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Old 5th November 2012, 07:16 PM   #971
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Without bypassing 110R I measure 35mA, still the same problem with voltage sag at the input reg, I bypassed the 110R to see what happens with the voltage sag. I'm waiting the warm up to measure again the voltage sag.
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Old 5th November 2012, 07:20 PM   #972
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302.4VDC at the input reg
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Old 5th November 2012, 07:23 PM   #973
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318VDC at the output PSU, I will try without bleeded resistor
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Old 5th November 2012, 07:29 PM   #974
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Quote:
Originally Posted by Deco-Doctor View Post
Hi Salas

Yes I found a solution. I have a pair of Partridge 977 SUT's in an external box. Now the grids of the input stage are at zero volts with the SUT's connected and the balance is better.

I guess the Sowter SUT's did not like the small DC on the secondary windings.

I just have to experiment now to optimise the loading on the Ortofon MC25FL.

I still have 47K input/loading resistors which is giving me a reflected load of about 1500 ohms on the cartridge, which is a little high for the Ortofon, but it still sounds very good, very quiet background too, the best phono stage I have used so far.
Could it have been some form of oscillation with the previous SUTs even? Does the new OK situation reflect to an uplift in perceived sound quality?

P.S. Try 18K-22K, it also gave me good square waves with the 977.
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Old 5th November 2012, 07:32 PM   #975
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Quote:
Originally Posted by merlin el mago View Post
Without bypassing 110R I measure 35mA, still the same problem with voltage sag at the input reg, I bypassed the 110R to see what happens with the voltage sag. I'm waiting the warm up to measure again the voltage sag.
There must be some drop when the secondaries face constant current draw for the caps I would guess.
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Old 5th November 2012, 07:36 PM   #976
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hmm with the two txs: R-Core 230V 120VA & EI Core 240V?
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Old 5th November 2012, 07:44 PM   #977
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Some drop, not huge, there is always when the Tx gets loaded. The very long wires run to the input of the reg must be terminated with a substantial capacitor it seems so not to interact its inductance with the wide bandwidth cascode CCS.
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Old 5th November 2012, 07:46 PM   #978
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Can be enough 27uF 400VDC MKP?
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Old 5th November 2012, 07:54 PM   #979
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Originally Posted by merlin el mago View Post
hmm with the two txs: R-Core 230V 120VA & EI Core 240V?
I use rule of thumb secondary x 1.33 for total Tx & rectification losses under load, not the theoretical x 1.414. That gives 306VDC for 230VAC. Most of the times falls between 1.30 to 1.35 in the end. Set the reg at 290 to see if it gives it new breath and to be more compatible with mains play.
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Old 5th November 2012, 07:55 PM   #980
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Can be enough 27uF 400VDC MKP?
Do the setting to lower first, to see what is the main holding factor.
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