Bottlehead Forum
Bottlehead Kits => BeePre => Topic started by: Analogluvr on November 10, 2015, 06:37:41 AM
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I've built a Beepre and I am loving it but always fighting with microphonics. I do have the potential to move my rack to the next room but it would be a huge pain in the butt. Anybody done this? What kind of gains could I expect if I did?
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Tell us more about how the microphony is induced. Is it from the speakers, footfalls, just when you turn the attenuators, etc. In most cases the best solution is to add mass to the tubes to reduce airborne vibration and to put some squishy damping material between the base and the shelf it sits on to reduce chassis-borne vibration. I have used vinyl covered lead rings for weighting flasks in chem labs on top of the tubes themselves and Herbie's Tenderfeet under the base and achieved a substantial reduction in ringing.
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I believe that I have use about every commercial and home grown anti-vibration damp product there is, 98 % of them really do not work except mass on the tube and Bright*Star Isonode anti-vibration feet. I have a quite a few Vibrapods, so I put the Isonodes on the Vibrapods, believe that this is only cosmetic.
The Isonode feet come in small (30lbs max per set of 4), large (42lbs), and extra large (?). I have tried sorbane round, flat, and 1/2 round, with very little effect. Doc's mass on the tubes is quite effective for reducing airborne vibration.
By using Dan's weight on the tubes and an Isonode under each corner of the top plate that sits on a triangular platform (piece of wood) in each corner I have eliminated all microphonics on my BeePre. The small Isonode raises the top plate above the base so that the top plate does not touch anything but the four Isonodes. I will put the large Isonodes under the bases feet, but from past experience this probably is not necessary.
My BeePre had some electrical problems that I could never solve so I started to rebuild the base and top plate. It has been over a year now and still not finished, the top side of the plate and the unfinished base look pretty good right now, I just have too many projects going at one time. But when it did work there was absolutely no microphonics.
Hope this helps!!!
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My room is rectangular and the speakers are located on the and shorter wall. The electronics are located halfway down the longer wall beside the end of the couch. If I continue further down that same wall there is a pair of French doors that lead to the next room where I could locate the electronics in the corner.
The microphonics our induced by my voice, changes in the controls etc. footfall and other stuff like that is not an issue as this is in a basement on concrete. Basically any sound waves are a problem it seems. I have a set of the vinyl covered lab weights on the way but they haven't arrived yet.
I can't help but think that there may be a lot of benefit in having all of the electronics including the turntables in the next room. I guess the only downside would be the pain in the butt to set it up and the fact that my fat but will have to waddle further to change an album.
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Mass is certainly your friend.
I'm also slightly curious about your amplifiers and speakers (make/model). Having a high gain amplifier and sensitive speakers being fed by the BeePre can potentially produce the symptoms you describe.
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The only downsides to putting the gear in the other room are as you say, having to get up and walk to the next room to adjust anything, and also you may find that the additional cable lengths required impact the sound.
Knowing that this seems mostly an airborne problem, here's a few thoughts -
Wait until you try the lead rings before you change the setup. That may attenuate the problem enough for you.
Moving the amps around in the listening room might help, but it's hard to say exactly how much or where they should go. In general farther away from the speakers is better, but you also may run into room modes that set the tubes off in certain room positions. Thus you may have to try a few different locations empirically if you go this route.
I also wonder if some room treatment might be helpful to control any particular room resonance that might be setting the tubes off.
And Peebs is right that this problem can be worse if using a high gain amp and sensitive speakers. If the BeePre is running with the volume knobs set quite low for normal listening levels that could be the case. A solution for that can be to install an inline attenuator between the preamp output and the amp input.
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Just a short note here - the main problem with inline attenuator is that it's hard to find some with high input impedances. Usually for tube gear you want 50K or greater, but the readily available ones are most often in the rang 1K to 10K. Fortunately this is not a problem for the BeePre, which can driver such low impedances with aplomb.
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I'm running tannoy Yorkminster's powered by home built Western electric 91B amps or Sophia electric 845 amps. Neither Amp is very sensitive. One other thought I had was to swap the 300B's for 6a3's. There was a poster on these forums that was talking about this tube being a direct drop in replacement. He also mentioned that it's not microphonic.
Thoughts?
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you may be referring to my posts. The combo that worked best for me was the lead rings Dan suggested, Herbies tall tender feet, placing the preamp on the floor and using the least microphones tube in my stash (and best sounding) which happened to be the Russian equivenent 6A3. With this combo I could place the BeePre next to a powered subwoofer and not hear an issue. Hope that helps some.
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The 91B is a very high gain amplifier.
The Sophia 845-05 is under 20dB of gain, which is nice.
I would recommend trying the -12dB inline attenuators before doing too much heavy lifting.
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I use 6A3's most of the time in my BeePre, not because they are less microphonic, but because I bought several used and NOS pairs for less than one pair of EML's cost. I don't have a microphonic problem with them or 300B's ( I just walked over and tapped the top plates of the BeePre and the amp, a Bottlehead prototype Stereomour with a 3B7 DHT driver which is more microphonic, but not a problem.) I have rubber o-rings around the 3B7 and under the BeePre is some dense form rubber packings that came from some Guy Fieri knifes I bought my wife. Nothing else, all stock.
All the electronics sit on an antique marble top, buffet type piece of furniture.
The speakers ( Altec 605B open baffle) are less than 5 feet away. Two subs are underneath the amps.
I have no idea if this makes any difference, but all electronics except the BHDAC is on balance power. An old step-down transformer with 62-0-62 output.
I don't have a turntable, so that may change things.
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Thanks for all the feedback everyone. As luck would have it my lead rings came in today so I will try those tonight. I also picked up a pair of nos tung sol 6a3's from the 1940's so I wanted to verify that I can just shove them in there. No resistor changes?
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Hypothetically yes but most of us that use 6A3's had to adjust the resistor value. For my regulated 120v using the Russian tubes, a 3.9 Ohm resistor got me within 5%. Results will be difference bars off of your wall voltage and tubes used in your amp.
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After reading elsewhere, it may be best l let the staff verify the use of the 6A3.
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So are you shooting for 5 volts or the 6 volts that the tube calls for?
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I have used NOS 6A3 (Tung-Sol, GE, Sylvania) with no changes, filaments measured 6.0V to 6.2V.
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Tried the lead rings and there is a huge improvement!! I had the Teflon rings and they did virtually nothing. Just a suggestion but maybe the powers that be at bottlehead could source a sack of these and sell them as an optio. With the Beepre. With a few dollar premium of course :) I would consider these a necessity.
Has anybody used them on their power amps? I'm wondering if the greater heat might melt the vinyl? I wonder how they would fare on the 845s as well? They kick out some serious heat!
Your feedback is appreciated!
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Tried the lead rings and there is a huge improvement!! I had the Teflon rings and they did virtually nothing. Just a suggestion but maybe the powers that be at bottlehead could source a sack of these and sell them as an optio. With the Beepre. With a few dollar premium of course :) I would consider these a necessity.
I tried to get some from the manufacturer but they wanted me to be a government agency or a university. There are knockoffs from China now that work fine. So if we did manage to buy enough to get some kind of price break, the next day some guy would say he found them cheaper on ebay and we would be stuck with a big pile of lead. Do try both the lead and the Herbies together. I found the Herbies take a little extra HF ringing away that the lead seems to miss. Even a bit better than one lead ring is two stacked up, which is what I use these days.
Has anybody used them on their power amps? I'm wondering if the greater heat might melt the vinyl? I wonder how they would fare on the 845s as well? They kick out some serious heat!
Your feedback is appreciated!
They will melt, burn and stink. But if that is acceptable and your fire insurance is paid up, I don't see any other issues.
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I wanna get "those rings" for my BeePre, but I couldn't find a model number. Does someone have specific model, size, and source (BelArt?) info for the coated lead rings? I'll be using 300B's or 6A3's. I've already found and ordered the Isonode feet thanks to this thread. Thanks, Kip..........
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https://www.amazon.com/Bel-Art-Scienceware-183070005-Round-Coating/dp/B0013J1UOC (https://www.amazon.com/Bel-Art-Scienceware-183070005-Round-Coating/dp/B0013J1UOC)
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https://www.amazon.com/Bel-Art-Scienceware-183070005-Round-Coating/dp/B0013J1UOC (https://www.amazon.com/Bel-Art-Scienceware-183070005-Round-Coating/dp/B0013J1UOC)
Thanks PB.....
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So with the lead rings and the 6A3s the microphonics went waay down. Then I went and got much more efficient Tannoys so they became more of an issue again. I'm looking to a attenuate the output of the pre. Can I not put in a pair of resistors inline between the pre and the amp? If so what values? The loudest I ever listen right now is with the coarse on the third click and the fine all the way up. So basically just over half.
Thanks in advance.
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The best place (IMHO) for the attenuation is in the power amp at its input. Can you, or would you be willing to, modify the power amp?
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Sure, I don't mind.
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So what size resistor should I use?
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Tried the lead rings and there is a huge improvement!! I had the Teflon rings and they did virtually nothing. Just a suggestion but maybe the powers that be at bottlehead could source a sack of these and sell them as an optio. With the Beepre. With a few dollar premium of course :) I would consider these a necessity.
Has anybody used them on their power amps? I'm wondering if the greater heat might melt the vinyl? I wonder how they would fare on the 845s as well? They kick out some serious heat!
Your feedback is appreciated!
I used them on my Stereomour (2A3's) and did notice some stickiness/melting. They did not stick to the tubes. I put some aluminum foil on the inside of the ring and it works just fine.
Those Teflon things....bah! throw them out... I don't think compression does anything noticeable. Mass! Mass! Mass!