SYMEF amplifier
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 16th May 2012, 03:09 PM #511 Tekko Banned   Join Date: Jan 2005 I used MJW21195 and MJW21196 instead of 2SC5200 and 2SA1943 with no problems at all.
 16th May 2012, 04:06 PM #512 AndrewT   R.I.P.   Join Date: Jul 2004 Location: Scottish Borders P = I^2 * R where I is the DC current. If you use AC current then you must use Irms for your modeling to be correct. If you use a sinewave as the test signal and you find it easier to measure an accurate Ipk rather than Irms then that Ipk must be converted back to Irms using the Ipk = Isinewave * sqrt(2). So back to that 20Apk value. An 150W into 8ohm capable amplifier will deliver 150W into 8r0 from 49Vpk (=34.6Vac) while meeting a current demand of 6.1Apk (=4.3Aac). A 8ohm capable amplifier, must be able to deliver at least two times resistive current demand and preferably three to four times that resistive demand from a reactive speaker reproducing fast transients. That three times the 6.1Apk comes out at 18.3Apk and four times comes out at over 24Apk. These transients currents are from an 8ohm capable amplifier of just 150W rating, not a 3600W amplifier. I do wish our Members would start to learn a bit of arithmetic. __________________ regards Andrew T. Last edited by AndrewT; 16th May 2012 at 04:10 PM.
sonidos
diyAudio Member

Join Date: Jul 2007
Location: Round Rock, TX
Quote:
 Originally Posted by Tekko I used MJW21195 and MJW21196 instead of 2SC5200 and 2SA1943 with no problems at all.
Tekko, thanks, that is reassuring. IIRC, I have the MJL3281A/MJL1302A sets in my parts bin.

nakamoomin
diyAudio Member

Join Date: Jun 2009
Quote:
 Originally Posted by AndrewT These transients currents are from an 8ohm capable amplifier of just 150W rating, not a 3600W amplifier.
You are correct!

Quote:
 Originally Posted by AndrewT I do wish our Members would start to learn a bit of arithmetic.
Hmmm, can't see anything hugely wrong with the arithmetic so far...

I think we're all on the same page. I was merely trying to demonstrate that huge transients (neighborhood of 20A) is completely possible in this design (@ 4 ohms) and therefore an air-core inductor is the only sensible choice. I was also trying to point out that the "3600W figure" is simply not possible as increased load @ 8ohms effectively halves the Imax at the stated voltage (+/- 40VDC == 80V p-p).

The equations I have provided are all assuming DC voltage (and are "worst-case" scenarios if you like). The 3600W, 1800W and 1500W numbers that are thrown around here (jokingly on my part, I assume the same for everyone else) are merely to demonstrate the maximum impulse power and in no way meant to say anything about the rating of this amplifier (which is somewhere around 150W into 4 ohms).

I hope I haven't confused anyone..

Last edited by nakamoomin; 16th May 2012 at 04:37 PM.

OnAudio
diyAudio Member

Join Date: Oct 2011
power supply design

here we go
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 16th May 2012, 07:48 PM #516 OnAudio diyAudio Member     Join Date: Oct 2011
 16th May 2012, 09:56 PM #517 meanman1964   diyAudio Member     Join Date: Oct 2006 Location: Belgium the land of chocolate Thanks!!!
 17th May 2012, 05:46 AM #518 Nico Ras   diyAudio Member     Join Date: Nov 2005 Location: East Coast of South Africa Hi Sondidos, I am sorry if I misunderstood OnAudio's comment on air-core, maybe all performance related comments are equally nebulous. In my opinion, if one wants the exact same sound character experienced by others that built and commented on this thread (or any other thread for that matter), the exact same components need to be used as the other constructors did. So you need to establish who's SYMEF sounded the best out of all the SYMEFs constructed and then use the identical components that was used in the "gold standard" SYMEF, including power components and wiring as well as build quality, etc. else nothing could be verifiably consistent. But first, establish which is the best sounding SYMEF amongst all the SYMEFs out there - One would do that, maybe by rotating all the amps amongst all the builders with a standard questionnaire until they all agree on the best sounding SYMEF then reproduce that best sounding one faithfully, in every respect. That is more or less how one would do it before going to production, to be able to deliver a consistent product. In a DIY environment like this, unless every componet is characterised and specified, nothing is consistent and all the comments about the "sound" is merely a figment of ones imagination. Besides you need to also use the identical source equipment, speakers, and probably the same recording to make any sense of it. Maybe the formula can be used to predict who's SYMEF actually sounds the best by inserting all the variables into the equation and then pressing run. __________________ Kindest regards Nico Last edited by Nico Ras; 17th May 2012 at 05:58 AM.
 17th May 2012, 06:10 AM #519 Nico Ras   diyAudio Member     Join Date: Nov 2005 Location: East Coast of South Africa Is this known scientific fact or just a personal arithmetical preference. "A 8ohm capable amplifier, must be able to deliver at least two times resistive current demand and preferably three to four times that resistive demand from a reactive speaker reproducing fast transients." __________________ Kindest regards Nico
Nico Ras
diyAudio Member

Join Date: Nov 2005
Location: East Coast of South Africa
Quote:
 Originally Posted by OnAudio here we go
I guess I will have to take your word how the SYMEF power supply is designed. Could this be the reason that everyone is experiencing the same sound character?
__________________
Kindest regards
Nico

Last edited by Nico Ras; 17th May 2012 at 06:34 AM.

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