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Old 20th February 2004, 07:40 AM   #21
tubeman is offline tubeman  Thailand
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Hello..
I have a problem about my 833A tube .
I test at Vp= 1,000V , Ip= 150 mA and Grid connect to Gnd.
Plate are red .
Is it normal ?
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Old 20th February 2004, 03:32 PM   #22
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Default red spot on plate...

Hi Bas and Tubeman,

sorry fo not answering faster......i'm not always on-line.

Bas: the transformers are (almost all) made by Heart. The owner is Rik stoet. Yes.....he started with import Chinese stuff. Nowadays he has his own transformer-winder. Not surprisingly for his father was owner of a transformer company. as was his grandfather.....He is the first to step over to audio-gear.
Look onder www.tubes4all.nl and www.heartaudio.nl and you'll see that there websites are really old. There isn't even a notification of there moving from Den Haag to Zoetermeer.
Doesn't matter.....their transformers are really nice !

Tubeman: No worries about the chery red plate. Currently i'm using the 833 with 1000 V as B+ and i can see a nice cherry red colour in the middle of the plate.
Look at the RCA TT-5 manual: "....plate shows an orange-red colour...." But that's on max specs.


I'll attach a picture of aa 833A in my amp. And i have somewhere a picture of a 833C wich is really orange !!! Remeber: that's a massive carbon-plate......

Reinout
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Old 20th February 2004, 03:36 PM   #23
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Default a 833C at 2500 V

Hi Tubeman,

as promised the picture of the 833C at 2500 V. As you can see you can push this tube hard.
Hope you're somewhat more relaxed about your more moderate red plate ?

Reinout
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Old 23rd February 2004, 01:07 AM   #24
tubeman is offline tubeman  Thailand
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Thank you ! ReinoutdV for your 833A picture.I'm to be relieved
And I can show you of my 833A Socket in this picture . I made it from epoxy PCB and clip fuse holder. Can you comment it.
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Old 23rd February 2004, 01:21 PM   #25
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Default 833 socket caution

Hi Tubeman,

great to see more people working with the 833. It's a nice sounding tube !

I do have to warn you about the tube sockets. The 833 can be very very hot.
When i first want to build the amplifier i just wanted to fix the tube socket on a glass plate (10 mm). Just for the looks (and doubles nice as an isolator). But the tube is really hot, not to mention the filament pins themselfes. The glass plate was continiously strongly heated at the same spot and i was afraid it was going to crack. So i had to fix a teflonplate in between the socket and the glass. The teflon is white (reflects heat) and disperses the heat to a larger surface.

Very usable stuff: teflon. It can take a real heat-pounding. Can your epoxy also suffer hard before break-down ? If it melts....you're in for a nice firework.

Also remember that the filament gobbles away 10V / 10 A. And there is a 20 Ampere inrush during warm-up. That is like a car battery with all well deserved warnings. So no flimsy connectors, lightweight hookup wire, crocodile clips and so on.

Foto included.

Keep us all informed about your progress ?

With regards,

Reinout
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Old 24th February 2004, 02:05 AM   #26
tubeman is offline tubeman  Thailand
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Default Thank you !

Thank you ! Reinout for your help.
Maybe I change Epoxy to Teflon plate but in Thailand the Teflon are very expensive than Epoxy. And the original socket for 833A can't find in Thailand .

Can you tell me about the ratio of interstate transformer (from your 300B to 833A ). Is it Stepdown IT ? Because I have a pair of Lundahl LL1671/50mA interstate and I should connecting it to 4:1 Stepdown for more current to drive 833A-grid and not require to Stepup because the 833A are Hi-mu tube. Can you comment it ?
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Old 24th February 2004, 04:57 PM   #27
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Default teflon + interstage

Hi Tubeman,

teflon is just as expensive in Europe. It is simply a great material to work with: perfect isolator, reasonable sturdy, machinable, heat resistant. And with a price to match.......
Sorry, this stuff is not cheap. But i've found no real substitue. And when you're stepping into the use of these tubes i don't skimp on safety !

Your step down ratio for the 300B-833-IT is exactly what i use: 4:1. It works nicely and makes use of the high mu characteristics of the 833.

And how you "fire up" a 300B: absolutely your own choice. And there are more than enough choices to pick from.....

What are you intending to use ?

Reinout

(picture of 833C attached)(currently i'm listening to different 833's.....fun !)
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Old 25th February 2004, 03:29 AM   #28
tubeman is offline tubeman  Thailand
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Default Driver state

Thank you ! Reinout
I think the 300B is the best for drive 833A but 300B I haven't and very expensive too.and I have many tube NO. KT66 , 6L6GC or 6384 (premium grade of 6AR6)
Can I use it ? Maybe I use pentode connect to triode mode tube in 6384 or 6L6GC.And I"m not sure it can drive enough . If I need power output 50-70 w in SE

I have five choice in this.

1) 6EM7 hi-mu direct couple to 6EM7 lo-mu - interstate 4:1 to 833A (maybe low power)

2) 6SN7-1st direct couple to 6SN7-2nd - Cap coupling to 6384 or 6L6 - interstate 4:1 to 833A

3) 6C45pi - Cap coupling to 6384 or 6L6 - interstate 4:1 to 833A

4) 6SL7 - Cap coupling to 6384 or 6L6 - interstate 4:1 to 833A

5) 6SL7 - direct couple to 6BL7 or 6BX7 - interstate 4:1 to 833A (maybe low power)

Comment it plese!
Thank you !
tubeman.
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Old 25th February 2004, 06:29 AM   #29
tubeman is offline tubeman  Thailand
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Hi ! Reinout
And this is a picture of my Tung-sol 6384 tube.

Thank you !

tubeman.
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Old 25th February 2004, 09:52 AM   #30
protos is offline protos  Greece
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Hi Reinout,
It really is a massive project you have done.
Since this seems not to be your first project can you tell us your opinion on the sound quality compared to any other amps or SET amps you have?
Also how much did it cost?
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