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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 6th March 2021, 07:48 PM   #61
workingman1893 is offline workingman1893  United States
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any hope for us Def Tech owners with bad sub amplifiers?
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Old 6th March 2021, 09:40 PM   #62
wiseoldtech is offline wiseoldtech  United States
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Quote:
Originally Posted by ostripper View Post
Could you share that circuit ?
I am "picky" too.
OS

Well, the replacement sub amp, a 100W model cost only $58 and is a well built reliable unit that I trust - MS 8A 100 Watt Amp


The sleep/standby circuit is featured on the Elliot Sound site (project 38), and I made some mods to make it perfect for getting around the power hungry MS8A main transformer. - Project 38


Because who wants a constant 50 watt AC draw of the sub amp when it's not in use?
The tiny 2 watts in standby/sleep mode are much better on the electric bill when you think about it.


I've added P#38 to my own home built sub as well, with a pair of LEDs showing through behind the speaker grille.
Green when powered on with audio, red when the amp itself goes standby, and both out when sleeping.
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Old 6th March 2021, 10:41 PM   #63
ostripper is online now ostripper  United States
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The Jun-Fu's would go (Nichicon's) , I'd even replace that EI with a toriod.

If I had to repair a few subs , i'd have a couple spare EI's to build a smaller
DIY amp.
I have noticed on some Toroid based units , they leave the Toriod fully connected. The standby on TDA792x or the slow start pin on the LM3886
brings these chips out of a low power state (plus input mute). Logitech does this.
Some Discrete's (like the polk) sent the OPS into class B , while muting
the input. So my Polk always ran that 50-80VA EI and just input muted and
shifted OPS bias.

Not much of a "standby" - deception even in design.
My Dayton 10" also did this Half-ar$ed design trick - EI was still always
warm , even in standby.

Rant .... Supposedly , since the manufacturer/marketers specify the design parameters to the bottom of the supply chain
(Make it have a standby).... who did this shoddy engineering ?
Polk or Dayton's team ? Or the Asian supplier ?

These companies often even print "designed in the USA" or similar right on
the units. So , this is equal "grifting" between company and supplier.

Logitech at least went halfway , relying on the low core loss of a Toroid and
the built in TDAxxxx's included onboard standby circuitry.
I would almost consider this "true" standby.

OS
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Last edited by ostripper; 6th March 2021 at 10:44 PM.
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Old 7th March 2021, 06:31 PM   #64
ostripper is online now ostripper  United States
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Default No rant on this one....

"Designed in Germany" .... not a lie !! (below 1/2).

Thonet & Vander Kürbis - Not bad , A 3A x 2 SMPS driving an ST TDA7294.
1600uf X2 + 30-0-30VDC , FR-4 and quite ample heatsinks all around.
Not a sub , but a better setup than the POS polk 10".

KMC capacitors = 105C Nippon chemicon ... not bad.

This would be a breeze to repair , uses easily sourced semi's . This
could last 20 years , Loud Vivaldi opera 8 barely made for any heat in this unit.
These units sound as good as my Polk Tsi 200's ... just not as loud.
Here we have strict guidance of the Chinese factory they outsourced to.
I wish more of our OEM's stuck to these business ethics.

These "wipe the floor" compared with any M-audio or Logitech's.

OS
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Old 9th March 2021, 08:19 PM   #65
maherjf is offline maherjf  United States
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I bought a JLB PSW-D12 in 2000, power supply caps failed two years later. Solved with a Crown DC-300. Some years later found the same model dead sub, amp removed but speaker still in good shape, on ebay and have enjoyed both for a few years on the DC-300. Nice solid base (xover at 85Hz using a dbx Drive Rack PA2. Works great for a small living room, about 400 sqft, and can hear 20 Hz pretty well. 12" Yamaha driver with a 2" vc (would prefer 3", but they perform quite well). I wanted to go with an amp I can trust so my DC-150 got a big brother.
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Old 9th March 2021, 08:47 PM   #66
mocenigo is offline mocenigo  Germany
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Quote:
Originally Posted by ostripper View Post
But the DSP - class D OEM plate amps are also POS. I've seen so many
reeeaaly burnt class D's.
[...]The only ones I would care for is a Hypex UcD180 or 400 matched with a
20K - 40K cap bank + Toroid.
The Hypex Fusion plate amps are also solid and sound excellent. I use two FA501s for my two subs.
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Old 9th March 2021, 09:55 PM   #67
ostripper is online now ostripper  United States
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Much cheaper to just get a plate of aluminum , 100euro's for the UcD400HG.
SMPS 400a400 , 109euro ... perfect.
Looks like standby , protection , +/- 15 Vaux is all in the SMPS.
Interface between SMPS and UcD - cool full amp/PS standby.
All you would need is a 20$ LP filter kit to hook to Vaux.

Wow , did not know Hypex made SM PS's.

OS
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Old 10th March 2021, 01:27 PM   #68
mocenigo is offline mocenigo  Germany
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An FA501 does not cost much more than a UcD400 plus a PSU and a plate of aluminium, and it offers better sound quality, integration, and a DSP.
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