HIFI-ish

[shooter]

The easy part is done, it powers up, nothing smokes, and it reproduces sound!, downside, it adds sound, got a hum issue, a bass circuit issue, so now the fun starts.

[sluckey]

Where did you get your power switch? I've used that style on my last three projects, but I had scrounged them and don't have a source for any more.

[shooter]

scrounged them

Same!, was in a proto-type build, originally bought at RS.

The copper sheeting was " harvested " from an old RF room, the chassis, a miss order by me.

[Willabe]

The copper sheeting was " harvested " from an old RF room

Copper sheeting? 

[shooter]

Copper sheeting

I "wrapped" the chassis in copper sheeting that was originally used as RF shielding in MRI scanners, most RF rooms now are aluminum panels.

I did it more for  aesthetics, than shielding, although I will be putting an aluminum plate on the bottom once I chase away the bugs!

[DummyLoad]

Where did you get your power switch? I've used that style on my last three projects, but I had scrounged them and don't have a source for any more.

i have some of those power switches in orange - send a PM if you'd like to have a couple more...


--pete

[sluckey]

Pete, did you get your orange switches from an old '90s power control unit for PC and peripherals? If so, I bet your switches are identical to mine. I have one more orange but would like to have a couple more if you are not gonna use them. I've grown attached to them because they sure simplify wiring the mains circuit.

I'll send you a pm.
 

[DummyLoad]

Pete, did you get your orange switches from an old '90s power control unit for PC and peripherals? If so, I bet your switches are identical to mine. I have one more orange but would like to have a couple more if you are not gonna use them. I've grown attached to them because they sure simplify wiring the mains circuit.

I'll send you a pm.

no sir, these were rescues... some ppl rescue animals, i rescue wayward parts! they were on their way to become land-fill material. you can have three of them: if you don't mind, please help out with the postage. :-) 


--pete

[DummyLoad]

please pardon the thread-jack shooter... carrion.    


regards,


--pete

[shooter]

please pardon the thread-jack shooter

No problem, I'm still dinkin with the amp, ok as an audio amp, pretty damn good as a guitar amp though!

design your own switch?;

https://www.e-switch.com/product-catalog/rocker/product-lines/r1973-series-illuminated-rocker-switches#.Va1mORHD90t

[DummyLoad]

shield the preamp bottles might help...


--pete

[shooter]

shield the preamp

My sockets are not shield type, could just set them on I guess. I swapped tubes around, was nice and quietish, played music for about 10min, still fine, plugged in the guitar, well, just because, got some nice OD tones, played for about 45min, unplugged the guitar and the hum is back.  120hz with a 1.5hz modulation riding on it, not on the pwr rail, but at both R's for V1's plate, with or without V1a's grid shorted to grd.  That's as far as I got.  Going to run a couple more tubes through V1, beef up PS filters.  All the DC No#'s are good. 

I have 4 10,000uF 450vdc caps, might add 2 just to see if there's any change.

I also have a couple points on the ground path I want to isolate, I used 2 points on terminal strips that are bolted to the chassis as "pre-section" ground.

[lego4040]

   these amps are great MP3 amps as well as iphones. I built one recently using the Edcor PT/OT and was thrilled. For the price of their trannies the wait is well worth it 

[shooter]

great MP3 amps

My last one was a QuadSE version, all Edcor, with great speakers and overall sound, but life hit and I sold the setup for pbj money.  hopefully this one will be as good, but like children, every amp seems to be it's own beast

[shooter]

Chassed the hum away, or just masked it, but its quiet!  I added a bypass cap, 22uF, to V1a's cathode, started at 2.2, but had to go up to the 22 to kill it.  then there was buzz

Shielded the bottom of the amp with a steel plate and walla, no buzz.  Now it's on to the bass pot issue, when I turn it past 7 the audio starts cutting out, so i'll scope it to make sure I'm not just driving the PA into cut-off.

I can dial in a full range with the TS now so it's not a big deal.

[MadMax]

You might sweep the bass pot with an ohm meter just to be sure it doesn't start losing contact above 7.

[shooter]

sweep the bass pot

did that before i built and after I noticed the problem, no glitchies i could discern.  Looked for DC in the TS, none.  Hopefully today I can get it on the bench with a scope and map out the AC path.  Still need to dial in drive and power.  I does sound very good, even through some cheapish bookshelf speakers.  Audiophile, probably not
 

[lego4040]

Get yourself a set of Polk audio bookshelf speakers used, I was looking at a few on febay last night and you'll be set. I love my little stereo amp, I've been toying with building a DIY Boombox with a tube amp built in.

[shooter]

Played outside all weekend so no amp progress, I have a pair of altec lansings that were!! nice but the cones are now religious  So I found replacements for bose 901's that should fit the boxes.  For now I'm running a set of 2 way Philips 4" and 1" that have got favorable comments from the few that have heard it.  This whole build was to have a good system to listen while I build my robotic arm, so the next money will be gears and shaft couplers and and and 

[shooter]

Finally took the time and dimed in the amp, close enough.  I was OD'ing the poor 84's, hitting them with 20vac rms!!  swapped in an AU, dropped it to 9vac, an AT about 16vac, settled for an AV7 at 11.4Vrms.

music sounds good, hiss n hum are all but gone

re-did the bias, from 9W to 12W idle, changed config of my vol pot.   This TS is very good!  Thanks to the Bogen engineering team

new schematic with DC volt #'s and schematic changes(V1a has a bypass cap - not shown ).

[shooter]

Ok, so I spent my robot money on a turntable!  Now I need to build an attenuation cable.  The phono out is to low for the amp and the aux out is to hot!, played around with a couple V1 tubes but nothing makes me happy.  MP3's with vol control work great, sound great, guitars work good, sound good.

Wanted to thank K for his link to the Z bracket article, I tried it, didn't help me, but for looks n giggles I set a RF pre-amp tube tween the trannies and it fit perfect!, glued it down and it works very well as a heat shield!!