Further update on the FE's.
Today I tried connecting the PGND terminals to chassis earth and success! The amps are now virtually silent. I cant hear any hum at all now from my chair.
If i put my ear hard up against the drivers I can hear a very faint hum, about the same as with my last chipamp and less than a lot of commercial amps produce.
Huge thanks to Dario, Bob, shoom, Marra, voxxonline and anyone else who helped me and is/was involved in this project. You are all good friends an a great bunch of guy's. I'll drink a toast to you all tonight.
Cheers
Davy
Today I tried connecting the PGND terminals to chassis earth and success! The amps are now virtually silent. I cant hear any hum at all now from my chair.
If i put my ear hard up against the drivers I can hear a very faint hum, about the same as with my last chipamp and less than a lot of commercial amps produce.
Huge thanks to Dario, Bob, shoom, Marra, voxxonline and anyone else who helped me and is/was involved in this project. You are all good friends an a great bunch of guy's. I'll drink a toast to you all tonight.
Cheers
Davy
We help because we all fall into the 
zone from time to time. You now have earned your "Pay It Forward" badge 
If anyone else has hum issues, check all connections through out the whole system and try connecting the PGND to chassis earth, worked well for me
It's perfectly fine to 'fix' the hum problem using the PGND connection but it's also the confirmation that a grounding problem is present somewhere in the chain.
Hi Dario, I was wondering if the LED illuminated mains power switches could be feeding noise back into the boards. I might try disconnecting them to see if that makes any difference. The thing is the amps are virtually silent with their signal inputs shorted out so I'm not sure it is the amps at fault.
The passive pre is as simple as it could be, I have rewired it and fitted a new volume pot and selector switch, don't know what else I can do there.
When I use the passive pre to feed my headphone amp and I max the volume on the headphone amp and use the volume pot on the passive to attenuate, I get hum through the headphones but with the headphone amp at normal range it is silent. The DAC has a commercial double insulated SMPS (which is made for it by the same manufacturer) powering it. I might try running it off a 12v battery to see if that makes any difference.
EDIT - nope, I tried disconnecting everything bar the passive pre, DCB1 and My-Ref's and that very faint hum is still there but I can only hear it with my ear pressed against the speaker driver so i'll live with it.
The system sure sounds good so I can't complain eh!
The passive pre is as simple as it could be, I have rewired it and fitted a new volume pot and selector switch, don't know what else I can do there.
When I use the passive pre to feed my headphone amp and I max the volume on the headphone amp and use the volume pot on the passive to attenuate, I get hum through the headphones but with the headphone amp at normal range it is silent. The DAC has a commercial double insulated SMPS (which is made for it by the same manufacturer) powering it. I might try running it off a 12v battery to see if that makes any difference.
EDIT - nope, I tried disconnecting everything bar the passive pre, DCB1 and My-Ref's and that very faint hum is still there but I can only hear it with my ear pressed against the speaker driver so i'll live with it.
The system sure sounds good so I can't complain eh!
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my Impression from K75-10 without bypass or bypassed with 0.1 FT3 Is that It Is completely unlistenable - there Is no bass at all - swappy midrange with distortion
I can not agree that It Is on par with Rike Audio
I can not agree that It Is on par with Rike Audio
I am sitting right beside a pair of 300kva transformers in the My-Ref's and a single 50kva in the DCB1 and when no music was playing I got a bit of mechanical hum from them. I sorted it out today. A pair of computer mouse mats cut into 11 and 7cm disks. I used longer bolts and clamped the toroidal transformers lightly between the rubber insulators, foam rubber disks top and bottom and the original metal plates in place on top.
It worked very well and it's cheap too.
It worked very well and it's cheap too.
What I now have is, chassis baseplate then two thinish layers of neoprene mouse mat rubber which are slightly wider than the transformer for stability, then the original rubber insulator, this makes a disk shaped sandwich about 8mm thick. The transformer sits on that with a similar stack of rubber on top finished off by the steel top plate. The whole lot is bolted together with just enough pressure to stop the transformer moving about and no more.
The result is brilliant, they are as quiet as potted mains transformers on a decent valve amp. I cant hear them at all now unless I put my ear to the enclosures. The low background hum I heard when putting my ear against the speaker drivers has also reduced even further now. These amps are now better than any amplifier I have ever heard never mind owned so I am now beyond my experience zone for want of a better term.
The result is brilliant, they are as quiet as potted mains transformers on a decent valve amp. I cant hear them at all now unless I put my ear to the enclosures. The low background hum I heard when putting my ear against the speaker drivers has also reduced even further now. These amps are now better than any amplifier I have ever heard never mind owned so I am now beyond my experience zone for want of a better term.
Very interesting. You are the first reviewer I have read that has found "no bass". I guess it just proves that each listener and each system is different. That's why we do DIY.
I'm guessing that you won't be doing further experimentation, but if you do, I would recommend that you try a smaller bypass cap. Again, no single answer for everyone, but I'm using a 0.001 uF polypropylene.
It sounds like you have the Rike S-Cap and like it. I agree that it is a very nice cap and, if it suits your system, you may be done experimenting. Enjoy.
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I had the standard rubber washers top and bottom, no bare metal but they were clamped tight, maybe a bit too tight
This is quite some forum aint it. I was reading peoples opinions about trying different capacitors on here. Then I read a thread in the parts section where some guys got totally slated because they said they hear differences between different capacitors.
I better not mention that I hear a huge difference between a carbon pot and a stepped attenuator, and that's not all either lol!
It's a mad world
I better not mention that I hear a huge difference between a carbon pot and a stepped attenuator, and that's not all either lol!
It's a mad world
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Hi Davym,
Two years ago, I was one of those guys that thought that all solid state amps were the same and that there couldn't be meaningful differences in components. After getting involved in this thread, I decided to go along with Dario's components selections because it was just as easy to build an FE with Dario's BOM or build it with whatever parts I found. Now I'm one of those guys that explores the component possibilities whether it be capacitors, opamps, whatever.
I understand those who don't think components are important because it is hard to explain the physics of why they should be different. In the end, I decided to follow Bob's advice and trust my ears.
Speaking of components, I noticed in a photo of your amp that you are using some kind of Sprague capacitor in C13. As C13 seems to have a noticeable effect on FE, I am always curious about what other people are using. What can you tell us about your C13?
Jac
Hi Jac, I have not tried any other type of capacitor than what came in the BOM I ordered from mouser, the Vishay/Sprague came with that lot. I think I have another Sprague type the right value somewhere, 2 large orange drop's. I'll need to check their voltage, i was thinking about trying them but I'm enjoying the amp's so much just now that I'm reluctant to mess about much with them. They sound very open and detailed with decent, tight bass response.
I have two more boards and a few of the components, chips, relays etc. In the long term, I want to build up the other boards with my own choice of components in certain positions so that I can more accurately compare them to the standard I already have.
I know well how short a memory for sound changes I have but I certainly do notice things - burn in for one, cable differences is another. I have an interconnect which came along with my turntable, a reviewer said it was a decent cable and worth keeping. To me it sounds awful, veiled, dark, chokes the life out of the sound. I have tried It feeding half a dozen different amps now and it always sounds bad. When I change back to my diy copper or silver interconnects it's a huge difference so I am a believer when It comes to cables, I just cant support the notion of spending thousands on them.
I think that the measurement/objectivist camp might be better off just buying pro-audio gear, it usually measures well which seems to be all that's important to them.
I have two more boards and a few of the components, chips, relays etc. In the long term, I want to build up the other boards with my own choice of components in certain positions so that I can more accurately compare them to the standard I already have.
I know well how short a memory for sound changes I have but I certainly do notice things - burn in for one, cable differences is another. I have an interconnect which came along with my turntable, a reviewer said it was a decent cable and worth keeping. To me it sounds awful, veiled, dark, chokes the life out of the sound. I have tried It feeding half a dozen different amps now and it always sounds bad. When I change back to my diy copper or silver interconnects it's a huge difference so I am a believer when It comes to cables, I just cant support the notion of spending thousands on them.
I think that the measurement/objectivist camp might be better off just buying pro-audio gear, it usually measures well which seems to be all that's important to them.
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