Anyone want to help me with a T-amp mod?
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ilikemonkeys

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I know these questions have been covered before, but I dont understand most of the technical jargon.

What do I replace the center cap with for increased bass response?

should I use an alps 50 or 100K pot?

in the mod schematic here why are the caps labeled differently, and where can I find those caps? I'm also looking for more info on finding the resistors too.

I'd really rather this not turn into a huge discussion either.....I tend to get really lost in the EE speak. I've got pictures, and I can make my T-amp look like the pictures if I can find the parts.

Thanks so much guys.....I just love that I can always come to the same place for a straghtforward answer.

BILL
 
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cmirza

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I'm also interested in this. I plan on upgrading to RCA inputs, binding post speaker outputs, 50k pot, upgraded caps and put all of that into a Hammond 1455 aluminum enclosure with a new power LED. If anyone has some experience in these mods I'd appreciate to hear your experiences and suggestions.
 
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dsavitsk

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Quote:

Originally Posted by ilikemonkeys
should I use an alps 50 or 100K pot?


Probably doesn't matter, but go with 50K if you can find one. They tend to have lower noise.

Quote:

in the mod schematic here why are the caps labeled differently, and where can I find those caps? I'm also looking for more info on finding the resistors too.


The caps should be the same. You can get the caps from percyaudio.com. You probably want the BlackGate N series, though I don't see a 2.2uF value available. I think you are safe moving up to the 4.7uf, however. Otherwise, I would assume that a 2.2uF film cap would be okay. Try the Aeon as I think it will sound better than the BG and it's cheaper (thoughit is a ton bigger -- with BG you are paying for the small size.)

There are lots of choices (and more opinions) on resistors. You are probably okay with about any 22K (or 22.1K) metal film. If you are going to get your caps from percy, then the PRP resistors are a good option. If it were me, I would get 22.1K Kiwame resistors that cost more, but sound more natural to my ear. Anything is fine, however, and you'll need a good souce, good connectors, good speakers, and good ears to tell any difference.

Percy also sells 50 and 100K Noble pots that are as good as the alps.

The upside here (not to advertise for percy, but I like ordering from him and I don't know that anyone else has all the parts in right now) is that with the pot, 2 caps, and 2 resistors you will just meet his minimum order of $25.

-d
 
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JWFokker

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I'd stick with a 50K pot, as it's what the stock T-Amp uses. Panasonic makes some good ones you can get from Digikey.

I'm not sure why he labeled the caps differently. Must not have been paying attention. I'd stick with Black Gates as they're pretty cheap for 2.2 or 3.3uf caps. Good film caps are quite large, and unless you get expensive ones (Auricaps or better), you won't hear much if any difference vs a Black Gate NX or Hi-Q. If you go much above 2.2uf though, you get this huge popping sound when you turn the amp on, which may damage your speakers. Then again, it might be a lot easier to find an average film cap. There's only a couple places to buy Black Gates these days.

The main cap to replace, other than the ones on the inputs, is the one right in the middle of the inductors and should be replaced with something around or above 1000uf and rated for 16V or higher. I used a Panasonic FM 1500uf cap, though it was too wide to fit between the inductors, so it sat above them. FMs are very good caps for the money, though if you want something better, Welbourne Labs sells Cerafine caps in high capacitances. To buy a Black Gate of that size would be exorbitant.
 
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Jon L

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Quote:

Originally Posted by JWFokker
I'd stick with a 50K pot, as it's what the stock T-Amp uses. Panasonic makes some good ones you can get from Digikey.

I'm not sure why he labeled the caps differently. Must not have been paying attention. I'd stick with Black Gates as they're pretty cheap for 2.2 or 3.3uf caps. Good film caps are quite large, and unless you get expensive ones (Auricaps or better), you won't hear much if any difference vs a Black Gate NX or Hi-Q. If you go much above 2.2uf though, you get this huge popping sound when you turn the amp on, which may damage your speakers. Then again, it might be a lot easier to find an average film cap. There's only a couple places to buy Black Gates these days.

The main cap to replace, other than the ones on the inputs, is the one right in the middle of the inductors and should be replaced with something around or above 1000uf and rated for 16V or higher. I used a Panasonic FM 1500uf cap, though it was too wide to fit between the inductors, so it sat above them. FMs are very good caps for the money, though if you want something better, Welbourne Labs sells Cerafine caps in high capacitances. To buy a Black Gate of that size would be exorbitant.




Are you talking about C10 stock cap? Why does one have to "replace" this PS to power pins? Since they're just caps, can't I just stack a big cap on top of the stock cap?
 
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motherone

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I've modded a few of them and here are my suggestions:

1) The space for the power supply resevoir cap is tight. If you're going to add one to the board, you have a few options. The first is to use the "tall" version of the 16V/680uF panasonic FC/FM caps over at digikey. These will fit in the stock location between the inductors with no mods. The second method is to skin the inductors. This will let you put a slightly larger (standard sized 680uF-1000uF Panasonic FM/FC) cap in it's place. The third method is to remove this cap altogether and solder it directly to the groundplane and power supply pins on the board. The fourth is to use a cap with the same pin spacing, or with creative lead bending, and place it on the bottom of the board.

2) To get the "best" out of the amp, you need to replace the input coupling capacitor. There's several opinions on this. If you can go with a 2.2uF non-polar black gate (N or NX), this should fit on the pins easily. Another option is stacking 2x 1uF SMD film caps, but this is more difficult. A third option is to dump the whole input filtering section and rebuild it off board. This involves removing jumpering a lot of components and doesn't really provide that much benefit.

I recommend going with a 2.0 to 2.2uF cap, as some folks have reported some nasty startup noises when the chip polarizes caps larger than 2.2uF. Going any larger than 4.7uF seemed to lead to MAJOR noises on start up and shut down. Your mileage may vary, as this seems to depend on the sensitivity of your speakers.

3) Replace the feedback resistors. This is easy. Swap the stock 33/36k (can't remember which it is) resistor for a 20k. This sets the amp to unity gain, and is supposedly the "optimized" configuration in the Tripath datasheet.

4) I've been using 10k Noble pots (the black metal bodied ones that look like Alps "blue velvets"). These work fine. They're not really easily available anymore, though -- I found mine on ebay. Replacing it with a 50k alps, such as the one from tangent's shop, should work fine as well.


Anyhow, be careful as these boards are very cheaply made. It's very easy to lift the pads. There's extensive threads in the diyaudio.com class-d forum on mods for these, including a list of the onboard parts and suggested replacements (posted by myself and panomaniac). You can take these further than what I've posted here (including replacing the output inductors), but you start running into the law of diminishing returns.

The mods I've listed here are what I feel offer the best balance of performance and price. This is a $20-25 amp, so putting $100+ worth of parts, plus all the time and effort, doesn't seem worth it to me. If you really feel like making something better, start with a better platform -- look at the amp3 from http://www.41hz.com
 
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Jon L

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So there's no problem using 2.2 auricap to replace the coupling cap right on the board? Even though Auricaps are labelled red and black, I don't believe they are polarized. If they are, does red lead goes to chip side?

That 41Hz board looks like the board I saw inside a Nuforce Monoblocks, which was impressive sounding in a high-end system. Probably the same oem board with extras for the audiophile market..
 
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dsavitsk

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Quote:

Originally Posted by Jon L
So there's no problem using 2.2 auricap to replace the coupling cap right on the board?


Should be better than a BG.

Quote:

Even though Auricaps are labelled red and black, I don't believe they are polarized. If they are, does red lead goes to chip side?


There is info on polarization of Auricaps here http://www.tnt-audio.com/accessories/auricap_e.html
 
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JWFokker

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Quote:

Originally Posted by Jon L
Are you talking about C10 stock cap? Why does one have to "replace" this PS to power pins? Since they're just caps, can't I just stack a big cap on top of the stock cap?


Why would you want to leave the crappy stock cap on the amp? You don't have to replace it, but it'll take up less space if you do.
 
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mono

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Quote:

Originally Posted by ilikemonkeys
I know these questions have been covered before, but I dont understand most of the technical jargon.

What do I replace the center cap with for increased bass response?



Anything the respective cap manufacturer specs as low impedance, low ESR. One of the favorites around here is a Panasonic FM or FC but there are several brands like Nichicon too. On the board 8mm diameter will fit. If you loosen the bobbin inductors' soldered leads and shift them angled outward a little from the cap you can then fit an 10mm diameter cap instead which allows larger values. I did not have to skin my inductors to get it to fit OK. Instead you could mount a 10mm diameter (or still 8mm of course) (max 5mm lead-spacing) cap on the opposite side of the board, remembering to observe correct polarity.

Quote:

should I use an alps 50 or 100K pot?


Yes you should replace the stock pot. Alps plastic bodied pots are good, their cheap carbon film with round metal casings aren't. Pot could be as low as 10K Ohm, 50K would be my first pick if you had a choice at a vendor or had it already. Other posters have mentioned some other potential brands.

Quote:

in the mod schematic here why are the caps labeled differently, and where can I find those caps? I'm also looking for more info on finding the resistors too.


They're just randomly labeled differently but both are same. You need not find those, are better off getting the Auricaps or any other ~ 2.2uf polypropylene film cap. As for the resistors, wherever you're buying parts, they're likely to have metal film 1% 1/8 or 1/4 watt. You could get .1% for better matching but personally I'd just buy a dozen 1% at a bulk price and use closest match- then you have some spares for other uses.

FWIW, I was a little leery of leaving a floating piece of wire or resistor soldered to those pads on the PCB as in the linked picture, so I first epoxied a bi-pin header onto the unused area on the bottom front corner of the PCB, then used transformer wire to jumper from the bi-pin header's rear to the solder pads, then after confirming a good connection,

I put a thin layer of epoxy under the wire (so it wouldn't short against the PCB), let that set, then epoxied over the wire too, ending up with a sturdy permanent method of easily connecting the input stage. Having finished it I might solder onto the bi-pins but haven't felt motivated to do it yet. That's not entirely necessary but I could see the potential to pull up the solder pads accidentally while playing with it.
 
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ilikemonkeys

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I just replaced that center cap this morning with a 2200 I pulled out of an old car amp. I really cant believe that it was going to make such a difference. It seems louder too. Now I need to get a new pot. Then I'll playaround with those Blackgates.

Thanks for everyone's help....I can be needy at times...but you all are real patient.

B
 
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JWFokker

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Replacing the input caps will make the biggest difference, but that's probably the most difficult mod if you're not familiar with soldering tiny parts.
 
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mono

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Quote:

Originally Posted by JWFokker
Replacing the input caps will make the biggest difference, but that's probably the most difficult mod if you're not familiar with soldering tiny parts.


Agreed. I found the easiest way to go was applying a little extra flux to some desoldering wick then placing it on the surface-mount resistor, heating the wick with the iron. The resistor lifts right off quite quickly and painlessly with no trauma to the solder pads. Of course that particular component removal means one needs a resistor in additon to the cap per channel.
 
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ilikemonkeys

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way over my head guys.

if you tell me what to replace with what, I can do it.

I dont even know what a desoldering wick is. I just pull stuff off with tweezers.

This is a great hobby, but I have to be spoken to like a 2 yr old.

Thanks,

BILL
 
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mono

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See the following two pictures. The resistors on pic #1 are those you would place desolder braid on top of, and heat the braid. Then the braid, excess solder, and resistor all just lift off while hot. It's easier with some flux added to the braid (which I did) but may work without too. Removing the resistor then breaks the original input stage circuit.

You'd solder a lead to the amp-side of the resistor pads (as pictured), and have a resitor, then cap, and pot, again as pictured, before the audio input jack (or after it really, so far as the audio path goes I'm describing it backwards).



 
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