[Audio-Me]

I guess what I'm trying to say is, would all that make much of a difference? Enough to make a noticable improvement anyway.

 

[roll-man]

in case anyone was wondering...my JMT CHA-47 sounds significantly better than my porta-corda (remember them?) and vastly better than my late 2001 Total Airhead.

 

[carlo]

audio&me,

sure. you're enjoying the sound of your custom jmt with upgraded caps, right?

will a different potentiometer make an audible chance to your ears? we both know who's got the answer... while some designers feel it's the circuit, not the parts, that make a hifi component (tim deparavinci comes to mind), consider that modded components can sound pretty damned different from stock ones.

 

[Audio-Me]

I didn't even know there were different volume control implementations, so it's hard for me to fathom its impact on sound, but I'll take your word for it.

Does JMT use better parts on the cmoy than the cha-47? Or is it a preference thing? I think someone said that they prefer using the cha-47 capacitors in his cmoy, yet was smoother sounding than the regular cha-47. I was under the impression that the cmoy was just a bigger unit of the cha-47 with crossfeed, different caps, rca jacks, and double 9V power supply.

 

[Audio-Me]

FS, I notice in your profile that you have the Ety ER-4P, yet your avatar says 4S. Do you use the P-S adapter? If so, could you describe any changes in sound when being driven by the cha-47? I have a strong resentment against sticking stuff in my ear, but I'll have to get over it, as isolation will become critical for me next year.

 

[Paul Laurens]

JMT made me a home unit version with gold RCAs, and the two 9 volts. The sound out of my cheapy portable is dramatically better -- bigger, way more bass and dynamics, with major omph, and tons more detail. The amp made listening to a portable enjoyable. I can hardly wait to try it with a good source.

 

[FlurkingShnit]

Quote:

Originally posted by Audio&Me FS, I notice in your profile that you have the Ety ER-4P, yet your avatar says 4S. Do you use the P-S adapter? If so, could you describe any changes in sound when being driven by the cha-47? I have a strong resentment against sticking stuff in my ear, but I'll have to get over it, as isolation will become critical for me next year.

I guess the best way to answer the question would be to briefly describe my Ety history.

The Ety 4p were my first "higher" hi end cans after my grado SR-60s. My Dad got them for me as a gift and for a long time I drove them simply out of my Aiwa pcdp, and was very satisfied.

I then heard about the incredible qualities of the Sony D-25S so I ordered that and drove my 4P's with it. The sound quality with this setup was impressive at the time. The bass was much more controlled than with my Aiwa, and everything seemed just so right in all areas of the frequency.

Then I heard about the 4P-S adapter. I snatched that up quick from Xin Feng and when I listened with it, everything changed. Deeper bass extension, smoother, extended highs, improved midrange.

When I got my amp from JMT and drove my 4p/s with it the final setup was: Sony D-25S, 1ft Kimber mini mini, CHA 47, and the Etys. And now as to what your asking, the changes in sound were indeed great. In terms of frequency response, the biggest improvement was the bass. The D-25S has a great headphone out but the bass was just smoother and even MORE extended. Another big improvement was the MUCH MUCH expanded soundstage. Up until the point where I used the amp for the first time, I really had no concept of what a soundstage was. I thought that "3 dimensional" its-like-you're-there feeling was something made up by audiophiles to empty my wallet

However, with the JMT, I quickly learned that it was indeed a reality.

Bottom line:

ER-4P - great headphone, slightly boosted bass that veils and clouds the midrange (to my ears)

ER-4S - the music is laid out very simply for you. Nothing is hidden, nothing is boosted, and you're left with great sounding music, assuming you have a good recording to start with.

CHA-47 amp - Probably the single most important piece of equipment that made me realize how much the Ety 4S are worth it and how good they are. Audio&Me, trust me, the amp will make you work out any problems you have with the fit just to discover how good the Etys sound.

 

[erix]

This is a funny thread.

RE: upgraded parts - My semi-random thoughts on the subject. NOTE! These apply to amps built on the Cmoy/Hansen/JMT board only (Cmoy amp and CHA47 amps).

There are two kinds of capacitors used on the Cmoy/Hansen/JMT board; the power supply caps (electrolytic) and the coupling/crossfeed caps (polypropylene film).

The power supply caps are the cylindrical ones standing on end at the back corner of the board. Their job is to filter the power coming into the amp (smmoth out the DC) and 'store' power. Fast transients and big bass demand more power than the battery(s) alone can provide. The big caps store power and give a little blast to the opamps when the situation demands it. You can upgrade these by either getting a better audio type (Elna Cerafine, Nichon KZ, Black Gate) and/or upping the capacity (470uF - 1000uF whatever will fit). There is a sound difference between the brands, however slight, mostly better faster bass (Cerafines anyway - only kind I've tried).

There are two caps (C1L and C1R) that are the input caps. The best upgrade for these is to eliminating them entirely - they are only in there to prevent DC from entering your amp from your source. Most (if not all) modern sources don't allow DC out. I have a D-25S from 1992 and there is no DC present on either the headphone out or the line out.

The rest of the caps are in the signal path only when the crossfeed is on. If you like crossfeed these should be good ones. Space is too limited for most of the exotics except Wima MKP4. The Panasonic polypropylene films are really good (and I suspect that is what JMT uses - are they kinda blood red?).

Resistors are the other little cylindrical things. These are in the signal path so they should be metal film and as close to their stated value as possible. JMT probably uses 1% resistors which means their actual value is 'spose to be within 1% of their stated value. It's not to critical that a 10K resistor measure exactly 10K - what is critical is that the value of the resistors on the left channel are as close to possible to those of the right channel. A good (and cheap) upgrade is the Mil-Spec RN55 resistors that Mouser sells. These are rated 1% but are much tighter tolerance in reality. You can try Holco or other exotic resistors but you'll have a bear of a time getting them in - the board has .3" spacing for resistors!

The volume control is at the front end of the amp - it's the first thing your signal sees. It should be a decent one with really close tracking (ie. at half volume the resistance of the left channel element is close to the same value as the right channel element). Just because you get a $30 volume pot does not gaurante (sp) close tracking. I've bought 5 pots to find 2 good ones - they are usually rated 20% tolerance!

So what does this all mean? Here's a list of upgrades in order.

1. Change the Power supply caps first. Go to 470uF or higher - whatever will fit - before buying fancy ones.

2. Remove C1L & C1R.

3. Up the voltage - use (2) 9V in series. This gives more power which means more clean headroom. You should have more power on hand before you...

4. Try different opamps. They must be duals. Try OPA2132, OPA2134, OPA2228, AD823... You'll be amazed at the sound difference between chips.

5. IMHO it's not worth the trouble changing the crossfeed caps or the resistors unless they are poorly matched. My guess is that JMT does match them so I wouldn't worry about them.

ok,
erix

 

[carlo]

erix,

thanks for the perspective and advice. could you point me in the direction of a link with a recommended parts list for the full blown cmoy?

thanks,
carlo

 

[erix]

Here is Chu Moy's original article - you can get component values from the schematic(s).

ok,
erix

 

[Audio-Me]

 

[Driftwood]

interesting pics! though I can't really judge it's size by them, but that is ok... I am interested in seing your custom bolder cable though... can you post pics of that?

Driftwood

 

[Audio-Me]

Lol, I tell you what, I'll take pics of my portable rig with a digital camera at school. (It's the school one, and it really sucks, heh)

 

[Audio-Me]

I recently sold the MG Head DT (stock tubes), but don't miss it, here's why:

I ordered a custom Bolder mini-rca cable to use with a meta42 which hasn't arrived at my door steps yet. So for the time being, I used it to hook up my cha-47 to the terratec ews88mt. What I heard was astonishing. For the first time in my system, I heard 3D imaging and everything in the music came alive. Not only was there tonal balance, but there was more detail. I heard nuances of voices I didn't know that existed, the rattling of cymbals faded away naturally, and everything else seemed to carry more texture while still being portrayed smoothly, which leads to a more refined sound. I cannot wait for the meta42.

This is easy listening folks... Stay tuned for results of the meta42.

 

[The Quality Guru]

Quote:

Originally posted by Audio&Me terratec ews88mt

May I ask what that is? I'd be seriously interested to know, because I have a CHA-47 Penguin, and I LOVE the sound of it now; improving the sound would be nothing short of "astonishing" as you put it . . .