Cambridge 651p phonostage
- Thread starter paskinn
- Start date
John Channing
fruit box forever
WIMA capacitors are the other change I have seen mentioned. I have a 651p, works nicely for the price.
Arkless Electronics
Trade: Amp design and repairs.
Well Paskinn I guess that answers your previous PM about whether my mods are also applicable to the 651P 
It would seem that yes that will be no problem.... with the caveat that having not yet had my hands on a 651P there may of course be E.G some change in layout that makes the mods more difficult.... but hopefully that will not be the case... or at least it may only need to be slightly different in application rather than more expensive or difficult.
The modded amp will be in many ways more Arkless Electronics than Cambridge Audio.. The whole first stage is bypassed and replaced, the RIAA network is re-calculated and rebuilt using much better capacitors (which it is looking like I'm going to have to have specially made! ). The gain is much increased and the loading can be changed for any cartridge by means of loading plugs which will go in the now redundant MM input sockets.
They will be supplied as either MM or MC as specified by the customer, but can be converted from one to the other merely by cutting two wire links on the board (to go from MC to MM, or solder the ends of the links back together to go the other way). They will be supplied with standard loading for a MM cartridge when used without the loading plugs, but with a fairly light capacitive load to allow for further loading for "odd" MM cartridges. The loading plugs will allow any combination of capacitance and resistance for whatever MC is used, but a set of plugs for a fairly universal load will be supplied as standard.
There will be only one electrolytic capacitor in the signal path, as opposed to three in the original, and the cartridge will now be directly coupled to the amp.
Further mods can be applied as asked for... such as bypassing the output relay and subsonic filter switches... (a change from something I had originally intended is that, as standard, the subsonic filter will still be usable... parties!?... I HIGHLY recommend, and cannot state this strongly enough, that it is not engaged though), the fitting of better capacitors as the only remaining cap in the signal path, and much better second stage op amps... these will be at extra cost of course...
Look out for the reviews of the two PFM members that are having theirs done first for some feedback on all this.... should be very soon now
Cheers,
Jez.
It would seem that yes that will be no problem.... with the caveat that having not yet had my hands on a 651P there may of course be E.G some change in layout that makes the mods more difficult.... but hopefully that will not be the case... or at least it may only need to be slightly different in application rather than more expensive or difficult.
The modded amp will be in many ways more Arkless Electronics than Cambridge Audio.. The whole first stage is bypassed and replaced, the RIAA network is re-calculated and rebuilt using much better capacitors (which it is looking like I'm going to have to have specially made!
). The gain is much increased and the loading can be changed for any cartridge by means of loading plugs which will go in the now redundant MM input sockets.They will be supplied as either MM or MC as specified by the customer, but can be converted from one to the other merely by cutting two wire links on the board (to go from MC to MM, or solder the ends of the links back together to go the other way). They will be supplied with standard loading for a MM cartridge when used without the loading plugs, but with a fairly light capacitive load to allow for further loading for "odd" MM cartridges. The loading plugs will allow any combination of capacitance and resistance for whatever MC is used, but a set of plugs for a fairly universal load will be supplied as standard.
There will be only one electrolytic capacitor in the signal path, as opposed to three in the original, and the cartridge will now be directly coupled to the amp.
Further mods can be applied as asked for... such as bypassing the output relay and subsonic filter switches... (a change from something I had originally intended is that, as standard, the subsonic filter will still be usable... parties!?... I HIGHLY recommend, and cannot state this strongly enough, that it is not engaged though), the fitting of better capacitors as the only remaining cap in the signal path, and much better second stage op amps... these will be at extra cost of course...
Look out for the reviews of the two PFM members that are having theirs done first for some feedback on all this.... should be very soon now
Cheers,
Jez.