Shunt Regulator ... Really impressive!

[Mucker]

I completed my Stereomour II a few days back. The first few days I was really impressed with the audio. The hum pots were dialed into 0.000V and all that could be heard out of my Kilispch RF-7II was a nearly undetectable hum with ear to speaker. Curiosity got to me so decided to do the DC filament upgrade sooner than expected and yes indeed, the hum went completely away, but I was wondering if what I was hearing was better or not. It certainly was different but it seemed the bass (and something else) was shaved off a tiny bit. Otherwise the sound was tight.

Enter the Shunt Regulator upgrade. I just completed it a couple hours ago and I can't quite believe the transformation. This is a major step up IMO. The sound stage is much larger, like someone in the band said "ok we're too close together, let's spread out some". The bass appears to have reappeared in spades, full and tight. Clarity and increased depth in all directions. Really crazy, I would have never thought the improvement would be this much. I'm usually skeptical of many claimed audio hardware improvements with upgrading, but this one is night and day IMO.

When I was doing the upgrade it was only then did I realize all the extra pins of the 12AT7 that were not wired. It seems now the 12AT7 is being fully utilized??? Is that what is contributing to the massive improvement? My Klipsch speakers have NEVER sounded this good. My 75 pound SS power amp is now being retired.

Anyway, this has been a really worthwhile journey building this amp. The instructions for all of it were flawless and the kits were not missing a single part. OUTSTANDING! One Mour upgrade to do, the MourQuiet.

[Paul Birkeland]

Yeah we wanted to be able to add the shunt regulated driver upgrade but it's tough with the space to be adding a second tube socket after the amp was constructed, so just one half of each 12AT7 is used in the stock build.

[Mucker]

Ah, roger that. The upgrade is very inexpensive for the amount of improvement gained. Total no brainer. Thanks BH for designing such a killer integrated amp.

[Paul Joppa]

The history of this may be interesting to some. My memory is not what it used to be, but this is how I remember it:

John "Buddha" Camille originally proposed shunt regulation (of output stages) in a Sound Practices (?) article; John Tucker had worked with Buddha and brought the idea with him when he moved from Texas to the Seattle area. I no longer remember which amp was used - it might have been an Afterglow. We had switched from paralleled 5965s to using just one half for a driver, which sounded better but left the second triode unused. I was wondering what we could do with the extra triode, and had the brainstorm to use it to regulate the driver triode power. I didn't expect much, since the C4S plate load should isolate the driver from the power supply by some 40dB. But Tucker went ahead and built one before I got around to doing anything. When we first listened to it, I couldn't believe it either - I literally turned the amp over right there on the carpet and inspected the build to see if Tucker was pulling my leg. He wasn't.

[Mucker]

Awesome complimentary information. Many thanks for that Paul and awesome engineering you fellas did!

[Karl5150]

Mucker, another happy S II listener here. To me the MourQuiet was a more subtle upgrade, but the parts alone (switches, overlay, etc.) make it a steal if you can live without the balance control. Good looking take on a great sounding amp, the finish reminds me of the premium paint being offered in the auto industry these days. Well done.
Karl

[Mucker]

You never fail to always leave nice comments Karl. Thank you! My paint jobs look good from a couple feet away but they are never prefect .