• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Help identify these opt.

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albertli

albertli

Member
Joined 2004
Guys,
Thanks for all the info and valuable suggestions.
My speakers are all 8 ohm and only couple pairs with 4 ohm. I don't need big power either for all the speakers are from 90-108 db. 5Watts will be ideal as reference of design. I'm thinking of a pair of 807 per channel, may be in triode for simple application.
Ideas will be welcome. I'm open to anything sounds good. 😀
Albert
 
albertli

albertli

Member
Joined 2004
6A3sUMMER said:
If you can build a negative power supply, you can use a current source and cathode coupled phase splitter to drive the output tubes.
That is pretty simple, and can be low distortion.
Just a thought.
We all have our favorite way to do things.

I am working on a circuit with the 6.3 filament secondary for the negative supply. no extra secondary required.
I have a couple of kinds of simple current sources that can use that negative supply.
Click to expand...
Is it possible to share your ideas with me so I could learn from you. I have no experience on pp. I did have finished making some triode amps.
Albert
 
6

6A3sUMMER

Member
Joined 2016
You are in luck. You have 8 and 4 Ohm taps, efficient speakers, only want 5 Watts, and want to use 807 tubes.
There should be several relatively simple topologies to get 5 Watts.

You are challenging me to work on my latest design ideas, thanks!
It is getting hot here, and I need to work downstairs to stay cool (a nice excuse to spend more time on amps).
The negative supply is the next step for that design. Let me do that and report back.
 
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albertli

albertli

Member
Joined 2004
kevinkr said:
I think they would be good with 807 running at relatively high voltage, say 550 - 600V. Use some gas tubes to regulate the screens. You'd get some powah.. ;)
How comfortable are you with that?
Click to expand...

Kevin,
I would prefer a low power good sound one to the big power one. 5-8watts will be ideal. 550-600v sounds horrible to me. I'd like to keep the B+ under 500v if possible.
Albert
 
albertli

albertli

Member
Joined 2004
rongon said:
Are these big and heavy? If so, maybe they're meant for over 40W output. They don't look very big to me in the picture. If they are indeed smaller/lighter, then they'd be of the 20W class meant for PP EL84 or PP 6V6 (4 or 5W triode, 10 to 20W pentode).

If they're the big/heavy type, 10k:VC is also good for PP 6L6 or PP EL34 in triode, if you're okay with a 10 to 15W watt amplifier running on a 400V plate supply.

According to Wavebourn, a big 10k PP OPT is just what you want for a pair of GU-50 in pentode. I think the usual recipe is about 600V on the plates and 200V on the screens. That would make a lot more power. But only if these are big OPTs meant for 50W output.
--
Click to expand...

I have some GU50. Any chance you have a schemetic handy? Wavebourn has some good designs with GU50 and I had finished one SE with his design. Can't remember right hand or left hand.
 
albertli

albertli

Member
Joined 2004
6A3sUMMER said:
You are in luck. You have 8 and 4 Ohm taps, efficient speakers, only want 5 Watts, and want to use 807 tubes.
There should be several relatively simple topologies to get 5 Watts.

You are challenging me to work on my latest design ideas, thanks!
It is getting hot here, and I need to work downstairs to stay cool (a nice excuse to spend more time on amps).
The negative supply is the next step for that design. Let me do that and report back.
Click to expand...

Take your time and I can wait.
 
albertli

albertli

Member
Joined 2004
6A3sUMMER said:
Cello, double bass, bass trombone, bass clarinet, basson, tuba, etc.
The harmonics fall into our ears most sensitive frequency region.
Sound wonderful when recorded and played back properly.
What more can I say.
Click to expand...

You read me.
Been trying too many ways chasing for the 'right' sound for many years, from TT to CD transport, from DAC to preamp then to power amp. It seems never reach the ideal goal but just keep chasing after and convince myself that I might find that something better if I make change to........... Eh.........again and again, it might be the fun part but sometime it may be quite frustrating. Keep going and it is DIY. Now I just wish I could make something to please my ears.
 
D

danFrank

Member
Joined 2005
Inject the AC voltage into the whole primary and take voltage readings at the secondary; your calculations will be much more accurate this way.
They look like either Fisher or Scott OPTs to me.
They are probably 6.6K or 8K primary impedance with C, 4, 8, and 16 ohms for the secondaries.

Edit: Yes, Or Bogen, like Palustris said earlier. I think he got it right... All my Bogen transformers have the date written on them with the same color ink as yours.
 
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albertli

albertli

Member
Joined 2004
danFrank said:
Inject the AC voltage into the whole primary and take voltage readings at the secondary; your calculations will be much more accurate this way.
They look like either Fisher or Scott OPTs to me.
They are probably 6.6K or 8K primary impedance with C, 4, 8, and 16 ohms for the secondaries.

Edit: Yes, Or Bogen, like Palustris said earlier. I think he got it right... All my Bogen transformers have the date written on them with the same color ink as yours.
Click to expand...

Good to know if these are the good opt.
now I just heading for a good schematic about 5-8w in triode.
 
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