Sonographe SA250 problem solved

[jimtranr]

Last Friday morning I turned on the bedroom system tuner feeding the c-j Sonographe SC25 preamp and SA250 amp (both of which stay on 24/7) and got only left-channel output. Component-swap troubleshooting quickly identified the problem child as the amp. Everything had operated normally the night before, but after I'd shut down the tuner I heard extremely low-level random popping for about five minutes that was impossible to localize and made me think initially--hold the :D's, please--that it was a nocturnal squirrel batting acorns around on my roof. I should note that during "normal" operation I could hear a trace of hum and what I thought was line noise if I put my ear up to the speakers--nothing audible beyond an inch or two.

Since I have a schematic and a local tech who knows what he's doing (he's the brick-and-mortar retailer whose demo Paradigm inventory I cleaned out when he shuttered his sales operation in March), I took the amp and picture to him that afternoon. I mentioned the popping and, as an aside, my discomfort with the virtual snugging up of the RCA input jacks to each other, especially since the plugs on the Kimber Select IC's feeding the amp are metal-jacketed WBT locking types and posed the possibility of a shorted connection. Could he reposition the jacks?

The tech initially thought the popping I heard might suggest a bad transistor, but today he e-mailed me that the problem derived from the design of the stock input jacks (an issue separate and apart from their snuggle-up proximity to each other). Their shells are pressure-fit types intended to make the ground connection with the amp's internal board. But they can be pulled out of the jack housing by heavy-duty IC plugs like...yep, the Kimber's locking WBT's. What killed the right channel was a blown power supply fuse for that channel.

The tech replaced the stock jacks with Vampires and respositioned them as well. The picture below shows the stock jacks near the bottom of the rear input-output panel, with the Vampires about midway between them and the speaker outputs. He ran tests today and indicates that everything's up and running normally...and no hum, no noise heard emanating from the amp in an "on," no-program state, not even through headphones.

Mentioned here in case someone runs into a similar hum/noise/channel dropout issue with an SA250.

http://jimtranr.com/SA250_revised_inputs.jpg

[joeinid]

Wow,

Lucky you had a great tech working on it. I'm happy you are back in business. I like the part about the squirrel. :) Funny.

Joe

[jimtranr]

The SA250's home, and it was immediately obvious upon feeding it program that securing the interconnect connection with upgraded RCA jacks and the consequent elimination of low-level noise/hum, however previously inaudible it was from my listening position, has effected a discernible improvement in sound quality. :banana:

The tech, whose own main system electronics are ARC (he used to be a dealer), had never heard a Sonographe amp before. He said that after making the repair he spent time listening to the 250 to make sure everything functioned properly. When I picked it up this afternoon, he made a point--twice--of saying, "This is a nice amp."

He's now looking forward to coming over and listening to the 17LS/MF2500 combo driving his onetime-demo SE-3's.

[joeinid]

Hi jimtranr,

Wow! Great to hear everything is working well. Makes me want to snag the Sonographe on agon for a different system.

Keep us updated :music:

[jimtranr]

Joe...As good as the 250 is--and I think the a'gon seller's characterization of it as one of audio's best kept secrets is apt--his starting price of $600 strikes me as a bit high, given that I've seen the amp typically offered in the $400-$475 range (I snagged mine on eBay bundled with the SC25 preamp for $710).

One of its "secrets" (and, aside from its intrinsic sonic quality, one of the characteristics that impressed my tech) is its current delivery capability, a real plus with high-energy-transient program material.

Jim

[joeinid]

Thanks Jim,

I don't know why Sonographe was never on my radar in the past. I must have overlooked many great products. I am glad you are enjoying yours. Maybe I can get him down in price :)

Joe

[jimtranr]

Joe...I don't think it was ever on many people's radar, though, IIRC, Stereophile blessed it with a Class B rating around 1998. There's also the SA400, rated at 200 wpc into 8 ohms (with, I suspect, correspondingly higher current delivery capability) if you need the extra punch.

If you do grab the a'gon 250, consider checking for any "give" to the input jacks when you touch them. Probably not a problem if you're not using "heavy-duty" interconnect plugs, but something to be aware of.

Jim

[joeinid]

Will do :)

[Rafale]

Jim
How the SA250 compares with the CJ MF2250?

[jimtranr]

Jim
How the SA250 compares with the CJ MF2250?

I actually have an MF2500, Philippe, though I'm sure there's a strong sonic family resemblance to the 2250. But since I have the amps connected in two different systems--the 2500 mated to the tubed Premier 17LS and Paradigm SE-3's, and the SA250 to the SS SC25 and SE-1's in wholly different rooms--I've not done a valid comparison between the two.

I will say this, however. The SA250, especially now with its new input jacks, is a midrange delight and enables the SE-1's to throw a surprisingly deep, layered, and believable soundstage within the confines of a small-to-medium-sized, sporadically-trapped, and furniture-stuffed bedroom. Winds, brass, strings, and vocals shimmer with nuance and timbral detail that conjure up "delicious." I don't want to overstate the amp's virtues (I probably already have as it is), so I'll leave it at this: I won't make the last owner's mistake of ever putting it up for sale.

Jim

[Rafale]

''No lesser person than Harry Pearson said recently that conrad-johnson had never built an unmusical product. He was lamenting a growing trend within the US high-end toward a sterile high-definition sound, long on information and very short on soul.''
Roy Gregory HIFI+

[jimtranr]

Turns out that the malfunctioning SA-250's core problem was not its squidgy jacks (though in any event I'd have had them replaced) nor even the 250 itself. Late at night about a week after it had returned from repair and had been on 24/7 in tandem with the SC25 preamp the rushing noise that had preceded the 250's fuse blow returned in the right channel.

On a hunch, and since I trust the competence of my friendly tech, I shut everything down and switched the IC's so that the SC25's left-channel output fed the 250's right channel and vice versa. And the rushing noise moved with the switch. I swapped in different cables to make sure that the IC itself wasn't at fault. The problem remained.

The SC25 is now with the tech, who determined during testing that the bias trim pot for the right-channel FET was dirty. Cleaning it eliminated the rushing noise. He's waiting now for C-J to respond to an inquiry he sent before returning it to me, as he has an idea that should make the preamp sound even better.

I'll let you know the outcome.

Jim

[joeinid]

Hi Jim,

I'm glad you have at least nailed down the source of the problem. Thank goodness you have a great tech you can trust. Please keep us updated.

Joe

[Rafale]

Turns out that the malfunctioning SA-250's core problem was not its squidgy jacks (though in any event I'd have had them replaced) nor even the 250 itself. Late at night about a week after it had returned from repair and had been on 24/7 in tandem with the SC25 preamp the rushing noise that had preceded the 250's fuse blow returned in the right channel.

On a hunch, and since I trust the competence of my friendly tech, I shut everything down and switched the IC's so that the SC25's left-channel output fed the 250's right channel and vice versa. And the rushing noise moved with the switch. I swapped in different cables to make sure that the IC itself wasn't at fault. The problem remained.

The SC25 is now with the tech, who determined during testing that the bias trim pot for the right-channel FET was dirty. Cleaning it eliminated the rushing noise. He's waiting now for C-J to respond to an inquiry he sent before returning it to me, as he has an idea that should make the preamp sound even better.

I'll let you know the outcome.

Jim

Hey Jim, do you believe that he can transform my LP140M into ART?:D

[Coppy]

To answer for Jim... no but if you call Spearit, they probably can give you a great trade on your amps for new ARTs. Well, maybe not outside the US but who knows.

[Rafale]

Thanks+++......I had several times contacts by e-mails with them they were reluctant to export and refused to make the voltage conversion but will try again if I see good opportunities

[jimtranr]

Hey Jim, do you believe that he can transform my LP140M into ART?:D

You mean like so?

http://jimtranr.com/LP140M_ART.jpg

[Rafale]

:roflmao::roflmao:
It is very attractive that would go very well to my room....

[jimtranr]

After talking with Ed at c-j to confirm operating parameters, my local tech substituted fixed resistors for the stock trim pots (and revised the schematic accordingly and wrote up the appropriate biasing procedure in detail in case any of the FET's ever need replacing due to failure and he's not around--he's the complete tech).

I'll let the new resistors cook for at least a hundred hours before I subject the SC25 to critical listening, but it's already obvious that the noise anomaly has been corrected.

Nice to have it back.

[joeinid]

Great news! and such a dedicated tech. He's a keeper, they are hard to find.

[Puma Cat]

''No lesser person than Harry Pearson said recently that conrad-johnson had never built an unmusical product. He was lamenting a growing trend within the US high-end toward a sterile high-definition sound, long on information and very short on soul.''
Roy Gregory HIFI+

Truer words were never spoken. I've been chatting with some other folks in another forum who are considering getting some C-J, and they are hemming and hawing over whether they should get this or that C-J preamp, and I keep telling 'em..."It doesn't matter, C-J couldn't build a bad sounding preamp if they wanted to. Just pick one and enjoy."

[joeinid]

Truer words were never spoken. I've been chatting with some other folks in another forum who are considering getting some C-J, and they are hemming and hawing over whether they should get this or that C-J preamp, and I keep telling 'em..."It doesn't matter, C-J couldn't build a bad sounding preamp if they wanted to. Just pick one and enjoy."

There seems to be a lot of that going around and Stephen you are absolutely correct, C-J stuff is really nice.

[Rafale]

Truer words were never spoken. I've been chatting with some other folks in another forum who are considering getting some C-J, and they are hemming and hawing over whether they should get this or that C-J preamp, and I keep telling 'em..."It doesn't matter, C-J couldn't build a bad sounding preamp if they wanted to. Just pick one and enjoy."

There seems to be a lot of that going around and Stephen you are absolutely correct, C-J stuff is really nice.

I observe that CJ gear is very quickly sold at the moment on Audiogon, there is a big turnover.... would there be an AA effect?:thumbsup:

[joeinid]

I observe that CJ gear is very quickly sold at the moment on Audiogon, there is a big turnover.... would there be an AA effect?:thumbsup:

From personal experience, I'd say YES! :smoking:

[Rafale]

From personal experience, I'd say YES! :smoking:

Joe you are asked to leave it for the others:D

[joeinid]

Joe you are asked to leave it for the others:D

Sorry, I did not mean to hog everything :smoking:, I'll stop now :yes:

[Rafale]

Sorry, I did not mean to hog everything :smoking:, I'll stop now :yes:

but I want that you buy the LP275M and that you resell them to me cheaper:buddy:

[joeinid]

We'll talk :)

[jimtranr]

I see that an MV60SE in Chicago hit Audiogon today at $1700. Let's see how long it stays up.

Meanwhile, the repaired SC25 now has almost 72 cooking hours under its chassis, and the fix--replacing the trim pots with 5% metal film resistors--has effected a quieter, blacker-background, less congested preamp than existed before the rushing noise problem manifested itself. I'll just leave my listening impressions at this: Given the initial acquisition price, and even with the repair costs to the 25 and the SA250, I feel like my picture should adorn a "Wanted for Highway Robbery" poster. Or should that be "Got Away with Murder?"

[joeinid]

I see that an MV60SE in Chicago hit Audiogon today at $1700. Let's see how long it stays up.

Meanwhile, the repaired SC25 now has almost 72 cooking hours under its chassis, and the fix--replacing the trim pots with 5% metal film resistors--has effected a quieter, blacker-background, less congested preamp than existed before the rushing noise problem manifested itself. I'll just leave my listening impressions at this: Given the initial acquisition price, and even with the repair costs to the 25 and the SA250, I feel like my picture should adorn a "Wanted for Highway Robbery" poster. Or should that be "Got Away with Murder?"

:roflmao: Wow! Very glad to read you are happy. Yea, I saw the MV60SE this morning. Looked like it was in a little better shape than the MV60 I'm getting.