Vacuum tube amplifiers

[efren]

thanks sir ric +1

looking at the schematic i see it as a double purpose tester and should have been titled "SIMPLE CAPACITOR TESTER & WIDOW MAKER"

just spicing up

[tony]

2 small traffos wired back to back will take care of that......

[ricdelros]

this will help sir...+1 sayo....

BTW, do you have any simple inductance meter schematics?

Does anybody knows how much inductance is present with a 40w flourescent ballast...will it be good to use as inductor on tubes amps...will it pass 0.43 amperes of current as indicated?

Read this..It says here 1.15 to 2Henry but its australian measurement..better check actual

http://sound.westhost.com/lamps/fluorescent.html

[ricdelros]

2 small traffos wired back to back will take care of that......

Thanks for the tip

[???]

Parang ito yung hinahanap kung tester ng cap. +1



Hmmm parang ...

[tony]

Thanks for the tip

no problem, like Efren says,use of isolation transformer makes your tester safer to use....

[Tukkar]

Read this..It says here 1.15 to 2Henry but its australian measurement..better check actual

http://sound.westhost.com/lamps/fluorescent.html

Thanks + 1 ulit sa site...i was thinking of using old ballast for tube power supplies as inductor filter..but the question is ...till how much current or power will it function?

[Tukkar]

I had used my 56v, 3a trafo fo to power up my stereo tube amp using a quadrupler and filtered with 4 1000uf/250v caps and a resulting final HT of 260v.... when the tube amp plays....mids and highs are good...but the bass is a crap.."sabog"...ckt is push pull using 6R2P's in parallel without feedback...i use opt 2.5k/8 15w... Idle current is  70ma per channel..

How can I improved the bass response? was it due to the quadrupler (not producing enough current) or the OPT? To the Tube experts...Sir Tony and company any tips please..

[ricdelros]

can you post the PS schematic? I smell a power supply  sag or drooping of PS voltage..

[efren]

I had used my 56v, 3a trafo fo to power up my stereo tube amp using a quadrupler and filtered with 4 1000uf/250v caps and a resulting final HT of 260v.... when the tube amp plays....mids and highs are good...but the bass is a crap.."sabog"...ckt is push pull using 6R2P's in parallel without feedback...i use opt 2.5k/8 15w... Idle current is  70ma per channel..

How can I improved the bass response? was it due to the quadrupler (not producing enough current) or the OPT? To the Tube experts...Sir Tony and company any tips please..

i understand you're using Deeco irons in your OPT right? this could be another cause (OPT material) aside from the PS mentioned by sir ric, though might not affect that much

try also to adjust bias resistor (lowering the resistance) of the output tube, but be cautious on exceeding the max operating point of the tube...

check the plate volts with respect to cathode, not on the ground, could also be "starvation" of the finals.... 

[Tukkar]

i understand you're using Deeco irons in your OPT right? this could be another cause (OPT material) aside from the PS mentioned by sir ric, though might not affect that much

try also to adjust bias resistor (lowering the resistance) of the output tube, but be cautious on exceeding the max operating point of the tube...

yes I've used deeco core for my 6p3s but bass is hard with that core....and the amp sound good..

30ma is the ideal idle current when using single tetrode with 680 cathode resistor...since i use parallel tubes...i use 330 ohm cathode resistor and measured 70ma idle for both channels...all measurements was close to the right values indicated in the design..

check the plate volts with respect to cathode, not on the ground, could also be "starvation" of the finals.... 

[efren]

then it's just a matter of zeroing in on the "sweet spot" operating points, but still i'm a bit skeptical about your OPT, if it worked fine in the 6P3S, it doesn't mean it will do the same for 6R2P ...can you post the schematic and physical pics of the amp? this might help....

calling sir tony...

[efren]

another thing is this tube is for UHF 300Mhz duty, unlike the 845 & other similar transmitter tube which is for AM transmitter duties in the Khz to lower Mhz region also works exemplary for hi-fi audio,.

6R2P on the other hand might need additional tweaks for audio use, have you tried the UL mode, this might improve bass response. You need a UL tap in the OPT for this...

 

[Tukkar]

Schematics is found here...http://www.diyaudio.com/forums/tubes-valves/201632-russian-6r2p-small-amp-3.html.

PSU is a usual quadrupler with 4 1000uF/250 caps then 100/10w resistor then 330uf/450v for final HT.... driver and grid supply is separated via regulated output but not from the quadrupler output...

[Tukkar]

I'm still not using the trafo like the one with the 6P3s...still on winding shop...anyway i'll try to tweak again...

[tony]

I had used my 56v, 3a trafo fo to power up my stereo tube amp using a quadrupler and filtered with 4 1000uf/250v caps and a resulting final HT of 260v.... when the tube amp plays....mids and highs are good...but the bass is a crap.."sabog"...ckt is push pull using 6R2P's in parallel without feedback...i use opt 2.5k/8 15w... Idle current is  70ma per channel..

How can I improved the bass response? was it due to the quadrupler (not producing enough current) or the OPT? To the Tube experts...Sir Tony and company any tips please..

how is the voltage when ou crank up the volume? what is the drop?

voltage multipliers are fine for low current applications, this is the first time i heard it used on a power amp...

please post schemes of the set-up or pics if you can...

[efren]

@ Tukkar-page not found on my pc on your link regarding the schematic .
have you measured the plate volts? from min volume to max observe the reading as mentioned by sir tony.

do this procedure also on the main rail, is there a considerable drop? Voltage sag as mentioned by sir ric.

Buckshot method muna tayo, hoping we hit something behind that door. it is nearly impossible to hit the target when you can't see it

[Tukkar]

Posting scematics and psu....

By jmabanta at 2012-02-09

Psu

By jmabanta at 2012-06-14

During testing with music the HT is dropping a bit from 262Vdc to 255vdc at mid volume...

i will be posting picture set up monday since i will try to tweak it again this weekend...

[tony]

then it's just a matter of zeroing in on the "sweet spot" operating points, but still i'm a bit skeptical about your OPT, if it worked fine in the 6P3S, it doesn't mean it will do the same for 6R2P ...can you post the schematic and physical pics of the amp? this might help....

calling sir tony...

could be the opt saturating as well.....

[Tukkar]

I'll try to change OPT with other opt to verify this and also the power supply...