Discussion in 'Building the Classics' started by FourT6and2, Jun 25, 2017.
It's time for everybody's favorite part of building an amp—heaters!
JK, it's the worst.
Decided to run DC on V1 and V2; regular AC on V3-V6.
Looking great, but I only see 3 preamp and 2 power valves - where is V6?
It's a ghost valve
very clean work
More progress today. Finished up the power section and did the power tube sockets, bias test points, impedance switch, and a few other things here and there.
That is one clean looking build. Pure circuit porn. Nicely done.
A bit more today. Having routed a bunch of stuff now, I'm making some notes about how to do it better the next time around. And by better, I mean more OCD lol.
Preamp tubes all done. In the home stretch now.
Just doing some testing now. I'm using a 47K 5W pot wired as a variable dropping resistor. This way, I just clip it to the filter cap and I can tune all the voltages in the amp. Typical value is 10K. I set it to 18K, which is what the Yeti uses (higher voltages). And my B+ is a whopping 515vdc! That's without power tubes though. Once I stick some in, it'll probably come down a bit. I don't really have a set goal in mind. But I'll play it with a few of the resistor values I have on hand and figure out which one to use.
I also got some new Tefzel hookup wire in some fancy colors for the next build. And I'm going to try to make the lead dress a little better next time around. I wanted to get this one done so I can start testing a few things first, tone wise.
Current voltages with no power tubes and 18K dropping resistor:
AC FILAMENTS: 3.47VAC
DC FILAMENTS: 6.09VDC
BIAS/PI SPLITTERS: -50 to -36VDC
PT SECONDARY: 375VAC
3: 511VDC - 515VDC
SECOND CAP AFTER DROPPER (18K): 381VDC
BOARD CAP AFTER DROPPER: 366.8VDC
Man, that turned out great.
Can't wait to hear your thoughts after final tuning.
What kind of wire is that, and where did you get it?
I'm fixing to redo my 5e3 with a turret-board and some mods, and I don't think I'm gonna use the original cloth covered wire this time.
Here's a clip. This is with a 10K dropping resistor. Probably my favorite value so far. The volume is as loud as I can get it without clipping the mic on my laptop, sorry lol. I'm working to upload the other clips with different voltages too. But it takes a long time for YT to process 'em. I'm still toying with a few parts here and there.
Black dog is such a rich song. Nailed very well
I just love that rhythm riff lol. I always use it to test an amp, even high-gain ones.
If you change the filament wire layout....there is no need for DC heaters.
It is possible to get 100% of the noise out by re- positioning the filament wires.
Means nothing with the tubes out. There is no load on the power supply.
The more the supply is loaded: the lower the voltage will drop.
Bias setting: will literally control the B+ voltage.
The hotter the bias is...the lower the B+ will drop.....because the B+ is loaded more.
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