UNSET is coming?

[jama]

George, wonderful solution. Perfect for all people around world.

[Francois G]

Originally Posted by Tubelab_com

I would like to make the "all in one" UNSET board something useful to the widest possible audience. I have been thinking, and re-thinking how to best do this, and I came up with yet another idea last night when I couldn't sleep.....

Any comments?

Hi George,

I admit that I have been overly vocal! And I apologize again for my impatience.

But this is great. I’m not particularly vested in the exact outcome, because I think you could adjust as the demand (for boards) lead you.

In general, I think an option for SS rectification is great. And please allow for the “big xLW6” tubes. That’s all I want for my Christmas this year.

[mike567]

BIG +1 for off-board output tubes
maybe include headers for outputs

[Hearinspace]

Originally Posted by Tubelab_com

Any comments?

If the output tubes are going to be off board to allow flexibility, can the driver tubes be off board too?

[hareynolds]

Personally, I like the idea of a power/interconnects board, as it gives max flexibility in both layout and tube pin-out.

I previously cobbled together a couple of "power drive" proto boards myself (to test the concept before I committed to the TSE-II monoblocks) which included the driver CCS, the coupling cap, and the MOSFET with resistor "network". Everything else was point-to-point. Worked surprisingly well, although it was pretty sloppy at the end, what with all the "edits". Also, I used a Pete Millett regulated fils supply, so I didn't need that on the board.

For example, the board could include:

B+ P/S filters (like SSE and TSE)
CCS (ie 10M45)
MOSFETs and associated resistors/trimpots

Rectifier, drivers, and Power tubes would all be "off board."

If the board (or boards, if mono) had a narrow form factor (say 2-1/2" or 3" wide) they could be mounted VERTICALLY, which would be a lot better thermally.
That's how I mount the Millet regulated fils supply, BTW.

That is, all of the heat-sinked "sand" could be arranged in a row, ie diodes/fils regulator/CCS/ MOSFET with a row of holes in the chassis directly above.

The counter argument, of course, is that off-board sockets increases the risk of screw-ups, some of which might be spectacular.

In addition, off-board sockets make care in wiring more critical, especially for the driver(s) and the filament wiring (although DC makes fils wiring lots less fussy).

IF the UNSET is intended to be dead-nuts simple and a good "first build" (like the SSE, which I think is the best beginner tube amp out there), then I think that at LEAST the driver sockets must be on-board.

HOWEVER, if as I suspect, the UNSET requires more sophisticated build and adjustment techniques (like the TSE-II and the Universal Driver UD board), then just give us PADS for wires to grid/plate/anode/screen/fils and we can figure it out.

Alternately, screw terminals for the socket leads would make a super-flexible prototyping amp that could be ENCLOSED and maybe even dragged "upstairs" to try-out on the good speakers...

None of these ideas are critical; many of us (George included) have hacked the TubeLab boards within an inch of their lives. I still have an SSE board which has hosted 6AV5s, 6BQ6s, and assorted other mongrels. Others have "glued" DHTs on there.

Just some thoughts....

[77seriesIII]

Second the BIG +1 for tubes off the board. Sounds like a plan George!

[dch53]

I must dissent! Output tubes not on the board, maybe.

The less point-to-point wiring the better. I always opt for putting as much as possible on any PCB. Much more reliable and fewer mistakes.

[Tubelab_com]

Originally Posted by Hearinspace

If the output tubes are going to be off board to allow flexibility, can the driver tubes be off board too?

The UNSET board uses a pentode driver with local feedback from plate to grid making it operate like a triode. The tubes that I have been using have a rather high Gm and are designed to operate at frequencies well into the VHF region. This makes layout somewhat critical to avoid oscillation. I'm sure that some builders could do a good job wiring up a socket to the board in a manner that would work, but just as many would be building radio frequency jamming devices.

It appears that a few builders would want something like the two boards I have been using. It works fine except for some possible thermal issues. The only way to quantify this is to build some amps. I have decided to get a small quantity of boards made like the two that I have, all parts on one board. I worked on board cleanup all day only to have my old Eagle 5.11 go off into the weeds and eat my work. I'll start over tomorrow. This board can use about 10 different driver tubes, and some of them are cheap.

The modular version will have a driver board with an even wider selection of suitable tubes

[hareynolds]

Sounds like a really good “hack” (I mean that in a good way, like “IKEA hack”) to avoid using those precious 5842 drivers. What sort of drive are we talking about, George?

BTW I’m good with driver tubes on the board; don’t relish using grounded coax to wire off-board driver sockets. Are we gonna need tube shields for our pentode? Just curious...

[hareynolds]

PS re: “thermal isssues”

I am using low-speed muffin fans in my TSE-II monoblocks, as they will live in a smallish cabinet tucked in a corner. Generally, not a good thermal formula. Once I have it sorted, will publish...but early returns say that the bias stays rock-steady with quite small CFM ( and therefore very low dBa fan noise)

Easily the best amps I have ever built, by far. Non-audiophiles comment on the sound: “ooo, that sounds good, what did you do?” A natural mate to my open-back, 6 dB 1st order cross-over 96 dB/W speakers.