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Old 21st January 2012, 12:01 PM   #3861
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Russian chokes? Dr-5-008? Whats the current through them? Do they warm up?
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Old 21st January 2012, 12:22 PM   #3862
M Gregg is offline M Gregg  United Kingdom
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Quote:
Originally Posted by Milen View Post
E88CC + EL34 SE, 5,5W @ 8 Ohm
Interesting,

Are the EL34's in pentode, triode or UL ?

I like wood and tubes..

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M. Gregg
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Old 21st January 2012, 12:46 PM   #3863
Milen is offline Milen  Bulgaria
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Quote:
Originally Posted by mindutis View Post
Russian chokes? Dr-5-008? Whats the current through them? Do they warm up?
Each is working at 50mA and are not warming up. "DR-5-008" means 5H 80mA


Quote:
Originally Posted by M Gregg View Post
Interesting,

Are the EL34's in pentode, triode or UL ?

I like wood and tubes..

Regards
M. Gregg
EL34's are in triode mode - 50mA/390V/-30V; Rk=560 Ohm


e88cc:

12mA/150v/-3,3v; Rk=270; Ra=15K

Last edited by Milen; 21st January 2012 at 01:01 PM.
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Old 21st January 2012, 09:12 PM   #3864
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Default forgotten tube

Hello All
I see alot of the contributors use alot of standard tubes, Ive built amps using EL34 and 6L6s and 6550's, hell I even did a couple KT66's.
But I got bored of the sound between some of these tubes, the EL34's are suprising sometimes, depending on how they are run, cold or hot! But I just wanted to mention that I havent heard anyone talk about the 8417.
This tube has the highest transconductance in a audio power tube than any other i know. Low capacitance also helps the range these tubes can handle. Did some research and these tubes were designed to be used as frequency motor drive controller.. I had and built many amps and this tube suprised me...got the bottom and mids of the EL34 and the sweet highs of the 6L6s in one package...unfortunatly this tube isnt made anymore, but hoping who ever bought the tooling from RCA will make them again... Anyway I enclosed a pick of my latest refurb, pair of Bogen MO200A's, these amps are awesome performers, specs on these things are 8hz to 50khz, and 200watts conservatively. So if you come across them get them... can be modified for 6550's by adding a extra gain stage.
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Old 22nd January 2012, 02:07 PM   #3865
M Gregg is offline M Gregg  United Kingdom
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Quote:
Originally Posted by Soundude View Post
Hello All
I see alot of the contributors use alot of standard tubes, Ive built amps using EL34 and 6L6s and 6550's, hell I even did a couple KT66's.
But I got bored of the sound between some of these tubes, the EL34's are suprising sometimes, depending on how they are run, cold or hot! But I just wanted to mention that I havent heard anyone talk about the 8417.
This tube has the highest transconductance in a audio power tube than any other i know. Low capacitance also helps the range these tubes can handle. Did some research and these tubes were designed to be used as frequency motor drive controller.. I had and built many amps and this tube suprised me...got the bottom and mids of the EL34 and the sweet highs of the 6L6s in one package...unfortunatly this tube isnt made anymore, but hoping who ever bought the tooling from RCA will make them again... Anyway I enclosed a pick of my latest refurb, pair of Bogen MO200A's, these amps are awesome performers, specs on these things are 8hz to 50khz, and 200watts conservatively. So if you come across them get them... can be modified for 6550's by adding a extra gain stage.
Very nice,

I love the hot rod wheels

What about an inside shot? (do you have any)

Whats the switch on the top for? (input select)

Regards
M. Gregg
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Old 24th January 2012, 07:57 PM   #3866
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Sorry for the delay response, night shift this week...I do have inside shot I will post it when I get off my camera...the switch is the screen standby switch...it's more effective at not causing tube sickness or cathode stripping. It works very well, switching screens stops 90 percent of current so when you warm up tubes the cathode can heat before current can flow, and since there is a small amout of current flowing you wont weakin or oxidize the barium on the cathode...if anyone likes this idea make sure you use a bypass cap across the switch terminals so you dont get popping in speakers fron the contacts arcing. .1 to .47mf..also use a good size voltage rating 600 to 1000v..
The best standby is switching rectifier filaments, if you have tube rectifier..some use fast diodes for the quickness. I personally use diodes before the rectifier tube incase it shorts, tube rectifiers when short send ac to everything including the speakers and if you have old and expensive speakers this will be your saviour...ac will destroy almost evrything in the power and output stage including your precious speakers. word for the wise...John
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Old 24th January 2012, 08:25 PM   #3867
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I have to share this one amp with you since I get alot of questions from this one, I call it Little Gem, lets see if you can figure this one out, I this amp is more than what it seems and somebody out there probably can tell right away...outputs are scotts and power tranny is Chicago...sound is really unbelievable which has everyone questioning who heard it...I'll also give you a pick of the KT66...
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Old 24th January 2012, 11:22 PM   #3868
mltube is offline mltube  United States
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Default 3C24 With 6em7 pre-driver class A2

Thought this may be a little more interesting than a standard pic, the sound quality is not the best with the camera that I have but it is just for fun anyway.
Sounds fantastic in person even with the Open Baffle test speaker.
Breadboarding for fun and pleasure.
Have fun watching...

http://www.youtube.com/watch?v=KXuDR...&feature=share

Last edited by mltube; 24th January 2012 at 11:25 PM.
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Old 25th January 2012, 02:01 AM   #3869
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Quote:
Originally Posted by mltube View Post
Thought this may be a little more interesting than a standard pic
Can you post pictures... i had to turn off the youtube about 15 sec in.

dave
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Old 25th January 2012, 03:07 AM   #3870
mltube is offline mltube  United States
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Default Pics of the 3c24/6em7/0D3 SE A2

Here are some photos of the breadboard setup. It is, well... a breadboard test, not much for appearance.


The sound quality is superb to my ears, and I have made many many amplifiers past and present. Sounds on par with my 45 set, but much more power out to my ears. I do not have tools for testing output or harmonics, but it is crystal clear with Bach, and other jazz samples.

I have a 5973 UL se amp with James xfmrs throughout, and this 3c24 with antique opt is blowing it away also.
I will need to make connectors to disperse the heat better on the plate and grid.
The wire I am using on the plate right now is off a tv flyback, but the insulation is beginning to droop 1/2-3/4" up from the top of the tube, however the rest of the insulation is cool elsewhere. I am running 297v on the plate and 37v+ on the grid of the 3c24 and the opt pri. is @3k. I am using an 0D3 to regulate the plate of the power section of the 6em7 which is maintaining the pos voltage from the cath to the grid of the output. The HV PS is at 75mA for the circuit. I will have to draw up a schematic to post, as this is another circuit off the top of my head. They seem to work better when I design on the fly. And the white masking tape on the leads of the black cat is just for rigidittty, no other function.

Next up is the 826 RCA for output....
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Last edited by mltube; 25th January 2012 at 03:12 AM.
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