audio-talk

Sounds good apart from the CCS idea. Why do you want to use a CCS ? Normally not a good idea, only application I've seen for that is JC Morrison using a CCS and a high-value load resistor in parallel to achieve insane amounts of gain in a phono stage . The anode resistor sets the gain in a pentode s...

Ah, moving target !
In pentode mode, no bypass cap, 35ma, but screen shunt current ( OA2 ~15ma) going through the cathode , you should get about 20 gain ; with cathode by-pass cap, about 30 gain .

Hang on a sec.. what's going on here
You just posted about 6V6 .... and I'm replying to that ; but your post disappeared
Help !

Interesting....yes... Maybe a bit lower on current, 30ma, and G2 at 150V . I know the data isn't on the sheets, but Thorsten reckoned as a driver ( pentode ) you should typically keep the G2 at or below the lowest swing of the anode from it's nominal position. Plenty of headroom on dissipation. I as...

Thanks for the info on HT Phil . I'd still favour either a beefy pentode , or an Aikido, myself. In each case you can get plenty of gain with only one coupling cap, and no low-end time-constants ( eg. from chokes or cathode by-pass caps ) of any significance, in the driver. Pentode could be EL86 or ...

I'm not sure how you'd use this one, but I'm sure Paul , Nick or James could comment better . It seems to be aimed at Class B usage, and the data sheet shows quite low current for Class A operating points . I'm concerned about grid current on the input for the higher current class B type operating p...

Mike H wrote:Sure sign the weather has turned much cooler as of today, have to keep dashing to the toilet every half hour

That's a good way to keep warm !

Dunno, depends what it is
Maybe I can work towards a better answer -
(i) Is 35 enough gain for your system ?
(ii) What is the B+ going to be for the GK-71 , and are you flexible about the supply voltage for the driver ?

I see Thomas Mayer has taken up my idea of using well nuts for mounting valve sockets :

http://vinylsavor.blogspot.co.uk/2013/0 ... r-mk3.html

( See third picture down )

For both Aikido noise cancellation and for Aikido distortion reduction to work the top and bottom sections need to match - the closer the match the better the Aikido works... J Ok, well I've learnt something here. How much of a match ? - Are we saying if the centre-point potential is off by 10%, sa...

Yeh, but an Aikido's not like push-pull, so how closely do you need them to match ?

Is it the bit below the blue thing ?

I will use the ones I already have, then, if they are not available till Owston .
I might get some of those better ( C0G ? ) caps and see if I can bodge them into place.

No, I shall be using Andrew's Mk.2 prototype boards , when they arrive

I think I'll try and build one channel of a horn-amp for Owston - common driver ( 4P1L ) , two output valves , probably 6B4G's, using the two types of Bud Purvine outputs. I will then try to construct a frame that will hold the AH425/Azura above one of the wooden bass/mid horns . Best check soon if ...