MonAmour, our new premium 2A3 monoblocks kit

[Paul Birkeland]

There is a bit of tolerance on the meter and what actual current will show, that's not super surprising. 

When you change to the 930 ohm resistor, the shield pin on the 5670 goes to the same grounding point as the signal ground to the chassis, so I wouldn't be too bothered if you just put the 930 ohm resistor between the shield pin and the driver cathode pin.  You can leave all the components on the PC board related to biasing up the driver cathode and just disconnect the wire between the PC board and driver cathode. 

Very technically, running the cathode bias resistor between the shield and cathode is "wrong", but in this instance the signal levels are large.

To convert to a #45 tube, you need to drop the B+ a lot (as you've observed), the 0.1 ohm filament dropping resistor needs to be increased since the #45 doesn't draw as much filament current as the 2A3, and lastly you'd adjust the cathode bias resistor.  The 3K output iron can work with a #45, but it will require a little bit of a different operating point compared to what's in the Stereomour.  I would want to run the #45 at the maximum allowable current, but a cursory glance at the datasheets isn't exactly informative as to what that is.  Maybe 250V PK at 40mA would be a place to start (or buying the SEX iron ugprade and using the 4K transformer out of there instead of the 3K transformer in the MonAmour).

[triode]

Thanks Paul.
I'll stick with 2A3 for now

[hitmanray]

WOW!!!!

Tonight I finished up the amps and just got through about an hour of low volume listening (because everyone else in the house is in bed already). I am already totally blown away by the improvement in my system. I am upgrading from a pair of Amp Camp Amp Class A solid state mono blocks that were very enjoyable build projects, and until about an hour ago, I thought sounded great. The step up in performance, even with "fresh out of the box" MonAmour amps with zero hours on them is frankly amazing. I can't really put my finger on anything specifically yet but they just do more of everything and better. The system is very musical and I found myself skipping through various favorite tracks and just grinning like a fool when I hear tracks I've heard countless times before but they are just better than I've ever heard.

Will get some more time on the amps and provide some more detailed feedback, but so far I am beyond impressed by what you guys have designed in this kit.

[Doc B.]

Thank you!

[keithp]

I finished my MonAmour amps on Tuesday and now have 12 to 15 hours of listening to them. I am upgrading from a pair of 18 year old Paramours with Sovtek 2A3 tubes driven by the BeePree. The biggest difference is how much quieter the new amps are compared to the Paramours. I use Voxativ full range drivers that are 100 db/w efficient and I don't detect a noise floor unless I put my ear to the speaker. Wow! The extra power and clarity are immediately noticeable, even on the lower voltage setting. Everything is bigger, faster, cleaner and extremely engaging. I was correct in figuring the Paramours were the weak link in the system. The MonAmours are a noticeable and significant upgrade. An absolute bargain in the world of vacuum tube audio. Highly recommended.

[Doc B.]

Thank you so much! The period between shipping the first batch of a new kit and the completion of those kits and receipt of feedback is always kind of a nail-biter. I appreciate the positive reports!

[BrucePoi]

Since I'm stuck "working" from home for at least a few weeks and may be looking for something to do if this drags out, I'm curious if anyone can compare their new MonAmours to a Kaiju.  I haven't heard 2A3s before and am curious how these might compare.  I currently have a BeePre/Kaiju setup with Zu Soul Supremes.

[Doc B.]

The sensitivity of the Soul Supremes certainly invites trying the MonAmours. I've been listening to MonAmours in my system pretty much since a couple weeks after we moved into the new space. My sense is that the similarities are greater than the differences. That said I think the MonAmours win out in the things that a little more open top end benefit from, like resolution and hall ambiance. The Kaijus win out in punch and rich lower midrange. I'm happy with either. Too bad the Soul Supremes can't be biamped. My next step is Kaijus on the Jager woofers and MonAmours on the tweeters - best of both worlds.