output...
The problem is this, the phono stage in the Croft seems to have a high ouput impedance (the reason why my preamp has 500K pots fitted) and if all three amps are connected, the bass all but disappears on the phono input - something I've commented on before. remove the "headphone" amp from the tape outs and all the bass comes back on vinyl and the Croft "magic" is restored in abundance. The line sources are simply routed straight through to the record outs with no buffering other than the resistor in series.
Musical Fidelity X10-D units now sell for their brand new price of £120 nigh on12 years ago :( and the V3 tends to go for nearly £200 as it's been discontinued. Is there anything else out there cheaper, or do any of you have such a thing, home made or not, that you'd sell for less than a ton?
The idea of this buffer is that its input impedance is around half a meg (500K) and the output impedance low enough for a 10K - 25K amp load. If I asked anyone to custom-make one, I suspect the price would be through the roof and I just can't do this at the moment.
Cab anyone help? I've asked an Ebay seller who tried to sell an X10D (it dodn't reach reserve) if he's going to re-list it, but haven't yet had a reply..
[edit] P.S. Glenn has kindly offered to modify the phono stage output to enable more available pots to be used and this may all but cure the problem, although I'd still like an active (valve/FET?) style buffer in circuit if possible.