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Old 6th February 2002, 10:19 PM   #11
PassFan is offline PassFan  United States
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Join Date: Aug 2001
Location: Central FL
PTL60:
Your stock just jumped a slew of notches. Welcome to the forumn.
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Old 6th February 2002, 11:13 PM   #12
Geoff is offline Geoff  United Kingdom
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Join Date: Apr 2001
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PTL60

From the limited information I have been able glean on the OBH-11SE, it is a zero feedback Class-A design with capacitor coupling on both the input and the output. With zero feedback amps it is imperative to minimise distortion in all stages since there is no overall feedback to correct any errors. Without a schematic (and maybe even with one) it will not be possible to determine if a proposed substitute output transistor will be an improvement or not. Also, care must be taken to ensure that the stability of the amp is not jeopardized. A substitute transistor with a higher gain or higher ft could well make matters worse.

I think that this is one of those cases where you will need to accept (or hope) that the manufacturer got it right in the first place.

Geoff
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Old 7th February 2002, 01:15 AM   #13
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Geoff,

Thanks a lot. I will definitely leave the amp as it is. The BD140 replacements(NTE185) worked out very well. I definitely did not want to replace them with something different unless I got some more information,such as what you told me. Actually,the amp is very good and I'm still happy with it's performance.

I now realize how just one component can change many things within a circuit. I was curious because I have heard of DIYers swapping out components for modifications. I'm glad I got my answer here before damaging my amp. Thanks again.

Pete
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