Gainclone heaven ?

[GerardA]

Hi Bigear and Paul,
On DIYaudio.com there is a lot of knowledge about the gainclones. But if you really want to know it's easy to build a gainclone and interchange the chips because mostly the're build on very small printboards.
But I think the real merit will be heard with all of them.
Since it is a clone of a design by 47-labs the components will not be the real gamebreaker. 47-labs uses some cheap components that can easily be bettered but that's the fun part of DIY.
And of course the power supply is very important!

[Scroobius]

The final amplifier layout with a change to the grounding arrangements hum is now down at very low levels http://www.phasure.com/index.php?topic=1844.msg18856#msg18856 and the heat sinks have been bolted to the case. Well maybe that was not strictly necessary but it was easy to do.

 

[GerardA]

Well I won't show such a beautifull amp, but the sound is amazing! I replaced my Hypex UCD180 and Stoetkit 300B with double chinese Gainclones and it is really an improvement!
Thanks for the tip!
It's like the music fits in the environment like a picture photoshopped into another picture without seeing where one starts and the other stops.

[PeterSt]

Congratulations Gerard !

[Scroobius]

Nice one Gerard and welcome to the club!!

Scroobs

[Bigear]

Hi Gerard,

did you get them from ebay?

Best,
   Quint

[GerardA]

Hi Quint,

Yes the're from ebay, including the powersupply which I did not use yet.
Just replaced the old Hypex amps with the new amplifierboard and connected the wires. Added a second one in the metal box and screwed it to the side for cooling. Really simple!

Later I'll put them in a small box on the back of the speakers to save a lot of space.
BTW. No hum at all.

[Nick]

Well I won't show such a beautifull amp, but the sound is amazing! I replaced my Hypex UCD180 and Stoetkit 300B with double chinese Gainclones and it is really an improvement!
Thanks for the tip!
It's like the music fits in the environment like a picture photoshopped into another picture without seeing where one starts and the other stops.

Gerard hi,

That's great congratulations ! That is now three of us with 300b SETs who have moved over now. Not that I have anything at all against 300b sets, but its amazing when you think of the relative cost of the gainclone amps and how they can sound driving suitable speakers.

KR,

Nick.

[Nick]

I have been considering changing my Gainclone amps and thought that I would post the idea.


To recap first, the amp is a bi amp Gainclone setup with options of direct input or volume control via TVCs. A further point is that the bass channel of my speaker system is active so  the system is tri-amped, the main point is that there is no bass power load on the gainclones.


The aim would be to take the gainclones off the mains and improve the power supply to the amp by using battery power. The hope would be to benefit from the air, transparency and natural tone of battery power, but to ensure that nothing is lost in terms of speed substance and dynamic slam.


I am still researching the exact approach (surprisingly I cannot find many posts talking about this) but the idea looks like this:


Batteries to give +- 19.2v rails, currently the amps mains supply's are running at 28v but with 103db sensitivity speaker I think 19.2v could give enough headroom. Not sure if the voltage drop could impact sound elsewhere though ?


Batteries will defiantly be LiFePo4 and most likely A123 brand, these things are fantastic things. Massive current delivery, superb transient current delivery and very, very quiet form a noise point of view.


I would like about 100 hours turned on with no music playing and about 20 hours playing at normal listening levels (quite loud :-) ). Also important is the ability to swop between battery and mains playback.


The main issue right now is finding a battery management system that will help me mange the batteries. LiFePo4's need clever and careful charging. I am prepared to have four separate BMSs in the case one for each battery /PSU rail. They will need to be capable of managing  a 19.2v (6 cell) 5.2Ah battery. The charge cycle on the BMS has to start automatically (eg I want to throw a play/charge switch and have charging start automatically.


No parts have has been bought yet, if it goes ahead it will be a winter project, it's still just an interesting option but I just have a feeling it might give some very good results.


If anyone has any thoughts and in particularly how to set up the BMS and where to get one that would be great.


Cheers,

Nick.

[PeterSt]

Hey Nick,

Before you dive into the obvious hussle of charging those battery packs, just know that my own GC's do not show any additional noise but the 21 or so dB gain which amplifies the input noise with exactly that. This doesn't necessarily count for your GC's, and all I want to say is : it can be done like this and normal mains power.
Well, you know my thinking.

Peter (not wanting to destroy your winter project !)

[Nick]

Peter hi,

Thanks for the information about the input and output noise values. A great amp performance even with mains 

I was thinking that given the low smoothing PSU capacitance used by gainclones, as the power consumption goes up that mains noise may start to rise. I know power supply noise rejection is very good but there must be a limit to what 1000uf or so of psu smoothing can do. There is also quite a lot out there about transformer size improving / regulated supplies improving aspects of the sound.

One question about the noise measurement, did you look at input / output noise with the amps at a reasonable working load ?

Best Nick,

Ps still searching for a practical charging solution and not that easy....

[PeterSt]

Well Nick, you got me thinking afterall ... (ok, that happens more often )

Of course I tested the lot "under signal", and it is this situation I talked about before (though I don't where that was) : all what is added is a small 3rd harmonic, and further it is an exact copy of the DAC what I see (FFT wise). The difference is the gain (21dB in my case). However ...

What I did not incorporate in this little story (and didn't think about yesterday either), is that the sheer connecting of the amp to the mains adds noise to the signal, just because "noise" creeps in by other paths. So, this is not exactly mains noise, but paths being created along which the noise travels from somewhere else. In my (great) example it is always that 380V PWM controlled pump motor (heating system). And, although very well under control (better than -100dB) *that* "noise" sure becomes audible just at connecting the amp to the mains.
To keep in mind : this noise is hammering against the NOS1 just the same, but as a self contained device under my complete control, I was able to 100% reject it from there. Not so with the amps, or I'd have to rebuild them from scratch. But for example, if I, in my current situation, could connect the amps to PE, that pump noise easily adds a 20dB of its frequency (which is at 17.8KHz).

So, it would be fair to say that indeed a battery feed will help ...
Or not, because the inherent noise can't go anywhere.
As usual, this is not so easy.

Anyway, for sonic performance you also have to wonder - in advance I mean. Already with the NOS1 experiments it was clear that battery feed would not go without a plunge of caps. No power in the sound otherwise. Dead. Lifeless. And this is the few mA of a DAC !! (ok, 200+ mA).

You could also do some nice math on what happens with this pile of capacitance added (assumed it is necessary indeed), and what happens after switching on the amps. Pop goes the weezle and the batteries might be half empty instantly ...

Maybe you'd be better off with putting two 12V car batteries in series, but don't forget those caps.
Notice that this it is not uncommon of course to put forward car batteries, but what might be less common is the reason why to do it. Not because "hey it should be better", but because of not creating ground paths, plus those caps could be a new thing. But never forget : you can't get rid of inherent noise either, unless via the signal path (interlinks).

Peter

[GerardA]

Hi Nick,

I read in DIYaudio.com that the higher the suplly voltage the more dynamic they sound. Think Peter Daniels uses 2x22V -> 2x32V to get a relaxed comfortable sound but people who prefer more action can go till 2x28V -> 2x38V max. (trafo AC/ rectified DC). So that's a lot of batteries!
If it's working out big time then I'll try it too, but not for now!
(Already have a car battery for my single tube preamp, if I forget to turn it off and charge it the battery is dead....)

BTW, for midd/high I shorted the inputcap since there is one already in the speaker and the preamp. So only one resiator and the chip.

@Gerard: These are the ones I bought, but directly from China. It seems now they are in stock in the UK, so that makes it even more easy. http://www.ebay.nl/itm/LM3886-Hi-End-AMP-Amplifier-DIY-KIT-68W-component-SET-/260836152041?pt=UK_AudioTVElectronics_HomeAudioHiFi_Amplifiers&hash=item3cbb0bd2e9

You could also try the Peter Daniels made gainclone, should even sound better but more euros, and not pre-built I think.
(See DIYaudio.com chipamps section)

[Flecko]

(21dB in my case).

Is the gain defined by the desing or by the chip of the chipamp? I am also looking for a low gain amplifier to reduce noise for high a efficiency speaker setup.
Greetings
Adrian

[Scroobius]

Hi Adrian - the gain is defined by the value of two resistors Rf and R3 in Peter Daniels kit and it will be similar in yours I am sure. You can change the gain by selecting different values for those resistors.

P