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KG Balanced Dynahi build discussion thread

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Kevin said that once you add the 1k resistors the current limit transistors won't blow up. So I guess the transistors in questions can be populated.

I am halfway through my build. Faced some problems with the bom and had to reorder parts unfortunately.

 

Would you be so kind and upload an updated BOM?

 

Thx,

V

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Sure I can. Infact, I used lilknight's preliminary bom; amended and supplemented it. For now, it is all over the shop and will need some time to put them together.

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I also have a somewhat updated BOM based on lil knight's.

I have not finished stuffing the boards, so I don't know if there are more wrong parts or missing parts in it.

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Please feel free and do me a favor editting the BOM in my signature. There are surely a lot of errors needed to be corrected.

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I'm cobbling together the parts for 2 channel dynahi (on the '04 boards) and was hoping you guys might be able to provide a little guidance regarding GR vs. BL grade transistors.

Amb happened to have a couple of 2SJ109BLs on hand recently, so I went ahead and ordered those up. I also already have a pair of 2SK389's (that I got along with the boards a while back), but I just noticed they are GR grade. I also have a line on some 2SA1349's and 2SC3381's (through the diyaudio forums), but I understand they are also GR grade.

Am I stepping in it if I use this combination in the same amp?

Guess no one answered you :)

 

You should be good on the GRs... that is pretty much all that is available. For the FETs (109/389), measure Idss and hopefully they will match OK. There really isn't an advantage to using the duals... some say that being on the same die, they should be matched better. Not in my experience. They are thermally bonded however.

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I did some adjustment to the dynahi amp and PSU BOM. I'll make more adjustments as I finish stuffing the board.

 

I'm wondering the difference between OPA445 and OPA27 as servo. I know the spec differences, but do these differences make one better than the other as servo?

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According to Kevin some older opamps lock up and cause trouble. best to use opa445 and no regulators.

For jumper pins accross the 7815 and 7915 its on page 3 or 4. However, 445 costs quite a bit more.

 

I am still going with opa27 and regulators.

 

I have finished populating but not got the time to get the heatsink "L" brackets done yet.

 

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Thanks for the answer!

I did miss the info on page 3 about the omitting of 15V regulators.

I'm going with 445 then.

The cost for the amp is rising very fast... and has already exceeded the cost of KGSSHV, which I didn't expect; but I'm sure it will all be worth the money and effort at the end, when it makes music.  :)

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It will have to be a 2 box build if you go with 2 psu, unless one intends to stack them up or use a super big box. I am going with 2 boxes as I constantly worry about the operating heat here. 

 

It cost more than the KGSShv for mine. To keep costs down I have decided to use the alpha pot.

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According to Kevin some older opamps lock up and cause trouble. best to use opa445 and no regulators.

For jumper pins accross the 7815 and 7915 its on page 3 or 4. However, 445 costs quite a bit more.

 

I am still going with opa27 and regulators.

 

I have finished populating but not got the time to get the heatsink "L" brackets done yet.

 

I always used TL071s (that is what Justin used for the Gilmore amps).

 

gs1_module_high.jpg

 

(apologies to Justin for borrowing his pic :) )

 

When I was building the pair of cetoole I/V stages for Ryan (recstar24), I found that TL081s worked the best for servo of all the single opamps I had on hand, including OP27s. That said, I would use the 445s for this and not bother with the 15V regs just for the servo.

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Definately two 2U400mm cases.

I decided to go full out and to use KG attenuator+LCDuino.

I think this will be THE dynamic amp I will have, so heck, why not.

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Would anything like the lme49710 or opa827 works here, instead of the op27?

Same question with the op27 in the T2 psu.

Edited by Lil Knight

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I'm cobbling together the parts for 2 channel dynahi (on the '04 boards) and was hoping you guys might be able to provide a little guidance regarding GR vs. BL grade transistors.

Amb happened to have a couple of 2SJ109BLs on hand recently, so I went ahead and ordered those up. I also already have a pair of 2SK389's (that I got along with the boards a while back), but I just noticed they are GR grade. I also have a line on some 2SA1349's and 2SC3381's (through the diyaudio forums), but I understand they are also GR grade.

Am I stepping in it if I use this combination in the same amp?

 

If you want 2SC3381 BL, Bdent would gladly sell them to you for $17.75/pc (yes, 17.75).

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Thanks Pars. Might take up your advice and go with the 445. Infact, that is what Kevin said I sould do, but I am a bit of a stubborn muel.  Trouble is that I will have to desolder the 7812 and 7912 (yes, by mistake instead of the "15"), which would still work and on top of that I bought quite a few of those regulators and opa27 as well. 

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I'm working on some pretty sweet design of a two-enclosure design via FPE/Schaeffer + Modushop Pessante.

Will willingly share when it's done.

 

However, I need some help.

 

Any recommendations on connectors for an umbilical? Sturdy, metal etc. etc. Especially if it's available through Mouser.

 

/V

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855-C90-3102R14S-6S

855-C90-3106F14S-6P

 

amphenol connectors are great, but the plugs for cable are just insanely expensive, often more than $100 each.

Harwin will work just as good.

Also, you should use female chassis mount for PSU; not that it really matters, because it's not HV, but it doesn't hurt.

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You must have looked at something different.. I don't think the Amphenol plugs for my T2 umbilical cables was anywhere near $100/ea, more like $30/ea...

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Guess no one answered you :)

You should be good on the GRs... that is pretty much all that is available. For the FETs (109/389), measure Idss and hopefully they will match OK. There really isn't an advantage to using the duals... some say that being on the same die, they should be matched better. Not in my experience. They are thermally bonded however.

Thank you Pars - I really appreciate the response and guidance!

George - thank you as well for your follow up and the heads up on bdent's stock. Given the relatively outrageous premium they are charging, and the fact that I would still be using GR grade 2sa1349s, I imagine it still makes the most sense to give the build a go with the 2sc3381 GR's I already have on hand.

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