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Old 25th August 2011, 02:11 AM   #11
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Me again...
Amazing what a good night's sleep can do...
Woke up this morning and just looked at my breadboard setup while sipping coffee when I saw that I didn't have my speakers grounded...

Had to run to work, but just addressed this little oversight and, voila, there is music! But...

My B+ is still at around 440V. The 300B look healthy, no glowing other than that of the filament.

Now I have to figure out whether to
1.) find another PT with a more appropriate voltage, or
2.) try a different rectifier tube (any drop-in replacement suggestions?), or
3.) scratch the 300B for now and convert board and iron for 45s

Besides that, it doesn't sound very 'clean'. I don't really know how to describe it other than a mix between foggy and almost scratchy; kind of like a speaker that has a broken cone foam (mine don't...).
As of now, NO comparison to my Simple SE build sound-wise.

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Old 25th August 2011, 02:45 AM   #12
w5jag is offline w5jag  United States
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2) Of the drop ins, a 5W4 has the most voltage drop - probably around 60-65 volts, but is only good for 100 ma or so; NOS 5Y3 will drop 55-60 volts and is good for 125 ma; 5R4 will drop a bit less than 5Y3 and you probably don't need to worry about its current limitations. Be advised that the Sovtek 5Y3 is not a 5Y3 - it's more like a reduced current 5V4.

A better way might be to remove the first capacitor in the power supply and use choke input - an LC power supply instead of CLC. That's how I ran my TSE.

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Old 25th August 2011, 04:00 AM   #13
rknize is offline rknize  United States
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You should be able to drop that 40V by reducing C4. Try 10uF or lower. Are you using a choke?
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Old 25th August 2011, 05:01 AM   #14
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Quote:
Originally Posted by rknize View Post
You should be able to drop that 40V by reducing C4. Try 10uF or lower. Are you using a choke?
I already went down to 4.7uF for C4 without seeing much effect.
Yes, I use a Hammond 193J choke. I haven't yet measured PT output AC voltage and haven't tried the 125V primary yet. I'll do both as soon as I get the time, which probably won't be before Friday.

As always, thanks for your helpful suggestions. I still have a lot to learn...
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Old 25th August 2011, 02:08 PM   #15
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Have you ever used PSUD? You need to drop it more. The TSE doesn't draw all that much current overall. Try 3.3uF.
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Old 25th August 2011, 02:16 PM   #16
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Quote:
Originally Posted by rknize View Post
Have you ever used PSUD? You need to drop it more. The TSE doesn't draw all that much current overall. Try 3.3uF.
Russ, four out of three Germans are bad at math and theory... I am two of them.
No, I haven't used any simulation software recently. A little bit of Spice in school a long time ago. That may be a good way to learn, too, if that stuff runs on Mac or in a VM. I'll definitely try it.

Having said that, I couldn't help but try the 125V primary tap after my post last night and I am down to 395V. The distortion seems to be gone, too.
More testing and simulations to come.
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Old 25th August 2011, 06:04 PM   #17
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I just downloaded PSUD2 and played around with it for a bit, plugging in my transformer and CLC components. The simulation seems to match reality pretty closely. This is going to be a really helpful [learning] tool for me, thanks very much for pointing it out, Russ!
And thanks to the generous soul that spent time designing & implementing this tool and making it available, wherever you are!

Can't wait to get home today to spend some time listening to the amp and play with the bias a little bit more.

THANK YOU for all your help and guidance, the newbie appreciates it very much!
Stefan
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Old 26th August 2011, 12:42 AM   #18
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Its a great tool. I originally ran the TSE with a different power transformer that i had kicking around. I removed that cap completely for an LC filter. Other than some buzz from the choke, it worked well.

Russ
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Old 27th August 2011, 02:45 AM   #19
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Default All checks out, but distortion at higher volume

So, after a couple of weird events (R3 silently died, one of the two 5824s with it), everything checks out. B+ is around 390V, bias set to ~70ma for now and pretty stable.
Sound is good, but not as good as the Simple SE built earlier this year. Maybe I a just got used to tube sound...

But, when turning up the volume while feeding a sine signal, at about 3/4 of total volume, the output shows a distortion. It doesn't look like clipping, but when playing music, it doesn't sound good at all.

Also, I noticed that the current across one of the 300B grid resistors seems to go up quite a bit at higher volumes (>100ma), which seems strange and can't be good for the tube.

What does an output signal form like this indicate, is this to be expected?
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Old 22nd November 2011, 01:53 AM   #20
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Any updates on this? I am too curious.
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