Integrated tube amp using of the shelf parts?

[pto892]

I'd like to build an integrated tube amp for office use, and have been toying with the idea of using a ST-35 board running in triode mode and combining it with a relay operated input switch and Broskie designed attenuator for volume control that I have laying about. The relay switch is commonly found on Ebay-I bought one from one of the Hong Kong based part suppliers and is run off of 9~12v ac input. It allows switching between 4 inputs without using a open frame mechanical switch hopefully eliminating a potential RF problem. Now for the stupid question-would it be worth it to run the tube heaters on DC voltage? I am off course worried about AC hum-but my stock diytube ST-35 doesn't hum in the slightest. This amp would however be used in an office environment with florescent lighting, computers, power supply noise galore, etc. Really all I am thinking about doing is just adding a fancy input switch and volume control to a ST-35 to make it "integrated". This seems to be almost too simple to me-am I missing something?

I need the multiple inputs for a tuner/MP3 player/CD player, etc. The real reason for picking a ST-35 board is that they're easy to build and I'm already familiar with it.

[SDS-PAGE]

Yes, it is simple as just adding an input switch and volume control if you're not planning on adding a RIAA equailization for vinyls. You don't even need those fancy relay switches that run on ac input. It might just contribute to AC induced hum. I use ones that cost about a coupleof bucks and they work great. Since you have one that you'd like to use, just make sure to use shielded cables for inputs tucked away to the side of chassis away from ac sources. And you don't need to run the tube heater on DC voltage. The stock ST-35 runs quite without it.

[EDIT] Here are some pictures demonstrating how easy it is to convert a power amp into an integrated amp (zero hum with AC heaters):

http://bp2.blogger.com/_i08-ibvZ150/R_2mmiIV13I/AAAAAAAAAyM/nCZ3euaNfP0/s1600-h/S5033111.JPG

http://bp3.blogger.com/_i08-ibvZ150/R_2mmyIV14I/AAAAAAAAAyU/YuuuEvA5R-Y/s1600-h/S5033112.JPG

http://bp0.blogger.com/_i08-ibvZ150/R_2mnCIV15I/AAAAAAAAAyc/7lBPKtGunBA/s1600-h/S5033117.JPG

[pto892]

Nope, it doesn't need a phono stage-I can use an eternal RIAA preamp for that if I need it. I was thinking that since I want to use the relay board that puts a 12.6v trannie on the chassis, so I could use that to supply 6.3v DC through a LM317 IC. Your point about avoiding AC hum is well taken though plus it's simpler to leave unnecessary parts off.

[DerekVa]

OK. Here's the converse...I want to pull the volume pot from a K-502M so it'll run as a pure power amp. Should I just jumper the input/output connections to the pot on the circuit board?

-D