Tube Amps / Music Electronics
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|5/26/2003 6:26 PM|
||Re: DC Filaments|
Steve I tried that mod on the g40v, but couldnt get it to work correctly.
So it didn't heat up the filaments or it didn't help with the noise? The G40V amp is pretty noisy and only some of the noise is coming from the ac filaments.
|5/26/2003 7:16 PM|
no, the filaments I couldnt get above 5.5vdc, initially the they were at 6.5vac. I tried different dropping resistors and then just pulled them still couldnt get near 6vdc. I think just twisting and running the ac heaters better probably would accomplish the same if not better results.
This is the noisest tube amp Ive ever played, im sure lack of quality components lends much to this.
I was pretty diasspointed in this amp, I got it cheap off ebay but still think its a waste of money. it pops, smells like impending doom, crackles, is very noisey. I tried tweaking it for a couple of days, but i soon realized that the entire thing needed a redo, cheaper just to stick to homebrews. Live and learn
|5/27/2003 1:44 AM|
Yeah, the G40V's a hummer, all right. Part of the problem's that everything's mighty crowded in there. Part is that it has separate wires running to the two sides of the heater circuit, not a tightly spaced or twisted pair. And part is poor layout on the chassis with preamp grid leads way too close to leads with strong AC fields around them. But other than the hum, I like mine.
I hope I can end up with my in-progress homebrew humming somewhat less than the G40V. (It has considerably more gain.) I've tried to keep all the AC fields from the PT and choke and associated wiring well away from sensitive preamp stuff, paid attention to wire routing (even if it does like like a rat's nest) and transformer orientation, and the AC heater leads are tightly twisted zip cord, pressed right down against the chassis, barely parted enough at the tube sockets to connect to the socket tabs. I decided to hold off on the +50V or so heater bias until I see what it sounds like, but that'll be my first step if it hums excessively.
|5/31/2003 4:02 AM|
Do you live in the US? I was just wondering because the one I got when they first came out had an AC filament voltage of ~7.2vac. My theory was that they selected a 100vac primary PT so that it could be used overseas as well.
In other amps, I've been using the Mesa Boogie Mark III circuitry mainly to power 5-6vdc relay coil while running all of the filaments on AC so I don't really care if the dc voltage drops much below 6vdc.
When I first got my "little pig", I was comparing it to Peavey Classic 30 I had been modding so I thought that it sounded pretty good right out of the box. I learned later that it was basically just a Marshall 2204, and a pretty crappy one at that. But still light years ahead of the stock Peavey Classic 30...
The build quality seemed to be very inconsistent... I bet that it was the first tube amp that the factory in China had ever made!
|5/31/2003 4:11 AM|
||6 volt car battery|
Now try not to laugh too loud... But, has anyone run the heaters off a 6 volt car battery---which in turn, was being constantly recharged off a separate charger circuit?
Talk about added complications...
|5/26/2003 12:37 PM|
||Re: DC Filaments|
If you're using a Hammond PT, elevating the heaters is a cinch and worth the effort. I usually just create another filtered node off the B+; it works really well. I'm not sure DC filaments really are much more of an improvement if you have properly twisted pairs and use a stand-off voltage. In addition, if you're using a tube rectifier, make sure to use the CT off the rectifier windings for your B+ since this also acts as a "hum-buster." :O)
|5/26/2003 5:48 PM|
I struggled w/this and couldnt get it to work correctly. Ive heard mesa/boogie runs dc pre and ac poweramp, but have been unable to find a workable schem on this
Here's what I came up with after studying the Mk III schematic:
I used a big ass bridge rectifier with 1/4" quick connect lugs mainly to give me a place to securely attach all of the components. I suppose it might be a good idea to work out a drawing using 1N4007 diodes on a multi-lug terminal strip...
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