[PintoDave]

So I have the parts on order and they should be arriving with-in the next week or two.
 
I have a pair of 12AU7 and three pairs of 12AU7A tubes I will be experimenting with.
 
I don't plan to use a circuit board, everything will be mounted to the enclosure and the rest "suspended", or wired together.
 
Any tips for wiring to avoid problems when not using a PCB?
 
Dave

 

[Eta power]

Quote:

Any tips for wiring to avoid problems when not using a PCB?

Check, check and check again. Also, remember to use a pair of cheap headphones for the first test run. I forgot to do this and got lucky, but it could have turned out very badly for my beloved SR80is.

 

[Eta power]

Double post.

 

[holland]

Quote:

Also, remember to use a pair of cheap headphones for the fist test run.

 
The first test run is with a DMM.

 

[PintoDave]

Good points! I won't forget! These will save me a lot of time and frustration, headphones to!

 

[PintoDave]

I used an old socket 7 cpu heatsink cut in half for the mosfets, and a $2 box I found at the thrift store for an enclosure. Had a few parts lying around which saved me some money as well. Not to bad for $56! I get my tubes from a local electronics recycler for $2 ea. Was surprised they worked!

Got it all assembled. Still some tweaking to do though, but it works great!

Need to rewire the pot, it is backwards right now.

Need to isolate the mosfets from the heatsinks, doing that first.

Waiting for the 48v power supply to arrive, currently using a 32v supply from an HP printer with the correct plug spliced on.

Also, getting some buzz/hum when the pot is adjusted more than 30 degrees, any advice? I'm thinking my power might be running to close to some of the audio circuit on the pcb I used for the central location for grounds and power connections.

 

[PintoDave]

I put some of the components on separate circuit boards so it makes more sense while troubleshooting.
 
Left and right tube circuits have their own, main power caps and resistors on one, and grounds on one.
 
Power on one side and grounds on the other side of the enclosure, or at least as much as possible.
 
Also grounded the pot to the input connectors to eliminate noise, and replaced the input resistors with 47k ohm vs the 100k ohm ones I was using before to adjust the gain.
 
Added a zinc plated steel ground plane to help shield noise as well.
 
Much quieter now!
 

 

[PintoDave]

Here are some updated pictures of the amp. It still looks budget, but I like that. I may not look like much, but sounds great! Definitely looks DIY!
 

 

 

[pontiusx]

looks nice, i'm in the middle of building one as well. what potentiometer did you use? I'm having some "hum" issues in mine as well. would you say wiring the pot to the input ground solved it? 

 

[PintoDave]

I am using the one listed in the build parts sheet from mousse.

Grounding the metal body of the pot to the input ground solved my issue. Mine was caused by the way I have my wires routed, but on the three other ssmh builds I just did, I dis not have to ground the pot to the input since the components are wired completely differently. You may want to look into how you have your power and grounds routed and be sure input wires and output wires are braided.

 

[pontiusx]

ok yeah ill check that out. I think i ordered that part too.. but i somehow ended up with a 10k pot instead of a 50k or 100k. anyway i ordered another one. I'll check those things out and let you know how it goes!  Thanks. 

 

[PintoDave]

I have successfully used a 10k pot in place of a 100k pot but using higher value input resistors to balance everything out