WD88VA schematic

[pre65]

Originally Posted by diceman

All info received.
Thank you all for your help.

One thing of note is that the mains transformer heater winding is detailed as being 7A and hence the KT120 requirement for upto 1.95A per tube or pretty much 8A for all 4 is higher than the transformer is rated for.

Quite so dear boy.

[bob orbell]

Yes, I think that the transformer is running very close to it's max, after 6 hours of it being on, the transformer is very hot. BOB

[diceman]

I have noticed the transformer gets very hot, I wasn't sure if it was as I push the amp quite hard driving Apogees (which it has seen off many higher powered valve amps in control and volume). A little extra however wouldn't go amiss :-)

I have already started having a look to see about alternative mains transformer and none of the Sowter standard products provide high enough heater current for 4 off KT120!

[bob orbell]

It's nothing to do with what it is driving, this amp. draws the same current with 0 input or max input, it is biased in class A, so the valves are switched on all the time. BOB

[pre65]

Is the WD88 wholly class A, or AB ?

[diceman]

Oh Ok. Driving apogees at loud levels made the LEDs on the front dim to the bass line and hence I had assumed that power was being diverted elsewhere for the bass. (to me that indicated that it wasn't totally class A)

I am still learning so please be gentle with me!

I need to read up more on class A and the impacts of PSU design. I kind of assuem that ESR of PSU capacitors isn't that important if they are operating at full load all the time?

[colin.hepburn]

Originally Posted by diceman

Oh Ok. Driving apogees at loud levels made the LEDs on the front dim to the bass line and hence I had assumed that power was being diverted elsewhere for the bass. (to me that indicated that it wasn't totally class A)

I think you are most likely over driving you amp having the amp up loud it’s not going to give off its best in sound quality the loud volume is clipping your amp
Run it at a volume level that fills the room with an enough level to comfortable; fit the room size and save your ears and enjoy the sound quality the amp was designed for and the amp should run cooler

[diceman]

Fair comment, I do normally listen at sensible or even quiet volumes at home.

The above detailed incident occurred once when I was demonstrating at a friends that a 35w valve amp could drive apogees to more than sensible volumes - which he previously thought was not possible.

[colin.hepburn]

Originally Posted by diceman

Fair comment, I do normally listen at sensible or even quiet volumes at home.

The above detailed incident occurred once when I was demonstrating at a friends that a 35w valve amp could drive apogees to more than sensible volumes - which he previously thought was not possible.

AHA OK
You gave me the impression you drive the amp loud that amp should drive most speaker in a normal sized room without any problem
So many of the younger beginners in Hi FI seem to get quality sound mixed up with bags of volume even me in my younger day mind you I did run big disco systems back then ah memories