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KG Balanced Dynahi build discussion thread


Vortex
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  • 2 weeks later...
  • 2 weeks later...

Got all my parts and boards ordered... Parts Bill so far is around $500 but this includes PRP resistors and a pair of Sigma22 board along with their components as well.

My plan is to put the PSU and xformer in it's own case so there's some added expense in that. By the time I buy 2 cases, panels from FPE, and a volume control I would think I'm into it for just about $1K

Could it be done for less, yes but I'm letting FPE and Par-metal do all the casework. I just don't enjoy that part anymore plus I want a gold point attenuator this time around. I figure go big, or go home

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  • 1 month later...

Got a bunch of J74BL from my local shop and have been matching them. IDSS readings are between 13mA to 20mA. These are too high and are obviously fakes.

Also got a bunch of K170BL and the IDSS is between 3mA to 5mA. The spec sheet says 6mA to 12mA for the BL and 3mA to 6mA for the GR, These are obviously not BL grade, and may be GR grade badged as BL.

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  • 2 weeks later...

Using a Dynahi to drive speakers is a bad idea IMHO unless you have huge heatsinks and a PSU which can handle the load. Even two Sigma22's will struggle to keep up so why not just build a F5 for speaker use with its super simple PSU?

I have run speakers off my dynamight, works fine... although I am using some bigger power supplies... I have even run some GS-124 laser galvos with it in a pinch and it worked great hehe

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  • 3 months later...
  • 4 weeks later...

I need help deciding the gain and volume control values. I know that when you go blanced the gain is doubled.

My first question is, what is the default gain when following the parts list?

what resistors control the gain?

I have Grados as well as high ohm cans so I need to find some sort of balance between gain and volume control knob sweep. Normally I use a 50K volume control but that only gives me less than half the knob sweep when using my grados with my original Dynahi. For that build I left the gain stock. I believe it was 10 or 11 I can't remember.

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  • 4 weeks later...

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?

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  • 2 months later...

I've just started building this amp and wanted to share with everyone since this thread hasn't seen much activity.

 

I decided to start populating the pcb's while I wait for the transistors for the amp boards.

 

Power supplies are almost finished but I wanted to ask Dr. Gilmore if we should still leave Q9,Q10,Q24,Q14,Q15,Q26 unpopulated or the fix suggested on post #25 solves this issues.

 

 

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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.

Edited by Victor Chew
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