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Lil knight among others have asked for an updated dynahi board.

Here it is.

http://gilmore.chem.northwestern.edu/dynahi8.zip

changes, remove 2sk389,2sj109, add lsk389,lsj109 2sk170,2sj74

you can use opa445 instead of op27 and then you don't need the 7815 and 7915.

2sa1349,2sc3381 can be replaced with the single versions.

I need to check this a few more times.

unbalanced input, balanced output version coming soon.

Edited by kevin gilmore
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aww, and I just last week finished procuring all the dual fets for my set of 4 rev. 1 boards :/

you're a true gentleman Kevin, updating this great amp for modern sand, for the sake of the community <3

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working on the balanced board now. Its a low impedance input with nelson pass's supersymmetry.

True balanced, and balanced or unbalanced input.

here is the balanced version as a work in progress.

I wonder what other case this will fit into :D

http://gilmore.chem.northwestern.edu/dynahibal.jpg

Ater that, i'll do up the dynafet boards.

I'm once again on a roll, and maybe the wonderful crema out of my new coffee machine

might have something to do with it. Slightly jittery though :D

Need some more of blubliss's hand roasted bean...

Edited by kevin gilmore
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Thanks for the great work, Dr Gilmore!

AFAIK, Ti has suggested some changes. Not sure if this applies with the current one.

  • Parallel a 680R resistor and 10k Trimpots to adjust bias and offset, you should pre-set the trimpots such that you measure 500R across them after installing it on the board, along with the 620R or 680R resistor. This would then be the initial power-up setting. (setup procedure using them here)
  • A 475 ohm resistor in series with the wiper to the amp board to buffer the board a bit from being shorted completely to ground (volume pot minimum condition) or connected directly to the output stage of the source (volume pot maximum condition).
  • Optional (well it's all optional I guess, but this one especially?): Reducing the gain to 7 by changing the global feedback resistors to 1.21KΩ and 200Ω (from 2KΩ and 100Ω) and increasing the feedback compensation cap value from the suggested 33pF.
  • Substitute the OP27 for a OPA134PA as it offers much lower DC offset.
  • Kevin's schematic showed no input resistor to ground, but the board is laid out for a 10K resistor. If you have a <100K volume pot wired up at the input, then 10K is too low a value. Anywhere from 10K to 1M is more "the norm" for a JFET input amp.

If nobody takes the job, I'm willing to do a small run of boards like last time.

Edited by Lil Knight
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much closer now. Since its now supersymmetry, with 10k input impedance, some things

have had to change. Will send to ti for comments.

You can certainly reduce the gain now by changing the 200k feedback resistors

and increasing the compensation caps. Obviously a 10k resistor in series with

both inputs at all times.

Same name, same place, for the board picture

balanced schematic

http://gilmore.chem.northwestern.edu/dynahiver2a.pdf

Edited by kevin gilmore
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Well the patent for super symmetry has run out, so i don't have to

even ask nelson for permission... :D

(not that i think that was ever a valid patent to begin with)

Current board size 9.12 x 5.22 target board size 9 x 5

People really want to use HE6's as room speakers and dump 60 watts

RMS into them, this will do the job for sure.

The only right way i know of to do unbalanced to balanced, and balanced to balanced

at the same time.

opamps, bah humbug.

If you go with the opa445 as the servo, you don't need the +/-15 volt regulators.

Anyone want to suggest additional power supply capacitor sizes. I have plenty

of room left.

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looking in PAIR Nelson has paid up his maintance fees on 5,376899, 17 years from 12/27/94 issue date still gives him the rest of this year

but from his various statements it seems unlikely that a "public domain" headphone amp project would be a problem for him

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People really want to use HE6's as room speakers and dump 60 watts

RMS into them, this will do the job for sure.

Aww, so would this make the HE6 sound like a speaker from a distant of 12 feet or more? :P

Need an overkill T2-like PSU too...

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sigma22 not good enough for you? :P

They would work just fine. But i want something that is

compatible with my stack of machined brackets.

getting close now.

http://gilmore.chem.northwestern.edu/dynahibal1.zip

trying to figure out which one of the 14 or so dynafets is the one

i want to start with :(

OH.. and this

Edited by kevin gilmore
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OH.. and this

Wow!

I have that album. Your post made me dust it off and listen to the whole thing.

The chilhood memories came floodin in...

Oh and btw, it sounded great on my new amp! B)

Now back to your regularly scheduled dynahi discussion. Great stuff! Keep it coming.

Edited by livewire
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first rev of both done. someone needs to do some serious checking

on these. Both boards identical size with identical mounting holes

and compatible with the T2 power supply angle brackets.

http://gilmore.chem.northwestern.edu/dynahibal1.zip

http://gilmore.chem.northwestern.edu/dynahifetrbal.zip

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