[devinkato]

What are you going to power it with? It has basically no filtration. Sure the Power cap is very low ESR, but unlike big giants in AB world, there is no filtration, or RF rejection of any sort.

Not determined yet.  Obvious choices are the normal switching power supplies (Meanwell), or a battery.  I'm curious, what are your thoughts?  I'm trying to keep it as small as possible.

I've been doing my testing with a regulated 3amp 12v power supply, and the results have been stellar.  I also tested with a larger 50amp 12v power supply and I couldn't hear a difference (post mods).

I've said it before, but thanks again for all your advice and guidance re: this amp!  I'm having tons of fun with it.

[Folsom]

I'm all about linear  .

3A is plenty.

But you should clean up power with some form of noise control. Can you get Teddy regs in 3a?

I just made a mock PSU with MSR860's and a Coilcraft CMC with 1uf X2 cap on transformer secondaries. My SMPS can't compete. In fact I intend to play around a bit with it, considering different voltage regulators and such.

You can also make boxes with linear that act as a better shield.

[Danny Richie]

Just now really taking a look at this amp. The lit says it is a dual bridge amplifier. Is this implying that it can be bridged?

[Occam]

Just now really taking a look at this amp. The lit says it is a dual bridge amplifier. Is this implying that it can be bridged?

No, it is saying that it only runs as a bridged amp. The stereo module has 4 amplifiers, 2 for each channel, with the 2 amps for each channel running antiphase and bridged.

[Danny Richie]

No, it is saying that it only runs as a bridged amp. The stereo module has 4 amplifiers, 2 for each channel, with the 2 amps for each channel running antiphase and bridged.

Ah, I see that now.

[devinkato]

I'm all about linear  .

3A is plenty.

But you should clean up power with some form of noise control. Can you get Teddy regs in 3a?

I just made a mock PSU with MSR860's and a Coilcraft CMC with 1uf X2 cap on transformer secondaries. My SMPS can't compete. In fact I intend to play around a bit with it, considering different voltage regulators and such.

You can also make boxes with linear that act as a better shield.

Woah - I'm just a beginner when it comes to PSUs, take it easy on me!    Much of that went WOOSH over my head.

So you say linear PSUs are much better than SMPS.  Gotcha - Where can I start researching/purchasing linear PSUs?

As far as noise control - In another thread, you mentioned that a mini capacitor bank could help with noise control, is that what you're referring to here, or an actual regulator like the Teddy Pardo product (http://www.teddypardo.com/resources/superteddyreg.html)?

[Folsom]

Teddies do work for some noise.

You want low ESR caps on 7297, or multiple ones, to reduce some noise. Basically everytime you double how many caps you use, you half the ESR so the capacitors look like a better conductor for noise compared to say the chip and your speakers.

You can use capacitors on AC side but it's another ball game. For a beginer, well, caution is adviced.

Linear PSU usually consists of a transformer to bring 115v from wall down to something else. But it's still AC until it goes to the diodes, where rectification occurs. Then you have something close to DC, and capacitors fill in the rest to have DC. I know it's a bunch of stuff to know... You just have to look it up and dig in. Someone else will have to link a website for you, I'm just on iphone atm. Diagrams and what not will be helpful, as they'll help you get it faster than me typing a small book of only text.

[gychang]

I just completed the mods - Holy moley, night and day difference.

I ordered the 3 parts as recomended here and plan to use my 12V2A, wallwart.  What kind of power supply did u use?

[Danny Richie]

Anyone tried paralleling the inputs and outputs to use both channels together making it a mono amp?

[Folsom]

Perhaps with a preamp that has some gain this would work. But I'm not certain the amplifier has any current deficiencies. I've had it hooked up to speakers that otherwise usually have a 250w Bryston (AB, constant current), and with a really cheap power supply was very close. I haven't re-tested it with a linear, but I suspect it will hold it's own maybe evenly until ear blistering volumes.

I'm not certain, but you may need 1uf caps (or two 2.2uf caps using my configuration) on each channel to retain frequency response, with this parallel layout.

[Danny Richie]

Perhaps with a preamp that has some gain this would work. But I'm not certain the amplifier has any current deficiencies. I've had it hooked up to speakers that otherwise usually have a 250w Bryston (AB, constant current), and with a really cheap power supply was very close. I haven't re-tested it with a linear, but I suspect it will hold it's own maybe evenly until ear blistering volumes.

I'm not certain, but you may need 1uf caps (or two 2.2uf caps using my configuration) on each channel to retain frequency response, with this parallel layout.

My thought is why not turn them into little mono-blocks. They are only $6 a piece. And there maybe something there to gain as well.

[Folsom]

Well it'd be nice to have the same power source not doing dealing with two channels. It might be just as smart to only use one channel. Sure it seems silly, but it'd work. As is this thing works on 87db speakers just fine.

I think alternatively you could just use one cap, .47uf, (or two 1uf) if you wire the channels together after it, instead of before, if you want to use both for sure. Then there wouldn't be any concern. (.22uf is too small, unless you want premature roll-off)

I'd be interested in building a sort of reference version, possibly.

[Danny Richie]

Yeah, my thoughts were that with both channels sharing one power supply cap that it might limit stereo separation.

My first thought was to just use one channel from each amp. Sure it seems wasteful, but it doesn't really cost anything.

Then I got to thinking about paralleling the two channels after a buddy suggested it. Output would be the same. Current capability would double. Damping factor would double. The input impedance will drop in half though. What was it to start with 47k ohms? Correct me if I'm wrong here.

I am not sure if I even want to use any coupling caps on the input. I have coupling caps on the output of my pre-amp.

And all of those cheesy connectors are going bye-bye too. I think those things are steel. 

[Folsom]

Input resistance is 25-30kohm. 12.5-15kohm is drivable, but not as good as would be preferred. I guess the whole situation makes this preamp/source dependent to not drop current by splitting and being able to drive it as the input resistance. What's your pre put out? You could always use some Lundel input transformers  .

Yes, you can skip the input capacitor if you know there's no DC on the line.

I haven't found any problem with stereo separation. The imaging is ridiculously good. But better is better! 

I sent you a PM about this and a few things, but it's best to not order these from China. I'm not even certain the tracings are copper given how solder doesn't stick to them as well as I'd like. Plus the chips are second rate, so getting two to match is much harder with these. It'd be better to order them from Mouser and just P2P, for one build anyways. Then again, I suppose you could have PCB made. Yes the cost starts to go up, but this little thing can certainly be worth it.

What kind of power supply you thinking Danny? This little guy has some timbre; it's interesting.

[Danny Richie]

Yes, I got your e-mail. Thank you.

My tube amp is a Dodd Audio. Mine has three outputs. Couple caps on two of them are Jupiter cap 3.3's by-pass by a .01uF Sonicap Platinum. On the third one it just uses a .047uF Sonicap Platinum to roll off the lows. I can drive tube mono-blocks and four servo amps off of it without issue.

My first listen was surprising. It definitely gave a lot up to my little mono-block tube amps, but then again I was using a cheap RCA to 1/8 plug that came from who knows what. And I was just using some cheap speaker cables since it had no binding posts or anyway to hook up any good cables. So I know there is a lot of improvement ahead from the get go and it wasn't that bad to begin with.

Right away I removed the pot and that was a nice improvement.

Oh, and I plugged it into the 100 amp hour Power Sonic batter that I run my tube amps with. So I have that part covered.

I was thinking this would make a really nice amp to burn things in with. It uses almost nothing for power consumption and it sounds pretty good to boot. And if I can make it sound even better with a little tweak or two then all the better.

[Folsom]

I'm still under the impression it can be anyone's main amp. You have some beautiful tube amps we've seen in pictures that I'm sure will be preferred, however.

If you still have the diode in, you got to get rid of that, and the film bypass cap on it! You really haven't scraped the ice on the windshield if all you've done is remove the pot  ; just removed the snow.

I actually prefer this things minimalist component layout, as it can out class more expensive amps that don't maintain the higher frequencies as well through the horde of components that some equipment happens to have (quality vs. watts and features, usually). But it comes at the cost of having to do all the work for noise rejection in the power area. Some would call it "crisis" design, but whatever.

[Danny Richie]

I'm still under the impression it can be anyone's main amp. You have some beautiful tube amps we've seen in pictures that I'm sure will be preferred, however.

I think for a lot of people it could. A real tricked out version of this thing might embarrass some high dollar amps. So long as you don't need a lot of power.

If you still have the diode in, you got to get rid of that, and the film bypass cap on it! You really haven't scraped the ice on the windshield if all you've done is remove the pot  ; just removed the snow.

Little yellow cap right over the diode? I thought you left that.

Yeah, I know there is a lot of improvement ahead. I just had to get a feel for it and see if it had potential. It clearly does. Now I am trying to figure out what all I might do to it.

I actually prefer this things minimalist component layout, as it can out class more expensive amps that don't maintain the higher frequencies as well through the horde of components that some equipment happens to have (quality vs. watts and features, usually). But it comes at the cost of having to do all the work for noise rejection in the power area. Some would call it "crisis" design, but whatever.

I like the minimalist approach as well. My Dodd pre-amp is along those same lines.

No worries here on the power supply. That big 100 amp hour battery is dead quiet. And it's cheaper than a decent power cable.

[Folsom]

My pictures show he little yellow cap because I thought it was an bypass to ground from a different point within the chip. You can do that easily on a 3875 and other chip amps, but on this one it's just bypass cap that causes ringing (you'll hear it not ringing when you pull it, no joke, and you can wiggle it off if you're feeling lazy). I edited to show the removal of that capacitor later. Sorry about that. Perhaps with the original junk capacitor it was helpful, but with a better one it's just a nuisance.

[Danny Richie]

My pictures show he little yellow cap because I thought it was an bypass to ground from a different point within the chip. You can do that easily on a 3875 and other chip amps, but on this one it's just bypass cap that causes ringing (you'll hear it not ringing when you pull it, no joke, and you can wiggle it off if you're feeling lazy). I edited to show the removal of that capacitor later. Sorry about that. Perhaps with the original junk capacitor it was helpful, but with a better one it's just a nuisance.

I just looked at it. Yeah, it just by-passes the main cap.

[dBe]

These amps have got to be one of "those" finds.

I talked to Danny this morning about all of the ins and outs of them and just ordered two of them.  What great low $$$ fun. 

In the past I have had great success using one channel of stereo amps.  Every time there was better sound and headroom.

Battery power is a no brainer when properly done.

Thanks for the tutorial and this thread. 

Dave