| T O P I C R E V I E W |
| Azazello |
Posted - 2012/12/23 : 21:12:20
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. |
| 9 L A T E S T R E P L I E S (Newest First) |
| Azazello |
Posted - 2012/12/25 : 18:03:48
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/. |
| pix |
Posted - 2012/12/24 : 17:09:35
Ahh 
Sorry my bad 
I got stuck in mind that these tubes where working in SE (klass A)
/Pix
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| Fuling |
Posted - 2012/12/24 : 16:05:35
Pix: The 820R resistors are for ground reference only. Take one more look how the power supplies connects to the output stage. |
| pix |
Posted - 2012/12/24 : 15:26:30
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 |
| Bernt Jansson |
Posted - 2012/12/23 : 22:12:01
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. |
| Azazello |
Posted - 2012/12/23 : 22:08:50
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. |
| pix |
Posted - 2012/12/23 : 21:54:17
Nice Azazello
I am just curious, have seen any output DC-drift on start-up, or over time?
/Pix
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| Azazello |
Posted - 2012/12/23 : 21:33:25
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 |
| pix |
Posted - 2012/12/23 : 21:17:09
Hi Azazello
A PSE without output caps or x-formers, seems to good to be true
A schematic would be appreciated
Best
/Pix |
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