VSSA Through-Hole Version by Jason - Page 30 - diyAudio
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Old 12th March 2014, 04:48 AM   #291
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You are rockin' ... J.

Having options is nice ...but it could confuse some... .

Your layout is cutting edge ... this simple CFA will most likely
be double digit PPM in normal use.

Some of your techniques were used on the "CFA-X"

OS
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Old 12th March 2014, 12:06 PM   #292
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Quote:
Originally Posted by ostripper View Post
You are rockin' ... J.

Having options is nice ...but it could confuse some... .

Your layout is cutting edge ... this simple CFA will most likely
be double digit PPM in normal use.

Some of your techniques were used on the "CFA-X"

OS
Thanks, OS. Again your comments are always welcome. I'm very humbled you used the phrase 'cutting edge' to describe my efforts .

I agree that too many options can be a bad thing and could confuse a newer builder - especially considering this design's simplicity is apt to attract a builder with less experience. I think I will try to curb my desire to make this 'universal' for a few reasons with avoidance of confusion being paramount.

I just thought I'd mention the resistive bias since it is another happy accident and requires no cutting or modification of the board at all. Neither the 1Q+LED CCS or the resistive bias techniques were considered during layout but fit perfectly as is.

In any event I will be a little while before being able to get this ready for production but will post some final images when I am ready to move forward.
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Old 12th March 2014, 10:59 PM   #293
Sheldon is offline Sheldon  United States
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Got mine all buttoned up. They're in a case with a pair of Symasyms. Power supply is a 500VA toroid with 20mF per side. Did a little testing on the scope and compared with the Symasym:

Square waves look good on both. The VSSA rolls off a little lower than the Sym, but that is due to the input filter. The Sym has 100pf across a 22k load resistor, as compared with 470p across 10k for the VSSA.

Played around with powering up the Sym and looking at the VSSA output, and visa/versa. If anything, the Sym is a little more influenced by the external load on the power supply, than the VSSA (taking into account gain - Sym is 32dB, VSSA is 27dB. In other words the VSSA PSRR is at least as good as the Sym. As I plan to use them for mid(sum) and high(VSSA) in a sensitive system, PSRR should not be an issue.

The VSSA does seem more sensitive to grounding. I can induce some overshoot and damped ringing on the VSSA by playing with the scope ground. I don't see the same with the Sym.

Next step is to listen in a few days.

Sheldon
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Old 13th March 2014, 03:38 AM   #294
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I put up a few pictures in the group buy thread if anyone would like to see the Rev 'C' boards fully stuffed. I didn't want to upload the same ones twice and don't know if you can 'recycle' your attachments to show in a second thread or not.

VSSA Through-Hole Version by Jason

Sounds like an interesting set-up you are going for Sheldon. Put up a pic or two if you are so inclined.
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Old 14th March 2014, 02:25 AM   #295
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OK, for those who need a little guidance with the BOM, or who don't feel comfortable choosing components, here is a Mouser specific BOM. It is not carved in stone, feel free to use whatever components that fit the board and your fancy, these are just my personal suggestions.

Note: The BOM doesn't list the Output MOSFETs since they aren't readily available from Mouser and I have been getting them from Tayda Electronics. Electrical connectors, stand-offs, mica / sil-pads are also not listed and are at the constructors discretion. I have made every reasonable effort to make this BOM accurate but please let me know of a serious omission or error and I will correct it and re-post or have a moderator replace the attachment if necessary.

I hope this helps anyone who might need or want it.
Attached Files
File Type: pdf JTK-VSSA Detailed Mouser BOM.pdf (26.8 KB, 188 views)
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Last edited by jkuetemann; 14th March 2014 at 02:39 AM. Reason: Added Comments.
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Old 14th March 2014, 03:02 AM   #296
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I think my build will look something like the attached pics.

SMPS and two modules in a compact chassis.
Attached Images
File Type: jpg IMG_1124.JPG (572.0 KB, 332 views)
File Type: jpg IMG_1128.JPG (435.0 KB, 313 views)
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Old 14th March 2014, 04:05 AM   #297
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Funny how clean an install can be using an SMPS. Have you fired it up with the SMPS yet? I can't hear anything that would lead me to believe it isn't just as good as my trafo and cap multiplier. Less than half the weight and space.
Beautiful case.

Blessings, Terry
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Old 14th March 2014, 11:53 AM   #298
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Quote:
Originally Posted by still4given View Post
Funny how clean an install can be using an SMPS. Have you fired it up with the SMPS yet? I can't hear anything that would lead me to believe it isn't just as good as my trafo and cap multiplier. Less than half the weight and space.
Beautiful case.

Blessings, Terry
You bet the install will be 'clean' with this SMPS in there. This thing is about the size of a 250VA toroidal transformer, never mind the rest of the supply. If it works as well as I hope it will I may never use a linear bulk supply again, except perhaps to recycle parts from old equipment.

I haven't tried it yet. I need to get some more mounting hardware, so it will have to wait until it can be properly mounted. My only debate is wether or not to centre the amplifiers on the heat sinks, which brings them in closer to the SMPS, or to leave extra physical room as pictured.

The case is quite nice. I'm planning on some kind of insert to block off the volume control mounting location. Perhaps a nice aluminum disc, raised and beveled with a nice 'VSSA' engraved into it. The piece I can machine in the garage and I likely have stock in the appropriate size too.
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Old 14th March 2014, 12:04 PM   #299
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Quote:
Originally Posted by jkuetemann View Post
You bet the install will be 'clean' with this SMPS in there. This thing is about the size of a 250VA toroidal transformer, never mind the rest of the supply. If it works as well as I hope it will I may never use a linear bulk supply again, except perhaps to recycle parts from old equipment.

I haven't tried it yet. I need to get some more mounting hardware, so it will have to wait until it can be properly mounted. My only debate is wether or not to centre the amplifiers on the heat sinks, which brings them in closer to the SMPS, or to leave extra physical room as pictured.

The case is quite nice. I'm planning on some kind of insert to block off the volume control mounting location. Perhaps a nice aluminum disc, raised and beveled with a nice 'VSSA' engraved into it. The piece I can machine in the garage and I likely have stock in the appropriate size too.
Nice work!
My opinion is,you MUST centre the amplifiers on the heat sinks.
The reason is that centre,is the only way for isothermal distribution.
Waiting for listening test with SMPS.
Transformers and capacitors are very expensive these days

Last edited by thimios; 14th March 2014 at 12:08 PM.
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Old 14th March 2014, 12:05 PM   #300
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Why not just install a nice 15K stereo pot in there? You never know when you might want to just plug a CD player in directly. For my A/B setup I plug direct through a couple 15K stereo pots with no preamp involved. I was amazed how good the amps sound.
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