Zed Audio Rebuild of a 400

Gibsonian

Gibsonian

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Another guy on another forum mentioned he was having his 400 rebuilt by his tech. Anyhow I asked him to send me pics of the finished product and he did. I've attached them. Outfit is Zed Audio that did the work. Seems they have had their own amp and backplane boards made to fit the 400's. Anyhow, just wanted to share. He says it sounds great.
 

Attachments

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Looks China made. Not impressed with the wiring. Something to research and look up later. Thanks.
 
That is crazy. Any outputs on the back? Don't see how.
 
He had some mods he did. Attached is a schematic of his mods from 2009. To me the most significant was eliminating the boot strap circuit. He was big on, if I recall correctly, base stoppers which is a resistor on the base of the predrivers Q8 and Q9. That was his solution to high frequency oscillation.

I'm sharing this as he didn't seem to consider it was proprietary.
 

Attachments

Marshall Leach did some stuff on them 100ohms resistors in transistor base
 
Please excuse my ignorance here but I am curious. Is this a knockoff of Joe’s design or a different approach?
 
Don't know definitive answer but looking at the design and looking at the business owner's history, I'm guessing it is all his design and no knock off. The owner of business has many commercial products under his belt it appears.
 
There was a car audio guy on the forum a while back who was promoting a series transistor topology over parallel(if I understood correctly). He got really pissed about something I didn't understand and left. May have been PMs. I think it's the same guy.
Glen built a unique 400 a while back with extra plastic transistor outputs. Think he may have put them in series using this guy's idea. One of those things I really wanted to know more about but was too busy with other things to investigate and ask Glen questions.
 
George S. said:
There was a car audio guy on the forum a while back who was promoting a series transistor topology over parallel(if I understood correctly). He got really pissed about something I didn't understand and left. May have been PMs. I think it's the same guy.
Glen built a unique 400 a while back with extra plastic transistor outputs. Think he may have put them in series using this guy's idea. One of those things I really wanted to know more about but was too busy with other things to investigate and ask Glen questions.
Click to expand...
I think Glenn rewired the driver as an output and used a TO3P (plastic) transistor as the driver. I presume this was to allow the outputs to run cooler. I'd like to try that. I doubt it would make much difference as the the area of the heatsinks is likely the limiting factor.

Dynaco used the stacked/series outputs. They were fairly reliable. I didn't like the design but had no data to indicate it was inferior. They sold a lot of them.
 
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