Stereomour II mods
- Thread starter hmbscott
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hmbscott
New member
I am happy to report that I completed the build late last night. It passed all tests first time through, and I had it singing minutes later. It sounds amazing, naturally 
, thank you Doc, Paul, Paul. The output impedance switching is interesting, very audible differences. More on that later when I have had a chance to digest it.
All that white wiring is 16ga braid-shield twisted-pair multi-stranded silver-plated teflon-insulated wire (sounds fancy on paper), but is an absolute bear to work with. Seemed like a good idea at the time, but I cannot recommend it. It does neaten the appearance of the 2A3 heater wire and the output spaghetti bowl. And, contributes to the amp being very quiet, the tiniest bit of heater hum from the left channel, but I need my ear 2" from the driver to hear it with very efficient speakers.
I am not completely finished. At a future point I will be adding the Shut Regulator upgrade, and I have some RCA 2A3 black plate NOS waiting in the wings. Oh, and I have some figured Claro Walnut I plan to use to make book-matched bases for the Stereomour and the Moreplay set.
Thanks for all your encouragement!
, thank you Doc, Paul, Paul. The output impedance switching is interesting, very audible differences. More on that later when I have had a chance to digest it. All that white wiring is 16ga braid-shield twisted-pair multi-stranded silver-plated teflon-insulated wire (sounds fancy on paper), but is an absolute bear to work with. Seemed like a good idea at the time, but I cannot recommend it. It does neaten the appearance of the 2A3 heater wire and the output spaghetti bowl. And, contributes to the amp being very quiet, the tiniest bit of heater hum from the left channel, but I need my ear 2" from the driver to hear it with very efficient speakers.
I am not completely finished. At a future point I will be adding the Shut Regulator upgrade, and I have some RCA 2A3 black plate NOS waiting in the wings. Oh, and I have some figured Claro Walnut I plan to use to make book-matched bases for the Stereomour and the Moreplay set.
Thanks for all your encouragement!
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Is there a good source for pre-milled claro walnut? I rebuilt some amps a while ago that came with bases made out of that, and people keep asking if I can make more.
On that filament wiring, adding the DC filament upgrade will remove both the heater hum and most of the potential noise induced by having those heater lines running around, though it sounds like your speakers aren't so extremely sensitive that it's an issue.
On that filament wiring, adding the DC filament upgrade will remove both the heater hum and most of the potential noise induced by having those heater lines running around, though it sounds like your speakers aren't so extremely sensitive that it's an issue.
hmbscott
New member
Hi Paul,
I bought my Claro Walnut here: https://nwtimber.com. They specialize in highly figured, musical instrument grade, etc. So pricy, but they sell very nice stuff. Another good source for more "mundane" Claro is https://www.macbeath.com. Both sell lumber, so I am doing my own milling of the base.
I'm hoping the hum isn't from heater wires radiating, because my right channel is silent, and the 2A3 heater leads are shielded with similar construction to the 12AT7 heater wiring. That said, I haven't spent much time fiddling with it so I don't really understand what's causing it. And, it's very minor anywise.
I bought my Claro Walnut here: https://nwtimber.com. They specialize in highly figured, musical instrument grade, etc. So pricy, but they sell very nice stuff. Another good source for more "mundane" Claro is https://www.macbeath.com. Both sell lumber, so I am doing my own milling of the base.
I'm hoping the hum isn't from heater wires radiating, because my right channel is silent, and the 2A3 heater leads are shielded with similar construction to the 12AT7 heater wiring. That said, I haven't spent much time fiddling with it so I don't really understand what's causing it. And, it's very minor anywise.
hmbscott said:
Yeah, everyone was like "wow, good job building those bases", and I had to break the bad news to them that I have no idea who made them or where they came from. I sure would like a few more though!
hmbscott
New member
Mucker said:
Yeah, I'm looking forward to experiencing that!. It's going to be a while. I'm currently breaking in my tubes, and boy did they need it! The first hour of listening was a bit ... it sounded good, but something was definitely a bit off, because I just couldn't settle down to listen through an entire song. It seems like 75% of the break-in happened in that first hour though, and now that I've got maybe 15 hours on it, it is sounding like butter! I'm going to give the stock Psvains a full month or so, and then swap in my RCAs. And then ...
hmbscott
New member
It's taken forever, but I have finally finished the Claro Walnut bases for the Stereomour and Moreplay. It was a painstaking process because I am terrible at mitering and this was an amazing piece of wood that I didn't want to F-up (required building a custom jig to do it properly). I wanted to book-match and grain wrap the bases and to try a french polish. It took somewhere between 30 and 40 coats of shellac, but I really wanted to do justice to the spectacular grain.
Over the past few months I have fully burned in both the original Psvane tubes (good) and a pair of matched NOS RCA Black plates (amazing), and damn! The Moreplay & Stereomour can really sing!
Up next, and I'm a bit afraid, because the Stereomour already sounds perfect, the Shunt Regulator upgrade and DC filament supply.
At some point I will talk about the output impedance switching I built in to my Stereomour, it's really interesting. I use it a lot more than I ever expected.
Over the past few months I have fully burned in both the original Psvane tubes (good) and a pair of matched NOS RCA Black plates (amazing), and damn! The Moreplay & Stereomour can really sing!
Up next, and I'm a bit afraid, because the Stereomour already sounds perfect, the Shunt Regulator upgrade and DC filament supply.
At some point I will talk about the output impedance switching I built in to my Stereomour, it's really interesting. I use it a lot more than I ever expected.
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Thermioniclife
Member
Great job, love the corner spline's.
hmbscott
New member
I installed the shunt regulator board a couple days ago, and the DC filament board today. The shunt regulator impacted high frequency performance the most obviously, introduced a touch of sparkle and high end clarity. To me, sonically similar to adding a Speedball to a Crack. Sounds even more awesome!
The DC board completely silenced a pretty loud heater hum, which prior to, could be heard from 10 feet away, so very nice!
Like a dunce, I was bending the lead of the very last 0.13 ohm 3W resistor needed to complete the DC filament install, and suddenly the lead snapped off, WTF ?!?! Because, as I discovered, I was "bending" it with my side cutters, doh. F it! Decided to voltage test the amp anyway even though it was missing that one resistor. After staring at the circuit for a couple minutes I realized the added resistors increase the voltage feeding the heater, being paralleled with the existing 0.15 ohm resistors, dropping the resistance to about 0.07 ohms. So, testing without one should be safe.
Turns out in my case my heater voltages are already running a bit hot, the socket with both of the new 0.13's installed was running too high (2.71 VDC), vs almost too high on the socket where I'd only installed one of them (2.62 VDC). I ended up removing all of the new 0.13 ohm resistors to get the correct target 2.5 VDC on both sockets. So accidentally cutting off that lead was the accidentally right thing to do. Hah.
And with that, my stripped-down pimped-out Stereomour II is officially finished. The Stereomour/Moreplay is an absolutely delicious sonic combination, thanks to the awesome crew at Bottlehead for creating them! And thanks to all who have offered encouragement and advice. Much appreciated!
The DC board completely silenced a pretty loud heater hum, which prior to, could be heard from 10 feet away, so very nice!
Like a dunce, I was bending the lead of the very last 0.13 ohm 3W resistor needed to complete the DC filament install, and suddenly the lead snapped off, WTF ?!?! Because, as I discovered, I was "bending" it with my side cutters, doh. F it! Decided to voltage test the amp anyway even though it was missing that one resistor. After staring at the circuit for a couple minutes I realized the added resistors increase the voltage feeding the heater, being paralleled with the existing 0.15 ohm resistors, dropping the resistance to about 0.07 ohms. So, testing without one should be safe.
Turns out in my case my heater voltages are already running a bit hot, the socket with both of the new 0.13's installed was running too high (2.71 VDC), vs almost too high on the socket where I'd only installed one of them (2.62 VDC). I ended up removing all of the new 0.13 ohm resistors to get the correct target 2.5 VDC on both sockets. So accidentally cutting off that lead was the accidentally right thing to do. Hah.
And with that, my stripped-down pimped-out Stereomour II is officially finished. The Stereomour/Moreplay is an absolutely delicious sonic combination, thanks to the awesome crew at Bottlehead for creating them! And thanks to all who have offered encouragement and advice. Much appreciated!
hmbscott
New member
I made a couple of upgrades recently: 1) rolled in matched Telefunken ECC81's (Used tested "near" NOS) for the original Sylvania JAN 12AT7WC. I'm becoming a fan of the Telefunken sound! 2) Upgraded my output caps, which were Audyn Cap Plus 3.3uF 800V MKP to V-Cap ODAM 3.3uF 630V. The Telefunken's were put in first and were very nice right off the bat. The caps are more subtle, but don't have a lot of runtime yet. Together the tube and cap upgrades are a nice addition to the amp, most notable is increased dynamics. The amp is also equipped with matched NOS RCA black plate 2A3s, which sound amazing. At this point I don't contemplate making further upgrades.
And, way back, I had promised to discuss my experience with output speaker impedance switching. Initially the amp was connected to 8 ohm speakers. I played around with it a lot at first and noted both louder and more high-frequency emphasis the higher I switched the impedance. Most notable, it sounded more exciting at 16 ohm, but also a bit more fatiguing, suggesting maybe more distortion. It may have reduced the bass at higher impedance settings, but that was hard to detect due to the higher output. 4ohm was a little muted, and at 2 ohm it just sounded lifeless and dull. I think a significant part of that impression might be due to reduced volume at lower impedance settings. I spent a lot of time listening at 16, 8 and 4 ohm, and eventually settled on 8 ohm as the best balanced.
More recently I have switched to 4 ohm speakers and after a relatively brief audition at various settings landed on 4 ohm setting as the best balanced although 8 ohm is not bad sounding either. A side note regarding my speakers, they present a flat impedance load at the nominal value to the amp from 0Hz up to about 5K gently rising to about double nominal at 20kHz.
And, way back, I had promised to discuss my experience with output speaker impedance switching. Initially the amp was connected to 8 ohm speakers. I played around with it a lot at first and noted both louder and more high-frequency emphasis the higher I switched the impedance. Most notable, it sounded more exciting at 16 ohm, but also a bit more fatiguing, suggesting maybe more distortion. It may have reduced the bass at higher impedance settings, but that was hard to detect due to the higher output. 4ohm was a little muted, and at 2 ohm it just sounded lifeless and dull. I think a significant part of that impression might be due to reduced volume at lower impedance settings. I spent a lot of time listening at 16, 8 and 4 ohm, and eventually settled on 8 ohm as the best balanced.
More recently I have switched to 4 ohm speakers and after a relatively brief audition at various settings landed on 4 ohm setting as the best balanced although 8 ohm is not bad sounding either. A side note regarding my speakers, they present a flat impedance load at the nominal value to the amp from 0Hz up to about 5K gently rising to about double nominal at 20kHz.
