Latter Day ST70 - MikeT - Tube DIY Asylum

Latter Day ST70

Posted by MikeT (A) on May 22, 2003 at 21:16:45

In Reply to: For a $500 parts bill.... posted by Sector-7G on May 22, 2003 at 17:28:44:

-ST70 power tranny, power supply kit board, and power choke from Uncle Ned.
-Shunt fed volume control using Alps pot or similar, or build a pair of 12 position shunt fed attenuators using Beyschlag resistors and Electroswitch rotary, all from Digi-Key
-12SN7 input stage, long tail pair, 20K plate load, -8V grid, 20 ma CCS for tail, should give 250V at plate
-5687 drive stage, long tail pair, 20K plate load, -12V grid, 30 ma CCS, should give 250V at plate
- Douglas: gives you a good chance to use your cascode CCS's!
- El34 push-pull, fixed bias, 100 ma per side, B+ around 430V, grid around 30V, I like Electro-Harmonix
- 5AR4 rectifier if you can find a brand you trust
- Hammond 1650N OPT's
- Hammond 17X14X3 steel chassis in black finish
- Panasonic ECQP film/foil coupling caps, .33uf, 400V, Digi-Key, $1.75 ea
- Use a 10 ohm 3W resistor to measure the current from each EL34 pair (.1V = 100ma :-) )
- Use Beyschlag 3W metal film resistors from Digi-Key
- Run the 12SN7 filaments from a floating regulated DC power supply, using a Velleman VR kit board with an LT1085, schottky diodes, and 25.6 3A Radio Shack PT. You will need to heat sink the VR with a good 10-15W heat sink.
- Use an Electroswitch rotary selector switch (Digi-Key)
- RCA connectors, power switch, power cord of your choice. I personally like Volex power cords from Allied, RS power switch, and Vampire RCA connectors.
- Use knobs like on the Foreplay, from Radio Shack, nice retro look.
- Cut a couple of black walnut side panels, 3/4" by 4", use a good tung oil finish.

Electrically, this is what I've done except I'm using Dyna OPT's and PT. Less filling, sounds great. If they introduced the ST70 today I bet this is how they'd do it.

Mike

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Follow Ups Full Thread

Topic - For a $500 parts bill.... - Sector-7G 17:28:44 05/22/03 (27)

I hope you post your final choice....... - Ryder 05:58:29 05/26/03 (3)

But of course... - Sector-7G 07:51:47 05/26/03 (2)

Hey, thanks... - Ryder 08:04:51 05/26/03 (1)

Re: Hey, thanks... - Sector-7G 12:08:20 05/26/03 (0)

Another Idea - Scholl 07:04:37 05/25/03 (0)

parts add up to $500 fast, even going cheap..... - throbbinnut 06:57:48 05/23/03 (0)

Re: For a $500 parts bill.... monoblocks can be had - maynardg 06:20:01 05/23/03 (0)

I'm building something like this.. - Scholl 04:39:11 05/23/03 (5)

Hammond - Alan Breece 05:40:19 05/23/03 (3)

Re: Hammond - Scholl 06:29:35 05/23/03 (2)

If Only they Weren't So Ugly - Triode Kingdom 17:25:17 05/23/03 (1)

Re: If Only they Weren't So Ugly - Scholl 10:48:52 05/24/03 (0)

Re: I'm building something like this.. - Scholl 05:31:53 05/23/03 (0)

Re: For a $500 parts bill.... - Jim Doyle 23:15:18 05/22/03 (0)

Re: For a $500 parts bill.... - 2wo 21:36:52 05/22/03 (0)

Latter Day ST70 - MikeT 05/22/0321:16:45 05/22/03 (4)

Hey Mike - Sector-7G 07:07:25 05/23/03 (2)

How About CCS Plate Loads? - MikeT 08:33:33 05/23/03 (1)

Re: How About CCS Plate Loads? - Sector-7G 12:39:27 05/23/03 (0)

Here's the Tab - MikeT 06:12:56 05/23/03 (0)

DiyHiFiSupply.com's "ELLA" for $499... - darkmoebius 20:22:54 05/22/03 (0)

Re: For a $500 parts bill.... - groverg 19:54:15 05/22/03 (0)

Re: For a $500 parts bill.... - korneluk 17:57:24 05/22/03 (4)

I hear you... - Sector-7G 18:21:24 05/22/03 (3)

Typical 2-stage driver vs. Interstage cost - Jim Doyle 23:31:08 05/22/03 (0)

Re: I hear you... - korneluk 19:18:07 05/22/03 (1)

Yes, I'm hung up on DIY - Sector-7G 19:38:59 05/22/03 (0)

Follow Ups

Latter Day ST70 - MikeT 05/22/0321:16:45 05/22/03 (4)

Hey Mike - Sector-7G 07:07:25 05/23/03 (2)

How About CCS Plate Loads? - MikeT 08:33:33 05/23/03 (1)

Re: How About CCS Plate Loads? - Sector-7G 12:39:27 05/23/03 (0)

Here's the Tab - MikeT 06:12:56 05/23/03 (0)

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