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Old 20th October 2010, 07:26 AM   #81
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Another resistor option is Ohmite Audio Gold non-magnetic, non-inductive 5W axial AG5NGR22E 0,22R/5W 2%.

http://www.hifituning24.de/hifi-tuni...etic/index.php
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Old 20th October 2010, 07:34 AM   #82
Luke is offline Luke  New Zealand
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Quote:
Originally Posted by bobodioulasso View Post
Matching is compulsary for a balanced amp.
Or it is not balanced.
Rather to build a regular F5 with them.
An N channel and a P channel typically deal with the different halves of the sine wave and I believe these can never really be matched correctly. In a balanced amp with unmatched parts, will it be any different? My understanding is that matching is more for current sharing and dc ofset, but they are not sharing current in this config and Im not sure how much offset I would need to deal with.
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Old 20th October 2010, 07:40 AM   #83
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Look at post 49.
Matching reduces distortion. Which
is the target.
F5 power amplifier

Last edited by bobodioulasso; 20th October 2010 at 07:48 AM.
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Old 20th October 2010, 10:58 AM   #84
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Matching resistors wheatstone Bridge


Well busy now got same dudas to match
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Old 20th October 2010, 11:03 AM   #85
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Old 20th October 2010, 11:20 AM   #86
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PS.
bobodioulasso

Tanks for the links to the jucy bits.
When I get a chance I will collate the lot.
Thus making the 900 page original tread usefull.

Al
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Old 20th October 2010, 02:00 PM   #87
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Quote:
Originally Posted by Bksabath View Post
PS.
bobodioulasso

Tanks for the links to the jucy bits.
When I get a chance I will collate the lot.
Thus making the 900 page original tread usefull.

Al

Bobodioulasso or Bksabath, could one of you post this guide to the "Juicy bits"?

Thanks,

russsellc
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Old 20th October 2010, 04:15 PM   #88
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Gentlemen,

I proposed a resistor for you which IMHO is good value for money and very good sonically. Just look at what they use in high end Japanese amps. If you want to use more fancy resistors, then you can try Isabellehuette PBH, Caddock MP930, Texas Components T220Z, ....... Plenty of choices. The PCB will have 9mm & 5mm pitch, for MPC74 (faithful to my original design) and any TO220 boutique resistors.

If you don't want to GB MPC74, it is just fine with me. I am just thinking ahead for those who want to build it exactly as I did mine.

As to resistor matching, this is how I do it myself (see attachment). But feel free to do it your way.

I'll still do the following as promised :

1) get a Gerber for my PCB layout done and send it to Variac, with standard DIYA mounting hole patterns,
2) give guidance and help to AR2 to build his prototype according to the way that I built mine.

He has the generosity to then share his building experience with you, and help those out who is new to the game.

What I will not do is to answer question like "what if I chance your circuit by this and that for xyz special application", ......, etc. I have not tried any other configurations than those I am going to publish, so I have no idea whether your proposed changes will work or not. I can only encourage to experiment and report back your experience. It is not so bad to burn a few transistors -- all part of the education.



So now I need to get the layout updated for Variac to check and agree, then Bksabath will get the ACAD files to convert to Gerber, according to my instructions.


That'll be it for tonight,
Patrick


PS My source says MPC74 +/-5%. I have no problems getting quad sets to much less than 0.5% for a batch of 40.

.
Attached Files
File Type: pdf Power Resistor Matching.pdf (14.8 KB, 1211 views)

Last edited by EUVL; 20th October 2010 at 04:19 PM.
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Old 20th October 2010, 04:31 PM   #89
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Quote:
Originally Posted by Russellc View Post
Bobodioulasso or Bksabath, could one of you post this guide to the "Juicy bits"?

Thanks,

russsellc
Do not know exactly, i think post 48, 49,...
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Old 20th October 2010, 05:00 PM   #90
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Quote:
Originally Posted by Russellc View Post
... Does this increase gain, or does that remain at 15 db? (Of course I mean with the standard feedback resistors)

Russellc
balanced gain is doubled (+6db)
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