Bottlehead Forum
Bottlehead Kits => BeePre => Topic started by: johnsonad on February 09, 2013, 11:19:50 AM
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What is the measured length from the lateral sides of the transformers to the edge if the chassis plate? I'm trying to figure out how large of a choke I can cram in there.
Thanks,
Aaron
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Hey johnsonad,
Did you mean under the chassis plate, or on top?
I measured under; just holding the transformer in place with the chassis plate in the base. I think the critical dimension isn't the edge of the transformer, so much as the edge of the pc boards that mount on the standoffs below. Looking at the placement of the transformer holes, which are outboard of the edges of the transformer, and allowing for the edge margin around the pc board holes, I'd estimate 1" 5/8" from the edge of the pc board to the inside of the chassis base - which would be touching on both sides. Obviously you might want to have some clearance to allow for lifting the chassis plate off and such. It would be possible to cut a relief in the base, I suppose, to gain more clearance.
Judging from the photos and looking at just the base, chassis plate and transformer, it doesn't appear there is a lot of room under the hood fore and aft of the transformer, either.
I didn't measure on top of the chassis plate, but it would be a shorter distance, say, 1 1/2" at most from the transformer side to the edge of the plate.
What are the dimensions of some of the candidate chokes?
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On second thought, if the choke was the right size, it might sit better on top of the chassis plate right outboard of the transformer with a bushed through-hole for the wires - granted, it would be safer under, but could be insulated or covered to mitigate the risk.
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On second thought, if the choke was the right size, it might sit better on top of the chassis plate right outboard of the transformer with a bushed through-hole for the wires - granted, it would be safer under, but could be insulated or covered to mitigate the risk.
This is indeed a good idea!
I have a pile of Triad chokes and a drill press at my place, feel free to bring your plate over and we can figure something out.
-PB
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On second thought, if the choke was the right size, it might sit better on top of the chassis plate right outboard of the transformer with a bushed through-hole for the wires - granted, it would be safer under, but could be insulated or covered to mitigate the risk.
This is the distance I am talking about. On top of the plate, to the left and right of the transformers, the distance from the transformer to the edge of the plate. I was thinking of the Hammond 158m which is 2" wide.
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I would appreciate hearing from builders who build the kit stock first and then add these speculative mods. It seems a shame to spend a year developing a design only to hear that it is being redesigned by the end users before they have even heard it. This kit has sophisticated regulation out the yin yang. Not saying folks shouldn't try some different ideas, just that you need to have a point of reference to start with. I think a choke might just make it heavier.
My approach to upgrades would be spend stupid money on the output caps first, and then if I was a masochist I might replace the really nice Cat5 cable that connects the inputs with some impossibly difficult to work with foamed Teflon coax. How impossible? If I asked PB to do that to mine he would probably quit. Then I would build a holography grade isolation table for it. I think the standard we used at Berserkeley was no more than a few wavelengths of red light perturbation, settling out in less than ten seconds. A shit ton of mass on an inner tube was the method.
I also plan to try some ridiculously expensive 300Bs - if we sell enough of these butt kicking preamps to afford them.
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In my personal experience, replacing the the 270 Ohm resistor makes a 5% ish difference for the better or has to my Paramounts and Eros. Though it may not effect this kit the same way.
I'm planning on using Neotech OCCC instead of the CAT5 as that's a PITA to go back and retrofit.
Tube wise I want to hear a few pairs before making that jump. The regulated heater voltage removed my favored EML's and I have little other experience with 300B's other that the TJ mesh and EH tubes. Hopefully I can find someone with a few different pairs locally to try.
First though, I need to receive my BeePre. All if this is speculative ;)
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I'm planning on using Neotech OCCC instead of the CAT5 as that's a PITA to go back and retrofit.
I'd be sure to shield this wire.
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I would appreciate hearing from builders who build the kit stock first and then add these speculative mods. It seems a shame to spend a year developing a design only to hear that it is being redesigned by the end users before they have even heard it.
I'm not really sure that any of the mods we've been discussing can really qualify as redesigning. I'm replacing the selector switch with a better quality one (or at least one that I like more), the ouput caps with Auricaps xo's -because I like Auricaps a lot-, the biasing resistors with cool Mills and yes, adding chokes instead of the power resistors. Chokes in the ps supply helped a lot in my Eros and Paramounts and even if they only add mass (I don't plan to carry the pre around) I don't think they'll harm.
Now, if only I could find me a pair of 10,000uf Black gates to bypass those Mills!
The Bee Quiet is indeed a slight redesign but I'm pretty sure it was you who said it had a very positive impact on the sound :)
Saludos
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Didn't make my point very well, huh. You guys are right that aside from adding the choke you are just talking about changing parts. And that's what it is all about for most of us. I sometimes see newbs reacting as if our kits are going to come out broken unless they add all this stuff to them. What I would appreciate is if anyone builds the kit stock (god forbid!) that they mention that it works fine as it comes, just so the newbs know.
And Xavier you are right, the upgraded volume control is a design change. It seems to make a lot more difference than fancy output caps, which I have played with just a little so far (tin foil and polypropylene). I have also been experimenting with Sorbothane hemispheres under the base, and the ones that seem to work best so far are 1-1/4" 30D ones. 3/4" 50D fit the bottom edge better, but they were a little undersized for the chassis weight, squished a little too much and didn't seem to isolate as well. The 1-1/4" ones are a pretty nice improvement in isolation for about $20. I got them on ebay.
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What I would appreciate is if anyone builds the kit stock (god forbid!) that they mention that it works fine as it comes, just so the newbs know.
Great advice Doc. I got that message years ago. I bought six Bottlehead kits to date and built them all stock first with one exception. That was my Crack that I put together with a 6SN7 up front. I only did that because I had some 6SN7's laying around gathering dust.
I've discovered over the years that not all upgraded parts necessarily upgrade the sound. That's why it's so important to know how the kit sounds stock. Spend some time with it and get to know it. Then proceed with your upgrade path slowly. Don't be tempted to change a bunch of things at once. Sometimes the path you take is not the right one. That's been my experience anyway.
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Doc, I think you gave excellent advice. I always build my kits stock spend some time listening and then changes things. This is the only way you can know what the effect of the changes you make are, you need a baseline to compare to.
When I get my BeePre I intend to build it stock first.
Deb
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In general, I've found that any tweak I've done to my kits only results in rather small changes that I sometimes feel are due more to the power of suggestion (e.g., placebo effect) than an electrically significant improvement. Of course, I say this as a psychologist, not an engineer. Building stock seems to get you 99% of the way there, though it is fun to keep poking around in the never-ending quest for the "perfect sound."
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I think that Natural Sound said it best. If you don't build stock to begin with you have no basis or benchmark to measure what improvements you bring with each modification.
My Eros has had the output caps changed to Mundorf Silver/Oil. But it is so hard to pull it from the system to mod it that is as far as it has gone. I have $60 worth of minor parts sitting in a drawer collecting dust.
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Thanks folks, and sorry if I sounded crabby. A BeePre pre-orderer (is that a word?) came by to pick up his kit yesterday and he will be trying some TJ mesh globes he has on hand and Mundorf silver/gold/oil output caps in his. The rest of the kits will be shipping out as soon as some back ordered standoffs and wire arrive.
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Thanks folks, and sorry if I sounded crabby.
Not at all, Doc. I think we all need reminding of this fundamental recommendation on occasion. It's all too easy to get carried away sometimes. Being dragged back to the basics is a necessity at times. I'm a big believer in KISS. In fact that is one of the things that draws me toward your awesome products.
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On second thought, if the choke was the right size, it might sit better on top of the chassis plate right outboard of the transformer with a bushed through-hole for the wires - granted, it would be safer under, but could be insulated or covered to mitigate the risk.
This is the distance I am talking about. On top of the plate, to the left and right of the transformers, the distance from the transformer to the edge of the plate. I was thinking of the Hammond 158m which is 2" wide.
I love the discussion but the original thread starting question hasn't been answered :) :)
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Aaron, there's 45mm from the chassis edge to each transformer.
Ha! It looks like my Hammond 157M won't fit. I'm being punished for building non stock first!
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Thanks Xavier :)
The 157m is 1.75 inches wide (by the product sheet) and there is 1.77 inches of space available. They should fit but it will be tight.
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Don't forget that the 157M is a channel frame style choke, so the base is in the middle of that 1.75 inches. In other words, if mounting on top of the chassis, you can gain some separation from the power transformer by letting the bobbin overhang the edge of the chassis. If mounting under, you would, of course, have to relieve the base to add clearance to move it over. Also, if mounting under, remember the transformer doesn't go as far outboard as the stack does on the topside - it might be that the choke bobbin flanges would land in between things under the transformer and allow placement without a base relief pocket.