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Old 20th October 2010, 05:06 PM   #91
EUVL is offline EUVL  Europe
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Incorrect. The balanced input signal is still being amplified by a factor of 6.

You do get higher output voltage level at your speakers, but this is not because the gain is higher.
It is because the input signal (= Vin+ - Vin-) is now 2x that of a single ended signal (e.g. Vin+ alone).


Patrick

Last edited by EUVL; 20th October 2010 at 05:31 PM.
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Old 20th October 2010, 05:32 PM   #92
EUVL is offline EUVL  Europe
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Calm down guys.

It's just a hobby. You are supposed to have fun with it.

Patrick
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Old 20th October 2010, 05:51 PM   #93
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EUVL

100% agree.

Just apears that some members have fun by putting others down

Supose we are only humans after all.

PS I am having fun.
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Old 20th October 2010, 06:08 PM   #94
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These days the "off topic thread" seem to make more sense to me than the "build threads"...
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Old 20th October 2010, 06:15 PM   #95
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I found cheap MPC74 there:
JAPAN FUKUSHIMA METAL PLATE RESISTOR 0.22 ohm 5W 12PCS - eBay (item 120608588546 end time Nov-11-10 07:01:37 PST)
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Old 20th October 2010, 08:05 PM   #96
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Thanks Patrick for your resistor matching procedure.
I will give it a go
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Old 20th October 2010, 08:18 PM   #97
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I thought I would bring this up because some people might be frightened off to build this.

I agree the N devices need to be matched to each other and the P devices need to be matched to each other. However I don't think it is absolutely critical to get perfect matching between N and P. If that was the case Nelson would not use IRFP devices which are not perfect complementary devices to start with.
Even the Toshibas which are better are still not perfect complementary devices.

So could either Papa/Patrick/Juma/Zenstar, comment about how critical all of this is.
This project should be about encouraging people to participate in it, rather than scaring people away.
It would be nice to put things into perspective for people, rather than just saying you need perfect matching.
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Old 20th October 2010, 08:41 PM   #98
Zen Mod is offline Zen Mod  Serbia
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current matching between all input jfets is a must ;
EUVL's combined source resistor/different Idss - as tricky bonus , for fun and builder's pride

current matching of same polarity of outputs is a must
current matching between polarity of outputs is splitting a hair , but can be fun if you like it

using THD meter and Papa's trick of additional source resistor in appropriate place in output is a cherry on top of cream pie ( and poke in the eye of our usual overengineering .... and above hair splitting )

but - some people don't care for cherry , especially not 2000 .



btw. - did I told you that I don't care which mosfets are in output ?

I like it lush
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Last edited by Zen Mod; 20th October 2010 at 08:45 PM.
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Old 20th October 2010, 08:55 PM   #99
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See F5 post
F5 power amplifier
These toshibas are nice complements.
It's tempting to match them..

Last edited by bobodioulasso; 20th October 2010 at 08:58 PM.
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Old 20th October 2010, 09:03 PM   #100
EUVL is offline EUVL  Europe
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THD meter does not tell you the whole story.
You need to watch the distribution of 2nd, 3rd, 4th, ...., up to 7th harmonics.
Read the Blowtorch thread.

The rest I already explained here :
F5 power amplifier


Patrick
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