Welcome Guest! To enable all features please Login or Register.

Notification

Icon
Error

Options
View
Go to last post Go to first unread
maxlorenz  
#1 Posted : Wednesday, November 1, 2006 9:31:10 AM(UTC)
maxlorenz

Rank: Member

Groups: Customer, Beta Testers
Joined: 10/31/2006(UTC)
Posts: 19

I will not call them "mods" because I believe Mauro made a coherent, well studied amp, that I (maybe noone) cannot improve (?). We can post proved or posible component swaps here ;-)

I am ready to build a pair of monoblocks. Some questions:

1) Electrolytic caps: I will replace almost all little electros for Rubycon ZL. Can I replace 220uF ones (except C9) for 470uF???

2) On the present PCB, I believe R12 (3K3) and C12(220pF) form a LP filter before LM318. I have here some Riken-Ohm resistors that I want to try but they are 3K9. Can I replace R12 to a 3K9 resistor safelly?

3) R3 is a 0R47 /7W cheap resistor. Has anyone tried a "more audiophile" resistor?
For example, MILLS non-inductive wirewound ( partsconneXion.com code is 66129) 0.47R MRA-12Watt is "only" $3.50/ea.

Thanks for watching...
Any advice/suggestion is welcome.
Cheers,
M

Obsessive-compulsive builder.
Russ White  
#2 Posted : Wednesday, November 1, 2006 9:38:53 AM(UTC)
Russ White

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,978
Location: Nashville, TN

Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
maxlorenz wrote:
I will not call them "mods" because I believe Mauro made a coherent, well studied amp, that I (maybe noone) cannot improve (?). We can post proved or posible component swaps here ;-)

I am ready to build a pair of monoblocks. Some questions:

1) Electrolytic caps: I will replace almost all little electros for Rubycon ZL. Can I replace 220uF ones (except C9) for 470uF???

2) On the present PCB, I believe R12 (3K3) and C12(220pF) form a LP filter before LM318. I have here some Riken-Ohm resistors that I want to try but they are 3K9. Can I replace R12 to a 3K9 resistor safelly?

3) R3 is a 0R47 /7W cheap resistor. Has anyone tried a "more audiophile" resistor?
For example, MILLS non-inductive wirewound ( partsconneXion.com code is 66129) 0.47R MRA-12Watt is "only" $3.50/ea.

Thanks for watching...
Any advice/suggestion is welcome.
Cheers,
M



Hi Max!

Your mods will work fine some notes:

1) I use caps like this all the time. In fact I have used those exact caps. I would not go much higher than 470uf, it would be hard to find any that fit anyway.

2) You are correct, and the value you state will work just fine, it will only lower the corner frequency slightly, not enough to change things much. If you wanted you could reduce C12 to 180pf or so.

3) Yes I have done this too, but not with the mills resistors yet. It is a good mod. It is worth noting that the new current pump amp I am designing which also needs an output resistor like this to set gain will be using Ohmite TA or Mills type non-inductive resistors in this spot.

Cheers!
Russ

Edited by user Wednesday, November 1, 2006 9:40:00 AM(UTC)  | Reason: Not specified

maxlorenz  
#3 Posted : Wednesday, November 1, 2006 12:37:49 PM(UTC)
maxlorenz

Rank: Member

Groups: Customer, Beta Testers
Joined: 10/31/2006(UTC)
Posts: 19

Hi Russ,
thanks for the fast reply.

Quote:
2) You are correct, and the value you state will work just fine, it will only lower the corner frequency slightly, not enough to change things much. If you wanted you could reduce C12 to 180pf or so.


OK. I can't hear above 100Khz anymore :-)
A shame that I can't calculate a simple corner F.
I have to find that Rev-C schematics to see if I can swap another R on the signal path...

OT: is it my age or are those smileys a little small on my screen?

Regards,
M
Obsessive-compulsive builder.
pearshaped  
#4 Posted : Friday, November 10, 2006 3:08:29 AM(UTC)
pearshaped

Rank: Member

Groups: Customer
Joined: 10/26/2006(UTC)
Posts: 5
Location: Mount Isa, Australia

R3 resistor,
I also intend to use some different parts on my second rev c board, when I get around to it. I thought a Mills 0.47ohm non inductive resistor for R3 would be an improvement on the standard inductive ceramic resistor that is supplied, especially since it is in the signal path.
I will soon be building mauro's Evolution amp, where he supplied standard 0.47ohm 5W ceramics in a similar position. I suggested using 12W Mills resistor substititions, but Mauro prefers that I use the 5W ceramics supplied. He says 5W resistors for both the base and full versions for the Evolution amp is ample and 7W resistors are unnecessary. I do remember Mauro writing that the 7W resistors can get hot in the rev c, and the Evolution I would think should be comparable, although it's output wattage is a little higher.

I don't quite know what to make of all this. I thought a "better" replacement component is generally desirable. Maybe the greater excitation of the electrons in a hotter (lower wattage) component results in better sound??

ps.
maxlorenz  
#5 Posted : Friday, November 17, 2006 4:26:21 PM(UTC)
maxlorenz

Rank: Member

Groups: Customer, Beta Testers
Joined: 10/31/2006(UTC)
Posts: 19

Hi pearshaped,
About your question, we will have to try and see...as this is an empirical hobby :-)
I finished mine, C9 retained the Pana M instead of Rubycon. I changed R2? from 33K to 10K, Riken, but had to reduce lead's width mecanically (I don't know what is name of the tool in english).
Now I'm waiting for funds to reapear to buy the transformers...too many projects!

Appart that, nobody talks about wiring and sound change. Perhaps I am too sensitive to wires?
Cheers,
M
Obsessive-compulsive builder.
pearshaped  
#6 Posted : Saturday, November 25, 2006 9:14:58 AM(UTC)
pearshaped

Rank: Member

Groups: Customer
Joined: 10/26/2006(UTC)
Posts: 5
Location: Mount Isa, Australia

Hi Max,

You are right - we all differ in our sensitivity to sound, and it is a matter of "try it and see".
Just like your sensitivity to wires (no doubt there are others), I seem to be far too sensitive to changes to my system setup than I would have expected at my age.
I think Mauro's aim in his designs is to achieve the best possible sound using standard quality components. he probably feels the performance of the Evolution amp will not benefit from the use of "better" components. mauro acknowledges though that the performence of the rev c amp is affected by some component choices, notably among them,C9 and C21.
It is worth remembering that a system is only as good as the weakest link, and improving the resolution of one piece of equipment may not necessarily bring an improvement in the sound of the system.

ps.
maxlorenz  
#7 Posted : Monday, November 27, 2006 1:51:37 PM(UTC)
maxlorenz

Rank: Member

Groups: Customer, Beta Testers
Joined: 10/31/2006(UTC)
Posts: 19

Dear PS,
Instead of waiting for my next transformers (Plitron, even standard are great, noiseless) to finish the monoblocks, I decided to swap the existing my-ref modules from my integrated amp for the new built modules with caps and resistor mods (only C9 differs on stock kit: FC v/s FM?) and see what happens. Then, if the mods pleases me I can do them on the original modules ;-)
Ah! Time!
Cheers,
M

PS: I will then try Silversonics Pro Studio shielded balanced cable as input. It's kind of expensive but I only need a few cm. This cable is very detailed and has a balanced, neutral presentation. A bit cold on midrange perhaps, but this is system dependant.
Obsessive-compulsive builder.
pearshaped  
#8 Posted : Wednesday, November 29, 2006 7:40:10 AM(UTC)
pearshaped

Rank: Member

Groups: Customer
Joined: 10/26/2006(UTC)
Posts: 5
Location: Mount Isa, Australia

Hi Max,
I used Rubycon ZA at C9 - seems to be ok. Panasonic FM would be comparable I would think. Pity the Black Gate N series do not fit.
For C21 I used Vishay Roederstein MKP1837,which are often recommended in such a position - also seems to do the job. On my next rev c boards I will try Black gate NX HiQ 0.1uF, 50V as C21. Might also use them to bypass the 220uF rail caps. Martin Colloms recommends them above all others as bypasses. They are inexpensive. I used them to bypass BG FK caps that I used as coupling caps on a MC preamp I was experimenting on, to great effect. They cleaned up the highs beautifully. ( I'm going to rebuild that preamp and use GB Super E- Caps instead).

For the input cable I used Cardas 2x21.5 AWG Twinaxial at $3.50/ft from Parts Connexion. I have no inclination to change it. It needs a very hot (400C)soldering iron to solder the litz wires though.

Regards,
ps.
maxlorenz  
#9 Posted : Wednesday, December 6, 2006 4:06:41 PM(UTC)
maxlorenz

Rank: Member

Groups: Customer, Beta Testers
Joined: 10/31/2006(UTC)
Posts: 19

Hi,
No time to do the swap yet.
I'm glad you like the little BG-NX 0.1uF. I also do the superE-cap. I found it works though our mates at DIYaudio (and DIYhifi.org) say that the explanation given by the inventor is BS :-D
I could do litz with a 26AWG OCC copper that is very detailed. Maybe I will make several input cables and test them...if time allows. (I only have 5 or 6 other projects, he, he...)
Best of lucks,
M
Obsessive-compulsive builder.
maxlorenz  
#10 Posted : Wednesday, January 3, 2007 3:51:09 PM(UTC)
maxlorenz

Rank: Member

Groups: Customer, Beta Testers
Joined: 10/31/2006(UTC)
Posts: 19

Hi,
I found time to swap some components after the festivities...
Thanks to my very solid heatsink strategy I could not take off the stock original power module and swap it for my already stuffed new modded module...so I desoldered some caps and did the mod on the original amp.

I swapped C9 for Ruby ZL 220uF/50V and the PS rails caps (whose exact number I forgot) for Ruby ZL 470uF/50V.
R2(33K) was substitued for 10K Riken that I had on hand. I did not address R12 (3.3K) this time.
That way my two pair of amps will differ on C9 (Pana FM v/s Ruby ZL), input cap (Wima MKS10 v/s Epcos) and R12 (stock 3.3K v/s Riken 3.9K). That should be an interesting comparison.
I couldn't swap those 100uF EL caps because Ruby caps had less distance between legs.

Sonics: I don't know...it must be a genetic trait or something but I allways found Pana FC sound good on bass but lean and dry on midrange and extended on highs but have that "razor sharp" quality that I dislike. All this is gone with the Rubycons: they are well balanced on the whole freq. spectrum; deliver rock solid deep bass, with punchy and "thick" midrange; they doesn't lack highs wich are delivered with superb transparency and detail.
The bad thing is that I will end with a bunch of Panasonic caps on my project box! :-D
A pitty that you can't offer them as stock or optional caps. It's very hard to get them.

Exited by these findings I also modded one of my Kookaburra's wich sets volume on my big system. I only get the four 220uf, PS caps, not the chips decoupling caps, but the swap already showed benefit in tems of increased coherence between freqs. ; rounder, punchier mids.
At first I hesitate to do it but I realized that the PGA2311 chip has an internal opamp and that the buffer opamps also must get the best quality power that I can give.

I also considered "snubbing" the rectifier diodes. I will post further findings on the proper Kookaburra page.
Changing some 0.1uF decoupling caps for BG-NX is also tempting as I've done this elsewere (Ruby+BG) with good results.

Bye,
M
Obsessive-compulsive builder.
maxlorenz  
#11 Posted : Wednesday, July 11, 2007 5:52:12 PM(UTC)
maxlorenz

Rank: Member

Groups: Customer, Beta Testers
Joined: 10/31/2006(UTC)
Posts: 19

Hi,
I finally got the time to assemble the first monoblock. The box is all hand made, from spare materials. I will post photos to see if anybody has seen an uglier enclosure :-)

It uses an EI 250VA transformer (locally made, with EMI filter/screen) closely mounted to the PCB: the amp is totally silent!
The sound as usual is awesome. I can't compare yet with my unmodded Myref but sound is very promising: soft, yet punchy and detailed throughout the spectrum.

The only drawback is a big turn-off "tump"! (DC offset is 2mV only!)

Could this tump be caused by swapping the electrolytic caps from the LM3886 PS from 220uf to 470uf???

Should the relay disconnect speakers on power off and thus avoid tumps? Sorry I don't remember that.

Regards,
M
Obsessive-compulsive builder.
Rss Feed  Atom Feed
Users browsing this topic
Forum Jump  
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.