TDA1514 Cambridge A1 power amp mod

[xennmaster]

Hi,

First post here, and I have a question that I'm sure someone can answer....

I've got an old Cambridge A1 mk3 SE amplifier which I use as a backup, though I never really enjoyed it's sound (it seems "grainy" to me, which I'm hoping is down to the preamp)

Anyway, It uses TDA1514 chipamps which are supposed to be decent, so I'm thinking of getting rid of the preamp parts, and sticking the power amp and supply in a smaller box as I have a use for a small power amp, and this would be free

Seems simple enough, and might be fun to further tinker with in the future to see how good you can make a £40 amp!

The question is......the connector to the preamp, carries signals into power amp....but also the +28v -28v power for the preamp....and I'm not sure what the correct thing would be to do with these? Diagram attached that might explain it better than I did

Any suggestions?

Mike

 

[PRR]

I have an unwanted lamp plugged in the wall. I unplug it, and verify that the electrical connections are not exposed, and forget about the issue.

Same here, except depending on the connector you may need ties or tape to ensure the hot terminals can't slap the chassis or other parts.

 

[FauxFrench]

The +/-28V is from a non-regulated power-supply. You can use as much of its current capacity you like or leave it unused.
As PRR says, disconnect the connector to the preamp, wrap some insulating tape around the connector and fix it inside the cabinet. When you turn the amplifier ON afterwards, make sure you still have +/- 28V on the power amplifiers.

 

[xennmaster]

Thanks guys, that's great, just wanted to check it wouldn't do something weird to the power amp.....I'm a tinkerer, but I'm not so good on the theory side of things yet!

 

[Mark Whitney]

You could test it before you start dismantling the amp. Disconnect CN11 and apply input signals via a potentiometer to R19 and R28. Save you a lot of time if, in the end, you are disappointed with the result.

 

[JMFahey]

What connectors will you use in your new repackaged amplifier?
How will you connect to power amp boards?

Since you are not using the preamp at all, in principle I would cut wires reaching the connector, safely tape +/-28V wire ends, tie them somewhere so they are not left dangling, and connect channel inputs and grounds to input connectors, hope they are long enough.

You might want to add a stereo volume pot (50 or 100 k Log/audio would be fine) between input connectors (RCA?) and power amp.