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Old 6th January 2013, 02:12 PM   #181
wicked1 is offline wicked1  United States
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I'll answer for him.. The transformers he used and published the info for in his last several posts has been w/ the dynaclone transformer.
Feedback is global.. same as the schematics on the website.
Feedback is what I was thinking about before falling asleep last night.. I may experiment for a while. I want to try local and e-linear. So far my build is going as per pete's schematic, other than i'm building voltage regulators. Once I start trying new things, I'll post what I find. I hope you all do the same .

Oh, does anyone know if I can run the 12hl7 screens at 150v? I am struggling to figure out the screen dissipation. (First time trying to figure out pentodes) To me, it looks like I would still be safe, but I'm probably wrong.. else Pete would have done his testing w/ this tube at 150v.

Last edited by wicked1; 6th January 2013 at 02:18 PM.
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Old 6th January 2013, 02:27 PM   #182
rmyauck is offline rmyauck  Canada
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Here is in #152

Mono push-pull driver PCB
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Old 6th January 2013, 02:41 PM   #183
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Quote:
Originally Posted by wicked1 View Post
I may experiment for a while. I want to try local and e-linear
I tried introducing feedback from the UL taps to the driver plates, using 30k resistors. It works well, drops the gain a little and lowers distortion a little. Maybe a small loss of max output power. I also lowered the global feedback resistor from 30k to 22k to drop the gain a bit. Something like 0.008% THD @ 1W now. I was also looking at IMD last night and it looks pretty good too.

Quote:
Originally Posted by wicked1 View Post
Oh, does anyone know if I can run the 12hl7 screens at 150v? I am struggling to figure out the screen dissipation. (First time trying to figure out pentodes) To me, it looks like I would still be safe, but I'm probably wrong.. else Pete would have done his testing w/ this tube at 150v.
The way I have things set up there is only 130V on the plates, so 150 might be pushing it. I tried 75V (0C2 VR tube) and 105V (6074/0B2), no difference seen in performance. Right now I have the 6074 in there (cheap, $2 at RES).

Pete
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Old 6th January 2013, 05:13 PM   #184
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Default Some 807PPP measurements

Did some measuring today of the 807 PPP amp. Pretty much the same configuration as I posted before, with the addition of feedback from the UL taps to the driver plates.

Now running ~450V B+ - I discovered I was inputting 120V to the 100V tap of the PT primary, and getting ~525V B+. The power transformer seemed fine with this, BTW, at least at 60Hz. So the max output power now is reduced, 43W @ 5% THD, or 37W @ 1%. I may go back and make more measurements on the 100V tap

See the attached PDF file for graphs and a schematic of the driver as of today...

Feedback is your friend!

Pete
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File Type: pdf 807_PPP.pdf (310.4 KB, 94 views)
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Old 6th January 2013, 06:19 PM   #185
wicked1 is offline wicked1  United States
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I was just about to calculate using lower value resistors (r15 and the 10k's on the plates) to see if I could bring the voltage up a bit, and maybe getting away w/ the 150v screen regulator, but this definitely puts a stop to that.
(and thanks for bringing the voltage to my attention.. I was looking at the V on the old schematic and not thinking about the lower driver b+.. But now b++ is low enough I could potentially run the driver off it.)

That's a big difference in output power... Seeing all the crazy ways people use transformers (putting HV on 12v transformers, etc) I'm hoping we can get away w/ 120v on the 100v taps.

Thanks for the PDF!!

(how do you pro's manage inventory? Every minor component issue sets me back a week waiting for delivery... I tend to order double of everything, but have been doing that for years, and still never have what I need)


-edit- Pete, did you really change r6 from 47k to 4.7k? (I re-read your website this morning, and so just read the bit about using a large resistor there) Sorry for so many questions. I'm honestly far more experimental w/ lower voltage (not tube) projects.. But you know... fear of death and explosions, etc........

Last edited by wicked1; 6th January 2013 at 06:47 PM.
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Old 6th January 2013, 07:43 PM   #186
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Quote:
Originally Posted by wicked1 View Post
Pete, did you really change r6 from 47k to 4.7k? (I re-read your website this morning, and so just read the bit about using a large resistor there) Sorry for so many questions. I'm honestly far more experimental w/ lower voltage (not tube) projects.. But you know... fear of death and explosions, etc........
I did. Probably makes no difference at all... 47k just felt too big...
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Old 7th January 2013, 09:15 PM   #187
pso is offline pso  Spain
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Hi, the version with KT88, is finished or still in progress?
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Old 7th January 2013, 10:54 PM   #188
wicked1 is offline wicked1  United States
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Pretty sure the kt88 works quite well as is.

I want to ask about the need for the additional feedback, and the not as good charts (High end drops off more, a bit more distortion) on the 807 version, compared to the kt88 charts on Pete's website w/ the Tango iron.
Is that because of the tubes, or the different, larger transformer? I'm just curious. I know it's a general rule that bigger iron means more high frequency losses.

I got my power supply built last night. The SiC diodes work fine. (Mouser does indeed get fields mixed up in their product specs. And omg, the amount of typo's and spelling issues I find just reading manufacturer datasheets is very bad.. yikes... Hopefully they get the numbers right!)
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Old 7th January 2013, 11:21 PM   #189
pso is offline pso  Spain
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Maybe a KT88 PPP.
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Old 8th January 2013, 02:52 AM   #190
roline is offline roline  United States
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I'm thinking a PP or even PPP with 18GB5's outputs.....
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