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Starving Student PCB's - Page 21

post #301 of 313

My two boards arrived today. BIG thumbs up to Fred for doing this. I imagine it's a lot of hassle for a couple bucks. Very high quality boards for such a great price.

Couple of questions for the group.

 

1) On that Mouser BOM that's been linked a few times, I don't see it including the Molex or other connectors. Are people just soldering to the board? That's OK by me. Screw type are OK, too. (I saw the parts listed in the thread)

 

2) I also have a Mac Mini case, but mine is metal and hard plastic. The top, which will house the tubes and the heat sinks, is mostly plastic with a thin sheet of metal below. Is that a terrible idea? Other option is to house heat sinks behind the board, still in the case. It's metal on the bottom. Or, just buy a case and use that one for another Class D project, with far less heat.

 

Thanks again, Fred!

post #302 of 313

Fred,

I received your boards a couple of weeks ago. Today -  I just finished it :gs1000smile:

Powered it up for the first time and no smoke - always a good sign!

It worked just fine. The sound is pretty darn good too.

 

To answer DaKubes's questions (above) - I ordered the standard Molex header (2.54mm or 0.1" spacing). They worked fine, except I had to slightly enlarge some of the holes on the PCB with a drill bit. Of course you then also need to order the pins for the cable connector. I found a "cheap" crimping tool on Amazon for $20 (search for HT-225D Full Cycle Ratchet)

 

Also, I think you'll have a problem with the plastic top. I found the tubes get up to 140 degrees F and the heat sinks for the MOSFETS get up to 125 degrees. You are going to want a metal case.

 

post #303 of 313

Are these still available?

post #304 of 313
Quote:
Originally Posted by elecen010 View Post
 

Are these still available?

 

 

I pm'd Fred several days ago and haven't heard anything back. I suspect they may still be available but Fred is not.    Hope it is just a vacation or a business trip and nothing less pleasant.

post #305 of 313
Quote:
Originally Posted by Wiljen View Post
 

 

 

I pm'd Fred several days ago and haven't heard anything back. I suspect they may still be available but Fred is not.    Hope it is just a vacation or a business trip and nothing less pleasant.

I received 2 boards from him just a month ago. So, they should still be available.

I had PM'd him and he got back to me after about a week.

post #306 of 313

I have a couple LED power supplies that are capable of 48V 2.5A per channel with 3 channels per unit that I was going to use for building an amp.  I have been thinking about building one of the SSMH or one of the GainClone designs.    This is usually when I start thinking stupid stuff like what would happen if you used the Tube stage from the SSMH as the pre-amp for the power stage of the Gainclone and combine the two?    Is this impossible, stupid, or something that might be an interesting thought?

post #307 of 313

I ordered four pcb's on March 20th and received them today in excellent condition. (From Australia to Holland in less than two weeks)

A big thanks to Fred for his speed and effort!

post #308 of 313

I've discovered a channel imbalance, the right side sounds a bit more full than the left side. Ive also noticed the tube on the left glows a tad dimmer. Would those two things be related? I've got access to multi meter and oscilloscope. How should I troubleshoot this?

post #309 of 313
Quote:
Originally Posted by brokentofu View Post
 

I've discovered a channel imbalance, the right side sounds a bit more full than the left side. Ive also noticed the tube on the left glows a tad dimmer. Would those two things be related? I've got access to multi meter and oscilloscope. How should I troubleshoot this?

You know, now that you mention it. Mine is kind of the same. I only notice it when I have the volume low. Seems okay at normal listening levels. But maybe I'm fooling myself. I'm guessing here, but I assume this was caused by the fact I didn't pay the extra money to buy matched tubes. I'm assuming one tube has slightly more gain than the other.

 

**Edit**

Hmm, I exchanged the positions of the tubes and the right channel is still slightly fuller at low volumes. So much for the tube theory. Maybe the volume pot isn't balanced. It has 2 separate windings for left and right and could theoretically cause this. That would also explain why the issue seems to go away at louder volumes.


Edited by snafu1 - 5/7/16 at 7:35pm
post #310 of 313

My starving, sounds good with my Hifiman HE-400 =).

 

https://flic.kr/p/HhoHbz


Edited by Phetu - 5/18/16 at 12:05pm
post #311 of 313
Quote:
Originally Posted by Phetu View Post

My starving, sounds good with my Hifiman HE-400 =).

https://flic.kr/p/HhoHbz
what box is that and what plug is that?
post #312 of 313
Box is Hammond 1444-8 / 152x102x51mm and Neutrik something, locking 6.3mm stereo
post #313 of 313

I'd like to finally build a tube amp to see what it's like and I've got a few general questions about the PCBs and the amp. It'd be truly appreciated if someone could help me out. Until now I've stuck firmly to SS amps.

 

About the PCB:

 

- The dimensions of the board are 76mm x 76mm, is this correct?

- What spacing do the potentiometer holes on the PCB have? Would this pot fit the holes on the board? http://www.taydaelectronics.com/potentiometer-variable-resistors/rotary-potentiometer/logarithmic/50k-ohm-logarithmic-dual-taper-potentiometer.html

 

About the amp and tubes in general:

 

- How much power do the FETs dissipate? Do I really need a proper heatsink or would a strudy aluminium enclosure be enough?

- What should I pay attention to when looking for tubes? I could get 5814A Philips tubes or ECC82 Valvo, RFT and JJ tubes, are all of these just fine and drop in replacements?

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