I'd ask for all the pictures of every pcb before buying anything from him.3.2K$ is not pennies...
That board has the rarest j-fets on earth too, the V type of selected 2sk146 which is made out of 2 matched 2sk170V.That's one j-fet you cannot source from anywhere...I mean...nowhere in the world.The same about the 2sc2545 ultralow noise and rbb transistors for the phono section.If the guy used the refurbishment action to steal those trz and replace them with other transistors you shouldn't pay for it.
I said that's the best phono preamp ever made for a reason...in the original form it has the best components ever used in a phono preamp and also the smartest and complex schematic of sorts.So if you buy it better buy it without modifications.The japanese site shows pictures with every detail .If you see anything different, don't buy it.The amps were originally sold only in Japan so better source one from Japan.Japanese guys are honest.
PS :
Modified the last teo posts.It seems that the shielded trimpots were used by the japanese restoration guy to replace the original bluish ones.At the end the guy performed even THD measurements and got better results than the original specs, there are some pictures with that too.
That board has the rarest j-fets on earth too, the V type of selected 2sk146 which is made out of 2 matched 2sk170V.That's one j-fet you cannot source from anywhere...I mean...nowhere in the world.The same about the 2sc2545 ultralow noise and rbb transistors for the phono section.If the guy used the refurbishment action to steal those trz and replace them with other transistors you shouldn't pay for it.
I said that's the best phono preamp ever made for a reason...in the original form it has the best components ever used in a phono preamp and also the smartest and complex schematic of sorts.So if you buy it better buy it without modifications.The japanese site shows pictures with every detail .If you see anything different, don't buy it.The amps were originally sold only in Japan so better source one from Japan.Japanese guys are honest.
PS :
Modified the last teo posts.It seems that the shielded trimpots were used by the japanese restoration guy to replace the original bluish ones.At the end the guy performed even THD measurements and got better results than the original specs, there are some pictures with that too.
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Very interesting.
Because I lack knowledge, I will try to find here someone professional that I can trust.
Maybe he will help me.
If I won't find, I think that the best solution is to try the Purifi because as much as I read, it's the most natural sound ever in class D.
I thought about NC1200 but it's much expensive and as I told you, I don't want to loose more money on my tries.
Thank you VERY MUCH for your great ideas.
I hope to find an answer here.
Just don't expect 40 years of use from any class d amp...If you get 3 of them you got what you paid for, if you get 5 clean years of use without repairs you're a lucky bstd 🙂
Hi,
Do you have any data for the failure rate of class D ? and which specific aspects of it fail, such as the IC in terms of the TPA32XX or components in terms of a more discrete design such as using the Infineon IRS2092 based amplifier, or even the Purifi or Hypex etc.
Thanks and regards,
Shadders.
It's not the ic's that fail first ...it's the low esr electrolitics...They simply die under high frequency ripple stress.The higher the power the more capacitors in parallel you need and the commercial kits never have enough of them.It's the same thing with computer motherboards.No matter how good the capacitors are, they eventually fail but computers don't show the kind of crest factors audio amplifiers do.Some caps are better than others...Even in a good batch some are worse than others...Caps manufacturers don't make low esr capacitors for audio...
Then try replacing 5 blown capacitors on a multilayer pcb designed for high frequency without destroying or affecting the traces, pcb isolation ...
You also buy the purifi usually with a hypex power supply, this hypex power supply more specifically:
https://www.diyaudio.com/community/threads/2-x-hypex-smps1200-dead-following-power-cut.374965/
If you don't buy a smps made with the cheapest chinese capacitors then you may buy a classic power source and your costs rise above the horizon at 5...800 watts drain...
Then if you have a good classic supply why not having a good class a , b or ab amplifier...the transformer is already the heaviest thing there...why did you buy an expensive class d amp in the first place? ...it's the lack of logic in choosing the right parts for any given technology once it hits the store's shelf that stuns me, not the technology itself, cause I've been accused allready of trolling the class d topics...I use class d things when they are lightweight, cheap, efficient and sounding good enough. I won't indulge into buying a Ferrary with a 1.6 l motor under the hood, sorry!
I've been a test, fix and callibration engineer for high power, high voltage and very high precision smps for xray machines, co2 and excimer lasers and ion implantation of silicon waffers in the microchip plants.I've seen hundreds of types of failure modes.I'm just addicted to assessing reliability...and switching power at high pace is not reliable enough in my opinion and I've tested and fixed switching power supplies sold for 7...100k$ each.I used to run 72 hours full power tests for power supply on resistive loads and one thing they never tell to a client is that you only switch it on and off once in 72 hours , the rest of it is just working at lowest minimum crest factor less stressfull than supplying a class A amplifier.Then you sell it, 3 months...1 year passes and the client is sending back the blown power supply even if he used it a less than half the max power you tested it.
Then try replacing 5 blown capacitors on a multilayer pcb designed for high frequency without destroying or affecting the traces, pcb isolation ...
You also buy the purifi usually with a hypex power supply, this hypex power supply more specifically:
https://www.diyaudio.com/community/threads/2-x-hypex-smps1200-dead-following-power-cut.374965/
If you don't buy a smps made with the cheapest chinese capacitors then you may buy a classic power source and your costs rise above the horizon at 5...800 watts drain...
Then if you have a good classic supply why not having a good class a , b or ab amplifier...the transformer is already the heaviest thing there...why did you buy an expensive class d amp in the first place? ...it's the lack of logic in choosing the right parts for any given technology once it hits the store's shelf that stuns me, not the technology itself, cause I've been accused allready of trolling the class d topics...I use class d things when they are lightweight, cheap, efficient and sounding good enough. I won't indulge into buying a Ferrary with a 1.6 l motor under the hood, sorry!
I've been a test, fix and callibration engineer for high power, high voltage and very high precision smps for xray machines, co2 and excimer lasers and ion implantation of silicon waffers in the microchip plants.I've seen hundreds of types of failure modes.I'm just addicted to assessing reliability...and switching power at high pace is not reliable enough in my opinion and I've tested and fixed switching power supplies sold for 7...100k$ each.I used to run 72 hours full power tests for power supply on resistive loads and one thing they never tell to a client is that you only switch it on and off once in 72 hours , the rest of it is just working at lowest minimum crest factor less stressfull than supplying a class A amplifier.Then you sell it, 3 months...1 year passes and the client is sending back the blown power supply even if he used it a less than half the max power you tested it.
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Sigma drive uses the two extra wires to remove the main speaker wire resistance.
When connected it is like the speakers have 1 foot of wire from the amp terminals.
Some speakers work better like this. Mine don't but some do.
When connected it is like the speakers have 1 foot of wire from the amp terminals.
Some speakers work better like this. Mine don't but some do.