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Old 23rd November 2012, 12:42 PM   #11
Fynn is offline Fynn  Germany
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I ended up buying an adjustable PSU (11-14V) which was linked on the ta2020 wiki page:
12V 3.2A Power Supply Transformer for LED Light Bulb (AC 110~240V) - Free Shipping - DealExtreme
So i will probably adjust that to 13.5V and be on the safe side.
0.5V isn't really going to make much of a difference..

Also bought 5 chokes: 10 H - 4,2 A - 0,036 Ohm - 28 MHz (Replacing all 5 of the original ones)
and 2x2,2F coupling capacitors which i will be using to directly go from RCA->POT->CAP->C20/21Input and bypass all that other crap.
(Why even have tone controls in the first place, it only makes it look like a cheap amp.. oh wait )

Stuff probably will arrive in 1-2 weeks. I'm really anxious to hear the difference!
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Old 24th November 2012, 06:16 PM   #12
Bare is offline Bare  Canada
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Quote:
Originally Posted by Redshift187 View Post
I've only spent $65 total on the amp, replacing all through hole capacitors and inductors and shipping. I can't imagine something better for the price. I certainly couldn't make something better for that.
True enough... UNLESS you had bought the proven 'pick of the litter' 41hz.com Amp 6 kit in the first place
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Old 24th November 2012, 06:26 PM   #13
Bare is offline Bare  Canada
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Quote:
Originally Posted by Fynn View Post
I recently bought this amp on ebay. (LP-2020A+)
Currently i have a PC-PSU hooked up to it, (12V, plenty of A).
Now i saw that you can get more power out of it(or lower distortion at the same power output), if you raise the voltage.
I was planning on hooking up a 14V PSU. (Relatively cheap and good availability)
The auction stated that the operating voltage is "DC10~14.4V3A" and it shuts down at >14.4V DC.

I was planning on modding it anyways, so I bought some replacement caps, pots and 4x40V 1A schottkys. (Datasheet says they are needed for >13.5V input)

Question is, will it even run on 14V?
I read plenty of reviews where it said, that it won't work with DC >13.5V
Are there multiple versions of that amp with different input ratings or do the schottkys do the trick?

Also: It is stated in the datasheet specifically, that the additional diodes should be connected to VDD1/VDD2 directly.
But VDD1,VDD2,VDDA&VDD is the same thing in parallel...
Is it because the circuit is shorter if it is directly connected to the correct pins and does it matter?
Those 4 'extra' diodes are to prevent + voltage overshoot/ringing? according to the Tripath Data Sheet >13.5 v.
Not yet seen a Chinee pcb fitted with 8 shotkys though, clearly they cost too much. I was prepped to fit 8 diodes on my DIY build, then decided it wasn't worth even the small effort. 12 v 5amps works Fine for my needs.
Ohh I think it may matter Tripath would not have bothered to publish either the "extra' Diodes OR the warnings if it didn't.
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Old 25th November 2012, 02:53 AM   #14
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Quote:
Originally Posted by Bare View Post
True enough... UNLESS you had bought the proven 'pick of the litter' 41hz.com Amp 6 kit in the first place
For $65 shipped including case, power supply, volume control, power switch, DC input jack, RCA input jacks, speaker posts?
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Old 6th December 2012, 03:23 PM   #15
Fynn is offline Fynn  Germany
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Finished most of my modding on that amp. It's hard to say if it sounds better, but I guess bypassing all that crap could help out in rare situations (high gain, etc.).
The volume pot feels way more useful now.

There is also another nice side-effect of bypassing the op-amps: The slight pop noises when turning the amp on/off are completely gone now!

Still waiting on that PSU though. I measured my old PC PSU and it only delivers 10.8V, down to 10V at high load. I guess the regulator on it doesn't like 12V rail only usage since the 5V and 3V rails look fine.

Once i get the adjustable PSU, I'm probably going to let it run as high as possible on idle(14V), so that i still have ~13-13.5V left at >50% Wrms after cable/internal resistance losses.
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Old 6th December 2012, 04:19 PM   #16
Bare is offline Bare  Canada
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I bought a Toshiba Laptop intended PS gizmo 12v 5A ~$10 ...delivered.
Works.. without issue Or drama.
Surprised that you didn't notice a significant improvement from wiping off the Tone control SMD junk... and directly attaching 2.2uf input caps to the input RCAs, to the volume pot then to C20, C21.
This assumes decent out put caps and fresh inductors as well though.

These can be Good sounding Amps.
But, nowhere near ...as good sounding as a decent quality 'conventional' amp.
Despite constant claims to the contrary.
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Old 8th December 2012, 06:31 PM   #17
Fynn is offline Fynn  Germany
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Well it is hard to compare how 2 amps sound if there is like an hour in between testing them.
I wish I had 2 amps and could switch back and forth to hear what the old one was like.
Here are some pictures of it right now:
Click the image to open in full size.

Click the image to open in full size.

Added a LED volt-meter so that big hole has some use at least
I ended up connecting the input RCA to the default ports, because I wanted to keep that 3.5mm input jack as an easy to access headphone-out. (Only put it in when I intend to use it)
But it goes straight from there over the cables to the pot and into the caps. (R36&R37 wiped off)

As input caps I am using WIMA MKS 2.2F.
I know some people don't like them, but I am quite resistant to hifi-voodoo.

The output inductors were SMD ones, so i had to solder in 2 legs first on which i soldered the inductors.

Also wanted to replace the output caps, but after one I gave up. They are just such a PITA to replace with little to no gain compared to the inductors which can easily saturate if they can't handle the current.
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Old 8th December 2012, 06:42 PM   #18
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It's easier to replace the output capacitors if you take them all off before you put any back and start from the middle, working out when you install the new ones.
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Old 8th December 2012, 07:50 PM   #19
Bare is offline Bare  Canada
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So far so good :-)
Need to remove the Tone stack bits as they DO interact even though input disconnected and or using the tone defeat button.
I found that replacing the Wima Input caps on My YJ ta 2020 board, although they were each as big as your Blue relay box, did make audible difference. I'm thinking Asian Wimas are probably Fakes.
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Old 10th December 2012, 01:09 AM   #20
Fynn is offline Fynn  Germany
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Well going to remove the op-amps then.

Some people said, that the voltage is capped at 13.5V.
That is not the case with this pcb design.
Tested with a 14.5V supply and 14.5V is what i measured on the VDD pins.

Also nice of lepai to provide solder points on the output traces, where i could attach the schottkys with relative ease
(I don't think it is possible to make it much shorter... 14+V here i come)

Click the image to open in full size.
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