The Russians are Coming
Hi Davy,
It depends on your system and what direction you want the sound to move relative to what you have now. Of the Russian PIOs or PIO hybrids, I recommend the K75-10 over the K40Y-9. In my experience, the Russian PIOs will have good bass and warm, even colored mid-range that is very pleasing in some systems. That said, on their own they don't have treble clarity or sparkle that other caps have. I use K75-10s with a 0.001 uF polypropylene cap in parallel. The poly cap brings out the sound stage and brings up the higher frequencies. The poly cap also seems to balance the sound and give a full, clear mid-range. Others have tried this and found that they didn't like them at all. So in the end, it comes down to individual choice, the best part of DIY.
If this sounds like something that might work in your system, then they are fairly inexpensive, so give them a try.
Jac
PS I wrote a post a month or so back on the Rike Audio PIO. That is a more expensive and very different PIO cap. Most PIO caps are some variation on warm mid-range, rounder sounding, but usually lacking the ultimate level of detail when used on their own. From the reviews on line, this is true of AmpOhm, Jensen, and Jupiter as examples. The Rike S-Caps were very interesting in that they are a very different character for a PIO. Emphasis on clarity and dynamic sound level rather than warmth. A very nice cap indeed if it works in your system. As always, humble homemade hifi is a good read for capacitor reviews.
Hi Davy,
It depends on your system and what direction you want the sound to move relative to what you have now. Of the Russian PIOs or PIO hybrids, I recommend the K75-10 over the K40Y-9. In my experience, the Russian PIOs will have good bass and warm, even colored mid-range that is very pleasing in some systems. That said, on their own they don't have treble clarity or sparkle that other caps have. I use K75-10s with a 0.001 uF polypropylene cap in parallel. The poly cap brings out the sound stage and brings up the higher frequencies. The poly cap also seems to balance the sound and give a full, clear mid-range. Others have tried this and found that they didn't like them at all. So in the end, it comes down to individual choice, the best part of DIY.
If this sounds like something that might work in your system, then they are fairly inexpensive, so give them a try.
Jac
PS I wrote a post a month or so back on the Rike Audio PIO. That is a more expensive and very different PIO cap. Most PIO caps are some variation on warm mid-range, rounder sounding, but usually lacking the ultimate level of detail when used on their own. From the reviews on line, this is true of AmpOhm, Jensen, and Jupiter as examples. The Rike S-Caps were very interesting in that they are a very different character for a PIO. Emphasis on clarity and dynamic sound level rather than warmth. A very nice cap indeed if it works in your system. As always, humble homemade hifi is a good read for capacitor reviews.
Thanks Jac. I'm gathering info for when I start putting together the second set of boards I have. I'd like to try a few different components in them to compare them to my first build in which i used the mouser BOM. The thing is I like the FE's I have built so much that I'm worried about compromising them. I was looking at K75-10's on ebay and had the idea that they may sound warmer but I don't want to loose out on the clarity.
I also have Sonicap's and Mundorf Mcap400's in my watch list. If I wanted to add a touch of midrange warmth but not loose out on bass weight/impact or overall clarity, do you have an opinion on which of these would be my best bet?
I'll look into the Rike Audio PIO too, it's not one I've heard of before now.
Thanks also for the humble homemade hifi tip, i'll check it out next.
I also have Sonicap's and Mundorf Mcap400's in my watch list. If I wanted to add a touch of midrange warmth but not loose out on bass weight/impact or overall clarity, do you have an opinion on which of these would be my best bet?
I'll look into the Rike Audio PIO too, it's not one I've heard of before now.
Thanks also for the humble homemade hifi tip, i'll check it out next.
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I was able to change out the rcas in the passive but with no change in hum with my phone as a source. I then removed the pot from the pre so that all wiring was the same just input and output conected together and conected my phone.no hum. Okay so maybe the pot is faulty and the time has come to get a real attenuator like a goldpoint etc. So then I connected my usual source a Yamaha blueray player. With the unit on and paused loud hum. I read through the article troy posted and it further confused me, figure 5 seems to recommend a ground connection at the source and the amp? I need to read up more on the design of the source to hopefully understand what is happening. This is activating! I should have just left pgnd connected and been happy
I was able to change out the rcas in the passive but with no change in hum with my phone as a source. I then removed the pot from the pre so that all wiring was the same just input and output conected together and conected my phone.no hum. Okay so maybe the pot is faulty and the time has come to get a real attenuator like a goldpoint etc. So then I connected my usual source a Yamaha blueray player. With the unit on and paused loud hum. I read through the article troy posted and it further confused me, figure 5 seems to recommend a ground connection at the source and the amp? I need to read up more on the design of the source to hopefully understand what is happening. This is activating! I should have just left pgnd connected and been happy
Have you tried connecting the phono socket body's to chassis in both your passive pre and your amp leaving PGND disconnected?
The other thing is that your usual source is probably a class 2 device (no mains earth connection) you can get sometimes problems connecting to an amp which is a class 1 device (has a mains earth by necessity).
If you have tried everything else and still get hum, the only solutions left (as far as I can gather) are either a safety loop breaker circuit in the amp or an isolating transformer between them - JENSEN TRANSFORMERS, INC. - ISO-MAX® Audio Isolator Products
I've no doubt missed something or made some error with description terminology in which case someone will be along shortly to correct me
Good luck!
I did miss something! the input rca body is usually insulated from the chassis with it's body connected to the main star earth. If this is not enough you can also try (in addition) connecting a 10nF ceramic capacitor from the rca body to the chassis. You can also try this trick with the input rca sockets on your passive preamp.
Also your volume pot should have a metal body so that it's connected to the metal chassis of your passive preamp via the faceplate.
I think that's it now but probably not
Also your volume pot should have a metal body so that it's connected to the metal chassis of your passive preamp via the faceplate.
I think that's it now but probably not
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Okay, right now pgnd has been disconnected for all experiments. All of the rcas in the amp and passive are isolated from their chassis. The pot has a metal face that connected to the chassis. When I tried connecting the grounds from the rcas in the passive to the chassis of the passive it resulted in loud hum.
So with the cd player-passive-amp setup I get very minimal hum with pgnd connected. Much like when my phone was connected to the passive. Rcas and cables have been ruled out. Pot must be injecting a little noise into the mix? Could be faulty?
All rcas should be isolated from chassis correct, or did I miss that tidbit somewhere along the way?
The mains earth is connected to the chassis of the amp. There is no connection from the amp modules to the chassis that is not insulated. There should be no interaction right.
So with the cd player-passive-amp setup I get very minimal hum with pgnd connected. Much like when my phone was connected to the passive. Rcas and cables have been ruled out. Pot must be injecting a little noise into the mix? Could be faulty?
All rcas should be isolated from chassis correct, or did I miss that tidbit somewhere along the way?
The mains earth is connected to the chassis of the amp. There is no connection from the amp modules to the chassis that is not insulated. There should be no interaction right.
According to the article posted on here. The rca socket body's should be connected to chassis star ground in each unit using a wire. They should be insulated from the chassis at point of entry but you can try bridging their body to the chassis next to point of entry using a 10nF ceramic capacitor. This is in addition to the wire I previously mentioned. Dario says to leave out the PGND tab to star ground connection if you do this.
The article has the following conclusions near the end.
Rule 3 - The shield of a single ended input or output that is not galvanically isolated MUST be directly connected to the system star ground.
Rule 4 - Any circuit associated with an input or output that is not galvanically isolated MUST have it's signal reference DIRECTLY connected to the system star ground.
At present my passive preamp has all it's rca sockets insulated from it's chassis but their body's are connected to it's ground point by short wires. The My-Ref FE's rca sockets are insulated from the chassis and the PGND tab is connected to the star ground in each chassis. This seems to work well.
EDIT- as long as you have got the mains earth connected to the chassis in your amp, I think the rest is a case of doing what works for your system.
The article has the following conclusions near the end.
Rule 3 - The shield of a single ended input or output that is not galvanically isolated MUST be directly connected to the system star ground.
Rule 4 - Any circuit associated with an input or output that is not galvanically isolated MUST have it's signal reference DIRECTLY connected to the system star ground.
At present my passive preamp has all it's rca sockets insulated from it's chassis but their body's are connected to it's ground point by short wires. The My-Ref FE's rca sockets are insulated from the chassis and the PGND tab is connected to the star ground in each chassis. This seems to work well.
EDIT- as long as you have got the mains earth connected to the chassis in your amp, I think the rest is a case of doing what works for your system.
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How have you wired your passive preamp?
I did the following-
R channel rca signal (hot) in to selector switch R channel in then selector switch R channel out to pot R channel in. Pot R channel wiper to R channel 'hot' out rca.
R channel rca socket body's all linked together then connected to chassis ground point.
R channel pot ground tab to chassis ground point.
Repeat for L channel.
I did the following-
R channel rca signal (hot) in to selector switch R channel in then selector switch R channel out to pot R channel in. Pot R channel wiper to R channel 'hot' out rca.
R channel rca socket body's all linked together then connected to chassis ground point.
R channel pot ground tab to chassis ground point.
Repeat for L channel.
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Davy,
I have experience with the Sonicap's and prefer the K75-10 over them, with the caveat that my system seems suited to the K75-10. I don't have experience with the Mcap400. Another inexpensive cap to consider is the Audyn Plus. They are very nice for the money. I prefer them for better soundstage when compared to caps like Mundorf Evo and I think they are very competitive to the K71 mentioned below. Of course, Dario recommends the Russian polystyrene, K71-4, as the preferred budget cap for C13 and I agree that it is a good match for the FE. The K71's are getting a little harder to find, but should be available. I've had luck with ebay seller valtek in Romania.
If you choose to try the K75-10, playing with a bypass cap should get you all the clarity back.
Have fun.
Jac
Thanks Jac, so many choices!
One I quite like the review of is the Mundorf Supreme. A more expensive cap but I might get a couple of them in the new year for the FE's I'm currently using - unless someone tells me to avoid them for some reason.
I'll have a look for the K71-4 on ebay.
One I quite like the review of is the Mundorf Supreme. A more expensive cap but I might get a couple of them in the new year for the FE's I'm currently using - unless someone tells me to avoid them for some reason.
I'll have a look for the K71-4 on ebay.
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My two cents - as reported, I went back to the betas with the Sonicaps last week. They still sound very musical and at first have an nice impressive "up front" character. Sadly some ear fatigue appears over long listening sessions. IMHO, the Audyn Plus is the better choice in that economy group. They are cheap but approach the cleanliness of some of the big boys. 
Hi Davy,
it seem I was not able to explain it clearly.
My_Ref, according his designer (Mauro Penasa), should have the following grounding strategy:
- inputs should be insulated from chassis
- the only connection of the My_Ref to star ground is PGND
- Safety earth, chassis, transformer's shield and My_Ref are bound to the star ground.
IMHO, the Audyn Plus is the better choice in that economy group. They are cheap but approach the cleanliness of some of the big boys.
I would avoid Sonicaps, Audyn Plus and Mundorf MCAP, they're not better than the Vishay-Sprague you're using.
K71-4 is an excellent choice for its stellar price/performance ratio but my preferred, and not too costly (14€ each from HiFi Collective), choice is Mundorf Supreme (plain ones, not 'oily' versions).
My Audyn True Coppers are collecting dust, from months...
Thanks Dario. The grounding scheme you describe for the original My-Ref is what I have currently. If I disconnect the PGND from the star earth point I get hum using anything mains powered as a source. The only thing I can use as a source and not get hum with PGND disconnected is a portable MP3 player running on it's battery.
I wonder if this is because every mains powered source I have is isolated from mains earth but the My-Ref is not, I have read that this arrangement can cause hum issues when no signal isolating transformers are used.
I've tried both plugging source's directly into the FE's AND running them through my passive pre-amp but it makes no difference.
So my passive pre-amp does not add hum in any way.
The Mundorf Supreme cap you mention is the one I was discussing with Bob, I read the review of them in humble homemade hifi and liked his description, that's why I thought they would be a good choice.
Cheers
Davy
I wonder if this is because every mains powered source I have is isolated from mains earth but the My-Ref is not, I have read that this arrangement can cause hum issues when no signal isolating transformers are used.
I've tried both plugging source's directly into the FE's AND running them through my passive pre-amp but it makes no difference.
So my passive pre-amp does not add hum in any way.
The Mundorf Supreme cap you mention is the one I was discussing with Bob, I read the review of them in humble homemade hifi and liked his description, that's why I thought they would be a good choice.
Cheers
Davy
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