RM-4+ and caps, caps, caps ...

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6BQ5

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RM-4+ and caps, caps, caps ...
« on: 12 Jul 2008, 05:05 am »
Well, I've never had a chance to experiment with these new fancy expensive caps being sold these days (Dynamicaps, Hovland, Mundorf, Auricaps).

Just came across this RM-4+ on A'gon that has had the cap treatment.

http://cgi.audiogon.com/cgi-bin/cl.pl?preaphon&1218736522

The seller says this was done with RJM's guidance. Not sure what to make of it.  :scratch:

I've read RJM saying that he chooses parts for performance. But when the design for the RM-4 and RM-5 went from schematic to build (probably in the '80s), none of these fancy caps were available back then. I wonder if RJM would use some of these new caps in designing an RM-4 today? My guess is probably not (no-nonsense engineer he is who is skeptical of marketing hype) ... but I'd love to hear God's opinion of the creation below.


6BQ5

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Re: RM-4+ and caps, caps, caps ...
« Reply #1 on: 12 Jul 2008, 05:12 am »
sorry, a duplicate

Roger A. Modjeski

Re: RM-4+ and caps, caps, caps ...
« Reply #2 on: 13 Jul 2008, 07:20 am »
Is RJM me? If so here's the scoop.

We made the RM-4s over a long period starting in 1980. We were one of the first to use second version of Wonder Caps clearly marked 3 uf/310 V white wonder caps. Those were in the RM-4 pictured at audiogon before they were changed to Dynami caps.

All the RM-5 preamps after the first run have caps made by the fellow who made the early wonder caps, Bass Lim. He has made more of the premium brand caps than anyone else I know of. They are marked "REL CAP" with RAM below the part number.

What's popular in capacitors changes like the weather and I have no objections to whatever someone wants to use. For a small fee I invite those who have a favorite to send them and I will put them in and make sure everything is OK.

6BQ5

  • Jr. Member
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Re: RM-4+ and caps, caps, caps ...
« Reply #3 on: 13 Jul 2008, 04:15 pm »
Hi, Roger thanks for the reply. That's exactly what I wanted to know.  :D

Roger, did you also read the ad in the description?

I'm curious about this warm-up bypass that was installed (turns off tubes but keeps current flowing through the rest of the board). That seems to be a great idea in keeping the caps in ready-to-go state (not requiring a long warm up). I remember once reading that JBL, when they designed the xover for their top-of-the-line K2 speaker, they install a small battery to ensure a small current is always running through the caps in the xover when sitting idle.

I also came across this shootout of 21 cap brands, no shortage these days to choose from. It's hard to imagine commercial products being built with such expensive caps and remaining affordable to mere mortals.

http://www.vhaudio.com/21capacitorshootout.pdf

Here is also another evaluation of caps. http://www.humblehomemadehifi.com/Cap.html 

Roger A. Modjeski

Re: RM-4+ and caps, caps, caps ...
« Reply #4 on: 13 Jul 2008, 05:52 pm »
6BQ5,

Thanks for the links. I hope everyone reads the first link. It was interesting to see that many of the expensive, often lauded caps are in class D.

As with cables and powercords the claims are astounding. That audiophiles would rather discuss this and that capacitor rather than drivers, crossovers and multi-amplification is astounding also.

The first is relatively easy to do and supports the American way: "Throw more money at it and it will be better".

The second is far more rewarding and can often be implemented for far less than the cost of a few capacitors or an expensive power cord or expensive cables.

I imagine I am going to get a lot of flack for this.... Just be nice about it, OK?

Roger A. Modjeski

Re: RM-4+ and caps, caps, caps ...
« Reply #5 on: 13 Jul 2008, 06:03 pm »
The warm-up switch is similar to what we are calling the "Forming" switch on the RM-200 MK II. It keeps all the caps 5-10% overcharged (a higher voltage than the operating voltage). When the amp is played the leakage currents are vanishingly small. Anyone who has monitored the charging of electrolytics will have seen that the leakage current never gets to zero, it's an asymptotic situation.


6BQ5

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Re: RM-4+ and caps, caps, caps ...
« Reply #6 on: 13 Jul 2008, 06:14 pm »
Let's see:

   2 V-CAPS = $100
 
  100 Vinyl LPs at local thrift store = $100

Seems like a no-brainer to me.  :duh:

Came across another hot-rodded RM-5, this one located in Japan.
http://www.eonet.ne.jp/~audio-interior/preamp.htm




The Google translation from Japanese is quite poor, but I gather in the Japenglish that upgrading the power supply made a big difference.




« Last Edit: 20 Jul 2008, 12:23 am by 6BQ5 »

IkeH

Re: RM-4+ and caps, caps, caps ...
« Reply #7 on: 21 Jul 2008, 12:32 pm »
Hi, 

This one actually belongs to a friend of mine.   I met through one of the audio clubs in Japan ( I know reside in US but I am originally from Japan)  and became friends since we both use RM-5 II (mine is a stock through)

I've visited his house and he uses his modded RM-5 for a systems consists of B&W original Nautilus (one actually looks like the Nautilus) driven by 8 power amps!  It sounded great!

He really admires Roger's pre-amp and his ingenuity in designing it.

Ike




rbwalt

Re: RM-4+ and caps, caps, caps ...
« Reply #8 on: 21 Jul 2008, 03:15 pm »
Ike i noticed that you do not have the input jack reinforcement brace on your stock unit.  i had one on mine and it kept the input jacks in place which had a tendency to work lose if you used a large interconnect cable. i believe in the later RM5 versions (MK4's ) roger did away with the selectable gain switches and it opened up the sound.

rob.

6BQ5

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Re: RM-4+ and caps, caps, caps ...
« Reply #9 on: 21 Jul 2008, 04:47 pm »
Ike, I'd be curious if you can provide a quick synopsis what he has done to the RM-5 (based on the website posting).

It seems that all the parts have been changed, not only the caps, but also the resistors in many places too, and not to mention the power supply.

IkeH

Re: RM-4+ and caps, caps, caps ...
« Reply #10 on: 15 Aug 2008, 02:38 pm »
6BQ5 sorry for the delay.  I've been vacationing at the beach with no internet conenction!

Before I get to it, the picture with two RM-5 actually shows two different units.  He borrowed one from a dealer and took a photo to show the changes he made to the stock unit (serial # 303 vs 552.)  He comments that the stock parts were different between the two units. FYI

In summary, he has done the following:

- Changed film caps to Dynami Caps in signal path
- Changed electrolytic caps to Sanyo OS-cons
- Changed some electrolytic caps in PS to Solen Film caps
- Added sheilds/heat sinks in various places (as shown in photo)
- Replaced RCAs with Cardas
- Installed DACT volume
- Power cable changed to AET (Japanese brand)
- Separate external PS for B+ using Plitron Torroid.
- He uses Cryo'd 6H23P (he swears by them)

For the phono section, he uses outboard phono amp he assembled using the DACT phono board.

Ike

 




6BQ5

  • Jr. Member
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Re: RM-4+ and caps, caps, caps ...
« Reply #11 on: 15 Aug 2008, 03:05 pm »
Thanks for the update.

Wow, all those parts swaps and not using the phono section onboard ... hmmm... he definetly changed the caps in the phono section, so obviously the DACT must work better for him.