ET250S hybrid poweramp

[jeffreybehr]

Ordered one Wednesday from Spearit--$4950 delivered for a new one. (Refurbs are $4250.) I had asked about the 7-days-for-cash-refund return privilege v. an amp that requires maybe 500 hours to break-in; the GM answered that he'll extend the return-for-cash-refund privilege to 30 days for the '250. Will be driving the MR and treble of my pair of Audio Physic Avanti III (Imp.).

One thing that influenced me was just how good my MET150 5-channel amp made both my CC speakers* sound. (The MET150 and ET250S** are brothers, and both use one 6922/6DJ8 per channel with triodes paralleled for Voltage gain.) So now I'll have seven channels of c-j poweramps AND a c-j 6-channel preamp.

* Vandersteen VCC-1 (Imp.) and Eminent Technology LFT-12 (Imp.)
** In c-j-speak, 'ET' means enhanced triode, 'S' is stereo, and 'M' is multichannel.

[Big Dog RJ]

Nice one Jeff!
The ET250S is pretty good driving a reasonable load, and will deliver all the wonderful characteristics of cj musicality.
My dealer chap has a couple of these driving Vandy Quattro's (very smooth overall, and deep musical bass). In another room, he's also using them on Naim and Jass speakers with the ET5 as the preamp. However, when it comes to the bigger Quads, not a good match; compared to the Evo2000 or Premier 350, the ET250s was not designed to drive "re-active loads."

Having said that, it will be a very nice amp to have driving your mids and highs as you've set it up for. I am sure you will be enjoying this one for many years to come. Great stuff mate, I think you also managed to close on a very good price range, that certainly sounds like a great-value deal for a top line brand in amplification.

Have a good mate,
Cheers, RJ

[bgiliberti]

FWIW, I found the ET-250S rather too laid back -- it never really made my Harbeth 30s come alive, We then auditioned it on a set of Sonus Faber stand speakers, same result. I went with the non SE MF2550, which is $4000 and am very happy. It has pulse, pace, and drive which I never got from the ET-250S, which BTW, was well past 1000 hours of break in on the caps. Your mileage may differ, of course. But if it doesn't work out for you, definitely audition a 2550 or 2550se. It's still very CJ, but quicker than the 250s. But again, the ET-250S got great reviews, and a lot of people really like it as well.

[jeffreybehr]

Spearit packed the LARGE c-j carton into another; the whole thing arrived in perfect condition. After unpacking, I pulled the top and bottom covers to insure there were no loose parts inside and also to fotograf it. There are lots of pics at http://s89.photobucket.com/user/jeffrey ... t=3&page=1

Here's a teaser.

Got to build a new amppad now!

The amp looks very well built, as it ought at US$8.5K RR. The first mod will be to move the input cables, the twisted quad of blue-and-orange wires...

...so that they exit the chassis early on the bottom of the amp so that I can add gain-reducing resistors* and the high-pass caps required by my Avanti III speakers**.

After about 4 hours of break-in, the amp already sounds quite listenable and almost as transparent as the J2s, but it definitely also sounds harsh on massed violins, a product, I presume, of the maybe-dozen brand-new Teflon-film caps in the amp. More later.

* The amp has 8dB more gain than my First Watt J2s which is about 15dB too much.
** The original high-pass filters for the MR drivers were inexpensive film caps on the x-over boards which I quickly removed in favor of much-smaller-value, much-higher-quality caps in front of the poweramps.

[bgiliberti]

wouldn't that void the warranty? In any event, I think it's one of the coolest looking amps ever. Love the Wrigley Field cutout for the tubes. Teflon Hell awaits for 400 hours. Definitely will not be harsh on anything after break-in. My issue with it was almost the opposite -- too "smooth." One thing I did not try, because it was a trial period, was replacing the input tubes. I probably should have. The unit I borrowed from Spearit had over 1000 hours on it, so tubes may have been a factor in the rolled off highs I experienced. Congrats on a beautiful amp.

[Joe Appierto]

Very nice indeed. Good luck with it and enjoy.

[jeffreybehr]

Day 3 and it still runs! Found a slightly larger pad and am now footing it with 4 Herbies Tall Tenderfeet at the edges because there's no bottom on the amp.


With the input cables lying loose, I patched in a high-pass-filter cap and a 56K resistor in series.

HP filter point is now c. 90Hz (so I won't destroy the MR drivers), and output level is reduced 3dB--with about 10 more to go.

[bgiliberti]

What do you mean "there's no bottom on the amp"?

[jeffreybehr]

What do you mean "there's no bottom on the amp"?

Read the 4th post; I removed the bottom cover to get at the input cables; the bottom cover is still off.

[jeffreybehr]

...much better than I thought it would at this point, and it'll only get better sounding!

'Getting better sounding' will be assisted by better speaker cable to both channels--now I'm using about seven feet of old 20g. zipcord wound around the spades to extend the left-channel cable to the amp on the right. Also, the 56K resistors and 0.01uF input-filter caps are jumpercabled onto the RCAs and input wire.

I've ordered a stereo level control to reduce the amp's excessive (IMO) Voltage gain of 28dB(!), and that'll be installed with new, super-high-quality RCAs (Furutech FP-901(R)s) and solid-silver wire inside the amp. Installing this level control will eliminate my having to do anything inside the amp to reduce its gain, and I'm happy about that. I've also decided NOT to replace the bindingposts.

FWIW, have finished the design of a new amppad. It'll be made of three 13/16" layers of very dense hardwood. There'll be two layers of ipe...
http://www.woodworkerssource.com/shop/p ... ipe44.html
...and one layer of goncalo alves...
http://www.woodworkerssource.com/shop/p ... gon44.html

At around 6 pounds per boardfoot, both of these woods weigh 60 - 70% more than hard maple or ash or birch and hence should have a VERY low resonance frequency and that resonance should have a very low Q. It'll be 20" wide, 16" deep, and about 2-1/4" thick, and I'll use the inexpensive-but-hard-steel spikes from Michael Percy to couple it to the concrete floor. The amp will be placed on 4 or 5 Herbies Tall Tenderfeet as it is now.

[admin]

FWIW, have finished the design of a new amppad. It'll be made of three 13/16" layers of very dense hardwood. There'll be two layers of ipe...
http://www.woodworkerssource.com/shop/p ... ipe44.html
...and one layer of goncalo alves...
http://www.woodworkerssource.com/shop/p ... gon44.html

That wood looks beautiful. Please post some pics when all done.

[jeffreybehr]

...totaling 2-1/4 inches just wasn't thick enough, so I just returned from buying another stick of goncalo alves for a 4th layer. The pad's weight will be, I estimate, c. 40 pounds. No wonder my wife has called me Mr. Excess.

FWIW, I've also decided to try to 'improve' this amp just a little, with new highest-quality Furutech RCAs (which I already have) and also by replacing each of the 4 'DNA*' caps with two BlackGate 470/160s. Two of these DNA caps can be seen in this pic...


I'll move 4 pairs of output-coupling resistors to the bottom of the amp, which will create plenty of room for the two-caps-high stack of BlackGates.

* an initialization of Distributed Node Architecture, a term invented, AFAIK, by Steve McCormack. It is the concept of adding small storage caps on the power-supply DC rails, located as close to the output transistors as practicable. McC has used lots more DNA capacitance in his amps than does c-j in their named amps, but the '250 does indeed have a pair of 470uF/100VDC Nichicon 'lytics in each channel, along with a pair of 0.47/350 Teflon-film caps bypassing the DNA bypasses.

[bgiliberti]

you should have bought the MF-2550 - it's a CJ reworked McCormack DNA 250, with the same distributed architecture, but much better components, and reworked circuit topology.

[jeffreybehr]

you should have bought the MF-2550 - it's a CJ reworked McCormack DNA 250, with the same distributed architecture, but much better components, and reworked circuit topology.

Really? How is it that you KNOW that, that you state it as if it's FACT?

[jeffreybehr]

Without changing any hardware in the last several days, the sounds seems to have tamed a bit more in the upper frequencies, as in I don't grimace mildly at higher-level chunks of massed violins. My favorite 'test music', Elgar's Serenade for Strings on a TELARC SACD, sounds almost 100% tonite.

And it'll get better!

[bgiliberti]

you should have bought the MF-2550 - it's a CJ reworked McCormack DNA 250, with the same distributed architecture, but much better components, and reworked circuit topology.

Really? How is it that you KNOW that, that you state it as if it's FACT?

I was sort of kidding about you should have bought it. That's purely personal, and the ETS250 is clearly built to a higher spec, and is a great amp. Didn't mean to be a wet blanket, which is the way it sort of came off. Apologies.

As for the rest, the similarity was well-discussed on several forums when the MF2550 was introduced. I also had both amps in my house for a while. Except for the brass face-plate, they are physically identical, right down to the heat sinks and weight. The near-identical distributed architecture is also obvious when you lift the hood. However, the MF2550 clearly has higher quality components (although the DNA 250 also had a lot of CJ parts in it), and the circuit architecture also looks a little different. The sound is similar in so many ways, yet the DNA 250 struck me as great home theatre amp, but the CJ is clearly, well, CJ sound.

[jeffreybehr]

you should have bought the MF-2550 - it's a CJ reworked McCormack DNA 250, with the same distributed architecture, but much better components, and reworked circuit topology.

Really? How is it that you KNOW that, that you state it as if it's FACT?

I was sort of kidding about you should have bought it. That's purely personal, and the ETS250 is clearly built to a higher spec, and is a great amp. Didn't mean to be a wet blanket, which is the way it sort of came off. Apologies.

As for the rest, the similarity was well-discussed on several forums when the MF2550 was introduced. I also had both amps in my house for a while. Except for the brass face-plate, they are physically identical, right down to the heat sinks and weight. The near-identical distributed architecture is also obvious when you lift the hood. However, the MF2550 clearly has higher quality components (although the DNA 250 also had a lot of CJ parts in it), and the circuit architecture also looks a little different. The sound is similar in so many ways, yet the DNA 250 struck me as great home theatre amp, but the CJ is clearly, well, CJ sound.

TY.

[jeffreybehr]

It's running 24/7 driving broadband pinknoise into the speakers. It continues to sound smoother--less harsh--in the upper frequencies. Also have been braking-in a pair of new JJ E88CC input tubes.

Have received the input pot, a TDK 2500-series stereo unit. Its 208K resistance in parallel with the amp's 120K creates a net-76K input impedance. I've received the high-pass filter caps, a 0.01uF SoniCap Platinum and a 0.01uF Jupiter Copper; they combine to 0.019uF and with the 76K load create a 110Hz filter point, just right! Haven't moved the amp to investigate whether there's room for the pot in the back panel adjacent to the RCA jacks; if there isn't, I guess I'll install the pot and the jacks in an outboard box attached to the amp.

And if my opening statement reads like damning with faint praise, I'm not--the amp sounds very good.