Lets see who does the first one. We have early British & Australian interest but Irish outsider late entry may steal the contest.
Not likely to be me at the rate Irish is running, I only have my valves and sockets. Plus, I'm off to the 5 day Blues and Roots festival in Byron Bay on the east coast of Aus; leaving in a couple of days until the end of April. Bob Dylan headlining, BB King, Elvis Costello... the list is endless. I'm afraid the pursuit of reproduced music will have to give way to the real thing for a while.
Best of luck lads. I'll check in to catch up on progress when I return... if I survive.
T
Thinking about aphrodite was nicer.....
An externally hosted image should be here but it was not working when we last tested it.
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Progress has been made....
I have the 2 heater supplies made up and also the HV shunt and all verified working OK.
But I have a couple of questions:
SSHV shunt: I have a transformer with 260V out, I'm getting 320V after the first cap and ~300V after the second cap. What is the output voltage I should set it at? Is 280V enough of a drop?
I have this really strange thing on the heatsink (both the 840 and 9240 mounted, using insulators, no continuity between any part of fet and the sink) - I get a floating voltage rising to about 30V on the sink. Doesn't go higher.... No continuity though....
Last question for now:
I have some choices for boxing up. Is it better to have a box with just the transformers, and then the regulated supplies near the valves, or should I put all the PSU stuff in one box and only have the circuit and nothing else in the second chassis?
Thanks all,
Fran
I have the 2 heater supplies made up and also the HV shunt and all verified working OK.
But I have a couple of questions:
SSHV shunt: I have a transformer with 260V out, I'm getting 320V after the first cap and ~300V after the second cap. What is the output voltage I should set it at? Is 280V enough of a drop?
I have this really strange thing on the heatsink (both the 840 and 9240 mounted, using insulators, no continuity between any part of fet and the sink) - I get a floating voltage rising to about 30V on the sink. Doesn't go higher.... No continuity though....
Last question for now:
I have some choices for boxing up. Is it better to have a box with just the transformers, and then the regulated supplies near the valves, or should I put all the PSU stuff in one box and only have the circuit and nothing else in the second chassis?
Thanks all,
Fran
You should be getting around 350V with solid state bridge and 260VAC Tx. Is it sagging on constant current draw? What is the value of R1 on the SSHV and the voltage drop on it, also what is put between the two PSU capacitors that drops 20 further Volt? 280VDC still will operate the phono within bounds. 20V drop across reg is ample.
Ground the sink in the final box and use proper fuse on primary and AC mains ground to chassis, don't skip any safety wiring. Insulators may always breakdown in the long run.
To have the SSHV in the same box with the phono circuit is absolutely recommended. The heaters PSUs may or may not be near.
Ground the sink in the final box and use proper fuse on primary and AC mains ground to chassis, don't skip any safety wiring. Insulators may always breakdown in the long run.
To have the SSHV in the same box with the phono circuit is absolutely recommended. The heaters PSUs may or may not be near.
I have 470R 5W between the 2 PS caps (220uF-470R-220uF) and I get the 20V drop right there. R1 is 47R and I get ~1.8V drop across it.
Tx gives me 260VAC unloaded, ~252VAC loaded, ~320VDC after the diodes (UF4007) and 300 at the second PS cap.
Maybe I should drop that 470R a bit.....
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Both chassis will be grounded.........
(like the new avatar Salas!)
Tx gives me 260VAC unloaded, ~252VAC loaded, ~320VDC after the diodes (UF4007) and 300 at the second PS cap.
Maybe I should drop that 470R a bit.....
************************************
Both chassis will be grounded.........
(like the new avatar Salas!)
While waiting for parts to arrive, I have the 2 chassis almost ready to go. One is recycled from a preamp, the other is a scrap instrument case. Another hour or 2 and the chassis work should be done..... which is great since chassis work is the bane of any DIYers life....
Another question:
Is there any good reason why I shouldn't add another set of RCA jacks and wire them directly to the circuit, by passing the step up transformers?
Lastly, I remembered I had a link kept for how to load MC carts following a step up Tx... http://www.kandkaudio.com/mccartsetup.html
Fran
Another question:
Is there any good reason why I shouldn't add another set of RCA jacks and wire them directly to the circuit, by passing the step up transformers?
Lastly, I remembered I had a link kept for how to load MC carts following a step up Tx... http://www.kandkaudio.com/mccartsetup.html
Fran
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All well theoretically, but there can be a couple of practical catches that I have referred before in this thread for this particular input stage at least. It is possible that some SUTs combinations will show more THD when loaded heavier than 47K on this one. Also showing less multiplication ratio than unloaded nominal. To the contrary the more than necessary reflected primary load impedance for the 12 Ohm coil cart did not show signs of tonal thinness. Bottom line is, try 47K alone to compare too in your final set up.
LL9206 and possible grid current
Hi Salas,
Nice project!
I have one comment on your circuit and the use of the LL9206 Tx. Since this is a transformer with a continous amorphous core it absolutely hates DC, even if it is small. One should nver put any dc on any of its windings, and if it is done one must demagnetize the core afterwords. With zero bias there is a fair chance of dc in the secondary and this must be avoided to give the 9206 a fair chance to its stuff.
BR,
Anders
Hi Salas,
Nice project!
I have one comment on your circuit and the use of the LL9206 Tx. Since this is a transformer with a continous amorphous core it absolutely hates DC, even if it is small. One should nver put any dc on any of its windings, and if it is done one must demagnetize the core afterwords. With zero bias there is a fair chance of dc in the secondary and this must be avoided to give the 9206 a fair chance to its stuff.
BR,
Anders
See the sch in the pic below:
He ties gnd on the primary side to gnd on the secondary. Salas, I note you didn't do this in your schematics, although there was some discussion about it back a little. Both version of yours are working fine? No need to follow that common gnd?
Made more progress tonight. The transformer box is done, next up is the umbilical from phono box to transformer box. Then I can start on the circuit itself - thanks to the arrival of some nice matched caps from Poros Island......
We will see which is most IMF-affected postal service... I'm already guessing it is the Irish one!
Fran
An externally hosted image should be here but it was not working when we last tested it.
He ties gnd on the primary side to gnd on the secondary. Salas, I note you didn't do this in your schematics, although there was some discussion about it back a little. Both version of yours are working fine? No need to follow that common gnd?
Made more progress tonight. The transformer box is done, next up is the umbilical from phono box to transformer box. Then I can start on the circuit itself - thanks to the arrival of some nice matched caps from Poros Island......
We will see which is most IMF-affected postal service... I'm already guessing it is the Irish one!
Fran