FS:Interesting Cambridge Power Amps

[Puffin]

I modified these amps about 5 months ago having bought the bridge adaptor boards from Everyday Practical Electronics. The article appeared in the October 2010 issue.

The result of adding the bridge adaptor is that the two sides of the power amplifier L&R are added and it doubles the output voltage across the loudspeaker. The resultant power to the loudspeaker is four times the power. There is a divergence of opinion (there was a heated debate on Diyaudio!) as to whether it does give four times the power. However what also happens is that the current delivery is greatly increased. In practice this gives much more grunt than the 65w per channel stereo output gave (6ohms)

One of the points of heated debate on Diyaudio was whether the original heatsinking would be sufficient to cope with the increased power.

I have used these monoblocks with several pairs of speakers of varying sensitivity. They have not really broken sweat and have never got anyhere near what I would consider a risk of damaging the output transistors, at the most they were moderately warm and for the most part lukewarm, and I have had them at some serious headbanging levels on occasion (smiley). I have used these amps everyday for the last 5 months with no problems at all.

I haev now sold the speakers of choice for these amps and so they are up for sale

IMO Cambridge does not always get the credit that it deserves. These amps are well designed, have a good quality toroidal transformer and include the Sanken five leg output transistors (said at the time to be a surprising find in a budget amp).

These amps can be easily returned to normal stereo use by re-inserting the white wire connectors in their original blocks.

I am looking for £60 for each monoblock plus P&P. I also have the matching C500 pre-amp that I need to take some pics of and list separately. This would also be £60 plus P&P

http://i73.photobucket.com/albums/i239/saxonsex/DSCF2031_zpsfa8c4488.jpg

http://i73.photobucket.com/albums/i239/saxonsex/DSCF2030_zps86b9f0a3.jpg

http://i73.photobucket.com/albums/i239/saxonsex/DSCF2029_zps2de03dfe.jpg

http://i73.photobucket.com/albums/i239/saxonsex/DSCF2033_zpsf479b433.jpg

[Haselsh1]

Just out of interest, is this modification the same as flicking a switch on a power amplifier that is so equipped and running both channels out of phase with each other...? I understand that such amplifiers can only drive an eight Ohm load or higher and certainly not anything lower...?

[Puffin]

Just out of interest, is this modification the same as flicking a switch on a power amplifier that is so equipped and running both channels out of phase with each other...? I understand that such amplifiers can only drive an eight Ohm load or higher and certainly not anything lower...?

Yes, NAD amps often have a "bridged" switch which does the same thing, and yes it is suggested that an 8ohm load be used.

[Haselsh1]

Yes, NAD amps often have a "bridged" switch which does the same thing, and yes it is suggested that an 8ohm load be used.

One of the things I know very little about are amplifiers and related electronics so if anyone could explain this out of phase thing to me I would really appreciate it. My present power amp has such a facility but I am not going down that route with 600 Watts per channel. It would be a bit daft I think.

[Puffin]

One of the things I know very little about are amplifiers and related electronics so if anyone could explain this out of phase thing to me I would really appreciate it. My present power amp has such a facility but I am not going down that route with 600 Watts per channel. It would be a bit daft I think.


http://sound.westhost.com/project20.htm