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June 19, 2019, 10:08:31 pm

Author Topic: Stereomour II 45 Conversion - Anyone Do It Yet?  (Read 3388 times)

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Offline Paul Joppa

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Re: Stereomour II 45 Conversion - Anyone Do It Yet?
« Reply #90 on: January 18, 2019, 03:39:10 pm »
It's hard to get a consensus on what is a real 2A3. By far the majority of 2A3s ever made are old-stock biplates (which look a lot like they are two 45s in parallel and in a single bottle). But the original version was a monoplate with the "harp" filament. It apparently had reliability problems; only a few were produced and they are now rare and expensive. The modern ones are mostly junior 300Bs, with a few like the JJ which is actually a 300B with a 2.5v filament. Can one actually talk about a 2A3 sound as distinct from a 45 or a 300B? I have my doubts.

A baby Kaiju based on the Stereomour kit would (IMHO) want 3K or 2.5K output transformers, and I'd add a larger plate choke as well. It would require 2A3-40s. or at least modern monoplates with the higher dissipation rating (usually 22 watts) - it would be too tempting to plug in regular 2A3s, which would overheat. That makes it less than practical for a kit. It might make 6 watts, which seems to me not enough more than the 3.5W of a 2A3 to be worth the effort.

My two cents.
Paul Joppa

Offline Deke609

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Re: Stereomour II 45 Conversion - Anyone Do It Yet?
« Reply #91 on: January 24, 2019, 02:33:47 pm »
The newly built SII 45 hasn't even fully warmed up yet, and has zero burn in, and the Raytheon 45 tubes only test "good", but ... it sounds wonderful.  Wow. Liking this a lot. More detailed, but without being dry/analytical; instead more expansive/ethereal. Only early impressions; it'll be months before I get a good sense of the new amp.

Listening to Link Wray's self-titled album from 1971. It was recorded on a three-track in a converted chicken coop. It's kind of raw. I've listened to the album through the SII 2A3 (JJ's) and through 45B (EML), and it sounded great with both amps.  But it sounds absolutely stellar on the new SII 45. Sheesh, this is good.

... I might be a 45 convert.

Derek

Derek
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Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and JJs)  -> Stereomour IIs (2A3 and 45 Conversion - both fully upgraded)  -> Audeze LCD4

Offline Tom-s

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Re: Stereomour II 45 Conversion - Anyone Do It Yet?
« Reply #92 on: March 09, 2019, 08:45:22 am »

... I might be a 45 convert.


And Derek, are you? :)

Love to hear your comparison of the 2A3 vs 45 Stereomour II with speakers and headphones.
With and without your balanced speaker outputs? Strong points/weaknesses etc.
Are they good/different enough to keep them both?

Keep us updated!

Offline Deke609

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Re: Stereomour II 45 Conversion - Anyone Do It Yet?
« Reply #93 on: March 09, 2019, 10:46:23 am »
Hi Tom - I'm going to give it another month or two before posting more listening impressions.  I also want to give the EML 45Bs more time to burn in. I may not have damaged them with my resistor value fiasco. They are sounding pretty good as drop-ins for regular 45s and getting steadily better.

Am I a 45 convert? Yes ... but not completely. As of right now, I can't see converting the other SII amp to 45. My overall impressions haven't changed: the 45 really is magical/immersive and like being "inside" the music; whereas the 2A3 is more of wide-awake caffeinated experience where you as listener are very close to, but still separated from ("outside"), the music. While I mostly listen to the 45, I still sometimes prefer the 2A3.  And I no longer think I want monoblocks for listening through my LCD4s.  Putting the BeePre in front of the SIIs gave me a big boost in dynamics and perceived volume -- so no need to double up. 

cheers
Derek
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Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and JJs)  -> Stereomour IIs (2A3 and 45 Conversion - both fully upgraded)  -> Audeze LCD4

Offline Deke609

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Re: Stereomour II 45 Conversion - Anyone Do It Yet?
« Reply #94 on: April 14, 2019, 02:21:49 pm »
Just a quick follow-up now that the SII 45 and EML 45B tubes have had more time to burn in.

I'd say I'm now a 90% 45-convert - meaning that 9 times out of 10 I'd prefer to listen to the SII 45 over the SII 2A3.

I still stand by my previous comments to the effect that, to my ears and in my setup, the SII 45 produces a magic and more enveloping sound whereas the 2A3 amp presents music in front of the listener as an object.  This is not a criticism of the 2A3 amp - just an observed  difference. 

The SII 45 produces a sound with more body and "mass". I don't know whether this is attributable to the 45 tube or to the fact that the 45 modification allows the OTs to go deeper in the bass, or some combination of both.

One place where the 2A3 amp continues to shine is on the attack of notes.  It punches quickly and decisively. In comparison, the 45 amp seems ever so slightly sluggish: as if the notes swell, taking slightly longer to reach full force. But I don't know which is more "faithful" to what was actually recorded. And let me be clear, the 45 amp has plenty of punch - it's not soft by any means. To use a boxing analogy: the 2A3 amp punches like Muhammed Ali - like a fast sharp knife. The 45 amp has a bit more Joe Foreman: slower but with a ton of follow-through.  On the flip-side, the 45 amp is so easy to listen to for extended periods; whereas the 2A3 amp by comparison can be a bit fatiguing.

Finally a big thumbs up for the EML 45B tubes. I am using them as a straight 45 drop in with no mods to the SII amp to take advantage of the tube's greater power handling capacity (I tried that initially and didn't notice much of a difference -- but I may play around with this again now that the tubes have burned in more). The tubes have taken a good while to come into their own (they are still improving every week). When brand new, I thought them clearly inferior to my various pairs of NOS and used OS 45 tubes from the 30's to 50's.  No longer. I now listen to the EML's almost exclusively.  And they barely get hot - I can hold my fingers on them with only minor discomfort (whereas the 2A3s and regular 45s get too hot to touch for more than a split second) - so I'm hoping the EML's will last a good long time.

cheers,

Derek
« Last Edit: April 14, 2019, 02:30:57 pm by Deke609 »
Derek
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Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and JJs)  -> Stereomour IIs (2A3 and 45 Conversion - both fully upgraded)  -> Audeze LCD4

Offline Deke609

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Re: Stereomour II 45 Conversion - Anyone Do It Yet?
« Reply #95 on: May 22, 2019, 06:23:38 am »
@PB or @PJ: Question re parafeed cap value: In the initial post to this thread, the instruction is to increase the 3.3 uF cap to 5 uF, with 4.7 uF being fine. I went with 4.7 uF. But I just came across an earlier 2017 thread where PB suggested 8-10 uF.  What would be the mean of the target range: 5 or 8-10?  I'm guessing that the 8-10 uF applies if the plate choke is not rewired for 40H and instead left at 20H?  But I want to be sure.

My slow descent into audio nervosa has begun.  :)

MTIA,

Derek
Derek
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Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and JJs)  -> Stereomour IIs (2A3 and 45 Conversion - both fully upgraded)  -> Audeze LCD4

Offline Paul Birkeland

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Re: Stereomour II 45 Conversion - Anyone Do It Yet?
« Reply #96 on: May 22, 2019, 06:26:09 am »
PJ's recommended cap value would be 5uF, with a pretty wide variation being OK.  I think in that post I used 3K for the transformer impedance accidentally instead of 4K.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Deke609

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Re: Stereomour II 45 Conversion - Anyone Do It Yet?
« Reply #97 on: May 22, 2019, 06:27:41 am »
Many thanks PB ... my nervosa is subsiding.
Derek
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Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and JJs)  -> Stereomour IIs (2A3 and 45 Conversion - both fully upgraded)  -> Audeze LCD4