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Old 6th May 2012, 08:58 PM   #21
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Default Schematic

I remain very interested in the Tubelab Spud design page and details and found a couple of earlier threads where Tubelab pursued the design around 2008.

This: Spud anyone?

Post shows a PDF schematic of a SpudSE design...kind of a proof of concept -- i.e. the "furball" and a schematic as an image file.

This: Spud anyone?

Post (replying to one from above proposing an alternate design), gives some of the values used in a prototype SpudSE design.

I have pulled as much information as I am capable from the threads and the Tubelab website photos to produce a TinyCAD schematic (.dsn filetype) and an image export of the schematic in EMF (Windows Enhanced Metafile) in a ZIP file. I am hoping in your copious spare time you surely don't have, you might take a scan of the schematic and see if it matches with what you designed originally.

However, some of your experiments replaced the triode section cathode resistor/cap arrangement for cathode bias with an LED to provide bias and that is shown in some photos and other posts in the thread referenced above.

Values that I could not decipher from your schematic that are needed (using the numbering scheme on the attached CAD file are: C10/C20 & R10/R20; C11/C21 (0.22 uF?); C12/C22 & R17/R27 (450/5W/20%); R16/R26; C1 (4 to 47 uF?)

An Antek toroidal power TFMR (250 to 300 VAC centre tapped) with a 6.3VAC filament winding could work and Edcor OPT's with a 5k primary.

The volume POT I have placed is a dual 50k log taper device as in your SSE design.

Note, I have added a small section on the filament winding for a power pilot light using a blue LED.

For a free electronics CAD app, TinyCAD is pretty good.


~Squiffy (aka Brad)
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File Type: zip SpudSE_Schematic.zip (38.6 KB, 45 views)
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Old 9th May 2012, 02:11 PM   #22
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Default Free help...

Quote:
Originally Posted by tubelab.com View Post
Is anyone else still interested in this thing?
Yes, I am...
Quote:
Originally Posted by tubelab.com View Post
If so I will have to make a spreadsheet...
The TubeLab.com spud pages indicate that the prototype board was stuffed with values from the "furball" experiment. In an earlier post, I threw together a schematic and tried to fill the values in from photos, a previous thread on the spud topic and posted the results in a ZIP file. I recognize that several values/tolerances on my schematic are NOT right and I will be adjusting a reposting shortly.

The 6LR8 tubes and B9A sockets are available from a couple of suppliers West of Toronto at a fair price.

So, the BIG question: At this point, is it possible to supply back a part values/tolerance list from your furball (e.g. just read back the values off the "stuffed board")?

Just the power supply and the values from one of the channels (i.e. left or right) would be wonderful.

While I certainly understand the design was not optimized, the opportunity to build an amp in this format remains of interest to me (and hopefully a few others), even point to point, since the stuffed board "sounded good". Cathode bias on the pentode section could be like other posters' adjustable values to achieve a cooler operating point. I have a little time on my hands, and I'm open to helping out, pro bono, of course.

Quote:
Originally Posted by tubelab.com View Post
Be back on Memorial day. Until then I won't have time for electronics stuff, and the soldering iron will likely stay cold and so will the tubes....
Just hoping to nudge you back into Tubelab before the 4th of July firestorm you've mentioned has happened in your neighbourhood.

Squiff (aka Brad)
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Old 10th May 2012, 02:39 AM   #23
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I'm leaving on a 3000 mile road trip Friday or Saturday (as soon as it stops raining long enough for me to finish loading my junk. I don't have time to install your schematic program right now....I know this Vista POS computer will fight me on it.

I printed out a PDF of the Eagle schematic, and I am looking at my board. I can provide values for the reference designators on my schematic. You will have to cross them over to yours.

R1 150 ohm 5 watt probably not critical (borrowed from SSE) or use a choke

R2 150K 2 watt Bleeder resistor, use whatever you got

C1 100 uF 450 Volt again not critical 47 uF will work

C2 150 uF 450 Volt

D5, D6, D7, D8 1N4007 or whatever your silicon de jour is

R11, R15, R21, R25 470K 1/2 watt lower value reduces gain I used 470K because I have a bunch

R12, R16, R22, R26 1K 1/2 watt yes....because I have a bunch

R10, R20, C10, C20 dunno....I took them out and put LED's in. Tried a bunch while measuring distortion. Thye are both different, but both yellow.

R6, R5 22K 2 Watt

R14, R24 150K 2 watt.

R81, R28 100 ohm 1 watt.

R17, R27 680 ohm 5 watt.

C12, C22 Both are suspiciously missing must have stolen them for another project. I would use around 1000 uF at 50 volts or so. Some people like smaller capacitance values.

Good luck, post the results here.
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File Type: pdf spud.pdf (18.9 KB, 48 views)
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Old 10th May 2012, 02:54 AM   #24
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Quote:
Originally Posted by tubelab.com View Post
I'm leaving on a 3000 mile road trip Friday or Saturday (as soon as it stops raining long enough for me to finish loading my junk.
I wasn't expecting anything until after Memorial Day. Wow...you're my hero. Have a safe trip (Hamfest in Ohio, right?).
Quote:
Originally Posted by tubelab.com View Post
I don't have time to install your schematic program right now....I know this Vista POS computer will fight me on it.
I will try some other apps that are more "Vista Friendly" if that's possible. I normally use Mac/Linux but this TinyCAD looked like it had a shallow learning curve and the library expansion looked pretty easy so...
Quote:
Originally Posted by tubelab.com View Post
I can provide values for the reference designators on my schematic. You will have to cross them over to yours.
I will do that and update my schematic and repost the results for all (and you) to use, gratis, of course.
Quote:
Originally Posted by tubelab.com View Post
Good luck, post the results here.
They should be waiting here when you get back.

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Old 10th May 2012, 03:36 AM   #25
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Quote:
(Hamfest in Ohio, right?).
The biggest hamfest in the world is in Dayton Ohio. I usually go to shop for tubes. This time, I'm selling them. We inherited a house in West Virginia where I may live when my job runs out.... I am going there for a while too.

Quote:
I will try some other apps that are more "Vista Friendly" if that's possible.
It's not....Vista sucks. I built this machine about 3 years ago. It worked reasonably well until Windoze 7 came out. Then it started misbehaving. It went through a freezing sickness right after MS installed some "updates" and the sickness was miraculously cured with the next batch of "updates"....Coincidence??? I don't think so......Intentional??????
Between the Windows boot manager and Norton Anti function, Open Suse 9.3 was broken more than it was working...I gave up on it.

I have assembled all the hardware for my next box from Newegg discount sales but haven't had the time to complete it yet. I am stuck with Windows for compatibility reasons (Cakewalk Sonar and others). I had good luck with Grub, but that was years ago on an XP machine. I'll look for a Linux based boot mamager for Ubuntu that coexists with 7.

There has been little interest in the Spud SE, but if anyone knows where to get cheap (Chinese maybe) PC boards made in small quantities let me know. (a 4X6 inch board for $10). To get reasonable prices on US made boards for the SSE, SPP, and TSE I must buy 100 at a time. They are still between $15 and $20 each with shipping and setup charges.

Quote:
They should be waiting here when you get back.
I should be well connected for most of the trip. The internet in West Virginia is way faster than here, and I'll have my phone at the hamfest.
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Old 10th May 2012, 07:10 PM   #26
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Quote:
Originally Posted by tubelab.com View Post
R10, R20, C10, C20 dunno....I took them out and put LED's in. Tried a bunch while measuring distortion. They are both different, but both yellow.
Is it fair to conclude then that you were trying to get about a 2.0-2.2V potential drop across the yellow diode and were finding variability in the cathode resistor/capacitor combo?

Is it possible that since the triode section of the 6LR8 is "12AT7-ish" that you used the same values as in the SSE (i.e. C10 1500 uF and R10 220 ohms)?
Quote:
Originally Posted by tubelab.com View Post
C12, C22 Both are suspiciously missing must have stolen them for another project. I would use around 1000 uF at 50 volts or so. Some people like smaller capacitance values.
OK...what would drive lower values as a choice? Remembering that I am just starting my journey into learning about "The Tubes" and other such mysteries.

Plugging away at the schematics...I am going to dummy one up for the 6LU8 as well for the 12-pin compactron option, since I am learning the library stuff in TinyCAD anyway.

~Squiff
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Old 10th May 2012, 09:33 PM   #27
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Default Updated Schematics

All,

Attached in line are updated schematics for the Spud Amp. These were prepared NOT as a design, but for others to scrutinize.

WARNING: I am very new to the world of tube stuff, so please do not use these as the basis of a point-to-point build at this point. The results could be dangerous if I've missed something fundamental that a more expert person would catch. I'd be remiss to not point this out, as Tubelab himself quite rightly warns about high voltage in these designs. If the attached files have an error in them, proceed at your own risk.

The files attached are JPEGs. The file ending in r0B is the 9-pin compactron 6LR8 version. The other is a version with the pinouts for the 12-pin compactron 6LU8, which I understand is the 12-pin twin of the 6LR8. I have TinyCAD .dsn files available if needed.

Why both 9-pin and 12-pin versions?

Reason? The 9-pin "Novar" (B9E I think) socket in a PC mount form is very hard to find. There appear to be more reliable 12-pin compactron sockets as NOS out there in tubeland.

Others please chime in...I am glad to work on TinyCAD, since I have some time in hand to bash through this. I am still interested in a spud amp with the only silicon being the P/S rectifier. The design is minimalist in both components and feedback techniques (UL mode only in use), which I prefer as a philosophy.

The push-pull movement, while compelling from a power and distortion perspective, does not interest me. I am looking for SE in a small package to drive efficient loudspeakers in a small room from a couple of nice, clean sources. The SimpleSpud certainly has my hopes it can become a PCB at some point. I will contribute, as I can, to assist.

~Squiff
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File Type: jpg simple_spud_r0B.jpg (145.3 KB, 201 views)
File Type: jpg simple_spud_6LU8_r0A.jpg (145.6 KB, 197 views)
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Old 10th May 2012, 11:12 PM   #28
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C2 in both schematics should be 150 uF, rather than 100.

...note to self: add to "oops file".

~Squiff
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Old 11th May 2012, 12:58 AM   #29
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Quote:
Originally Posted by squiffiness View Post
Reason? The 9-pin "Novar" (B9E I think) socket in a PC mount form is very hard to find. There appear to be more reliable 12-pin compactron sockets as NOS out there in tubeland.
John at Pacific TV has both chassis and PC mount B9D "Magnoval". I'm assuming this is the correct size (0.687" pin circle dia.), but best to ask.

Pacific T.V. - Vacuum Tube Sockets

jeff
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Old 11th May 2012, 01:23 AM   #30
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Quote:
John at Pacific TV has both chassis and PC mount B9D "Magnoval".
Magnoval sockets have the correct pin circle diameter, but NOT the correct pin diameter. The correct socket in a Novar. Both have the same .687 pin circle, but the Novar has a .040 pin while the Magnoval has a .050 pin.

I know that Stan at ESRC has the right ones because I got them from him at the Orlando hamfest. I picked up a 6LR8 and tried them before buying.


Quote:
C2 in both schematics should be 150 uF, rather than 100.
It probably won't matter much, but I bought a hundred 150 uF's so that's what I use for everything.
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