McCormack DNA-750 pair is here and running

jeffreybehr · « **Reply #40 on:** 17 Mar 2012, 11:57 pm »

Quote from: K Shep on 17 Mar 2012, 10:13 pm

Looks like a Conrad Johnson CT5 in the rack...NICE!

Actually it's my 6-channel version of the CT-5...sort of. It's an MET1...

...now discontinued, and is of the 'propylene-and-'styrene generation. New, it sounded very nice if not the most-transparent preamp in the world. I've replaced the front-L&R output-coupling caps with Sonicap Platinum (Teflons)...

...and have replaced the 1st- and 2nd-pole PS-output caps with Jupiter HTs bypassed with small Platinums.

It now sounds VERY good...more transparent and cleaner than the original. Soon I'll be replacing the centerchannel's output-coupling combocap with a MultiCap RTX ('styrene) bypassed with small Platinums.
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...and replace it I have.

That's a 2/200 MultiCap RTX bypassed with a stack of SoniCap Platinums totaling 0.155uF.

tdinut · « **Reply #41 on:** 19 Mar 2012, 09:53 pm »

Thanks for sharing Jeffrey! Awesome job on the amps. I appreciate the updates along the way. Please keep it up.

Joe

K Shep · « **Reply #42 on:** 19 Mar 2012, 10:49 pm »

Quote from: jeffreybehr on 17 Mar 2012, 11:57 pm

Actually it's my 6-channel version of the CT-5...sort of. It's an MET1...

I hope you don't listen at "70 - 70" I've owned a CT5 and now an ET2 and the loudest I listen is "60", but if you're driving 5 or 6 speakers perhaps it requires more umph?

jeffreybehr · « **Reply #43 on:** 20 Mar 2012, 01:07 am »

Quote from: K Shep on 19 Mar 2012, 10:49 pm

I hope you don't listen at "70 - 70" I've owned a CT5 and now an ET2 and the loudest I listen is "60", but if you're driving 5 or 6 speakers perhaps it requires more umph?

I listen at settings as high as in the 90s, intentionally. Somewhere in my above-ramblings about poweramps, I wrote that I've reduced the Voltage gain of my poweramps by almost 19dB just so that I can run my preamp in its gain range instead of its cut range. (It has 25dB of gain, and the level-control range is 99-1/2dB, so at any setting below 75, it's cutting the input level, and at any setting above 75, it's boosting the signal.) The typical range for music is 70 to 85.

The principal determinants of level-control setting is poweramp gain and speaker sensitivity...and, of course, listening level desired.

tdinut · « **Reply #44 on:** 24 Mar 2012, 04:02 pm »

Jeffrey,
Enjoying the music?
Joe

jeffreybehr · « **Reply #45 on:** 24 Mar 2012, 05:11 pm »

Quote from: tdinut on 24 Mar 2012, 04:02 pm

Jeffrey, Enjoying the music? Joe

Indeed I am. The music is full, rich, detailed, effortless. Just ordered the last batch of 65VDC BlackGate-Ns to increase the highest-quality energy storage at the DNA positions, and a quad of 1/100 RTXs are on the way to replace the quad-each of OrangeDrops on the boardbottom.

Apparently these bypass caps ought to be filtering hi-frequency noise, and I was advised that the RTXs are better at that than the O'drops.

And YOU are enjoying your new Premier 350SA, JG?

tdinut · « **Reply #46 on:** 24 Mar 2012, 08:33 pm »

Quote from: jeffreybehr on 24 Mar 2012, 05:11 pm

And YOU are enjoying your new Premier 350SA, JG?

Oh boy am I !!! That is one amazing amp. I do think she needs some break in. After 4 years in hibernation and not sure what came before that, I sense a little forwardness in the treble region. I hope as the caps break in and I get more time on it, things will come together. The bass is bottomless and the musc seems to want to explode from the speakers. Just beautiful. That glorious CJ midrange and layering is right there in full glory. All I need now is to match it up with a GAT and I'll be home free.
Thanks again my friend. Your skills (in photography and audio) amaze me.
Joe

jeffreybehr · « **Reply #47 on:** 25 Mar 2012, 12:35 am »

Quote from: tdinut on 24 Mar 2012, 08:33 pm

Your skills (in photography and audio) amaze me.

Ah...shucks...

jeffreybehr · « **Reply #48 on:** 27 Mar 2012, 05:15 pm »

Bought a quad of MultiCap 1/100 RTXs and replaced the quads of 0.47uF O'drops I had added to the frontend-PS 1st-pole caps.

So now the only O'drops in the amps are a pair of very small values in either the frontend PS or the frontend signal circuitry that are in parallel with resistors and are not on the schematic, and they're staying there.

I'm still waiting for the big batch of 680uF BlackGate-Fs to arrive. Those will increase the DNA capacitance from the original 3760uF per amp (or 5440 currently, with single 680s per position) to 16320uF per amp, plus I'll use 4 per amp to bypass the main-PS caps.

jtwrace · « **Reply #49 on:** 27 Mar 2012, 05:18 pm »

I hope you have done a full set of measurements to before these mods so you can confirm that the amp is working the same after.

jeffreybehr · « **Reply #50 on:** 27 Mar 2012, 09:00 pm »

Quote from: jtwrace on 27 Mar 2012, 05:18 pm

I hope you have done a full set of measurements to before these mods so you can confirm that the amp is working the same after.

Huh? Measurements? Not a chance. The amps work and sound great.

jeffreybehr · « **Reply #51 on:** 8 Apr 2012, 05:59 pm »

Received 50 more 680/65 BG-Ns today and got 2 pairs installed in one amp. These are bypassing the main (output-stage) supply caps.

I had wrestled with buying enough to add 8 or 16 per amp and...ahem...yesterday forgot I had settled on 8 per amp and so installed just 4 in one amp.

Today I'll tackle the 2nd amp, installing 8, and probably will add 4 more in the first amp if my back doesn't hurt too much.

Thirty-two of the caps will be added to both amps' 16 DNA-cap positions which already have 16 of these BG-Ns in them. Each original DNA cap was a 470uF Nichicon (times 8 per amp = 3760uF per amp). Currently 5440uF of 680uF BG-Ns stand in those positions, and when my goodbuddy finishes his part of this project, 16320uF of BlackGate-Ns will stand in each amp...plus 1320uF in each pole (times 4) of the main PS. If I could find some higher-quality 'lytics to replace some or all of the 8 main PS caps, I would.

jeffreybehr · « **Reply #52 on:** 8 Apr 2012, 11:39 pm »

...and I've managed NOT to let the smoke out again!

Got the pairs-per-pole BG-Ns installed in the right-channel amp, and it still works! It's astonishing how lucky I get sometimes.

...and the bottom.

I LOVE how easy these things are to work on.

A simple way to think about all these caps here and there is to understand that each original amp had (8-times-470uF =) 3760uF of Nichicon 'lytic caps bypassing the main-PS caps. Each improved amp will have (32-times-680uF =) 21760uF of world's'-best-'lytic-caps bpassing the main-PS caps...plus MUCH-better-sounding film-type bypass caps.

Of course, if the amps didn't sound excellent originally, any and all of this 'improving' wouldn't matter much.

tdinut · « **Reply #53 on:** 9 Apr 2012, 02:02 am »

Hi Jeffrey,
As always, awesome to watch the progress. I sit in amazement. Do you know if Conrad Johnson or McCormack Audio offers any upgrades to the DNA-750's? Maybe as a way to preserve the warranty and have factory sanctioned upgrades for us, ahem, lesser qualified individuals. I never contacted them about it but I am curious.
Thanks!
Joe

jeffreybehr · « **Reply #54 on:** 9 Apr 2012, 05:15 pm »

Quote from: tdinut on 9 Apr 2012, 02:02 am

...Do you know if Conrad Johnson or McCormack Audio offers any upgrades to the DNA-750's? ...
Joe

I understand that c-j experimented with a better-caps version of the '750 but decided not to offer it as a complete product nor upgrade. I'm sure Steve McC could and would improve them and surely better than I can--guys (like Steve, Ric Schultz, and Dan Wright) who offer this kind of service are GEAs who can hear immediately whether one change improves the sound and by how much. I can't; I just keep doing things that I 'know' will help--hence my compulsion with powersupply caps.

I'm looking more seriously for better main-PS caps; we'll see.

BTW your Premier 350SA was built with better caps--cj's 'propylene-, 'styrene-, and Teflon-film caps--and would not be much of a candidate for this kind of 'improvement'. Also, based on pictures and descriptions, the '350 would be more difficult to work on.

tdinut · « **Reply #55 on:** 10 Apr 2012, 02:25 am »

Thank you for filling in some of the blanks. I thought so.

Joe

jeffreybehr · « **Reply #56 on:** 12 Apr 2012, 10:36 pm »

I have all the 680/65 BG-Ns on hand, and my goodbuddy has begun the process of adding them to my amps. He has 6 (of 16 in both amps) single-DNA-cap postions increased to triples--here are 2 of them--

...and will complete the rest soon. I'll get the SoniCap Platinum bypasses back on...and I might decide to add only one BG-N to each of the 2 center positions. That'd have 16,600uF (per amp) of BlackGate capacitance in the 8 DNA positions that had, originally, 3760uF of Nichicons.

I've decided to replace the main-PS caps, 8 Nichicon 12000/80s per amp, with Nichicon Muse Super Throughs, their best audio-powersupply cap. Net of the 10-piece discount, the 16 are $20.65 each, delivered. They're somewhat larger than the originals, so it'll be a little tricky to get them in--fancy that--but I expect I'll get it done. After that, I think I'll be finished. After I do this and increase the 4 center DNA-cap positions per amp to 2 and not 3 caps, total capacitance in each amp would be 93,600uF, just 6% less than the original 99,760uF and probably just right.

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...and install two BG-Ns and the Platinum bypasses I did, at least to one side of one amp.

After Pat does the dificult work in the corners, this stuff in the middle is not bad at all.

jeffreybehr · « **Reply #57 on:** 13 Apr 2012, 03:14 am »

...and here's the other side.

With the on/off switch in front, there wasn't enough room on the board to stand the Platinum, so it's glued to the DNA caps.

jeffreybehr · « **Reply #58 on:** 2 May 2012, 06:50 pm »

The amps and the Audience aR2p-TO powerconditioner (p-con)...
http://10audio.com/audience_ar2p-to.htm

...continue to break-in and sound excellent. In fact, this is the best my system has ever sounded.

Meanwhile I've filed our taxreturns and received and begun improving a used Audience aR12 p-con for the frontend of the system.

Seems to be my year for powerconditioning.

Life is excellent.

jeffreybehr · « **Reply #59 on:** 10 May 2012, 07:50 pm »

Where do the Japanese get these names? The KG series are Nichicon's best powersupply caps and include the Gold Tune and the Super Throughs, their best. I got these from Michael Percy.

My verygoodbuddy Pat and I finally got to installing these. They're significantly larger than the originals--fancy that!--and took some headscratching (and moving one resistor to the boardbottom) to get them in. These eight (per amp) 10,000uF caps replaced eight 12,000uF caps; with the 28-per-amp 680uF Black Gate-Ns replacing eight 470uF 'DNA' caps, total capacitance is 99% of the original amount. Will be plastic-tie-wrapping them to the board soon. Used all UPOCC-copper wire to connect them--single 12g. common and double-18g. (= 15g.) for each of the + and - leads.

Knowing what I know now, this should be the first thing to do in improving the amp; then replace the DNA caps, with at least 2 680uF BG-Ns per DNA position; then add best-quality filmcap bypasses at the 4 corners of the DNA positions; then replace the frontend-supply final caps with BGs and best-quailty filmcap bypasses; and then the other OrangeDrop replacements. Live and learn.

The last step in improving these will be replacing the 8 rectifier diodes with Fairchild Stealths, which I'll do soon.

The system sounds SO good.