[sbelyo]

I can't seem to find an explanation on how to bend the leads for the output transistors on the Dynahi. I will have the heatsing flat on the board with the tranny's mounted to the heatsink. So how do I bend the leads with a perfect 90 degree angle?

Also, what is the proper grounding scheme for the 2 channel version with the PSU and toroid in the same case? Should AC ground go to chassis? Should inputs and outputs only be grounded to the amp boards? And what are the extra ground terminals for on the rev c PSU board?

 

[Juergen]

The AC ground from the power cord should be tied to the chassis. The PSU and amp board grounds should be tied together. Do a search for "star ground" here and you should come up with a thread discussing the subtleties of this concept. Tying the chassis and signal ground has solved hum problems for some people. I am in the middle of casing my Dynahi and was thinking about that last night. Right now my RCA jacks are not isolated from the chassis.

My amp boards were built by SFT so I can't help you on the tranny lead bending. I seem to remember someone rigging up some sort of jig to get consistent bends. Unfortunately there were no details on the jig.

Edit: Some search results
http://www6.head-fi.org/forums/showt...hi#post1105321
http://www6.head-fi.org/forums/showt...ound%22+dynahi

 

[sbelyo]

Once I get the transistors, I'll think of something.

So for the ground I should connect the PSU ground to amp board ground?

 

[grasshpr]

Does bending the leads perfectly for the output transistors really make any audible difference? All I can think is that it makes it look a little bit prettier...

I just bent the leads with my bare hands and it works fine

 

[n_maher]

One thing that I've been told is to mount the trannies to the heatsink first and then make them fit the boards. This way your connection to the sink is your first concern and gets done right so you get proper heat transfer and don't end up with a smoking Dynahi.

Nate

 

[sbelyo]

Quote:

Originally Posted by grasshpr Does bending the leads perfectly for the output transistors really make any audible difference?

No, I don't think so. I just wanted to assemble the tranny's to the heatsink/board before soldering. That way they have full contact with the heatsink

 

[sbelyo]

Quote:

Originally Posted by n_maher One thing that I've been told is to mount the trannies to the heatsink first and then make them fit the boards. This way your connection to the sink is your first concern and gets done right so you get proper heat transfer and don't end up with a smoking Dynahi. Nate

That's my plan

 

[grasshpr]

I see now. Anyway, then Nate's suggestion is what I did as well. Mounted them onto the heatsink first and then soldered them afterwards...

 

[Juergen]

Quote:

Originally Posted by sbelyo Once I get the transistors, I'll think of something. So for the ground I should connect the PSU ground to amp board ground?

Yes. Connecting the PSU/amp ground to the chassis/safety ground is up for debate.

 

[sbelyo]

Quote:

Originally Posted by Juergen Yes. Connecting the PSU/amp ground to the chassis/safety ground is up for debate.

I see...

I've now got a slightly bigger problem. Looks like the 2sk389 is discontinued. B&D won't be getting any more and they said it's discontinued???

 

[grasshpr]

Quote:

Originally Posted by sbelyo I see... I've now got a slightly bigger problem. Looks like the 2sk389 is discontinued. B&D won't be getting any more and they said it's discontinued???

You might need to wait til MCM has them available. However, they have been out of stock since December. Its unfortunate though...