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Old 23rd June 2010, 03:10 PM   #8191
udailey is offline udailey  United States
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Quote:
Originally Posted by acold7dusta View Post
amp's running much more stable (cooler and less noise), and sounds much more "relaxed", with an increase of upper midbass...interesting
What did you do to get this gain in sound quality and stability?
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Old 23rd June 2010, 06:47 PM   #8192
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I finally got my FETs in and I am wondering how you guys go about matching (or if you bother). I have 20 of each JFETs and 6 of each MOSFET. I read somewhere that there were many more needed (1000 comes to mind) to get a good match. Please reply back with methods, circuits, links etc. so that I can compare what I've read to experienced guys. There's a lot of information out there for a newbie.

Thanks,
Everett
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Old 23rd June 2010, 07:11 PM   #8193
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I am building a F5. However, I have problem with thermal drift. I use 5K NTC thermistors. Output DC swings up to 100mV and idle current swings up and down too.

I attach the thermistors to the power MOSFET with glue. What is the proper way to mount/attach the thermistors? Would some one help. Thanks.
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Old 23rd June 2010, 07:34 PM   #8194
Bidoux is offline Bidoux  France
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I have to apologize, I didn't read the whole thread, but it is quite obvious, seeing it's lenght. So maybe my question has already been asked.

Here, on figure 15 we can see an amp that looks like a F5 with bipolar instead of fets. The author says it is a design to avoid.
Is the F5 so much different that the topology is no longer a problem ?
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Old 23rd June 2010, 07:44 PM   #8195
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Hello
Please use the melting type of glue . That has great conductivity .
In case if the mosfet and the thermistor has different temperature .
Greeting
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Old 23rd June 2010, 07:50 PM   #8196
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Quote:
Originally Posted by udailey View Post
What did you do to get this gain in sound quality and stability?
It was a matter of not sounding right, vs. sounding normal. I removed my zobel network (cap & R in series), and swapped out my high capacitance cat 5 speaker cables, with normal 12ga wire, and tweaked the bias. I'm now at .685V on the left with <1mV dc offset, and .687V on the right with ~1mV dc.

The right channel still gets very hot after about 2 hours, so i definitely need to give it more air to breathe (open rack is on the left of my speaker)
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Old 23rd June 2010, 07:55 PM   #8197
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Quote:
Originally Posted by Nelson Pass View Post
Some capacitance across the 100 ohm feedback resistors will
stabilize that. Start with .001 uF and work up to .01uF.

Thanks, what kind of effect will I look for on a scope? still new to scopes
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Old 24th June 2010, 10:48 AM   #8198
Marra is offline Marra  United Kingdom
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Has anyone used transformers from Toroidy.pl. I seem to remember that someone said they were going to try them and post results but I havent come across any more posts. I still have another 100 pages to read so maybe I havent found his results yet.
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Old 24th June 2010, 11:14 AM   #8199
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there's one on page 696, from doing a simple search
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Old 24th June 2010, 12:36 PM   #8200
Marra is offline Marra  United Kingdom
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Thanks for the pointer
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