Complete mod of the AMP6

[Benoit76]

Hi
I built a first AMP6 a few time ago and I will make anotherone starting from the begining with good components instead of modding it after.



For the input caps (C14/C15) I will choose paper in oil caps.

For C1819 and C99 I was planning to buy some Panasonic FM series caps (2200µF/25V for C1819 and 18000µF/25V for C99) but the FM series stops at 6800µF.

I don't know what are C2,C5 and C100. They are respectively called "+5V bulk cap", "Charge pump output decoupling" and "Voltage regulator ripple rejection damping" and are Panasonic FC series on the original kit I think.

For all ceramic caps, are they critical ? If not I will keep those from the original kit.

and what about the output caps C13/C25/C22/C28/C27/C12 at the bottom of the PCB? Should I replace them?


Thanks

[sharpi31]

I built an amp6 basic recently and replaced all capacitors with 'better' ones. I tested all the resistors that came with the kit and these were very closely matched, so I didn't bother replacing them.

I used a 330uf black gate standard on the board for main reservoir cap, and added 5x 470uf/35v sikorel 125 off-board to beef up the PSU capacitance.

I used black gate N for the signal coupling caps and for all other caps >0.1uf. I used 0.1uf black gate NX throughout.

The amp sounds great, although I have not heard an un-modded amp6. It is much fuller, richer and fleshed out than my modified t-amps (which sound shrill in comparison). It has better resolution than my gainclones, but is not as relaxed or powerful.

I have recently played around with the volume control configuration and quickly settled on a fixed series resistor and alps blue 100k potentiometer for a variable-shunt. I have tried a few different series resistors (22K1 to 55k1) and have found that 39k was the best balance of dynamics and warmth. I use a tda1543 non-oversampling dac with passive i/v conversion, so your milage may vary... I particularly like the richness of allen bradley 2W carbon comp I use at the moment.

I'll be hung for this next comment: the amp sounds very valve like compared to other class-d configurations I have heard.

Please don't think I blindly use black gate caps for everything - I wanted to experiment with this amp and see what all-BG amp would sound like. I can't draw conclusions about the component choice, but can say I'm very happy :-)

I bought 100x sikorel 125 470uf/35V caps on ebay, and could spare a couple if anyone wants....? email me

[Pano]

Salut Benoit! I got your mail, but I will reply here for the benefit of others.

I have built a lot of AMP6 kits and like them very much.

As to caps.

Input caps: My favorites for this amp are the Obbligato paper in oil. Great caps, great price, but huge. But they really are smooooth. The copper tube Obbligato are also very nice- and huge. Any good film/foil cap will work here. They all sound slightly different.

C99: This is the smoothing cap after the rectifier. I have always used the cap that comes with the kit, but you might do better. You want a high quality cap here, 10000uF or more. 25V is a minimum, 35V would be safer.
The stock caps is 18000uF/25V. That means a lot of filtering for the DC. It's going to be hard to find a bigger/better cap that will fit, but if you do - let us know!

C18/19: The TANK cap. My only gripe with the kit. I wish Jan had put two caps here for left/right. Using only one doesn't help crosstalk. In this place you need a fast cap, one that has low ESR at 1MHz and above. The job of this cap is to supply power to the switching transistors. The bigger and better the cap at this point, the better the amp will sound. The kit has various brands for this cap. I like to use a Panasonic FM 1800uF/25V. The FM series is very good at cleaning up the large amount of high frequency noise that this switching amp generates.

If you can squeeze a larger cap in here, it will help. I worked on a Trends TA-10 that used 2x2200uF for the tank caps and it was great. Really helps dynamics and bass. In my Octopus Amps I connected 1 or 2 10000uF stiffener caps in parallel with C18/19. Nichicon Gold Tune was my favorite here.

C100 Used in the power supply regulation. The cap supplied is of good quality, better than you’ll find in most gear.

C2 Used to decouple the internal 5+ generated inside the chip. You might try a very small value cap in parallel here to help decouple the highest frequency noise. Tripath does not call for it, but it’s worth a try. Something like 0.1uF.

C22/25/27/28 These are part of the low pass filter that removes the ~700Khz switching frequency from the outputs (along with the inductors). It’s best to keep the same value, but if you want to try other caps, you may. The output filter can make a difference to the sound of the amp, for sure. The ceramic caps supplied are of good quality, but you might try some others for fun. They need to be able to work at the radio frequencies used in the amp, as well as not affect the audio band too much.

C12/13 A final RFI filter on the speaker lines. They don’t have much effect on the audio.



sharpi31 Glad to hear that you got the amp up and running and that it makes you happy. FWIW, I do not like the Blackgate caps in these amps. They make very poor filters at the frequencies inside these amps. So they don’t clean up the power supply noise nearly as well as caps like the Panasonic FM series or Elna Cerafina, for example.
I’ve also used them for input caps and really don’t like the sound, they seem dull and lifeless to me. I suggest that you try a good quality film caps like the Obbligato, Auricap, Mundorf or similar. You should be able to hear a big difference. Power caps better adapted to this use might help too. But if you’re happy with it, no worries!

Hope that help with your parts quest.

[Benoit76]

Salut panomaniac

thanks for this answer.

Originally posted by panomaniac
Input caps: My favorites for this amp are the Obbligato paper in oil. Great caps, great price, but huge. But they really are smooooth. The copper tube Obbligato are also very nice- and huge. Any good film/foil cap will work here. They all sound slightly different.

I think I will order some Obbligato from ebay (http://cgi.ebay.com/Obbligato-premiu...QQcmdZViewItem)
But which ones should I take. Are the foil caps the first of the list or the second. He sells some of 2.2µF at 10.25$ (they seem to be films caps) and some 2.0µF at 5.50$ (the foil ones?).

I hadn't heard of Obbligato caps before you talked of it on another post. What do you think of them? A comparison with other caps I can find : Mundorf MKP, Audin-Cap Plus MKP, Solen MKP (I can't find Solen foil), SIC safco (paper in oil) and other paper in oil caps that are a bit expensive (Mundorf Suprême Silver/Oil, Jensen, Audyn Cap Fine First )
And have you heard of Siemens MKV B25839 and B25834? They seem to be excellent (http://www.audioasylum.com/forums/HU...ges/19889.html ).
At the moment I hesitate mainly between Obbligato and AudynCap Plus (I will probably buy both to compare).
By the way, which value do you advise me? 2/2.2µF or more?

C18/19: The TANK cap. My only gripe with the kit. I wish Jan had put two caps here for left/right. Using only one doesn't help crosstalk. In this place you need a fast cap, one that has low ESR at 1MHz and above. The job of this cap is to supply power to the switching transistors. The bigger and better the cap at this point, the better the amp will sound. The kit has various brands for this cap. I like to use a Panasonic FM 1800uF/25V. The FM series is very good at cleaning up the large amount of high frequency noise that this switching amp generates.

If you can squeeze a larger cap in here, it will help. I worked on a Trends TA-10 that used 2x2200uF for the tank caps and it was great. Really helps dynamics and bass. In my Octopus Amps I connected 1 or 2 10000uF stiffener caps in parallel with C18/19. Nichicon Gold Tune was my favorite here.

I will buy a Panasonic FM (easy to find even in France). 1800µF is the maximum value in 25V but does it fit the board? I wanted to add a stiffener cap too but I can't find Nichicon Gold Tune. Do you have other brands/series to advise? And would it be useful to put a small value cap in parallel of C18/19 to reduce ESR?
Concerning the stiffener cap : is it a problem to run a small cable from the PCB to the cap (because I won't put it on the board)? It risks raising impedence and perhaps to be like a little antenna that will catch perturbations.
In order my PCB to fit in the case I think I will do it for C18/19, C99 and the stiffener cap (I've got just 4cm-1.587" height).
Perhaps will it be OK with shielded cable .

C2 Used to decouple the internal 5+ generated inside the chip. You might try a very small value cap in parallel here to help decouple the highest frequency noise. Tripath does not call for it, but it’s worth a try. Something like 0.1uF.

Do you mean a ceramic or a film one?

For other modifications : do you think it's worth replacing all the little elctrolytic caps (that are originally Panasonic FC except C2) by Panasonic FM?

Thanks

[Benoit76]

Sorry the maximum in 25V for the Panasonic FM is 2200µF (with a 12.5mm diameter, and you can find 2700µF with 16mm diameter).
So I will choose the 2200µF (can't find the 1800).

[Pano]

Salut encore!

I do like the Obbligato caps very much, and they are not expensive for a premium cap. The copper tube comes in 2.2uF and the paper in oil (boite noire) comes in 2uF. They are both very nice. The PIO is smoother and more detailed in the midrange, but it's very close.

If you can find SIC/SAFCO paper in oil, they are a great cap, one of the best. Big, tho.

I have often used the Panasonic FM 2200uF for C18/19. Good choice. And this cap is already decoupled by C6/C7.

As for the stiffener cap, I don't know what you can find in France. Years ago we used to use ITT brand in the Hiraga 20W Class-A. Huge caps! In England some are using the Aerovox brand for stiffener with good results.
Elna Cerafine or any low ESR type will work.

Don't worry about the leads to the stiffener; just make them short and fat. Mount the stiffener beside the board. I did not find that decoupling with small caps helped at all. Maybe because there is already C18/19 and C17/C6 on the PCB.

For the 0.1uF any small film cap should do. Or ceramic. It's just to drain off some noise.

No need to replace the little FC caps with FM. The FC caps are very good.

I hope that helps. Cap away, mon ami!

[Benoit76]

Thanks for this answer.

I will buy an Obbligato PIO (and they are even less expensive than the copper tube ones)

A last question
My problem is that because of the place in my case I can't mount the biggest caps directly on the board. Is there a problem in putting some wire between the PCB and the cap?

thanks

[Peteruk]

On my Amp4, I'm using Jensen Copper Foil PIO for the input caps. Not cheap, but the same as the acclaimed Red Wine Sig 30.

For the output caps, I changed all the Polyester caps into Wima MKP2 Polypropylene. Jan wasn't sure how much difference this would make, but the cost was small so I tried it anyway.

You might also want to consider changing the inductors, as they're supposedly the most inlufential part of the Tripath amp. I'm using cotton-insulated silver on Metglas anamorphous cores.

As for positioning, some of the new larger components I can fit on the underside of the PCB (I figure there would be no problem doing this), while others, such as the Jensens, will have to be off the board.

I would like to know though, if anyone can help out, whether there are any of these 'tank caps' (like the C1819) on the amp4. I'm thinking perhaps the C102, C103, C1000 and C1001?

Good luck!

Peter

[sharpi31]

last night I added a 0.1uf+1ohm snubber across my offboard capacitor bank (5x 470uf sikorel).

Result: better focus and clarity from top to bottom, also the amp seems less confused with busier passages of music.

Maybe worth a try?....

Pano: thanks for your feedback. I've modded several sonic impacts and used panasonic fm & fc, sikorel & black gate in the PSU. I've also tried loads of input coupling caps (pio, teflon, BG etc.). I always liked the BGs with sonic impacts as the fullness, warmth and lack of high frequency hash (probably the same influence that makes them sound dull and lifeless to you!) nicely tamed the over-bright and over-strident sonic impact. It's very possible the amp6 doesn't need this added warmth, but the amp sounds good to me. I will take your advice and try a full panasonic fm loaded version for comparison.

I know a gainclone is a very different beast from t-amp, but I have always preferred BG gainclones over panasonic fm..... Different situation (noise frequencies and level, current requirements) so can't draw conclusions....

I have had great success combining teflon coupling caps with BG psu caps - the teflon speed and edge definition seem to blend well with the resonant warmth of the BGs.

[Benoit76]

thank you for all these advice. I may try a Blackgate version another time when I have some.

- What do you think of the Panasonic TS-HA series for the stiffener caps? It's one of the only I can find. http://www.farnell.com/datasheets/76113.pdf
is 10 000µF a good value or I should put a bit more

- About off board components : is it a problem and should I use shielded wire?