F5 power amplifier - Page 148

bubba177 · 23rd July 2008, 06:53 PM

all the .47R 3W panasonic resistors at digikey are gone-who would of done such a thing?

chrismercurio · 23rd July 2008, 06:57 PM

I bought mine from Mouser.

Part number: 71-RS02BR4700FE12

h_a · 24th July 2008, 07:21 AM

Patrick, I'm now completely confused: are your findings for the stock F5? I thought you build only balanced?

Of course thank you very much for your insight and measurements! Very interesting!

Have fun, Hannes

morfeas · 24th July 2008, 12:42 PM

Excuse me, but are you able to hear distortion levels that low (0.0x%) ?
Or is it that those figures give you info on other more significant parameters of the amp?

Thanks

PS: just a tube guy been happy with THD <5%.

EUVL · 24th July 2008, 01:39 PM

> I'm now completely confused: are your findings for the stock F5? I thought you build only balanced?

I do.

The gain balancing refers to one half of the balanced circuit, with the intersection point of the X in the latter grounded.

a) There are folks who want to build only single ended.

b) Even for the balanced version, there is no harm to get some distortion cancellation on each half first.

Having said that, the strategy for the balanced version is different from the single ended. In the latter case, you might want minimum THD, or maybe minimum 2nd. In the former case, you don't care so much about even harmonics, as long as they are equal on both sides (left & right), but you might want to minimise the odd harmonics instead.

Patrick

h_a · 24th July 2008, 01:44 PM

I see! Thanks for clearing it up for me! All the best, Hannes

bubba177 · 24th July 2008, 02:19 PM

here are a couple of pics of my F5 "mule" amp. this was done on the cheap and made to be able to take apart and fiddle with-going to attempt P2P boards this weekend!

bubba177 · 24th July 2008, 02:21 PM

and another pic

chrismercurio · 24th July 2008, 03:08 PM

Quote:

Originally posted by chrismercurio
I bought mine from Mouser.

Part number: 71-RS02BR4700FE12

Sorry. These were Vishay, not Panasonic.

Nelson Pass · 24th July 2008, 06:54 PM

Quote:

Originally posted by EUVL
In the former case, you don't care so much about even harmonics, as long as they are equal on both sides (left & right), but you might want to minimise the odd harmonics instead.

I believe I have mentioned previously that one of the strategies involves
cancellation of 3rd harmonics as well if you can play off the "compressive"
vs "expansive" 3rd.

The transconductance of push-pull fets is expansive with respect to increased
current and voltage and compressive with decrease voltage and current.
Generally, current is increasing with decreased voltage, and vice versa, and
you can look for a load line that minimizes 3rd.

24th July 2008, 07:21 AM	#1473
h_a diyAudio Member Join Date: Sep 2006 Location: Graz, Austria	Patrick, I'm now completely confused: are your findings for the stock F5? I thought you build only balanced? Of course thank you very much for your insight and measurements! Very interesting! Have fun, Hannes __________________ fresh matched IRFP240/IRFP9240 fets \|\| AlephJ/JX-kits F5 transistor kits \|\| Burning Amp BA-1/2 transistor kits

24th July 2008, 12:42 PM	#1474
morfeas diyAudio Member Join Date: Jun 2003 Location: Athens	Excuse me, but are you able to hear distortion levels that low (0.0x%) ? Or is it that those figures give you info on other more significant parameters of the amp? Thanks PS: just a tube guy been happy with THD <5%. __________________ Common sense is not that common.

24th July 2008, 01:44 PM	#1476
h_a diyAudio Member Join Date: Sep 2006 Location: Graz, Austria	I see! Thanks for clearing it up for me! All the best, Hannes __________________ fresh matched IRFP240/IRFP9240 fets \|\| AlephJ/JX-kits F5 transistor kits \|\| Burning Amp BA-1/2 transistor kits

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23rd July 2008, 06:53 PM	#1471
bubba177 diyAudio Member Join Date: Jan 2005 Location: missouri	all the .47R 3W panasonic resistors at digikey are gone-who would of done such a thing?

23rd July 2008, 06:57 PM	#1472
chrismercurio diyAudio Member Join Date: Aug 2006 Location: Silicon Valley	I bought mine from Mouser. Part number: 71-RS02BR4700FE12

24th July 2008, 01:39 PM	#1475
EUVL diyAudio Member Join Date: Oct 2003	> I'm now completely confused: are your findings for the stock F5? I thought you build only balanced? I do. The gain balancing refers to one half of the balanced circuit, with the intersection point of the X in the latter grounded. a) There are folks who want to build only single ended. b) Even for the balanced version, there is no harm to get some distortion cancellation on each half first. Having said that, the strategy for the balanced version is different from the single ended. In the latter case, you might want minimum THD, or maybe minimum 2nd. In the former case, you don't care so much about even harmonics, as long as they are equal on both sides (left & right), but you might want to minimise the odd harmonics instead. Patrick

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