Dont do the resistor thing I posted above until after you sort out the power supply. I didnt think about the voltage reference being based on a funky B+
[SripBoard Design] Starving Student Millett Hybrid Vacum Tube Amp - Page 16
Head-Fi's Best Sellers
- 9,224 Posts. Joined 3/2006
- Location: Atlanta
- Select All Posts By This User
EDIT: This is old. Please, go have a look at the lastest post as the Stripboard design as greatly improved and i hope will be operational soon. Here is Rev 3.7: LINK
Components are ordered, Will start building soon.
Looking into a 1 Tube re-design to the SSMH: LINK
Build Started: LINK
Build Finished / Pictures: LINK
Ok so here is the Final Design, It works great and is simple to build. I have come a long way since I started this thread.
I used DIYLC for this project and HERE is the board design, feel free to modifie it and share it around. It would be nice, if you choose to use this, to post results in this thread.
Note that the red marks are cut strip
Great Source of Info BOM ect: DIYForum
Special Thanks to:
Digger945 For 1) Sending me the parts 2) Taking Lots of his time explaining electronic concepts 3) Being such a nice person?
nikongod For helping Troubleshooting the Amplifier
Fred_fred2004 For inspiring me and general help.
zammykoo Brother in SSMH
And thanks to all the others for your support.
Fantastic effort, thanks so much for sharing (also of course thanks to everyone who helped you), I'm starting my build using exactly your stripboard design. It might be a bit of an obvious question to most people, but where did you connect your LEDs; also I know it was quite a while ago but are you able to post any photos of the top of the board showing the components in place. many thanks
Edited by Frodo - 11/23/12 at 2:20am
Most people connect the LED across the tube heaters. Since it's around 14v, you don't need a large resistor as would be necessary if connected directly to the power rail. Plus the power already is at the socket, so you don't need extra wires.
Many thanks , I soldered everything onto the board today and the case is already done, so hopefully I can start testing it out in a day or two.
I noticed that R6 is missing from the stripboard design, was there a specific reason for this? I've been though the whole thread but couldn't find anything.
Edited by Frodo - 11/23/12 at 7:41am
R6 is there, just above R12, it's just been mislabelled as R8. I'm personally using a large resistor for the LED as I feel that it must affect the bias across the tubes, I don't have any evidence to support this though, and Kim knows more on this subject than I do. I don't think you can go wrong with either method.
Thanks I'm glad you told me about R6, I had a the R8 390k resistor there, so actually R8 & R10 are missing from the diagram, am I right in thinking that the jumpers either side of C4 are wrong and should actualy be R7 & R8 and the and in place of R7 in the current diagram in should be R10?
Yes you're right, however all the resistors are actually on the diagram, but it's not just R6 that's mislabelled.
The two resistors on either side of C4 are actually just vertically positioned and are indeed R7 and R8 and yes the one labelled R7 is R10.
A good rule of thumb is that any amp like this should be more or less symmetrical (here the only bits that aren't quite symmetrical are the two decoupling capacitors as the amp is single rail)
Good luck with your build,
Hmm yeah now that you're saying, there are some errors in the drawings. R7 ans R8 are there, positioned vertically, but unidentified.
Here, I fixed it and clarified a few things.
- Corrected the resistors to match Millett's schematic.
- Added signs for the capacitors' polarity, at the point where they go trough the board.
- Clarified what the white square with red dot means.
- Added some squares where you should cut the strips. The strips carrying signal should be cut as short as possible.
- Moved the plate's wire up a strip and added information. The cyan dot, did it really have a reason to be on the strip it was? This wire carries signal and is sensitive to noise. I moved it up a strip, removed the jumper and shortened the strip.
- Added the MOSFET TO-220 pinout, picture taken from the datasheet.
- Changed pin 4's color, to distinguish it from the right channel's signal input.
- Corrected the labels of the outputs.
@TestSubject, I know I should probably ask before modifying your drawing, so if you have anything against it just tell and I'll remove the image.
These aren't errors per se, just recommendations:
- R16/R17 should be soldered directly to the pot's pin to lower noise.
- Ideally, R14/R15 should be connected directly to the tube socket, and the signal wire from the pot should go directly to this resistor, to lower noise. It's a bit silly to make the signal go trough the board just for a single resistor, especially since this signal is the most sensitive to noise in the whole circuit. This is less a problem if you already twist the wires together, though. In this case you should use two grround wires to the pot, and twist one with each signal wire.
- C7/C8 is confusing on the drawing. Make sure it's connected on the same strips as R5/R11, and not the ones over and bellow it. Take the polarized caps as example: the + and - are where the leads go trough the board.
I'm struggling to tell from that picture (it's never easy to take clear ones of this sort of thing). But I would guess that yes they are of incorrect polarity.
I'm also slightly worried about the length of your wires inside the box - my advice on that would be to try it and see whether it works, if it you get noise then you know where you should start looking. Anyway, I'd just sort out the issues that are known to be issues, try it and worry about the unknowns later. Good luck with it.
Nice work again Kim, you're always extremely helpful on this sort of thread.