October 20, 201114 yr Good Job! Glad to know swapping out the PRP reduced the noise for sure. Now I have to find new use for these prps...
October 20, 201114 yr I was told to use the xicon resistors. I was not told why. Or i was told why, but did not understand. The spec on the prp resistors says 500 volts across the resistor. It says nothing about leakage from the resistor to ground or other parts of the circuit. They do leak about 150 nanoamps to ground at 500 volts. And probably moisture in the air makes a change in that number. For most stuff even including the kgsshv, this is not an issue. Properly adjusted, this amp is good for a 95 to 100db signal to noise ratio. Input tubes make a huge difference. Compared to the original which has oodles of hum from the unregulated power supplies there is a night and day difference. Its a tube amp, it is supposed to make some noise. Thermal noise from the output tubes is just the way it is. Kerrys solid state front end version should make less noise.
October 20, 201114 yr Properly adjusted, this amp is good for a 95 to 100db signal to noise ratio. Input tubes make a huge difference. you mean 115dB /rudi
October 20, 201114 yr :prettyprincess: I replaced two resistors in the batteries and the noise is almost all gone (very, very slight now. WUHOO!!!
October 20, 201114 yr Author Well, I just found out what is holding up my resistors... they are in Dubai... Somebody at Mouser made a slight error as to where I am in the world.
October 20, 201114 yr Author Allied Electronics used to do this all the time though they just sent my packages to Israel. I mean IL and IS are pretty much the same thing... right?
October 20, 201114 yr "Allied Electronics used to do this all the time though they just sent my packages to Israel. I mean IL and IS are pretty much the same thing... right? " Being part of the Stax Mafia, They should have sent it to Italy.....
October 20, 201114 yr Well, I just found out what is holding up my resistors... they are in Dubai... Somebody at Mouser made a slight error as to where I am in the world. All islands look alike to us Americans.
October 21, 201114 yr I just replaced R37, R38 which sit pretty close to some other PRP resistors and the noise is almost entirely gone now. I'm hearing some very slight static every minute or so at turn on and slightly more frequent as it warmed up. I'm going to replace R35, R36 next. These resistors are only seeing about 185V each so it is no where near the working voltage but replacing them had a big impact. I'm starting to think that leakage is looking better as a cause for the noise issue. The noise floor (now that I can hear it ) is very low. With SR-404's it is bearly perceptable. On the O2's I really can't hear anything in the way of hiss or noise.
October 21, 201114 yr I had the volume set down all the way. I also tested it by turning off the source with the volume half way up. Sounded pretty much the same to me.
October 21, 201114 yr Author Well my resistors are now in Dhaka but I think it would be a good idea to replace all of the battery units. All islands look alike to us Americans. Sadly there is a lot ignorance when it comes to other regions. For instance a PM I got over there complaining about my bias boards having gone up in price with time. It's not like the USD has lost value or anything like that... Edited October 21, 201114 yr by spritzer
October 25, 201114 yr There is another fully functioning T2 in the world I had to spend some time replacing resistors and getting the second channel working again. I had shorted out the battery while I was testing a month or so ago. I replaced all the sand in the one battery, 4 2SK216's in all and the protection zeners (100V). Good news is that even though the zeners died, the 2SJ79's were all fine. I adjusted the voltage across the 22K resistors in the batteries to 6.55V first with the 2K POTs centered. Then I ajusted each battery to 740V with the 10K POTs. I didn't need to further adjust the 2K POTs since it was really quite already. The servos are working nicely. The + to - differnce is mostly under 100mV and the outputs with respect to ground sit at about 4V for the left channel and 14V for the right. All good. The really story is how great this amp sounds. I did some comparative listening with the Blue Hawaii and the T2. There is a striking difference and it is really remarkable. The highs sound more extended which really seems to open up the sound stage. The bass is very tight on the T2 and it has really great extension and slam. I was listening to some high def Dianna Krall (Quiet Nights). I was so in the music that I couldn't stop smiling. I've got a few mechanical items I need to address (screw holes misaligned, etc), but I will have this baby polished off pretty quickly. I'm excited to get the second channel of my Blue Hawaii / T2 combo amp working. The first sounds great, but you really can't tell until you've got stereo. Edited October 25, 201114 yr by Kerry
October 25, 201114 yr There is another fully functioning T2 in the world I had to spend some time replacing resistors and getting the second channel working again. I had shorted out the battery while I was testing a month or so ago. I replaced all the sand in the one battery, 4 2SK216's in all and the protection zeners (100V). Good news is that even though the zeners died, the 2SJ79's were all fine. I adjusted the voltage across the 22K resistors in the batteries to 6.55V first with the 2K POTs centered. Then I ajusted each battery to 740V with the 10K POTs. I didn't need to further adjust the 2K POTs since it was really quite already. The servos are working nicely. The + to - differnce is mostly under 100mV and the outputs with respect to ground sit at about 4V for the left channel and 14V for the right. All good. The really story is how great this amp sounds. I did some comparative listening with the Blue Hawaii and the T2. There is a striking difference and it is really remarkable. The highs sound more extended which really seems to open up the sound stage. The bass is very tight on the T2 and it has really great extension and slam. I was listening to some high def Dianna Krall (Quiet Nights). I was so in the music that I couldn't stop smiling. I've got a few mechanical items I need to address (screw holes misaligned, etc), but I will have this baby polished off pretty quickly. I'm excited to get the second channel of my Blue Hawaii / T2 combo amp working. The first sounds great, but you really can't tell until you've got stereo. Congrats Kerry, really good to hear this
October 25, 201114 yr Congrats! It's great we have more DIYT2 units working in the wild now. How many units are we up to right now? :D
October 25, 201114 yr For some reason, I am completely thrilled by this news! Congrat Kerry and thanks for all the hard work!
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