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Azazello
Starting Member
8 Posts |
 Posted - 2012/12/23 : 21:12:20
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I build just prototype of exotic tube amplifier without output transformer or output capacitor, /tubes are direct coupled to the speakers/, parallel SE 6AS7GA & ECC81 & PCC88.
Quality of sound is for a level higher, comparing with my SE-s 300B, 2A3 RCA, 4P1L...Monster bass and big dynamic, very deep scene and sharp details. I though I never go back to regular SE, because every cheep or expensive transformer press the sound, scene and dynamic.  
Very, very ugly amplifier, but sound is incredible.
https://picasaweb.google.com/109570777566485968551/Amplifiers#5771387320833103202
In future I will build two mono blocks. |
Hi-End is back proportional to the number of composite parts! |
Edited by - Azazello on 2012/12/23 22:10:49 |
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pix
200.000-klubben
4175 Posts |
Posted - 2012/12/23 : 21:17:09
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Hi Azazello
A PSE without output caps or x-formers, seems to good to be true 
A schematic would be appreciated
Best
/Pix |
"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued", Radiotron 3rd edition. |
Edited by - pix on 2012/12/23 21:31:57 |
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Azazello
Starting Member
8 Posts |
Posted - 2012/12/23 : 21:33:25
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http://www.diytube.com/phpBB2/viewtopic.php?f=4&t=5363&start=15
Please, read my two posts on the page.
input stage is regular with PCC88....screen res.-500 kohm, plate res. - 20 kohm, plate U - 150 v, cathode res.- 390 ohm, cathode cap - 1500 uF/Panasonic, interstage cap/russian K-78/ - 0.33 uF |
Hi-End is back proportional to the number of composite parts! |
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pix
200.000-klubben
4175 Posts |
Posted - 2012/12/23 : 21:54:17
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Nice Azazello
I am just curious, have seen any output DC-drift on start-up, or over time?
/Pix
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"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued", Radiotron 3rd edition. |
Edited by - pix on 2012/12/23 21:55:25 |
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Azazello
Starting Member
8 Posts |
Posted - 2012/12/23 : 22:08:50
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U on the common resistor is about 0 - 0.1 v. I connect the speakers after about 2-3 min, when the tubes are just with current 60 ma.
There are and fast fusses about 0.3 - o.5 A, if something will wrong with some tube, and the speakers are really protected. |
Hi-End is back proportional to the number of composite parts! |
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Bernt Jansson
400.000-klubben
19763 Posts |
Posted - 2012/12/23 : 22:12:01
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Thats a Circlotron, not PSE. Looks similar to Atma-Sphere OTLs.
I do not doubt one second that the sound is excellent! With the right load OTLs sound marvellous.
I have built a few OTLs too, Futterman style. |
MVH Bernt Mitt system
"Det enda man kan vara praktiskt taget säker på är att en rak tonkurva alltid är fel." - Ingvar Öhman
Jobbar för Jorma Design och gillar bashorn
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pix
200.000-klubben
4175 Posts |
Posted - 2012/12/24 : 15:26:30
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Azazello,
Just some friendly thoughts
If you could find a suitable choke to replace those 820R cathode resistors, the efficiancy would increase substantially
I am not sure what plate current you are using, but the power lost in those resistors must be hugh 
That power could be better used by adding some more 6AS7 pairs to futher decrease the output impedance
I am not into Circlotrons, but I gusess a 1 Henry (low R)-choke would be a good start to try (rememer to readjust bias after change!)
Those chokes are not to difficult to find in some old vintage scrap-gear.
Even though an optimized current-rate choke is hard to find, a bit overrated current chokes is fine (underrated current chokes shuld be avoided due to signal (AC) swing margin)
A general rule of thumb is to use prox 50% of the max magnetic flux for the DC-current, and the other 50% for the signal swing
An other idea is to use one cathode-resistor per triode.
Or rather a power-resistor with a variable resistor in series, per triode. This would make it possible to ballance the current within each output phase.
A common chatode resistor require very closelly matched triodes to share the load.
/Pix |
"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued", Radiotron 3rd edition. |
Edited by - pix on 2012/12/24 15:36:58 |
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Fuling
DIY-Harry 2006, 200.000-klubben
7954 Posts |
Posted - 2012/12/24 : 16:05:35
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| Pix: The 820R resistors are for ground reference only. Take one more look how the power supplies connects to the output stage. |
"För mig påverkar inte priset kabelns elektriska egenskaper och därmed deras påverkan på ljudet" |
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pix
200.000-klubben
4175 Posts |
Posted - 2012/12/24 : 17:09:35
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Ahh
Sorry my bad 
I got stuck in mind that these tubes where working in SE (klass A)
/Pix
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"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued", Radiotron 3rd edition. |
Edited by - pix on 2012/12/24 17:11:46 |
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Azazello
Starting Member
8 Posts |
Posted - 2012/12/25 : 18:03:48
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Guys! Thanks for Your views!!
I'm not also in Circlotrons, but this is my best sound and I'm very glad! My "tube" friends, that listened it, are almost really shocked!
Next amplifier maybe will be with 6S33S for my friend with 12 inch Tannoy..../I think build better Cyrclotron, that have risk with high voltage tubes again with output transformers, with maybe, I think, not best sound, IMHO/. |
Hi-End is back proportional to the number of composite parts! |
Edited by - Azazello on 2012/12/25 18:12:04 |
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