The new "My Ref" Rev C thread

Re: Re: Re: Cap switching box

VictoriaGuy said:
Good idea- I'll free up a slot for a straight wire.

You're welcome John! :D

Tom, regarding C21, now I've 10nF MKS2 to directly compare to 100nF MKS2 originally used and I could confirm that value is a issue here.

The 10nF MKS makes voice closer, I would say in the right position comparing to my Marantz power section. :cool:

Next week I should have also the others values to fine tune. :smash:

I've tried also 10nF Wima MKP2 and they seems better than Wima MKS2, more transparent and bass is tighter. ;)

So I would say the right value for C21 seems between 10nF and 68nF.

Both MKP2 and FKP2 are available from Mouser in these values. :cool:
 
Nice MCap Dario! I think John will choose the PIO but if he puts in a straight wire he will choose that. Just my bets. I like the idea of burning in the caps.
I dont know if I told you guys but I did DC couple a few days ago. Better soundstage, more transparency, better separation of instruments, .... muddy bass? Well I have to put it all back together again after messing with it last night. Give it a better listen then.
Uriah
 
udailey said:
I dont know if I told you guys but I did DC couple a few days ago. Better soundstage, more transparency, better separation of instruments, .... muddy bass?

Muddy bass?
Yes, it's the Panny FM in C9 ;)

a Wima MKP2/FKP2 (<100nF) in C21 helps a lot :cool:

ClaveFremen said:
- Panasonic FM is quite good, dinamyc and involving, but has a bit of harshness and basses are a bit bloating
 
Re: Offboard caps

ClaveFremen said:
I've tried also 10nF Wima MKP2 and they seems better than Wima MKS2, more transparent and bass is tighter. ;)

Sorry, it's FKP2 in place of MKP2

Tony X said:
Just a note for anyone who may try some large caps off board. Keep them well away from the relays or they will pick up a lot of hum, buzz and hiss at the same time. It took me days of frustration to find that out.

Hi Tony,

you were experimenting Obbligatos in C13, right?

Tried others caps?
 
you were experimenting Obbligatos in C13, right? Tried others caps?

Yes, Dario, It was the Obligatos. Mine are big brutes, 2.2uF 630v coppercase. They actually give already a nice sound once they are moved away from the relays. They will probably be great when I get the other things fixed. I have a Speedlight on order from Uriah and some Silmics are on the way from Germany. I am waiting for you guys to decide on the other pots before looking at C13 again if necessary.
 
Tony X said:
They actually give already a nice sound once they are moved away from the relays.
...
I am waiting for you guys to decide on the other pots before looking at C13 again if necessary.

Strange, other caps I'm trying doesn't seems sensible to position, it could be that copper body of Obbligatos has a role picking up noise... :rolleyes:

If you are referring to C9,C21,C4,C5 and so on, yes, it's a long quest... ;)
 
hiss issue

So last night I connected the secondary ground(s) to chassis/earth. I know Troy doesn't like this because it mixed clean and dirty ground (I can see his point). I tried this first since my original setup (no case yet) was done that way and it worked well. (Also because this is recommended practice according to Rod Elliott.) That made the hiss essentially go away. I say essentially because if I really strain and with just the right setting of my pot I can still hear just the faintest version of this buried in what is otherwise the noise floor on my input. But with the speakers I have I barely go above the 9 o'clock position on the pot and then the speakers are dead quiet with source connected and active, but no signal running. So, for now this is good enough. For the next case build I will probably go the long shaft route to really separate sections more cleanly.

Next thing I gotta do now is find a D/A with lower noise floor. Right now I am running off an Entech 205.2 but I don't like the level of white noise. I have some other DACs. Let's see how much of a difference that makes.

peter
 
Mixing grounds is not a "BAD" thing, it is just old engineers being stubborn and saying proper engineered equipment shouldn't require it.

But if tying signal ground to earth ground quietened the amp then you have power ground issues between the amp and the source feeding it.

Connect your RCA cables between source and amp and measure the AC and DC voltage between the chassis of both and the RCA grounds of both.

That might also be contributing to the noise floor of the DAC as you mentioned.
 
troystg said:
That might also be contributing to the noise floor of the DAC as you mentioned.
Yeaaaaah. I have to do some more forensics... I just reread the measurements on the Entech (from stereophile) and they show a noise floor at well below 100dB. I should not be able to hear any of that... Even with my high efficiency speakers (92dB Fostex FF125k in a 3m BL Horn...).

Peter
 
VictoriaGuy said:
Inside 2
...I sure hope the 'upgrade' will allow multiple attachments and allow for quicker posting.

Oh yes. It also makes the participants better looking, and often cures athlete's foot.

Could someone tell me what "Rev C" refers to? Thanks

Edit: I didn't phrase that well. Is the OP just referring to his own work, or to a public design?
 
billyk said:
It refers to the amp that originated in this thread. I believe it refers to "My Reference Revision C" or Ref C for short Or something along those lines. Someone will correct me or expand on it I am sure.


No that pretty much sums it up.

Mauro did a great design (original, Rev_A) shared it with us, somehow it morphed into a Revision_C, Twisted Pair made some kits and they work and sound great. (Thanks guys!)

Peter and Uriah came along behind TP and offered additional kits. Again they sound terrific. (Also you two!)

Mauro GAVE his design, some people are never happy and complained, Mauro left the Forum. Sad day for us. I think when things like that happen the negative posters on the thread should be banned not the kind people who give and ask for nothing in return other than acknowledgment.

Hopefully history will show Mauro did well and was kind enough to share with us. :angel:
 
Today in my mailbox I've found some Nichicons... ;)

I've Nichicons Fine Gold for C1, C2, C9 and KZ for C6, C11.

Tried Fine Gold in C1, C2 and they sound great, bass is more controlled, no harshness and a gorgeous medium :D

In C9 positions they've a nice sound but soundstage is flat.

KZs in C6, C11 have a nice sound but soundstage is flat.

But they're brand new, I'll post again as soon as they burn-in :smash:

I've some news also about C21, 10nF FKP2 is also too small, it sound fantastic but music seems somewhat 'simplified'.

Hopefully next week I should receive other values to try.
 
frog993 said:
In the moment I´am building my Ref_C and thinking about
to change C1,C2,C9 with Panasonic FCs because i have some FCs laying around.

Dario, what do you think about the FCs ?

Also for C13 i have some MKPs from Intertechnik.

Hello Udo,

I think that FM included in kit are much better than FC, I find FCs harsh.

Probabibly MKP Q4s are better than R46, but Q4s are also baseline caps, you could surely do better ;)

For instance PHE426s in the low cost area are quite good (from RS components they costs not much, but you have to buy 10 of them..)

ClaveFremen said:
Hopefully next week I should receive other values to try.

I was wrong, I've found them this morning in the mailbox :D

It's simply incredible, as you change value from higher to lower you could clearly hear voices closer! :eek:

From this first test I would say that the better C21's value so far is 22nF.

This value doesn't add nor subtract nothing to the music, it only clear-up things.:cool:

Nichicon burn-in is going on and only after 4 hours flatness is gone and it seems that they will be a nice alternative to Silmics
 
build

Peter,

Nice job on the build! I like your layout.

SP_A1766.jpg
SP_A1771.jpg


I have a question about the "pan" for your transformers. Is the pan made of steel? Does it have to be a ferrous metal to isolate the transformers or can aluminum be used?
 
Yes, FM's are better than FC's. I don't know why some people believe the opposite. We were very fortunate to get FM's in these kits at no extra cost.

I've been busy building enclosures, so I haven't changed anything in my amps recently. The Mundorf SIO's at C13 have finally settled down. I don't think they're worth the cost. I'm not going to take them out now that I've spent the money, but I wouldn't buy them again. The AudioCap Theta was also very nice, at one-third the cost.

Dario, you have now selected 0.022uF as the optimum value for C21? What do you hear with no C21, the way Mauro first designed the circuit? I have been going back to the original thread and rereading what Mauro had to say about his circuit design. All of these bypass caps were added by Russ White to Mauro's design. Mauro wasn't entirely enthusiastic about puttig them in. I intend to remove the PS bypass C19 and C20, then possibly C17 and C18.

I've got some standard Blackgates on order for C6 and C11.

I'd also like to try a different resistor at R3. In the original thread, someone built the amp with a .33 ohm value and it still worked but didn't sound good. That means the value is important but not critical. I'm thinking that .5 ohm would be close enough, and I might try a Caddock power resistor there. Mauro specified low inductance, but I don't know what the actual acceptable value might be. The Caddock's are 10nH. I don't know how that compares to the cement resistor in the kit, and I can't find any data on it. Does anyone know?

Peace,
Tom E
 
madisonears said:
The Mundorf SIO's at C13 have finally settled down. I don't think they're worth the cost.
...
The AudioCap Theta was also very nice, at one-third the cost.

My C13 caps are still burning in (except Obbligatos, not yet arrived) and so far, compared to DC coupling, the best are PHE426 and MCAPs Zn (0,80€ and 11€) both are quite transparent with MCAP Zn clear winner, but at a much higher cost...

All caps I've tried are better than R46, white MCAPs are 'restricted' and Wima MKP10 are nice sounding but a bit closed and definitively coloured compared to DC coupling.

madisonears said:
Dario, you have now selected 0.022uF as the optimum value for C21? What do you hear with no C21, the way Mauro first designed the circuit? I have been going back to the original thread and rereading what Mauro had to say about his circuit design. All of these bypass caps were added by Russ White to Mauro's design. Mauro wasn't entirely enthusiastic about puttig them in. I intend to remove the PS bypass C19 and C20, then possibly C17 and C18.

I agree, I like a lot how the amp sounds without C21.

I've tried all values between 1nF to 100nF and they adds or subtracts something to the music, only a 22nF bypass seems, so far, to not harm and clears-up things.

I can't explain why a such silly value works and others don't...someone has any idea?

madisonears said:
I've got some standard Blackgates on order for C6 and C11.

I'm curious to hear from you about their effect. :D

madisonears said:
I'd also like to try a different resistor at R3.

If I remember correctly, Brian or Russ in their support forum wrote about that.