BeePre2 Output Upgrade Impressions

[Toobuzz]

I have completed the Output Upgrade for the BeePre2 and would like to post some early impressions/observations.

Build Process

• The build experience was exactly as expected, very well documented with great photos.
• It was a fun build process that took me about 10 hours in total (I finally started to work slowly and carefully instead of racing through. it)
• I did have an issue with the left channel at first that took me 2 additional troubleshooting sessions.  I was getting intermittent gurgling that was not changing with the volume adjustment. In the end I think the root cause was either a jumper wire on the new regulator board that I pinched when tightening the board down to the standoffs or a not so perfect solder joint at 51U or the center pin of the D socket.
• After 2 days of flawless performance I swapped out the Daytons for some VCap ODAMs

Speakers (solid state amps into 87Db speaker)

The bass response has changed so much that I need to retune my subs.  My Vandersteens have controls to set the Q, the level, and also 11 room correction pots (per speaker) and they all need to be readjusted before I can really evaluate (or even listen, lol).   My guess is that output impedance has dropped so significantly that the Vandersteen crossover (between the BeePre2 and the SS amps) is behaving much differently.  There is too much bass right now (not complaining!)

Headphones

A very unexpected and unbelievably pleasant surprise was how awesome the BeePre2 sounds feeding the Mainline.  I remember testing this combo on the stock BeePre2. I never tried it after the first upgrade, but I am trying it now.  I have long XLR cables running from my DAC to the back wall of the room where my various headphone amps sit.  I use XLR to RCA adapters for the Mainline.  This balanced output of the BeePre2 is amazing because I can leave my speaker amps connected to the RCA outs and connect these long XLRs to the new BEePre2 output!  This also makes listening to vinyl through headphones a breeze as all I need to do is switch the input selection on the BeePre2.

The sound of the BeePre2 > Mainline is intoxicating and addicting (Clear and HD800).  I may have to drag all this to a headphone meet coming up in October. 

Sam

[Paul Birkeland]

Looking classy as always, and that's excellent that you were able to sort out the issues you had along the way.

[sl-15]

Hello, very nice looking BeePre2. Did you spray paint the top plate? And what tubes are you using? They look great. Thanks, Best, Stefan

[Toobuzz]

Thanks!  I’m shocked that the paint job came out as good as it did, being that it was a matte spray paint. I primed the bare aluminum chassis plate (basic gray), then sprayed Rust-oleum Universal in Matte Harvest Orange.

Rust-Oleum 282814 Universal All Surface Spray Paint, 12 oz, Matte Harvest Orange https://a.co/d/a8dRkgC

The tubes are Sofia Electric from around 2004 and I can’t really find a link to them anywhere. They say “SET 300 b/n” on the base. 

Credit must be given to the iPhone 13 camera’s night mode.  It really exaggerates the filament glow. The room was almost pitch dark, with only the hallway light coming in through the open door. The camera takes an amazingly evenly lit photo that is somehow in-focus, even though I can barely see anything in such low light!

[Toobuzz]

I wanted to follow up on how things have been going after the second upgrade.  My amp has changed, it’s now a Mark Levinson 332. The amp has little impact on what I’m about to say, but it’s a darker amp and I wouldn’t be using it now if I hadn’t found these specific 6CM7 tubes.

I did’t want to admit it at first, but the output upgrade was not initially to my liking. Any 6CM7 that I tried, made everything sound more veiled.

*Please keep in mind that this in on my specific system and I could see folks who thought that the BeePre2 was a bit bright, may love the output upgrade with the supplied GE NOS tubes.

Anyway, I tried all the Tung Sol and GE, and found them both to too thick for my taste. I felt like I lost some of the magic that I had prior to the 2nd upgrade.  Then I found these 6CM7s from Amalgamated Wireless Valve Co. from Australia. A guy in Quebec seems to have a cache of these.  They sound super transparent, and even have that cool filament flash when you turn them on!

https://dbtubes.com/en/amalgamated-wireless-valve-coptyltd/3310-5663-6cm7-black-plate.html#/2-condition-new_old_stock_new_in_box

I also tried his Australian Phillips Mini-Watt with short gray plates. They are good too, but I feel like these Amalgamated Wireless are best for me. What the heck, they’re like $5-$8 each, and he’ll match the triodes for you too (although that cost more than to tube, lol)!

[sl-15]

Thank you for the detailed answer and your follow up review, much appreciated!

[sl-15]

I am actually not sure how they are matching the triodes because the 6CM7 has dissimilar triodes. I just emailed them about it. And I am also curious if matching is necessary for this kind of tube in this kind of use in the BeePre2?

[Toobuzz]

He’s not matching within the same tube. He gives you measurements for each side of the tube and chooses a pair that measure similar.  I’d imagine that it would be important to have the output buffer triodes in the ballpark of each other, but I’d have to defer to those more knowledgeable than me to be sure.

[sl-15]

Yes, if he compares from tube to tube that would make sense.

[Paul Birkeland]

I’d imagine that it would be important to have the output buffer triodes in the ballpark of each other

This is not at all critical for this application.

[sl-15]

Sounds like matching is not necessary then, thanks Paul.

[Brissie]

Hi Sam,

I hope you're still following this old thread.

Thank you for posting your experience with the BeePre2 output upgrade.
You mentioned you upgraded the 10uF caps with ODAM capacitors.
The output upgrade adds two additional 10uF caps on each channel.
I assume you only swapped the 4 Daytons in the signal path for ODAM capacitors, or did you do all 6?
Was there a noticeable improvement?

Thanks, Steve

[Paul Birkeland]

When I build these with ODAMs, I do not use one for the -Ve leg of the XLR jack.