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MyRef_C with Ultimate BOM

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I thought maybe you were feeling crabby :)
For sure I will save them for you Tom.
I think filing down the ends would work. I dont like drilling on a board either. Its risky.

OKAY VOLUNTEERS <> 3 Stereo Sets will have Shinkohs and PRPs for those 2 positions. You guys will have to promise to build within a month of getting them and report back. The Shinkohs are about $4 each so each of you is ending up with $16 of extra super resistors and we would like to know if you hear a difference and if so what do you hear!?
Sonidos and I will both try them as well since I got 10 of each and I started this whole group buy basically because I want to hear what Tom and Dario are hearing.
Uriah
 
Uriah,
I cannot claim to have audiphile ears (daring to have them is, at least, prepotent), but I am in for the shinkoh test. I will sincerely open my ears and try to squeeze every little detail. I don't promise I will hear any difference (maybe there isn't any), but it will be an unbiased comparison.Maybe in the end I need worth of 100k$ system to discern an unique resistor change, but will be of everybody's interest to know if they really worth the price. Maybe is one of the lasts jumps for the MyRef_C to reach the higher-end possible in its class. Along with audiophile fuses :p

Regards,
Regi
 
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Hold on there guys. I appreciate you're trying to get the best possible kit you can, but you (and we) could end up chasing our tails for ever trying to find the best component.

As a paid up customer I'd rather you send the amp as it is now so I can hear it, and then change components as and when.

Remember, nothing is perfect, but the kit so far is closer to perfect than most items. And those of us who want to tweak it can do so at our leisure.:)
 
Great to see volunteers jump forward. A couple notes:

Uriah, these are Shinkoh tantalum resistors, correct?

Testing these amps against the "standard" kit supplied last time is a no-brainer. This new kit will sound like a completely different amp, better in every respect. I really liked the sound of the original kit, but I am thrilled by the same circuit with better parts.

What we're interested in is a comparison between two specific components, and for that you will need to build the new kits complete with either PRP or Shinkoh's. I recommend using PRP's first because they are easier to insert and remove, and once the Shinkoh's are in there you might not want to remove them. I suggest you not swap too soon after building, as some of these parts, especially the Blackgates and probably the film/foil input caps, require extensive break in. You will need to put a couple hundred hours (no lie!) of playing time on the new kits, then swap resistors. The resistors do not require much break in (at least, that I could detect), so the listening comparison can be pretty soon after change out.

I don't think you need a super system or golden ears to detect subtle changes. If you can't hear a difference, we need to know that. You need an open mind and some extended, concentrated but relaxed listening to familiar music. Another pair of ears always helps. Everything else in the system must remain the same between tests. Get your sources and cables and stuff settled before you begin. That's why letting the amps break in first is critical.

When I made my comparisons, I changed only one amp at a time, then listened to each one through the same speaker with mono source material. It's hard to find good mono music, but there is some old jazz and classical, even a few remastered pop and rock items, that will suffice. Good mono FM might also work. When I played two amps with different parts (especially the input caps) through a stereo system, sometimes they sounded so different that it screwed up the music completely and I couldn't tell what was going on. If I switched one amp off at a time, I could ususally hear the difference even with only half of a stereo signal. Mono worked best.

So, yeah, it's kind of a pain to do the test, but you will earn our gratitude and respect, plus a better amp.

Peace,
Tom E
 
Wester,
Dont worry. All kits ship at the same time. Tom used Shinkohs in his and he suggest they may have improved sound over even the PRPs in these 2 locations on the amp.
I wanted to buy Shinkohs for the kits but they are super expensive when PRP might be just as good in these two positions. So the kits will ALL ship. 3 guys will get PRP and 2 Shinkoh resistors. They will, as Tom suggests, try PRP first, then Shinkoh in the 2 locations that Tom used Shinkoh. We are not holding up the process, just continuing the experimentation. These 3 will report back as well as myself and Sonidos. We will all tell you all what systems we have and what we heard with each setup. Then if you decide you want to invest another $8 or so per channel you can upgrade those 2 resistors to Shinkoh on your own and so can everyone else.
Tom, what you are saying is exactly what I intended. I think thats the best way and I agree its a no brainer against the old GB kits but these guys have already built it and are obviously converts to MyRef's so I think its good to have them getting the Shinkohs to try out. Plus, they know all the pains you and Dario took to find the ultimate solution with this amp last time.
Time to put the kid to bed.
Uriah
 
For testing both different resistors, it will be necessary to burn-in the amp like 100 or 200 hours at least as madisonears points out. Sound character change is soooooo notable in chipamps that not waiting will skrew your results for sure. If you start with the PRPs while burn-in and then change to the Shinkhos, you will notice increased bass and other aspects not directly attributable to the Shinkohs. This changes were going to happen anyway. I have noticed it specially with electrolytic capacitors and input foil caps.
 
What do you guys think of recommending 22 or 24vac toroids instead of 25vac? No load on a 25 will give us quite a bit over 35vdc.... I think 22vac is a good number. Its what I and a lot of other people used last group buy. I would not go lower though. Open for thoughts ideas suggestions here. Remember some Silmics are 35V which is right there at max with a 24vac toroid.
Uriah
 
I would go with 22 vac. Is a bit on the low side, so the amp will be happier driving lower impedance loads.
The only downside will be with 8ohm or higher loads. Your maximum output voltage swing amplitude will be a bit lower that with 24vac or 25vac, so the maximum volume you will achieve will be A BIT lesser. At these power levels, a few volts are not gonna make an audible or important difference.

You must account that our ear volume sensivity works logaritmically, so the volume perception difference between a 60W amp and a 68W amp will be.....wel.....pretty negligible.

Just my 2 cents,

Regards,
Regi
 
25Vac will give ~ 30% more maximum power than 22Vac. That is just a tiny bit over 1dB louder.

When you take account of both transformer regulation and mains voltage variation then 22Vac is near the maximum for use with 35V smoothing capacitors.
 
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Good information. Thanks Andrew and Regi. A lot of folks used 22VAC last GB, me included, and I appreciated the sound very much. I think the 25vac secondaries are going to be pushing the limits of the silmics. Heck, 22VAC pushes them a bit as it is.

TOM - could you post a pic if you have one of your heatsink for the caddock. I know what it looks like, just curious if you could show it on the board.
I am going to solder up a bunch of components in a board today. Wonder if it would be better to put the 220uf FMs underneath to accomodate that sink a bit more. Or, maybe you faced it the other way.
Uriah
 
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