diytube Poseidon driver mods & docs (discontinued)

for Dynaco Mark II/III/IV and DIY PP monoblocks

diytube Poseidon driver mods & docs (discontinued)

Postby Shannon Parks » Mon Mar 27, 2006 6:21 pm

Engineered as a replacement driver for the Dynaco Mark III & IV as well as your own DIY monoblock, the diytube Poseidon uses a 12AX7 and a 12AU7 for pure triode perfection allowing use of an almost limitless selection of NOS and new tubes. This driver uses the classic modified Mullard topology with constant current source in the tail of the phase splitter - a perfect mix of performance and warm tube sound.

It is a bare driver kit without components meant for experienced tube hobbyists, including:
* FR-4 fiberglass construction that will last a lifetime
* top & bottom silkscreen ensuring easy assembly and friendly modding
* a ruby red solder mask finish that will never make your amp look like a science fair project
* a drop-in replacement with no other changes needed
* detailed schematics & a parts list with Mouser.com part numbers and easy cut-n-paste Mouser BOM
* email support provided and Poseidon forum

Most parts can be purchased easily through Mouser, and vendors are suggested for the others (ie tubes and tube sockets).

New Mark III with Poseidon (no parts supplied with PCB):
Image

Manual:
Poseidon Manual for Dynaco Mark III and Mark IV Monoblocks
Ned Carlson's tubezone Poseidon Manual

Cut-N-Paste BOM (Bill of Material):
Poseidon BOM for Dynaco Mark III
Extra Parts - Poseidon Page Two BOM for Dynaco Mark III
Poseidon BOM for Dynaco Mark IV
Extra Parts - Poseidon Page Two BOM for Dynaco Mark IV
or
Poseidon BOM for Dynaco Mark III Mouser Direct Link
Extra Parts - Poseidon Page Two BOM for Dynaco Mark III Mouser Direct Link
Poseidon BOM for Dynaco Mark IV Mouser Direct Link
Extra Parts - Poseidon Page Two BOM for Dynaco Mark IV Mouser Direct Link

The parts list strives to be 100% inclusive for those building from a bare chassis.

Instructions for using 6CG7-types as the LTP and rotating the 12AX7

New Additions:
Full Original Dynaco Mark III Manual hosted at Dynakitparts.com
Full Original Dynaco Mark IV Manual hosted at Dynakitparts.com

Rev History:
7/1/12 - Updated Mouser Direct links for PCB parts for a couple back-ordered items. These supersede the manual parts list.
4/6/09 - Added Mouser Direct Links.
7/19/08 - I updated the full parts lists in the manual to match the BOM. Also updated the Triode Electronics lists. Added BOM texts for the second page of supplemental parts.
7/15/08 - Switched the 500k pot to the Bourns model which seems to be in stock more often.
12/9/06 - Slight update to the BOM. Changes the plate resistors to 3W, as 2W is out of stock. Should fit fine.
11/21/06 - Sprague .1uF/600V caps are out of stock. I can supply these four caps for $4 extra with any Poseidon order. Also, these are available at most tube resellers when you get your sockets.
7/20/06 - BOM only changes:
-updated the 1M resistor to be compliant with the Mouser database
-subbed the LM234Z for the LM334Z (RoHS backorder)
4/19/06 - MKIII only: Changed CCS set resistor to 10 ohms. Changed long tail pair plate resistors to 68k.
3/16/06 - Minor schematic fix for ref numbers. New octal suggestion.

Image
Last edited by Shannon Parks on Sun Jul 01, 2012 5:46 pm, edited 16 times in total.
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Insulated Phono Jack Notes

Postby Shannon Parks » Mon Mar 27, 2006 6:48 pm

Though I don't know how relevant insulated phono jacks are for the Mark III design, I'll post the following anyway. I was able to get pretty good noise floor performance using either the original wafer jack or insulated RCAs. For those using the wafer RCA jack from Mouser, I'm interested in hearing how it fairs.

I used the Japanese-made Kobiconn RCA jack from Mouser, p/n 161-2002. It comes with two plastic shoulder washers that don't appear on the datasheet. The shoulder is very thin, and looks to just slip into a slightly oversized .250" hole. So this by itself seems to be ideal for any DIY amp, like the ST35. But these washers don't fit well into the original Mark III RCA hole, which is .375". So I used a separate shoulder washer from Mouser, p/n 561-SW25. One trick, though, is that it sticks through the chassis too much - a flush fit is needed for a solid connector that doesn't wobble. I used some 100 grit sandpaper and sanded the shoulder of the washer until it was flush with the chassis.

I then needed insulation for the securing nut on the inside of the chassis. The length of the jack didn't permit using anything thick, so I cut a 1/2" square piece of heavy duty plastic from the clear, molded packaging stuff that drives me crazy. I then used a paper hole punch to get a perfect .250" hole in the center. Viola!

So:
RCA jack -> Shoulder Washer -> chassis -> square plastic 'washer' -> metal washer from RCA jack -> washer with ground tab -> Nut from RCA jack

BTW, be sure to check isolation with DMM before wiring up. In the end, it's very solid and works fine. Doesn't look cheap. Total cost is $1.18 per jack.

Shannon
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4/19/06 Revision for Mark III Poseidon

Postby Shannon Parks » Wed Apr 19, 2006 6:50 am

Don't worry, as this is a minor tweak and not a problem fix. ;)

Currently the 12AU7 phase splitter ends up with around 300V on the plate and across the tube (due to the minimum of wasted voltage in the LM334Z tail). This isn't an issue with the 12AU7 as the currents are fairly low - around 2.7mA per half.

But we end up 'wasting' some usable voltage. I determined the best use would be to slightly increase the CCS set resistor and also the plate resistors. This drops the plate voltage down to around 230V and gives us a slight increase of linearity. LM334Z bias is still above 9V. The 2W plate resistors only dissipate about .8W.

With this revision, I'll release the test data. Don't worry Ed, as there's 12BH7 data, too!

Shannon
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Postby WA4SWJ » Wed Apr 19, 2006 7:29 am

Shannon,

Can't wait to see the 12BH7 results.

I'm going to build my other two units this coming weekend so I'll be anxious to see the component value changes. I have not built two of the boards yet but that's about to change!

How 'bout a preview of the component values?

Thanks!
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Postby WA4SWJ » Wed Apr 19, 2006 7:34 am

OOPS!!!!

Just saw the component changes above.

I've got some of those values believe it or not.

Regards,
Ed Long
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Postby erichayes » Wed Apr 19, 2006 4:08 pm

Hi All,

Regarding the homemade washers for the input jacks, I had a similar problem last year when I restored a first generation (Philadelphia) ST-35. I wanted to eliminate the common-chassis shortcut that Dynaco was so fond of, and use a ground bus. This meant the input jacks had to be lifted from the chassis. I wound up using the same contemptable material as Shannon, but found some punches made by General (the scribe and machinist ruler people) at my local hardware emporium. They range from 0.125" to 0.500" in 0.062" steps and are relatively expensive--around $6~12.00 each, depending on size. Definitely outside the paper punch realm, but if you need to punch thin insulators, these are the way to go. They're usually located in the same area as brass grommets, as their intended use is to punch holes in canvas (or Dacron, Tyvek, whatever) to make tarps and sails with grommets. I have the 0.125 and 0.375" and use them in conjunction with a high density polyethylene cutting board and a 12 oz ball-peen hammer.
Eric in the Jefferson State
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Postby EWBrown » Thu Apr 20, 2006 6:24 am

I haven't yet tried it, but it looks like the front-mount (the one where the nut installs behind the panel) insulated RCA jacks from AES should fit these ST35 jack-holes. (can I say that here?) Yellow_Light_Colorz_PDT_02 They fit a 3/8 inch hole (the rear mount insulated jacks need a 1/2 inch hole).

The AES (or similar) dual binding post will fit the slot for the phenolic speaker terminal strip. There will be a litttle "air" on each end, but I found it not to be a problem.

I have three (and a half) ST35 carcii "on deck" for new PC boards, and I/O jacks, and C Chong Cap boards and C354s. So many projects, so little time...

/ed
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Postby Ty_Bower » Sat Aug 25, 2007 8:02 am

I think I found a typo in the Poseidon manual...

On page 11, it shows the P-782 as the transformer in the Mark IV power supply. I was scratching my head, trying to figure out why the voltages shown for the IV were lower than the III. The schematic for both appear to be the same, at least according to the Poseidon manual.

I think the Mark IV actually used the P-135 power transformer. It's rated 370-0-370, which is slightly lower than the 400-0-400 of the P-782. By the way, the correct part number for the transformer is shown on page 14.

It's not a big deal, but if someone is trying to scratch build a Mark IV clone (why?), they'll have quite a time trying to get the B+ down.
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Postby Rex Everything » Sun Mar 01, 2009 12:35 pm

Am I correct in thinking the BOM list is only for one board and that it should be doubled for two boards?

Also what parts don't I need if I'm not scratch building but modding an exsiting pair of Mark III's?

And lastly this part is out of stock

2W 5% Small Metal Oxide Resistors 6.8Kohms 5% Tol

Any replacement suggestions?
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6.8K 5% 2watt or higher

Postby hilldweller » Sun Mar 01, 2009 4:18 pm

Rex Everything wrote:Am I correct in thinking the BOM list is only for one board and that it should be doubled for two boards?

Also what parts don't I need if I'm not scratch building but modding an exsiting pair of Mark III's?

And lastly this part is out of stock

2W 5% Small Metal Oxide Resistors 6.8Kohms 5% Tol

Any replacement suggestions?

I got mine from Radio Shack (6.8k @ 5%)
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cad

Postby maynard999 » Sat Feb 11, 2012 8:22 pm

Shannon,

Do you have a DXF or any CAD of the board? I'm doing a ground up build and laying it out in SolidWorks. I plan to have waterjet top plates made for my chassis. I'd rather not guess at hole locations. I'll be happy to contribute the final files to the forum when finished.

Thanks.
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Re: diytube Poseidon driver mods & docs 7/1/12

Postby Stevedel » Wed Oct 14, 2015 3:30 pm

Well, Shannon, as long as I am going to start collecting parts for a pair of Mk-IIIs, I might as well begin with a pair of Poseidon Mk-III driver boards.

It looks like there is plenty of room for some Mundorf Supreme coupling caps. I'm sold on those.

Regards, Steve
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