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The tale of two subs - solid state Consumer puffery (rant and solution).
The tale of two subs - solid state Consumer puffery (rant and solution).
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Old 2nd March 2021, 05:40 PM   #11
OldDIY is offline OldDIY
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PS 1000 schema ( 2) - It is just tip35/36 driven by a CHIP - 3886
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Old 2nd March 2021, 07:22 PM   #12
ostripper is offline ostripper  United States
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Fully class B , I suppose it does not matter with a sub. I would still like to see
AB with >.05% THD for 500$ +++.

PS - LM3876t "little brother" to the 3886. I they used parallel bridged LM3886's they would have
a much better amp . "Paradigm advanced research" equals - how to shave a few $$$'s of the design of a toy.

OS
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Last edited by ostripper; 2nd March 2021 at 07:30 PM.
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Old 2nd March 2021, 08:32 PM   #13
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Was it 1995? Class AB+C. Class D is now used

Last edited by OldDIY; 2nd March 2021 at 08:44 PM.
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Old 2nd March 2021, 08:33 PM   #14
jaycee is offline jaycee  United Kingdom
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Got the same problem here with someone's M&K Sound sub... this was not a cheap sub! He told me it stopped working and would do nothing but hum... well.. found out why.

The two large electrolytic caps (Jun Fun brand.. more like Who Da Fook)... were so dried out they RATTLE inside...

That amp is supposed to do 150W into a 4 ohm load.. with one pair of 2SA1943/2SC5200. I suspect they are relying on power supply collapse to avoid the transistors exploding. The overtemperature protection circuit seems to rely on reducing the signal level rather than actually switching off.

The circuitry is being gutted and replaced, as the cabinet and the drive unit itself are worth keeping.

(edit) oh yeah, the thing has gotten so hot that the insulation on the wires has become brittle. Those two thin wires at the bottom run off to the preamp to power it. Soldered on top of big dropper resistors which got so hot, they have lifted the tracks from the board. What a joke.
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Old 2nd March 2021, 08:46 PM   #15
Ian Finch is offline Ian Finch  Australia
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The tale of two subs - solid state Consumer puffery (rant and solution).
Make that <.05% THD for $500 and I'll go along with that . Just don't plan on any large PCB that is susceptible to vibration. Placing on-board mechanical relays and large components soon develops into a difficult resonance problem.
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Old 2nd March 2021, 08:56 PM   #16
jaycee is offline jaycee  United Kingdom
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I thought about using MJL21193/4 at first but.. bleh, waste of a good pair of BJT's. Looking at MOSFETs now, they are at least rugged enough and even IRFP240/9240 can do a pretty good job
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Old 2nd March 2021, 09:03 PM   #17
jaycee is offline jaycee  United Kingdom
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The supply capacitors were the biggest joke.. there they are on the right, 25mm diameter and barely 50mm high. Versus some I have on hand which are 35mm diameter and 60mm high. I will probably get some 105c rated Nichicon or so for this though.
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Old 2nd March 2021, 10:26 PM   #18
ostripper is offline ostripper  United States
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Quote:
Originally Posted by jaycee View Post
Got the same problem here with someone's M&K Sound sub... this was not a cheap sub! He told me it stopped working and would do nothing but hum... well.. found out why.
M - K sub's go for 1500 - 3K $. V series has the class A/B amps.
Ebay has V75 4 device A/B for 175$ used.
Miller & Kreisel M&K V-1250 Subwoofer Power Amplifier | eBay

This M and K amp looks better than yours. Glass epoxy PCB and what looks like
10Kuf + caps @ 63V. Acceptable , but M & K's prices are crazy.

OS
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Last edited by ostripper; 2nd March 2021 at 10:34 PM.
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Old 2nd March 2021, 10:27 PM   #19
ostripper is offline ostripper  United States
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Quote:
Originally Posted by jaycee View Post
The supply capacitors were the biggest joke.. there they are on the right, 25mm diameter and barely 50mm high. Versus some I have on hand which are 35mm diameter and 60mm high. I will probably get some 105c rated Nichicon or so for this though.
Ohh ho ho JUN-FU caps ... like smokin' kung-fu. Yikes !!

Oh , Samwha caps ... one of the best electolytic formula's out there - very reliable.
S. korea = good stuff.

I'll stick to to my Nichicon's. OS
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Last edited by ostripper; 2nd March 2021 at 10:36 PM.
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Old 2nd March 2021, 10:42 PM   #20
ostripper is offline ostripper  United States
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Quote:
Originally Posted by OldDIY View Post
Was it 1995? Class AB+C. Class D is now used
But the DSP - class D OEM plate amps are also POS. I've seen so many
reeeaaly burnt class D's.
OEM class D is the same outsourced garbage , sometimes even worse
than the class A/B's.
The only ones I would care for is a Hypex UcD180 or 400 matched with a
20K - 40K cap bank + Toroid.

(BELOW) is BIC usa class D POS example. Look at the switching FET's out on wires ,
all these burnout in 3-4 years.

OS
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Last edited by ostripper; 2nd March 2021 at 11:01 PM.
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