May I have it , too? Please, please...
Hi,
may I have it, too?
brunoravera@yahoo.com
Thanks a million!!
Bruno
Hi,
may I have it, too?
brunoravera@yahoo.com
Thanks a million!!
Bruno
I checked the SCH lightly...
and i must say, that I was expected more
from Unison Research...
~
Anyway we have circuit with main undesireable caracteristics
~
1. solid state rectifier PSU section
2. two (incomplet, shorted) SRPP sections input and driver...
3. DC heat of 845 output tube...
4. Feedback loop...
~
that is main points of possibile upgrade...
and i must say, that I was expected more
from Unison Research...
~
Anyway we have circuit with main undesireable caracteristics
~
1. solid state rectifier PSU section
2. two (incomplet, shorted) SRPP sections input and driver...
3. DC heat of 845 output tube...
4. Feedback loop...
~
that is main points of possibile upgrade...
I wonder why? Because of the gorgeous wood or the mag reviews? They're all built to make a nice profit and at least the 'Smart' series seem all to share the same topology.
I wonder if there is a commercial 845 amp with vacuum rectification. Unless it's a monoblock there are not so many rectifiers available anyway.
Yeah, but they use 'approved for highend' and easily available tubes. And most importantly allows audiophiles to tube-roll
They could have done dc better of course. Maybe in the 'UltraSmart" series
They could have done this at least switchable. Hopefully it helps soften the effect of the cheap passives...And maybe even the output transformer.
Yeah, it's difficult to blame people who are cynical towards the high-end.
How to improve it? Without an entire redesign (something along the lines of Cary 805?) there isn't a whole lot to be done.
A real bottle-neck from my POV is the shared PS between input and driver. An extra choke/cap will surely bring a big improvement.
And btw there is absolutely no need for the input coupling cap.
Hi Zoran !
Well, I don't really bother about SS rectification if well established, except for in rush voltage.
Perhaps some TV damping diodes could be used, they have vy Hi Vfk allowing for a bridge or a doubler (!) configuration.
Roughly, both the input and the driver stage seems to be powered at roughly 600v.
Not a bad idea indeed, just the Vfk seems a bit above ratings.
I can't see why you tell it's incomplete or shorted ? What do I miss ?
More interrsting is your remark about DC heat of the 845, Could you develop ?
Feedback loop .... looks light, but so easy to remove anyway.
Still roughly, the 845 is powered at some 900 to 1000v.
I'm working at a project with that tube, if interrested, search for a thread named "Another 845 SET" in this forum.
Somewhat different approach for the input and the driver and certainly criticable as well.
The master piece is of course the OPT.
IMHO, 30H primary L would be sufficient and promises a -3dB point near 10Hz assuming the 845's Rp is around 1700 Ohms.
More will need more turns and/or more iron, but it's already a huge 5Kg thing to keep total induction below 1.2 Tesla at 30Hz, 30W Po.
And more turns also imply higher leakage inductance and parasitic caps wich looks to me even more penalizing looking to Hiz needed (7 to 10K)
I doubt we could learn how Unisson Research buit the OPT
My thoughs !
Yves.
Well, I don't really bother about SS rectification if well established, except for in rush voltage.
Perhaps some TV damping diodes could be used, they have vy Hi Vfk allowing for a bridge or a doubler (!) configuration.
Roughly, both the input and the driver stage seems to be powered at roughly 600v.
Not a bad idea indeed, just the Vfk seems a bit above ratings.
I can't see why you tell it's incomplete or shorted ? What do I miss ?
More interrsting is your remark about DC heat of the 845, Could you develop ?
Feedback loop .... looks light, but so easy to remove anyway.
Still roughly, the 845 is powered at some 900 to 1000v.
I'm working at a project with that tube, if interrested, search for a thread named "Another 845 SET" in this forum.
Somewhat different approach for the input and the driver and certainly criticable as well.
The master piece is of course the OPT.
IMHO, 30H primary L would be sufficient and promises a -3dB point near 10Hz assuming the 845's Rp is around 1700 Ohms.
More will need more turns and/or more iron, but it's already a huge 5Kg thing to keep total induction below 1.2 Tesla at 30Hz, 30W Po.
And more turns also imply higher leakage inductance and parasitic caps wich looks to me even more penalizing looking to Hiz needed (7 to 10K)
I doubt we could learn how Unisson Research buit the OPT
My thoughs !
Yves.