"Balanced power amp" option for Amps

[richards13]

I would like the option to order either the KEL84 or 88 as a low senitivity power amp with fully balanced operation through to the output stage.
No one has a kit of this spec on the market and the WAD Pre would be ideal match for it.

[david beard]

mmmm can I check both boxes? I certainly like my WD88VAXL as it is, in fact I love it, I would however like to have the option of a balanced input although to be honest I'd like to see this on the integrated as well as the power amp versions.

(Peter - here's an opportunity to get a bit of upgrade kit business from existing users if there's a reasonably easy way you could do a "balanced input upgrade kit" - I would suggest something able to convert one of the integrated's inputs to balanced or of course the single input of the power version - maybe worth a thought?)

Cheers
Dave

[tomtidswell]

PeterCom has already indicated recently on one post, that a valve based monoblock amp with balanced inputs (to go with the pre3 XL version) will be out early this year.

Can't wait.

Tomtidswell

Originally Posted by richards13

I would like the option to order either the KEL84 or 88 as a low senitivity power amp with fully balanced operation through to the output stage.
No one has a kit of this spec on the market and the WAD Pre would be ideal match for it.

I second that - fully balanced to the output stage (not just balanced inputs).

Also I'm led to believe Unison Research are going down the balanced route in some new pre and power amps.

[Shian7]

I get the feeling there's 'something on the cards' here!

[richards13]

Hi
I have no longer such a requirement, as I haved botched my KEL84 and i am quite happy with the result.
In case anyone is intrested:
Remove ECF80's and remove restistors from power line to them.
Replace 2.2k resistor on powerline with 1k, which was the ecf80 feed, connect this to string of 5W zeners to give 270V screen grid supply and connect amp in pentode mode.
replace first 100uF cap with 12uF motor start cap to drop 330 to 297volts on el84 anodes.
Feed balanced input straigh to grid reistors on el84's from dbx driverack pa.
dbx driverack can supply +20DBu, 7.7 volts which is not far from the 10V the cathodes on el84's are running at.
EL84's have a common 100ohm resistor into a 50ohm ww pot to balance dc on output valve pairs, with bypass capacitor.
The amp runs with no feedback, a trace of hum through Lowther DX2's, el84's which are matched on gain.
Its nice to be lucky, once in a while.
Naim Nap150x now sold, I had prefered it to the orginal KEL84 on the Lowthers.
The DBX Driverack filters all signal below 150Hz to sub-woofer, avoiding bodged KEL-84 and Lowthers. So I have no idea if this amplifier is any good in the bass, now the gobal feedback has gone.
Future maybe's, ecl-82 regulated grid supply and set-up input transformers.

Regards

Richard