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General Category => General Discussion => Topic started by: Deke609 on June 14, 2019, 08:38:29 AM

Title: May need to reinforce the chassis
Post by: Deke609 on June 14, 2019, 08:38:29 AM
New caps for the upcoming Kaiju build.  Ridiculous!


That's a 10uF Dayton on top of a 10uF Miflex.

Edit: Just noticed that the Dayton is 250 VDC rated, whereas the Miflex is 600VDC. I imagine that a 600 VDC rated Dayton might be twice as big as the 250. So the size discrepancy isn't quite as large as in the photo.
Title: Re: May need to reinforce the chassis
Post by: Deke609 on June 14, 2019, 08:44:44 AM
Weight comparison in grams.


For the non-metrically inclined: that's 6+ lbs each.  ... This is going to be a crazy build.
Title: Re: May need to reinforce the chassis
Post by: oguinn on June 14, 2019, 08:46:12 AM
Just build the amp on the caps.
Title: Re: May need to reinforce the chassis
Post by: Paul Birkeland on June 14, 2019, 01:27:27 PM
They aren't as impressive as your taste in channel locks.
Title: Re: May need to reinforce the chassis
Post by: Deke609 on June 14, 2019, 02:10:57 PM
You mean the Knipex pliers? I like them - really easy to adjust and low profile. 


As for "impressive": I think a combination of "absurd" and "imposing" is a better fit for these caps. I get a kick out of the ridiculousness of my having chosen them.  They say it's healthy to laugh at yourself -- a few more projects and I should be the epitome of health.   ;D
Title: Re: May need to reinforce the chassis
Post by: Tom-s on June 14, 2019, 11:32:33 PM
Those are the largest caps i've ever seen!  :o

To fit these, take inspiration from the all film cap powersupply Stereomour.

*(And since the Kaiju will grow this much, there's room for an all film cap powersupply).  :P

https://bottlehead.com/smf/index.php?topic=9539.0
Title: Re: May need to reinforce the chassis
Post by: Deke609 on June 15, 2019, 04:23:19 AM
Thanks Tom for linking to Jamie's build (and thanks Jamie for the detailed pics and build description). I think Jamie's threaded rod suspension solution is definitely the way to go - that will let me put the 12 lbs of additional weight near the edge of chassis where the chassis is supported by the base - I think the Kaiju chassis is probably strong enough to resist warping however I suspend the caps -- but why risk it?


I also like how Jamie used spacers between wood pieces to allow for nylon ties. I will do something similar. The rubberized coating also seems like a good idea - but I may go with something easier like a film of silicone caulking on the areas that contact the cap.  Just because I'm lazy.


As for an all film cap power supply ... hmm, not sure.  Jamie didn't think it did that much. Maybe down the road as something fun to do. But I'm hoping to add only 2-3 inches of additional height to the base. My rough estimate is that suspending the caps 2 to 2 1/2 inches off the chassis should allow the caps to clear the OTs and the DCF board -- and may even give me space to add PB's/Alonzo's use of a film cathode bypass cap in place of the electrolytic.  Or maybe a Jensen aluminum or Mundorf mlytic if the film cap won't fit? But I'm not sure that the latter would offer any potential benefits over the stock electrolytic.  I can't figure out from the Kaiju manual pictures the brand of the stock 100uF cathode resistor bypass cap. 


But an all film cap PS might require a REALLY BIG base cabinet. With the Miflex installed, there's not going to very much free real estate left. Not sure I could do this without having to build over top of the Miflex -- which would make for an absurdly large base.  ... which does hold a certain attraction for me :)  But as of now, I'm not willing to add even more additional height to the base to accommodate a possible future all film cap PS.


cheers,


Derek





Title: Re: May need to reinforce the chassis
Post by: Paul Birkeland on June 15, 2019, 06:07:56 AM
You may need to consider getting a custom chassis made of 1/4" AL.
Title: Re: May need to reinforce the chassis
Post by: Deke609 on June 15, 2019, 06:52:31 AM
You may need to consider getting a custom chassis made of 1/4" AL.


Hmm. I'd like to avoid that if I can. If putting the support rods near (e.g., 1" inside) the edges of the chassis isn't enough, I'll probably take a different approach: cradles that sit on the table/shelf surface when the chassis is inserted in the base. I have an idea about how that might be done.
Title: Re: May need to reinforce the chassis
Post by: Jamier on June 15, 2019, 07:26:59 AM
I think a film cap PS might be beneficial if you can get the lead length to be relatively short. I tried several orientations and just couldn’t get them shorter than that without sacrificing access to the rest of the amp for future upgrades, changing OPT connections, etc. I could ( and will eventually) shorten the leads to the 100uF caps. I really believe that I have lost some of the benefit of those big caps in the leads. I want to mention that after 2 years with the amp it does have a certain “something” that the other SIIs don’t. I just don’t think anyone should go this route without having realistic expectations. It probably is an improvement for the amp, but it is not the best “ bang for the buck” mod you can make.

Jamie
Title: Re: May need to reinforce the chassis
Post by: Deke609 on June 15, 2019, 10:13:31 AM
Well, hell, now that you've gone and said this:
it does have a certain “something” that the other SIIs don’t.
I have to try it. That's audio crack (or freebase, if you will, so as not to confuse BH products) ... a certain je ne sais quoi quality to the sound, you say? My mind instantly assumes that this is what I've always been missing but never knew existed.


So ... I am considering (not yet committed to) new plans. Bigger chassis and different material. I can expand it to a max of about 19" x 14". Copper plate reinforced with alu bars (I've been meaning to do a copper chassis for a while).  Maybe even 3 separate chassis (don't know what the plural of "chassis" is): as much of the power supply on the center as is do-able, and the left output on one and right output on the other. In fact, three chassis pieces will likely be easier than one big one - copper is weak; one big piece would need a lot of reinforcement. I'd just need to find some quality quick connects for the power supply.


Assuming the kit will arrive sometime in the first half of August, I might be done by Xmas.  :) 


Title: Re: May need to reinforce the chassis
Post by: Paul Birkeland on June 15, 2019, 10:21:47 AM
I wouldn't recommend the separate chassis approach.  Things can get very complicated very quickly. 

Copper looks cool, but it's very soft and heavy, and a 19" x 14" x 1/8" chassis plate will be $300 before you get any machining done to it. 

If you absolutely have to have motor run caps, consider making the chassis taller and laying them on their sides.
Title: Re: May need to reinforce the chassis
Post by: Deke609 on June 15, 2019, 11:23:32 AM
Thanks PB. All wise words.


I wouldn't recommend the separate chassis approach.  Things can get very complicated very quickly.


No doubt. I haven't even sketched a layout diagram yet. I'll at least play around on paper with some ideas and then weigh the costs/benefits against those of one big chassis.

Quote
Copper looks cool, but it's very soft and heavy, and a 19" x 14" x 1/8" chassis plate will be $300 before you get any machining done to it.
.   
A 12 x 18 piece of 1/8th goes for about $150 USD - but, yeah, a custom size could add another 100 onto that.  So maybe a standard would be the way to go. And I know that it is very challenging to work with -- but from what I've gathered, it's doable with a drill press, coolant/lubricant spray (apparently milk works well!), and either specially blunted bits or a step bit to keep the bit from biting into the copper.  I would cut the right angle holes with a gigantic jeweler's frame saw.  It would take forever, but I've been wanting to do it for a while.

Quote
If you absolutely have to have motor run caps, consider making the chassis taller and laying them on their sides.


That's a good idea. Simpler still, as another forum member recently suggested to me, might be to replace only the last cap in the ps and swap in a choke for one of the resistors. 


However I end up building it, I intend to first build it largely stock, with the exception of the parafeed and interstage coupling caps, and my usual additional copper shielding (although, having studied the very well-spaced layout of the Kaiju, I am less enthused than usual about the additional shielding).  My goal is to settle on a chassis size/layout that will enable me to play around with things relatively easily down the road. I think the PS experiments would best be done after full burn in of the amp with new tubes and caps.  Once the sound is stable, I could then listen for differences.

Title: Re: May need to reinforce the chassis
Post by: Paul Birkeland on June 15, 2019, 11:28:05 AM
Machining copper is super easy, I wouldn't be worried about that.  When you drill a hole in the wrong place, that's where things can get pretty rough. 
Title: Re: May need to reinforce the chassis
Post by: Deke609 on June 15, 2019, 11:50:32 AM
Machining copper is super easy, I wouldn't be worried about that.


You're the first person I've come across to say this. Although I suspect most of the horror stories of shattered or jammed bits are from people trying to machine thick copper bars in the same way they would machine aluminum. If it's ok, I'd like to follow-up with you later about how you've dealt with copper -- whether on this project or another, I will definitely do at least one copper chassis.  I wonder whether the softness of copper would allow for holes with a machinist's hole punch set?


Quote
When you drill a hole in the wrong place, that's where things can get pretty rough.
  I would be insanely careful when transferring the layout to the copper.  I'll likely create a 1:1 stencil.
Title: Re: May need to reinforce the chassis
Post by: Jamier on June 15, 2019, 04:30:05 PM
Derek,

     I have no experience with the Kaiju, but I can tell you adding a PS choke in resistor position 2 of the SII PS was not beneficial. It did not reduce the noise much and seemed to kill the top end of the amps response. I have no explanation for this, only my experience with the change. The choke That I used was a Hammond with the appropriate specs ( I forget the model number, but I have them around here somewhere if you want to know the model). I think that in a parafeed amp the plate choke shields the OTs from PS noise so any mods to the PS will have less influence on the noise and might even hurt your performance in the long run. You should probably change your PS in a step-wise fashion so that you will know when you have gone too far, if going too far is possible. Maybe PB or Doc can give you more input on this.

Jamie

Title: Re: May need to reinforce the chassis
Post by: Deke609 on June 15, 2019, 05:38:01 PM
adding a PS choke in resistor position 2 of the SII PS was not beneficial. It did not reduce the noise much and seemed to kill the top end of the amps response.


Thanks Jamie - that's an interesting result. Regarding lack of noise reduction - I wonder whether the stock filter circuit is already so low ripple that the choke adds nothing (does the voltage doubler help with smoothing?) -- in which case the noise is coming from elsewhere? Perhaps the heater voltage or just the operation of the output tube?  Or the choke itself? Dunno. As to how a choke in the power supply might attenuate high frequency response, I'm stumped and baffled. 


But to your point about taking it slow and doing one bit at a time: absolutely. The only tweaks I'm married to are the film cap replacements. My experiences with film caps in my SIIs have convinced me that I like what copper foil caps do to the sound.


Despite my willingness to play around with shielding and layout, and to swap in different caps, I am loathe to change any elements of the circuit design set out in the schematic for simple, obvious reasons: (1) I have no idea what I'm doing in that regard; and (2) the guy that designed the circuit (PJ - in the case of the SII, Kaiju and Beepre) very much does.


So the choke-for-resistor swap, if I were to do it, would be an experiment. And as I think more about it, I'm inclined to do some of these power supply experiments on a little scratch build "Nickel Wonder" preamp that PB turned me onto - something I've been meaning to experiment with, but just haven't gotten around to.


So, time to dial it back a bit. I still like the idea of a larger copper chassis - so I will focus on whether it is doable and something I'd enjoy doing.


cheers,


Derek


Title: Re: May need to reinforce the chassis
Post by: Paul Birkeland on June 15, 2019, 07:26:02 PM
I wonder whether the stock filter circuit is already so low ripple that the choke adds nothing
Yes.
in which case the noise is coming from elsewhere?
Yes.
Perhaps the heater voltage
Until you add the DC filament supply, yes.
or just the operation of the output tube?
Once the DC filament supply is added, then yes.




Title: Re: May need to reinforce the chassis
Post by: 2wo on June 16, 2019, 05:06:35 AM
If you do consider a film power supply, the caps after the voltage doubler are 2 caps in sieres to handle the higher voltage. Each pair could be replaced with a single ~100u >450V film or motor run...John
Title: Re: May need to reinforce the chassis
Post by: Deke609 on June 16, 2019, 09:02:49 AM
Ah, yes, I see that. Thanks John. That would make things simpler and  smaller. I am definitely considering it for down the road and hope in the next month to settle on an enlarged Kaiju chassis/layout that will permit me to try it without much hassle.


And then I plan to rebuild one of the SII's on the stock Kaiju chassis. Lots of room for parafeed caps and other stuff then.  And just for PB: imagine all the copper tubing I could pack into that!   ;D


cheers,


Derek