2. amps-preamps
  3. 128359-41

Amps Atma-Sphere M-60 Mono blocks OTL design

I just purchased a used OTL Atma-Sphere M-60 mono blocks that I have sent to Atma-Sphere to be upgraded to the current model 3.3 and I also added the option of a higher quality power supply and V caps.

I have sold my old trusted Eggleston Andra 2’s speakers and have built some monitors using Aurum Cantus ribbons (102db) and Aurum Cantus midwoofers (90db) that are both rated as 8 ohm nominal. I have a DEQX Premate and will be crossing over to (2) JL Audio F-113 subs at 80hz.

Currently I am using a solid state high power stereo amp (Pass Labs) that I used with the Andra 2’s.

The Atma-Sphere M-60 is rated at 60 watts class A and is said to work better with higher impedance loads.

It will probably be a few weeks until I get the M-60 and was hoping someone could provide opinions of what to expect.

I listen to late 60 early 70’s classic rock music mostly. Sometimes loud.

ozzy

128x128ozzy
almarg's avatar
Ag insider logo xs@2x
almarg
9,670 posts
 
+1 to Jon's wise counsel.

Ozzy, regarding the DEQX calibrations, to be sure it's clear I was envisioning that in addition to the effect of the amp change on the balance between the main speakers and the subs, the DEQX measurements (and the resulting calibrations/corrections) of the DIY mains themselves might change.  The reason being differences in impedance interactions between the mains and the very different output impedance of the M-60 vs. the Pass amp.

It sounds, though, like you're intending to re-do the entire DEQX measurement & calibration/correction process, which of course would address this.

Continued best of luck.

-- Al
 
ozzy's avatar
ozzy OP
7,421 posts
 

Just found out why the center image was missing. I had a wire reversed on one of the jumpers to my external crossover. I must have done it while repositioning it on the amp stand. It did sound like it was out of phase.

I just posted some pictures of the amps and the external crossover on my systems page.

ozzy

bigboltz
55 posts
 
Ozzy

Ive had my M60s for about 7 months. I bought them used and they came with a ton of the Chinese power tubes. The seller didnt indicate which ones were good or not. So it took and evening of swapping ( and a box of fuses) to get them up and running and holding the DC offset.  Since then, I've had 2 tubes fail. Each took out the fuse by the power cord.  Otherwise, they have been rock solid. I play them at least a few hours each evening and sometimes all weekend long.  Dont get discouraged.   I plan on re-tubing with the Russian variety soon.  

Soundwise, I swapped them out with a pair of Quicksilver monos( which are great amps in their own right) and it was quickly apparent how special they really are.  The Quickies seemed slow and veiled by comparison.



ozzy's avatar
ozzy OP
7,421 posts
 

bigboltz,

It sounds like I need more fuses on hand. BTW, I have had a problem finding 3A slow blow fuses. With no more Rat Shacks,  and hardware stores don't carry them.

The M-60's are settling in nicely. I wonder though on the copper V-Caps and how long they may take to fully break in. The soundstage is becoming very wide and deep. So much so that I am fiddling with toe in / toe out.

Someone mentioned earlier that to reduce the light on the yellow and red indicater lamps to try 12v versions. I actually found some 12V-3 watt and that really did the trick! Lamps illuminate but don't overpower the tubes.

Question: At the moment I have a mismatch of tubes. Could that cause a shift in soundstage?

ozzy

atmasphere's avatar
atmasphere
11,753 posts
 
If in the driver tubes, possibly. If some of the power tubes are blown out in one channel that could do it too. Check the power tubes against what you see in this article on the Support section of our website:

http://www.atma-sphere.com/Resources/6AS7G_Visual_Inspection.php

Some say the copper foil V-Caps take about 150 hours, be we experience them sounding very good right out of the box. However, with all the updates done on this set of amps, they're going to need some break-in time; as they break in they will become more lucid.

Since you're trying to nurse those old power tubes you might want to get some 3 amp slow blow fuses off of ebay or amazon. We sell them also.
More to discover