[jimdgoulding]

Jeffrey- Are those crystals on the top of your tubes?  If so, can you describe their effect?

[jeffreybehr]

Jim, no; no crystals.  The green or yellow dots are blobs of paint.  I used green to identify my least-microfonic tubes and yellow to label the mediums.

The rings and whitish cylinders around the lower-left tube are, of course, Herbies' tube dampers.  I had them so I use them.

[jeffreybehr]

Don't know why, but I wasn't as satisfied with the M-60s as I'd hoped*, so I bought a quad of of Marantz MA-24s from 1991's MusicLink series.
http://www.dutchaudioclassics.nl/?strPage=Info&strBrand=Marantz&strType=Marantz_MA-22_Music_Link_power_amplifier&blnSefURL=true
They're rated at 30 into 8 and 60 into 4, so with the 5As' 6-to-4-Ohm impedance, 4 will deliver a max of around 200 Watts.  The brown-steel-bricked amps are for MR/treble--and each is first on the dual-outlet IC--while the low-frequency amps are graced with black-steel bricks.  The black bricks are 3/4" by 3" while the browns are 1X3"; both are footed with Herbies' grungebuster round pads.  I use a lot of Herbies' products in my system, and I believe they help the system sound its best.

I've installed the hi-pass filter required by the 5As in the lower-frequency amps, so there's NO possible degradation of MR/treble sounds due to an extra capacitor in the line, and I've upgraded some powersupply parts in all the '24s. 


Had a pair of 2-outlet ICs made by Sonic Craft, of Neotec NEI-3001 and Xhadow connectors.


Am now considering replacing the preamp's centerchannel output-coupling caps with the same Sonic Craft Platinum (Teflon-film) caps as are in the L/R channels, and probably, when I recover from buying the quad of amps and a new video projector--the old one died--I'll replace the Oppo '83SE with a '95.  Notice the little Marantz MA-22 now in centerchannel service?


* I've said many times that I'm NOT a golden-eared audiofile, so it takes me sometimes months to draw relatively firm conclusions on sound quality.  But eventually I can and do.  Maybe the folk who wrote that the M-60s probably would be a bit short on power were right.   

[jeffreybehr]

Finally finished the gain-reduction and hi-pass-filtering work, which took lots longer than I initially imagined.

Replaced the gain-reduction pots in the LF amps with single resistors in series, which reduced their Voltage gain by 19dB (to c. 11dB), and then selected a resistor to feed the UF amps' pots to match that Voltage gain.  Now the pots work beautifully, allowing me to reduce the upper-frequency energy by a dB or 2 quickly and repeatedly.  The hi-pass-filter-cap value eluded me until I determined that the value of the series resistor preceding the cap affected the filter point just as the following load resistor did.  A pair of old 4700pF Siemens StyroFlexes created a filterpoint right where I wanted it...just over 60Hz.

The pic shows the StyroFlex in and the pot no longer in the LF amp, and in the HF amp, the new BlackGate decoupler on the front of the board and the tops of the final SoniCap Platinum output-stage-powersupply bypasses, 3 Teflon-film caps totaling 1.503uF in each pole.


I'm thrilled to be able to say that my system has NEVER sounded better--more transparent AND smooth*.  An SACD I love, of string suites played by the Rotterdam Chamber O--TELARC, # SACD-60623--contains the Elgar Serenade for Strings.  The first time I heard this disc, with the improved Monarchy SE-160s, I thought it sounded great.  The first time I heard it with the Atma-Sphere M-60s driving the 5As, my jaw dropped open at how smooth AND transparent this recorded music sounded, but only in several short sections at low levels.  Since then, the system with these MA-24s has sounded at least that good.  This week, the majority of the 10-minute work sounded that jaw-droppingly transparent and smooth.  I think I'm on to something great.   

Finally I can see me actually completing the improvements to these amps.   

Have ordered new, all-Neotec-UPOCC-silver-conductor speakercable for the upper frequencies.

* That is, NOT edgy or grainy.

[zybar]

Jeffery,

Glad to hear that the recent changes improved the system for you.

Quite a switch going from Atma-Sphere OTL's to the Marantz MA-24's.  Never would have guessed that this would produce the results you are hearing.  This goes to show that you shouldn't judge a book by its cover!!

George