dx amp 33v psu

[martin766]

hi my name is martin and i live near montreal canada, im used to build tube amplifiers but i found the nice dx amplifier on greg website and decide to build the base one ...on the website it is specified that a power supply of plus -minus 35v would be ideal but will it work the same with 33v psu (less power of course) thank for your answers and sorry for the bad english

[Ian Finch]

If the VA rating of your transformer is adequate - say 300 VA for both channels, you won't notice any difference. Smaller rated transformers will work too but the supply voltage and thus output power will then drop further as the signal drives the output closer to full power. This is not so good for audio either.

[Ian Finch]

Something I overlooked: You did refer to AC voltage from the transformer, I hope. as this is specified at 35V and converts to +/-50V DC rails - not 35 or 33V DC which would amount to much less power, even if the amplifier functions normally.
However, it may still be an acceptable amplifier driving 4 ohm loads, I think.

[martin766]

thanks for your answer , this amplifier specified a +/-35v dc on the rails but my power supply is only 33v+/- dc , (with 25v ac transformer) the amp is this one :Greg's Web Site it was made by a skilled person on this forum i do know he tested it with many voltage but i dont know if i have to modify something from the bias circuit or the offset... will it be out range for adjustement ??

[jaycee]

It should work fine with just a tiny bit less output power.

[martin766]

tanks a lot to you ...i realise suddenly that i have a long way (may be painfull)to go from tube to solid state !!!

[AndrewT]

Obviously you must read all of Greg's site.
But, add PASS, ESP & Decibel Dungeon to your reading list.

[martin766]

i do evereything but it dont work ...

[martin766]

i do all they say on the site , i check all ...maybe three or four times .....i look for shorts on pcb there no shorts ...

[jaycee]

Firstly, are you sure your power supply is a symmetric one ? This is a common mistake made by tube guys who are used to only one very high +B voltage (and heater supply).

Solid state amplifier circuits typically require a symmetric supply - this means there are two voltages, in the case of the DX amp it means 35V above ground, and 35V below ground, often written as +/-35V. This typically requires a transformer with a centre tapped winding, or two identical windings connected to form a centre tap.