I specifically avoided any solid state in the amp because it was supposed to be 'pure' (tube) but, yes, you could use a CCS for cathode bias. It's not needed, though, with 'real' OPTs (like the Edcors).

Even with the SPECO the intent was to avoid solid state and for idle 'current balance' I used a modified (adjustable) garter bias like this



Cross connecting the bias makes it close to self adjusting, if one tube conducts more the other is adjusted, with the pot being for fine trim. It's implemented as a side chain of resistors so a small (low power) trim pot could be used and I successfully used that mechanism on Top Cat.

For the 6HB6 amp I'd probably modify the circuit a bit because I was concerned with raising cathode voltage on Top Cat (due to not much B+ headroom). Technically a garter should double it (equal resistors on each side of the bias chain) and I edged it toward the low side for that reason. But the 6HB6 is already about half cathode bias so a normal garter would bring it back to almost the same bias as a 6BQ5.

I think a new thread would be a good idea.

Is that the same as the 10-8K Peter? It shows a 10 8-8K. Just want to get the right one this time.

Here it is. Please go and bring it up to date.
Thanks Flip.
viewtopic.php?f=12&t=307525

New thread for the Princely Pauper amp. Go here.
viewtopic.php?f=12&t=307525

I've posted there.

Twin CCSs only causes the idle current to be equal so that they cancel in the OPT windings. It does not 'match' the tubes.
It is self bias, period. No similarity to fixed bias.

Actually, in some way it's 'worse' than a plain ole bypassed resistor in that when driven to the 'B' portion (of Class AB) cathode voltage rises faster due to the stubborn attempt of the CCS to keep current constant.

Whew! Finally back in the states! When I have power in my workshop in a couple of weeks I'll FINALLY be able to fire this guy up and get some double sided goodness going!

Welcome back. Was wondering what happed to the project.
... good news.
will wait with bated breath....

So close on the workshop(work shipped me off for a week)! It's insulated, AC installed, wiring almost done, just needs walls and benches.

But I did order some 5902 tubes to have here to play with and measure for solder spacing.

A guy on ebay is selling bags of these 5902s NOS for ~$58 for close to 100 tubes. I got a bag of 35 and have a lifetime supply. Part of me wants to order more but that's just the hoarder within.

That sounds great Kyle!
BUT.... what's the status of the 6AQ5 pc board?
Have you applied power yet?

I've been holding my breath waiting to see how it came out?
Does it work?


BTW... I just ordered a bag of 75 of those 5902wa tubes too.
He priced them at $35.
But I got 'em for my $30 offer.

GREAT deal.

That receiver is in the attic until the shop is done but it will be the first thing on my electrical bench so I can listen to music while building the vacuum lab and glassworking station!

That or rip my hair out at fried parts.....

Hi Kyle:
Are we talking about the same thing here?

I didn't know anything about a "receiver".

I thought you were building the 6AQ5 amp as a stand alone amp to be fed from any audio source like an Mp3 player.
This amp:

Yup, same board. I 3d printed brackets and was able to mount it into an old Nikko receiver I've got. I though I posted that but maybe not.

Anyways, it should be powered up for the first time soon. I want to have it done by the end of the month.

I am waiting to see how it turns out w/great anticipation.
Several of us are interested in buying some boards.

I too just bought 75 5902 tubes from that same vendor for $30...
So if you have a way to accept those pin arrangements... in your next board run.. I'd like a some.

Yeah I feel terrible that its taken me so long to get this actually powered up. I'll get it soon, don't you worry!

If anyone needs 7 pin submini sockets, oldguyradiola has plenty.
http://www.ebay.com/itm/401002322478?_t ... EBIDX%3AIT
He accepted my offer of $50 for 10. Fast shipping too! Now I just need to start building/fixing all of the stuff that I already have.

Thanks:
Those are interesting... 7 pins in a straight line.

The 5902 sub-miniature tube has 8 pins in a circle.
However three pins, 8, 4 & 2 all have a common internal connection to the cathode, so you can get away with using only 6 pins if you cut two off.


So I suppose you could try to arrange the circle of pins into more of a straight line and get those sockets to work.

The more appropriate style sockets are known as type "B8D" and they look like the ones shown below... although there are various different mounting styles and other ones that are similar to these.

Here are some round 8-pin subminiature sockets available on Ebay now. These are the highly desirable saddle type for top chassis mounting made by Cinch:
http://www.ebay.com/itm/NOS-8-Pin-Submi ... Sw5dNWka8G

I got 91 tubes off of that same vendor for $40 plus shipping. Now I also have a lifetime supply.
You can't hardly beat about 53 cents each!