Posted by Tnuctipun [ 205.188.116.67 ] on March 19, 2005 at 13:16:28:
In Reply to: Millett's amp posted by manualblock on March 19, 2005 at 10:58:31:
why do you think Pete decided not to use ccs but instead goes with tube regulation?
He has a pentode running as a SE voltage amp. The g2+plate current thing was giving the diff amp fits as its cathode is CCS-ed. THe cascode triode takes care of this( as long as teh upper valve stays out of grid current operation). The upper grid is also ref'd to the cathodes, a feat which is harder to do properly with a screen grid.
I ask only because you said you worked on the E-Linear thing in tandem. Is the fact that that amp is SE have anything to do with it?
I came up with the idea on the way back from a lunch outing. We re-arranged a test amp immediately, and were quite taken. I kept my mouth closed about the discovery. ~4 months later Peter posted on AA's Tube/DIY what he had been working on and I went public with the PP version soon after.
Also for the more electronically challenged, how do you do the bias wiring and tie-in the ccs1 to the A- leg?
The CCS is attached to an earlier stage of the bias voltage filter circuit. It is not too critical since it is such a good CCS/regulator. It should go at least one stage before the bias pots os that they can be quite clean of ripple.
I am going to point out here that as a begginner the Guinevere wireing job had an intuitive feel that could be expressed directly from the schematic; however this is another animal. I look at this schematic and see nothing but questions and few answers pop out at me.
What are the catastrophic failure modes possible here. Over voltage on B+ and failure of the CCS2. I am not sure what would happen, since I have not had one fail yet. This is the most critical and 'close to the limits' set of parts on the amp.
and am I seeing this accurately or is this one of those things that look more difficult than they are?
It is really fairly simple. One B+( L-C filter, single recitfier), two coupling caps, the plate laods to the front end goint to their corresponding g2 connection or dedicated tap point.
The filaments each have their own winding, two secondary Hammonds of 185 series are quite good for this app. One filament TX for each amp. ONe 50R hum pot for each of the finals.
Also can we get a BOM on this ?
Yes we can. I will put one together tonight and set it up for discussion.
Also; I don't see a committment to any particular tube, has this been left open or is it cemented in yet?
If you go with UX5 sockets, there are at least three which will work. two are DH, the 1624 and HY69 and the IDH 807 will all plug in with a filament voltage adjustment. This is how I would suggest proceeding.
regards,
Douglas
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