Custom Chassis?

sKiZo,

I added 1" to both the depth and width and 1 1/4" to the height so not a radical difference from stock enclosure just a little more room for relocating the quad cap and rerouting power switch wiring to front and input to rear.
Another option for achieving a smooth large radius is to bend metal over a pipe of the desired radius the option for radius size are almost limitless.
Thanks for the link to front panel express interesting may try in the future as my time is very limited (Dam job always gets in the way LOL)
I ordered the same single pin bias sockets used for the M 125 mono blocks and plan to install flush under top panel, screw driver access will be through a small hole.
I'm really excited to move on the the next phase of the project building of the enclosure.
Thanks for the heads up on the up grade chokes and the grounded power cord

So what are the benefits of up grading the the C 17X Chokes??

I was figuring on using a roundover bit in my router to radius a board and use that for a guide on the bends. Should work, and even allow me to do a bit of gentle forming with a composite hammer and dolly if needed. Fairly certain it'll bend nicely without a lot of persuasion. Once formed, I'll attach the wood sides and finish the enclosure before building the electrics. Wouldn't want to take a chance on flexing the metal any more than necessary.

******

Way I understand it, the chokes are all about filtering AC noise from the audio output. The chokes provided with the kits are a bit of a compromise due to space limitations in the Dynaco chassis. Get rid of the size limitation, and you can move up to a better and quieter choke, as long as it's electrical characteristics still work with the design and current. You also need a certain amount of saturation within tolerance one way or the other or the choke won't work right. The Triad is a "smoothing" choke design which requires bigger iron. Not sure about the ones that come with the kits.

Anyway, makes an extra $40 sound like a pretty decent investment then.

I found this too ...

https://dynacotubeaudio.forumotion.com/t1091-st-120-choke-substitution?highlight=choke

Thanx for the clarification.

OK then ... From reading BadDog's post, I was under the impression that the plan was to use TWO of the larger C17X chokes as one to one replacements for the C24X chokes that come with the kit?

And brings us back to the question of why and what benefits might be gained. I'll have plenty of room in the custom chassis ...

(And I've already ordered two of the C17x, so even if there's no discernable difference, would it hurt to do the one to one swap?)

Regarding the chassis ... I've managed to bump the fabrication price for the panel up to around $200 with all the fiddlybits!! Whoa - Big chunk o'change there! Did some digging and the aluminum MainTarget recommended AND a full set of decent stepped drill bits would set me back around $60. If it all goes south, I'd only be out around $30 for the metal as the bits are handy to have in the shop anyway. My time playing with the FPE software won't be wasted either - that allows you to print full size layouts and I can use that to transfer the drill centers to the metal, then have at it with the drill press and dremel. And there's the challenge of doing it myself, which is half the fun. If it works out, I can take the money "saved" and spend it on tubes!

Kewl ... er ... kewler! I was figuring the larger chokes would heat less ...

Got some of this for all the audio signal wires ...



Nice stuff. Mogami twisted pair 22 guage with the extra shielding. I also figure to do a metal box around the jacks for additional isolation and solder the extra shield directly to that. Total exposure shouldn't be any worse than the stock setup with the jacks on the front. In case you were wondering, the two sets of jacks will be in series so I can do a full tape loop connection to my receiver preamp without having to do a "Y" adapter ... be a simple cable swap from my current amp to be up and running.



Also playing with the idea of going full isolation on the ground and a three wire plug. I've got some 8x12" copper phenolic plate that I can sandwich against the underside of the chassis. Hook all the circuit grounds to that and then run the third wire on the AC plug directly to the chassis. Not sure what all I'd accomplish electrically, but that copper would sure look nice under there. Theory is it would minimize any chance of hum going with the three wire AC plug. I've also got a bunch of non-grounding solder posts for routing wires and stretching transformer leads if needed.

Well, had a cheep attack and am going to try the DIY approach to making the panel. I mean, what's the worse that could happen.

(Oh ... the humanity. Film at 11)

I split off the back panel as I figure bending that back corner would be a bit more than my garage shop could handle. I'll go with a full height wood panel back there and cut it out for a metal insert for the doodads. Squeezed all those together to allow for the wood cutout approach. I'll still go with the sloped panel for the front controls. That should be easy enough as it's not much of a bend.

Also took Bob's advice to heart about the RCA jacks and shuffled those to the sides to keep them away from the power transformer. I also split the panel into two sections. Also gone are the crescent shaped cutouts around the driver tubes. I increased the hole size to 28mm (same as the power tubes) and should get plenty of chimney effect right thru those. One other detail was adding the holes for the bias test points alongside the power tubes.



Gotta love the software approach ... took maybe fifteen minutes to make all the changes. I almost feel guilty now using the FPE software seeing that I won't be ordering from them. Maybe just get a dress up panel for the front somewhere down the road.

Oh. Notice the reference center points. Those will come in REAL handy at the drill press.

nice work on the various amp chassis guys! slightly off topic, but just wanted to show more photos of my latest SP14 preamp chassis
on that other thread,
https://dynacotubeaudio.forumotion.com/t1646-new-style-sp14-chassis
so make any comments about it on the other thread

You're a bit farther along than I am ...

I do like the look of the tubes though. I mentioned earlier adding spacers to drop the driver board, but I may make those a bit longer to hide the sockets completely.

Been looking around for some trimmer pots that I can mount right to the chassis plate so I don't have to go digging inside with a screwdriver. These should work?

Alpha 50KA / A50K Pot potentiometer 15mm 1/4W


Wondering how long I could stretch the leads from the VTA board? Doesn't seem like location would be all that critical. I've got some ribbon cable that would be tidy for that. Be perfect if I could locate the pots along the left and right sides of the chassis outside the power tubes, right by the test points. No singed fingers that way. Maybe even put them on the front panel between the meters ... they're small enough ...

While this is not Dynaco, it is a custom chassis build I made several years ago for a headphone amplifier. The top unit is a source selector / cross-feed circuit. The middle unit is the amplifier which uses (3) 6N1P NOS Soviet military tubes and is based on a circuit design by Bruce Bender. The bottom unit is the power supply. The chassis' were made from aluminum extrusions obtained from ProCo Audio and cut to dimension sheet steel from a local vendor. I did the drilling and punching in my workshop as well as building the shelf to hold all three pieces. Thought you might enjoy seeing this.

Best Regards,
Charlie

Nice job Charlie looks very nice indeed!

Thanks sKIZo you asked the questions I was thinking on the chokes I was thinking replace the two originals kit supplied units with two upgrades,
I'm still not sure I understand the benefits though, glad to hear your going the diy route heck whats the worst that can happen........... never mind LOL
Looking forward to hearing about your success.
Regards

I'm looking forward to not telling about my failure.

The better ... er, strike that (I stand corrected) BIGGER chokes came in today - that was fast! For anyone expecting a subtle difference in size, think again ...



Definitely want to have those handy when you're laying out parts as they take up a bit more real estate. Heavy little rascals too as you might imagine. That's a whole lotta iron compared to the originals.

Benefits? They ARE rumored to be quieter, but as quiet as the ST-120 is already, it might not be all that noticable. I'd think the biggest benefit would be reduced heat. Maybe lower saturation and more predictable performance under any load. I expect I'll be running the amp fairly hard, and that could come in handy. One other potential benefit is a larger choke tends to tone down the high frequencies some - for near field listening, that can be a good thing, depending on your speakers. My McIntosh XR16 big boxes have some serious tweet to them and I do currently flat shelf eq them down quite a bit over 8k. I also read that the choke works in tandem with the filter capacitor but is a LOT faster. Stands to reason that the larger iron would offload some of the cap's duties and make the system more responsive.

And ya ... all that is just what the innernet tells me, and half the lies it tells you are not true.

Good thread. Here is my latest 160 watt custom amp under construction during the testing of the primary wiring. First shot shows the two C-17_X chokes. The other shot is the top side with the 800DCV toroid power trannie and the 2 Edcor output trannies. I used a rotary switch for bias selection and a digital meter. All I have to do is select the tube and adjust the pot. Switch has an off position when done. This amp has 2 separated bias boards, the square holes on top are the bias pots. It also has 2 power supplies and 2 rectifiers. The holes on each side of the lettering are LED's that are red until the warm up is done then they turn green. Circuit has a lot of Dynaco DNA.

Serious hardware there ... my amp wants to grow up to be just like yours ...

Where'd ya get the rotary switch? I was looking for one in case I decide to go with just one meter. If I stick with the two, I'll just do the front/rear switches for each bank.

One other minor change on mine - a couple nice bat handle toggle switches instead of the sliders. Tried cutting a square hole today with the dremel and although it worked, it wasn't as clean as I'd like. Round holes are much easier. Grainger has a nice punch ... for only $80. I'll pass ...

sKiZo wrote:I'd think the biggest benefit would be reduced heat.

Why do you say there would be less heat? Aren't the chokes, no matter what the size doing exactly the same work? So their heat output essentially should be the same? True with one much larger there will be more mass to dissapate that heat, hence a perception of it 'running cooler', but won't the heat output be exactly the same?

OK ... semantics really ... let's call it less warm as opposed to less heat? The increased surface area and greater mass should allow whatever heat is created to percolate to air faster, which technically means the choke should run cooler.

Can't really comment on the efficiency of the larger choke in the circuit, but that could also work to reduce waste heat.

No comment on the pros or cons of moving the bias trimmer pots off the driver board, so I'll plan to do that also using the B50k linear pots I mentioned earlier. Got those, some knobs, and a neat little pushbutton power switch coming, and I think that's the last of the parts I'll need. Should be able to get started when the metal shows ...

Skizo:
Here is what the raw plate looked like before it was bent at a metal shop in a sheet metal brake. This was also back cut on the bend lines and notice there are no stress lines in the earlier picture in this thread.
I strongly recommend bending in a shop as 2.5 mm. is a lot stiffer than you might think. Cost me $15
I had a couple of failures with stress lines bending another one at home because the bending pressure needs to be evenly distributed across the entire bend length or you WILL! have stress lines.
The rotary switch is a "Lorlin" CK series from Mouser. I used a "Shurter IEC power input module with both the on/off switch and fuse cartridge onboard . No slider or other power switches are needed. Less holes, easier and/or cheaper.
Good luck. I like your enthusiasm





FYI:
Toroid transformer:Custom 800VDC "Sumner"

It's my enthusiasm that usually gets me into trouble. This started out as a simple kit build. dOH!

You've obviously got the bug too, and a lot more practice than me.

*****

Naked toroid!!



Quality stuff. The efficiency is really quite amazing. And they're much purtier than a standard stack. I've got em in my Sansui QRX-9001 and 8080db and they never really seem to be working all that hard ...

*****

I did notice the power setup in one of your earlier picks, but my amp is gonna be fairly high up and the back will be kinda hard to get to, so I like the idea of a front panel switch. Here's what I got ...



Another advantage of a bigger chassis ... thing takes up a lot of real estate! It's got a blue annular ring LED light - not sure whether I'll use that or not as LEDs can be a bit noisy. And it might detract from the glow of the tubes. Maybe hide a mini toggle to make the light optional.

< < < DIY METAL BRAKE > > >

As said I'm gonna go with a separate back panel, so the only bend will be the angle for the front panel. That should be around 30 degrees at most. Found this on YouTube ...



https://www.youtube.com/watch?v=xQlHqdudPvU

Might be just the ticket. Only thing I'd do is roll the edge of the top angle iron for a softer bend, or maybe try it with some scrap using a piece of steel pipe instead. Not much of an investment - zero really - as I have all the parts kicking around the shop anyway. I did order two blanks, so if I screw one up, I can always beat it flat for the chassis bottom and take the other one down the road to a real metal shop.

Switch - shorting or non-shorting. Got a number?

One thing on that purdy toroid you show: Take a look at mine. I had all the wires clustered together on each side so I only need two holes in the plate. That one you show they are strung out and you will have to make a lot of holes to mount it on top of the plate. Mine only needs 2 and they are hidden underneath. Otherwise reach for your wallet and buy a can for it that covers them. that makes it bigger as well. Hope you have the room.

Progress report ...

Not much, really. Got caught up in spring gardening and a couple outdoor construction projects.

Got the metal for the chassis plate, and that didn't go all that well. Got some good "accurate" sockets, bu t they just didn't have that "finished" look I was aiming for. Didn't like the look or tone of the unfinished metal either. Could have lived with that, but killer was that my drill press didn't have a deep enough throat to do the rectifier socket, so ... ordered a simplified version of the panel from FPE - it should be here next week. Here's the final version as ordered.



This does the CNC work for all the holes with exposed edges, and the two up front for the meters which are bigger than my bits. Keeps the costs down enough I was able to add back the "purty" around the pentode/triod switches. Any holes that will have covered edges after assembly, I'll do myself. The back plate will be machined separately and inserted into a cutout in the wood case. That I can do too.

I'm also planning to leave the transformers naked, with just a couple coats of Never Dull to polish them up. I may regret that, but they do look right nice at the moment. Never Dull is a good metal protectant (made for motorcycle chrome) so I don't expect any rust issues, and I can always touch them up later if needed. The bells surprised me - turned out a nice silvery gray semi metallic finish just rubbing them smooth with some 00 3M pads and the Never Dull wadding. Moderation is the key as too much and you'll rub the finish off.

Got all the parts ... I'm running out of excuses for not gittin er done!

PS ... got the switch ... it's got a real solid feel to it. Still debating on whether to wire it for the annular light ... cross that connection when I get to it. Hopefully not literally.

Something ya gotta love about Panel Express ... they certainly do keep you informed on progress.



In case anyone is wondering about the "infill" part, that's the ink fill on any printing. I did get one gratuitous bit of bling in the design.



One check mark I'd like to see is "Buyer didn't make any really stupid mistakes during the design phase."

Machining a groove to thin the sheet aluminum where the bend is going to be is is a good idea. Use a ball nose cutter and perhaps round off any sharp edges the cutter may create before bending to reduce stress risers in the material. Another possibility to help hide stress marks is to perhaps anodize the aluminum after forming. Just a couple of suggestions. Blake

I decided against the groove ... that silly little back cut added a LOT to the cost of the panel for whatever reason. Multiple passes, flip and new CNC program, that kind of stuff. I figure to do a more gradual bend with a fairly moderate curve to it and keep my fingers crossed. Here's a quick and dirty concept drawing I did a while back ...



Lots of changes to the design since then, and excuse the funny looking stuff on the front panel. That all got some serious parallax issues when I "bent" the panel in photoshop.

PS ... now that it's too late, I'm thinking what I SHOULD have done was add a few closely spaced shallow relief cuts on the front of the panel right at the bend. That would have covered up any stress marks (which knock on wood, I won't get anyway) and also tend to act as guides to keep the bend where it belongs. Also, I think it would have added a nice touch to the looks. Ah, well ... next time. If I DO get some stress marks, I can always add some pinstripe tape ... waddaya think ... flames or chains ...



I think I got some skulls here somewhere too.