SDS LABS Capboard help

[TomMcNally]

You take an octal base plug, or take an old octal base tube -
and break away the glass and unsolder the wires from the pins.
Then solder two diodes into it -

pin 4 anode ->|- pin 8 cathode
pin 6 anode ->|- pin 8 cathode

A lot of guys try to find an old metal based tube that
you can replace the top cover on after you remove
the guys and solder your diodes in.

[burnedfingers]

For some unknown reason I thought you meant to solder diodes to the tube socket. I have a old tube socket that has diodes in it that I used with my first Dynaco Stereo 70.

[Ty_Bower]

Just get a pair of SS diodes (like 1N4007) and a 8 pin tube base.

Tube base:
http://www.tubesandmore.com/scripts/fox ... =P-SP8-476

Solder one diode into the base from pin 4 to pin 8. Solder the other diode into the base from pin 6 to pin 8. Make sure you get the polarity on the diodes the right way. I think the banded end of both diodes need to end up on pin 8. Eric described the technique here:
http://www.diytube.com/phpBB2/viewtopic.php?t=374

When you are done, you can just plug the thing in like it were a 5AR4. Just remember it won't have much voltage drop, and it doesn't soft start like a 5AR4.

edit: Oops. I didn't see Tom's post above. Guess you beat me to it. :)

[burnedfingers]

I found the one I made a while back.

Thanks guys

[TomMcNally]

I was concentrating too much on my lovely ASCII art -
fixed.

Yeah I used to make those things years ago for friends
with guitar amps. It's also possible to put a 10 watt
resistor ... maybe 10 to 50 ohms in the socket to help
soften the startup and lower the B+ a little.

[Shannon Parks]

no answers to my questions? Yellow_Light_Colorz_PDT_14

Burned,

Haven't you printed out the SDS manual? Look at page 4.

[burnedfingers]

I assume page 4 is a copy of the board if I have the correct manual. It shows two diodes a spot I should say on the board. Just thinking of another way to do it. I thought of the switch to allow one or the other without having to pull the rectifier tube out.

Sometimes I like the sound of a tube rectifier and sometimes I like the SS sound depending on what I am listening to.

[audiowize]

Please do not put a switch in on those high voltage AC lines. 99% of the switches you will be looking at online are rated at 250VAC maximum, and the Dynaco voltages exceed that.

For my SDS boards, I actually stuffed them with Solen film caps. If you're looking to replace the Panasonics that come with the board, you might just upgrade in that same line to the Panasonic FM series.

Also, depending on the choke, you might want to add a bit of capacitence after the choke, as the Dynaclone 1.5H/55 ohm choke should be followed by a cap of 80uf or greater (by the general rule that C*H>.1) Other options for chokes may also be considered. I went to a 6H-150 ohm choke followed by a 47uf cap.

Also, what is it about the diodes that you like over the tube rectifier? If you're running a stock ST-70 transformer, I wouldn't bother with the diodes.

[Blackburn Audio]

We have designed a new version of the SDS Labs capacitor board that addresses some of the issues we have heard from customers over the past few years. First of all the PCB board is of a much higher quality with 2oz copper and plated through holes, the board size has been shrunk down and a cutout on the back of the board allows enough space to mount binding posts in the amp without hitting the board. We have also scrapped the nasty surface mount resistors and now have standard 1/2W axial metal film resistors that mount from the top. The capacitance has been upped to 40-195-135-135 and now includes Wima MKP series metallized polypropylene bypass capacitors for each section. The diodes have been taken off of the board since it is a much better solution to use a SS plugin unit as tom described rather than having to rewire the amp internally each time you want to switch between tube and SS rectification. Of course the board still includes all the bias supply components and the filament grounding caps as well. These new boards arrived a couple of weeks ago and wow do they sound great, I am very pleased with the results. The plated through holes make the install much easier since you can mount the board into place before you solder the connections to it. Feedback on this new design is welcome, just shoot me an email with your suggestions.



-Matt at Triode

[Ty_Bower]

Are you planning the same improvements for the Mark III cap boards, too?

[Blackburn Audio]

Yes we do have a short run of about fifty of the MkIII capboards that are the higher quality style with plated through holes but I have yet to overhaul the whole board yet so they are still basically the same as the MkIII boards we have always had but better quality. I'm hoping to revise them to include the bias circuity on the board like we have on the ST-70 boards but I haven't had any time to work it out yet.


-Matt at Triode

[audiowize]

Ha ha, I wish I had read this before I overhauled my MK IV's. I'm definately happy that the capacitor values have been corrected a bit, although I did like the addition of the option to put diodes on the boards. The through plating will also be a big plus, it's not always easy to get everything connected while the board is loose.
-Paul

[Brinkman]

There is an updated version of the SDS labs capboard now available from Triode Electronics. The total capacitance has been increased to over 1mF, the first section's capacitance is now closer to 40uF, clearance has been made for longer speaker binding posts, and there's now Wima bypass caps across each section.
I mention this because the original SDS capboard improved the sound of my ST70 quite a bit, so I look forward to installing this updated version.
I would consider the SDS power supply upgrade (or equivalent) an integral modification for any revamped ST70.

Best,
Brinkman