dorm amp build

[jim]

My nephew was ogling an Orange Tiny Terror rigtht before college started in the fall.  It rocked, it was small, and he fancied it as the perfect "dorm" amp.  I told my brother "No Way" and proceeded down a path of no return.  I came with this amp and built it small.
It includes a London Power two channel pre-amp, concertina splitter, pait of 6V6GT's in PP with dual bias pots in a 12 X 8 X 2 box.  It is a Christmas gift and was built cheap using mostly pulled components.  My nephew is a budding guitarist and I am not sure he will develop his hobby so......The sockets are from a salvage Fender,  has cheap electrolytics, components are junkbox, and the PT is Chinese 550 CT.  The OT I had accidently retained from a MM upgrade for a customer's Deluxe Reverb RI.  Even the tubes are mismatched and with repaired center pins.  There was no room for a board so I built it "ugly".   It still sound fabulous.  I used a Tweed one knob tone control for the clean channel l to save tone stack real estate.  When the amp is sitting on the floor (on top of a 1 X12 Vintage 30) it is bright enough to stand up and play guitar and still hear the music.  There is a tiny amount of ground loopy buzz at full master volume but no more noise than any other high gain amp. The buzz is still present with the MV removed from the amp     I used DC heaters (rectified 5V winding) for the preamp and AC heaters for the power amp. My question is this--Should I have isolated the (-) DC preamp heaters leg from chassis? I'm thinking that mixing the heater grounds might be my ground loop.
 

[TIMBO]

Good Stuff, I done DC heaters and floated them but have always ended up with a buzz generated by the rectifier circuit and used a 51ohm resistor from the - side of the AC supply to kill the buzz.

[RicharD]

Cool amp.  I always ground my DC filament supplies.  It looks like you're star grounding to the chassis and I suspect one of your bolts is not making good ground contact to the chassis.

[LooseChange]

Very cool!

I like stuffing amps into that 12x8 box. Been wanting to do an SE with an LP Preamp in a chassis like that. You managed to stuff  two more tubes in there including a pase inverter. Kudos to you!

I would have isolated the heater ground from the chassis or used the DC standoff circuit.

[jim]

Thanks, I'll try these suggestions.  It gets hot too--I'll add a fan.   Jim

[TIMBO]

This was a quote from LC from another topic.
"I would have isolated the heater ground from the chassis or used the DC standoff circuit."

I have built a couple of circuits for DC haeters/relays and ended up having to chase the BUZZ  thankfully it was an easy fix.
Circuit A was standard with the schem design and B was made to order and they both caused me greef  (seem to do this a lot)

I have floated both circuits and ended with the same results, WHY?

It seems that some do and some donot ground these circuits.Any thoughts