10 lbs of ____ in a 5 pound bag?!

Wow. This has turned into a packaging adventure! :scratch2:

Working on my Pilot/Motorola/Seeburg-parts-with-the-Stromberg-circuit amp yesterday.

Combination of small Pilot chassis + integrated amp (added preamp) + 8 big @$$ .1uf/630v epoxy-dipped coupling caps = whoa nelly, where does it all go?

Got it mostly figured out... and if I say so myself, it's pretty well organized and even rather neat looking. And only one jumper wire required (so far- I will wind up with a few others between the phase inverter and the output tubes, I think). Got all the stuff shielded/ twisted pair wired/ arranged where it should be pretty quiet, too. :thmbsp: All I gotta do now is get the phase inverter wired up... if I can get the 8.2uf 250v dipped caps in there, I'll have it made, I think!

I will definitely post a pic of this, once it's all in there. Doesn't quite rival the Bell & Howell Filmsound amp pics someone posted a while back, but it's not THAT far off...

Oh- BTW: Technical question- anyone see any problems making the two leads from the phase inverter to the outputs on each channel, a twisted pair between the terminals of the phase inverter triode and the coupling caps of the output tubes (i.e, between the split-load/cathodyne phase inverter and the outputs)? I'm thinking of LOOSELY twisting them together, to keep down (i.e, hold down by making it common-mode between the two opposite phases, which should cancel out) any hum/buzz that might want to invade. I'm thinking a cathodyne has low enough output impedance that this should be OK?

Regards,
Gordon.

Dense-pack construction can be a satisfying triumph when it is successfully done. But such construction can make any needed de-bugging a real bitter pill. AMHIK.... Although I've had good luck on occasion; an FM tuner I built a number of years back is a nightmare of very dense "dead-bug" squalid-state construction, with lots of shielding between stages. As I completed the build my stomach was tying up in knots in anticipation of trouble at start-up. But, lo, the unit fired up and worked without problem, and performed quite well once the front end and IF cans were tweaked--no debugging needed!

As for the coupling between the split-load phase spitter in your project I think the amount of hum and buzz picked up at that point in the signal path is apt to be negligable--unless the phase splitter is way across the chassis from the outputs....or running along with filament leads--which should also be balanced and twisted.

But at the same time I can't see where the few pfs of capacitance built up in twisting the leads would be significant either, so there should be no harm in doing this. At the same time you might want to consider dressing the two blocking caps close together along the same line of philosophy.

Old1625 said:

At the same time you might want to consider dressing the two blocking caps close together along the same line of philosophy.

Click to expand...

Already was thinking that. They're about as physically close together as can be, given the space constraints...

I think I'm probably going to be OK here... at least I can physically see everything at once, and it's going to be pretty easy to make sure that signal and power wiring is meeting at something close to right-angles wherever they cross... no parallel power and signal cabling, for the most part, and where it is near parallel, the signal cables are coax shielded...

One thing that should help me, too, is that I sort of inverted the layout of the amp. Pilot had the original input stage tube over next to the rectifier tube and power transformer... I changed that, to where the input tube (the preamp) is over between the output transformers, and the two tubes near the power supply are now the amp input gain and phase inverter for each channel... higher level signal there. Got the input selector and volume control on the other side and other end of the amp from the rectifier tube, as well, by doing that, and managed to get a pretty straight-line signal path, in relative terms...

Regards,
Gordon.

Ahem........

:worthless

Pics indeed! I've got a personal stake in this one.

WIRING COMPLETE!

I think. :scratch2:

This thing is so packed in, I'm inclined to do the "put it on the end of a 100ft extension cord and plug it in, WAY over there" routine.

Actually, I think I'm OK. Tested all significant connections with a multimeter (looking for shorts or improper conections), and all the connection impedances make sense. The only possible hiccup is the polarity of the output transformer... I'll DEFINITELY be plugging it into some junk speaker drivers (with no tweeters!) for initial testing, to make sure I don't get the SCREECH of positive feedback, before I determine that it's polarized right...

Will be putting it on the variac tomorrow... if it works, pictures will be shortly forthcoming!

Think it should sound good... I actually found an entire set of ALL-RCA tubes for it (NOS RCA 6CG7 clear-top preamp tube, two NOS RCA 6GH8 preamp tubes, four RCA 6BQ5s outputs, and an RCA 5U4GB rectifier). Neat gimmick, huh?

Regards,
Gordon.