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January 17, 2022, 09:21:05 PM

Author Topic: PreBee 2 for me?  (Read 152 times)

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Offline Ivan303

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PreBee 2 for me?
« on: January 04, 2022, 05:47:38 AM »
Maybe?

But a few questions and a preface.

I am currently running newly constructed MonAmours into a pair of 106 dB EdgarHorns.  After much work, such as lifting the ground on the preamp AC input and running it to a separate 'GFCI' outlet due to ground loop issues and... Constructing a small 'L' pad using AudioNote non-magnetic 'tants' on the input to the MonAmours to get rid of the latent 'tube rush' present at all volume settings from the 6SN7 pre I am currently running....  I can now pretty much stick my head into the mid-bass bins and salad bowels of the EdgarHorns and hardly tell if the the system is on.

The MonAmour replaced a near 20 year old pair of DIY HIFI Supply 300b monoblocks which I was running with real WE 300Bs that are still quite OK(and maybe the least microphonic 300B one can get their hands on), so what do do with them?  PreBee 2 maybe?

So my questions would be...

Quiet?  Guessing quieter that the toob PS 6SN7 pre I am currently using?  Horns being more directional so microphonics no as big of a problem when using horns set in front of the toob gear?

Does the stepped pot upgrade (BeeQuiet? Also referred to 'first upgrade' in posts below?) have the same top plate to use to set levels/inputs as that upgrade on the original PreBee did?  Wife uses the system and the volume control is her only tool so she uses it.  Two volume controls (left and right) might be an issue if not easy to see that the levels are matched.  Also, how may steps?

About when (and how much) for the 'second' upgrade (shunt regulator?) which includes more tubes?  (More 'toobs' is good!).  Know that's a hard question and maybe too far future to know?

Need a winter project so PreBee2 might be it.

Offline Paul Birkeland

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Re: PreBee 2 for me?
« Reply #1 on: January 04, 2022, 06:49:59 AM »
Quite a bit of the impetus for making the changes to the BeePre circuit had to do with noise and very sensitive systems.  It's completely possible that you may still need some inline attenuators at the input of the Moreplay, but then again maybe not!  With the BeePre volume pot turned all the way down, the output of the preamp is shorted to ground, so you don't   The BeePre is very, very gently on 300Bs so using your WE tubes in it isn't such a bad idea. 

The stepped attenuator upgrade does use the same top plate label overlay, and it's a pair of stereo switches, with one having a large step in volume and the other having a small step. 

I have a little work left to do on the second BeePre upgrade, which keeps getting pushed back since we are getting a pretty heavy volume of custom build orders at the moment. 

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Ivan303

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Re: PreBee 2 for me?
« Reply #2 on: January 04, 2022, 08:18:36 AM »
Thanks, valuable information as I thought the two volume controls were 'left-right' not course-fine.

So does the stock PreBee 2 have a balance control as the third knob?

Maybe happy with just that?


Offline Doc B.

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Re: PreBee 2 for me?
« Reply #3 on: January 04, 2022, 08:24:45 AM »
The third knob is the input selector. No balance control on the upgrade. It's a very precise stepped attenuator and doesn't really need it.
Dan "Doc B." Schmalle
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Bottlehead Corp.

Offline Ivan303

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Re: PreBee 2 for me?
« Reply #4 on: Today at 06:20:29 AM »
Saw a reply somewhere here that recommends doing the 'whispers' stepped attenuatior mod BEFORE the shunt mod (if and when it is available).

Is that a hard rule and if so why?  One of the appealing features to me is that the BeePre2 has a balance control. 

If the shunt regulator mod is an improvement, why does it require the stepped attenuator mod to be effective or is it something to do with the way the volume control is on the output that makes a balance control not work with the shunt regulator?

Thanks




Offline Paul Birkeland

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Re: PreBee 2 for me?
« Reply #5 on: Today at 06:29:56 AM »
The attenuator modification comes with the active loads for the 300B plates.  Since we remove the resistive plate loads and replace them with something that is a higher AC impedance, this provides more freedom in terms of what's optimal for the stepped attenuator.

There is a way to retain the balance control with the BeePre 2 and its upgrades, but you'd need to install the balance control in a hole on the wood base or somewhere else on the chassis plate.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Ivan303

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Re: PreBee 2 for me?
« Reply #6 on: Today at 12:45:09 PM »
Ah yes...

Gotta read the fine print below the 'related products' section.

"This manual is divided into two sections, as the C4S active loads can be installed and evaluated on their own prior to installing the BeeQuiet attenuator."

That's likely how I would do it.

Then try to figure out how to drill another hole in the chassis, which appears to have plenty of real estate.


Offline Paul Birkeland

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Re: PreBee 2 for me?
« Reply #7 on: Today at 02:33:52 PM »
It's easy enough to pop a hole in the wood base and mount the balance pot to that.  Heck I even think you could mount it on the side of the wood base.

When you've gotten the first set of upgrades done, I can walk you through how to put the balance pot back in the circuit.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man