i am using 330R across spk+ and spk-
but i put them after the spk delay (at binding post)
so i think that's the problem, i should putting them before spk delay... thank's.
btw, should i keep the spk delay, or just remove them?
Another Singing Bush was born.
I was already happy with my SissySIT, a magical amplifier that gave me many hours of satisfying listening and that I considered the best I had ever built ... but here appears the ZenMod genius who shamelessly evokes the end of a myth ... my myth Sissy. I had a couple of my SIT 2SK180 TOKIN that I kept in reserve and when I saw the SB and especially when my dear friend fabiodipietro27 built it and described it to me, my absolute interest in building it began. Proceeding with my usual calm and cold blood I put it on.
I used Power supply boards designed by me inspired by those of "rhthatcher" which I thank.
the buffer calibration procedure went smoothly, the voltage controls were in place, the only hitch was the bias calibration as on both channels I could not go beyond 428mV. It was enough to change the value of R3 on the Mu board (from 100 to 220 ohm) to easily obtain 460mV with a potential on the drain of 37V.
Even if the SB has just been born, it has made it clear its royalty. An authoritative and sumptuous sound. Sculptural and wide acoustic image. Detail and fluidity. Magnificent amplifier.
But there is an annoying problem: buzz .... which makes it difficult for me to eliminate it. I have adopted the measures that I usually perform for a correct grounding by referring the GND of the PSUs on the chassis by interposing a CL60 in a single point, but nothing. I believe there is a ground loop and I was thinking of trying to implement the ground lift present on the PSU board (2 diodes + resistor). rhthatcher seems to me to have had the same problem but I don't know if it solved and how. I accept suggestions.
I was already happy with my SissySIT, a magical amplifier that gave me many hours of satisfying listening and that I considered the best I had ever built ... but here appears the ZenMod genius who shamelessly evokes the end of a myth ... my myth Sissy. I had a couple of my SIT 2SK180 TOKIN that I kept in reserve and when I saw the SB and especially when my dear friend fabiodipietro27 built it and described it to me, my absolute interest in building it began. Proceeding with my usual calm and cold blood I put it on.
I used Power supply boards designed by me inspired by those of "rhthatcher" which I thank.
the buffer calibration procedure went smoothly, the voltage controls were in place, the only hitch was the bias calibration as on both channels I could not go beyond 428mV. It was enough to change the value of R3 on the Mu board (from 100 to 220 ohm) to easily obtain 460mV with a potential on the drain of 37V.
Even if the SB has just been born, it has made it clear its royalty. An authoritative and sumptuous sound. Sculptural and wide acoustic image. Detail and fluidity. Magnificent amplifier.
But there is an annoying problem: buzz .... which makes it difficult for me to eliminate it. I have adopted the measures that I usually perform for a correct grounding by referring the GND of the PSUs on the chassis by interposing a CL60 in a single point, but nothing. I believe there is a ground loop and I was thinking of trying to implement the ground lift present on the PSU board (2 diodes + resistor). rhthatcher seems to me to have had the same problem but I don't know if it solved and how. I accept suggestions.
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yeah, typical Italian calm and cold blood ....... 
- buzz same/equal in both channels?
even prior to replying to that, R Core xformer is too close to signal pcb on that one channel, at least for my liking
I know some people like them ( even I have few in non-critical duty) but I can't forget how one of Greedy Boyz pretty much pulled all his hair, fighting with buzzin' Iron Pumpkin ..... and once when he replaced fancyshmancy RCores with decent small Donuts - suddenly no buzz and hum ....... that and few other examples made me suspicious when RCore is enywhere near signal traces
connection between case and audio GND is arbitrary ...... it must exist - be it direct or through NTC or through bridge thinge ....... any is good, best one is with no buzz
I didn't had any buzz even in my Ikebana style prototypes, let alone properly made amp
- buzz same/equal in both channels?
even prior to replying to that, R Core xformer is too close to signal pcb on that one channel, at least for my liking
I know some people like them ( even I have few in non-critical duty) but I can't forget how one of Greedy Boyz pretty much pulled all his hair, fighting with buzzin' Iron Pumpkin ..... and once when he replaced fancyshmancy RCores with decent small Donuts - suddenly no buzz and hum ....... that and few other examples made me suspicious when RCore is enywhere near signal traces
connection between case and audio GND is arbitrary ...... it must exist - be it direct or through NTC or through bridge thinge ....... any is good, best one is with no buzz
I didn't had any buzz even in my Ikebana style prototypes, let alone properly made amp
Hi Zen Mod and thanks for reply .
I, even if not very convinced of the responsibility of the R-core trafo, removed it and replaced it with a toroid. The noise is present in both channels slightly decreased in intensity (too little to tolerate it). .... I continue to keep my blood cold...
I, even if not very convinced of the responsibility of the R-core trafo, removed it and replaced it with a toroid. The noise is present in both channels slightly decreased in intensity (too little to tolerate it). .... I continue to keep my blood cold...
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problem is evidently in combination with upstream component (preamp?), most likely having common GND for both channels
solution can be in arrangement how to connect audio GND to chassis
please confirm - as I see it , you did made SB as dual mono?
if yes, you probably have one NTC between each separate audio GND/channel and case?
however - you can immediately try trick from Yore ( Hafler, for instance) - insert 22R resistor on one RCA , GND lead
solution can be in arrangement how to connect audio GND to chassis
please confirm - as I see it , you did made SB as dual mono?
if yes, you probably have one NTC between each separate audio GND/channel and case?
however - you can immediately try trick from Yore ( Hafler, for instance) - insert 22R resistor on one RCA , GND lead
the SB I made it dual mono.
The audio-GND connection on the chassis is made in a common point (see photo) without NTC (direct .... before they were present and now I have removed them).
are you suggesting me to put a 22 ohm R in series on the GND cable of the RCA?
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what is upstream of amp - preamp?
what happens if you install 20-ish R in line with both RCA gnds?
looking at pics, I can't understand why you decided to put pcbs having signal input and those big input caps being well inside case volume, in dirty side of case?
it would be logical to have these near input RCA, and Mu pcbs closer to Donuts
not saying that this is culprit of present issue, but anyway
what happens if you install 20-ish R in line with both RCA gnds?
looking at pics, I can't understand why you decided to put pcbs having signal input and those big input caps being well inside case volume, in dirty side of case?
it would be logical to have these near input RCA, and Mu pcbs closer to Donuts
not saying that this is culprit of present issue, but anyway
if I unplug the RCA cable from the preamplifier or short circuit the input the amplifier is completely mute. So the noise is not generated in the unit but outside ... if it were a ground loop maybe I could solve it using the ground breaker set up on the PSU cards ... I haven't tried it yet. Your suspicious inference about my arrangement of the cards does not explain why the amp is mute with the RCA unplugged. My preamp is tube with transformer output. It uses the CV181, it has a gain of 25dB. It didn't have any problems with the sissySIT or with a pair of MoFos or other amps.
"not saying that this is culprit of present issue, but anyway"
just for giggles - have you any chance to try amp with other source, say routing signal from CD/DAC trough passive pre ( simple vol attenuator)
even if we can say that problem origin is outa amp, we must find a cure for system as whole, curing eiter (new) amp to became resistible to buzz origin, or preamp itself (as final option)
if you test it as above, we will know more
question - preamp OPT secondary - is it floating , or having one end grounded?
just for giggles - have you any chance to try amp with other source, say routing signal from CD/DAC trough passive pre ( simple vol attenuator)
even if we can say that problem origin is outa amp, we must find a cure for system as whole, curing eiter (new) amp to became resistible to buzz origin, or preamp itself (as final option)
if you test it as above, we will know more
question - preamp OPT secondary - is it floating , or having one end grounded?