My take on the BeePre

[johnsonad]

  I'm not sure at this point Paul.  I will say that when microphonics are low, I hear more of and deeper into the music. Remember that when I first fired up my BeePre I could talk a foot away from the tubes and it would ring through the speakers.

It wasn't a  turn key perfect design for my system (too much gain) but man can it sound good If you are willing to do a little trial and error. I still feel this is a home run for the Bottlehead team. My system wows all that have heard it and I only nit pick because I'm in front of it everyday.

[Chris]

Beautiful Bee pre.. is that a beautiful piece of koa I see?...

[johnsonad]

No, very figured black walnut with a tung oil hand rubbed finished. It looks much better in person.

[Chris]

Wow, I have worked with Koa before (can be a very beautiful wood), and this looks quite alot like it... Nice piece...

[johnsonad]

Thanks Chris but praise goes to my carpenter. All hand cut dove tail joints and each side has a different personality. I'm going to try and get him to build similar bases for all of my BH kits.

[johnsonad]

This morning I got around to measuring top plate temperature differences with tubes. I used my trusty kitchen thermometer and rested it on the chassis plate front to back near the right tube. With the 6c4c which draws 1 amp the plate stays at 110 F. With the EML 300B which supposedly draw 1.3 amps, it raises to 118 F. The house temp is set at 73 F. 

[johnsonad]

I'm trying to listen through this cap break in and I'm using a full Wagner Ring cycle (Solti, VPO) to do it. I can't explain it but cap break in is real. In the BeePre, the tube/cap combo is highly adjustable. So far so good on the Jupiter's.

[HF9]

I'd love to see a photo of the amp with the Jupiters inside. They are relatively large, how did you rig them up?

[johnsonad]

I can do that.

Today I listened to the Jupiter's at the 100 hour mark and feel that they have a while to go still. I'm going to pull them out and put them in the burn in rig for a few weeks tomorrow.  I contacted Chris at Jupiter and he said they can take a while in low output usage such as in the BeePre.

For the Jupiter's I had to add about 3 inches of wire to get them to reach. Then I put spacer insulators against the cap and let them gravity hang against the heat sinks. It worked better than expected and they stay just warm  to the touch when you reach underneath the amp.

I also received some Herbie's Tender Feet (tall, soft) today and put them to use. I didn't notice any sound difference but they sure look better and raise the BeePre enough to drop the top plate measured temp by one degree.

[johnsonad]

While the Jupiter's are burning in, I put back in a pair of caps that caught my attention but were not given a fair chance do to the arrive of the Jupiter's.  They are a Russian KBG MN PIO caps.  To get the 10uF or greater value with the caps I had on hand I had to parallel a couple of 6uF.  These had been previously burned in and sounded great from the beginning.  Really, these sound great and seem to be the sound I was looking for in combination with the EML 300B's.  I'm a little afraid that when the Jupiter's are ready, I'm not going to like them as much as these Ruskies. 

Sound changes which are system and user preference based are hard for me to describe.  The KBG's have great attack and decay of notes, sounds are presented in a nice dark background, there is plenty of ambient room info (though not as much as others I've tried).  My favorite part is the tone.  Music is a little rounder or more whole, almost palpable.  Piano notes decay and you feel them linger.  Female voices are inviting.  Basically I feel more emotionally involved when using this combo of KBG's and EML tubes. 

I held off posting on these until I secured a pair of 10uF caps and a few just popped up on the ePay (no association of course).  They are cheap and worth giving a try but I'll warn you ahead of time, they don't fit.  I have them on foot long leads sitting to the sides of the preamp. 

Second, an update on tubes.  The EML's are the sound for me. I'm keeping a pair of 6C4C as they will work with the modified current settings needed for the EML's and offer a slightly brighter sound for those times I need reminding how good the EML's are (to my ears). 

Lastly, once I'm finished goofing around with capacitors, I'm considering the choke mod that Xavier did and listen for any change for the better.

[earwaxxer]

Thanks for the in depth reporting Aaron!

[HF9]

Very interesting impressions Aaron. The Russian caps always prove to be great values. I did note that the KBGs are offered in 10uf 200V versions. They're rather large at 65mm x 35 mm x 108 mm, but maybe some creative mounting might work. One thing I noticed was the +/- 10% tolerance, so you might want to get four and hope that two are close enough to be a good match. Please let us know your findings when the Jupiters are burnt in.

[johnsonad]

Matching capacitors will make zero audible difference in this application. From my experience with these caps, they are close enough, especially the 10% versions.

Capacitor matching is important in crossovers and in the RIAA of a phono stage where they set the curve.

[HF9]

Gotcha, I always like to match caps and resistors on each channel, probably just a CDO thing.

CDO is kinda like OCD, but in alphabetical order, the way it should be

[johnsonad]

A small update. I'm really enjoying the pairing if the BeePre and S.E.X. amp so far but with this large change I've got to re-learn the sound if the system before tweaking any more. I've found one area to revisit and that's the noise transmission through the BeePre.

With the Quad amp I had it to an extremely low level due to compensating for the extreme gain of the Quad. The SEX does not have this gain and I'm now hearing more of the ring through the BeePre tubes. So far I have Herbies rings on both the EL84's and 300B's, lead rings on the 300B's and Herbies Tenderfeet under the chassis. The BeePre is 6 feet away from the left speaker against a wall.  Not ideal but it's the best I can do with this room at the moment. If I sit next to the speaker with my ear near the large driver and talk in the direction of the BeePre I can hear it ring through the speaker at a low level. It seems to only excite the tubes in a certain frequency range, around a males voice level and a little lower.

The vibration is both air and chassis born and efforts are focused on these two areas. For the airborne vibration I'm going to place some dense rock wool between the preamp and the direction of the speaker.  For the chassis born vibration I'm going to try the same approach that worked well with my Altec horns and place Dynamat Xtreme on the underside of the base plate. My decibel weighted multimeter is in for service but once it returns I should be able to give some hard numbers to these efforts.

One last thing, the SEX amp has no business sounding this good!