Beginner's Gainclone, HiFi LM1875, The Amplifier Board

Thanks, I'm a Nichicon KZ and Elna Silmic II believer.
Nichicon KZ, Nichicon FW and Panasonic FC are suitable for your solid state and chip amplifiers. The "ideal" varies per each amplifier, so I'm sure you'd want caps that are known good with LM1875 and LM4702. When researching this, do beware that caps were re-formulated after the ROHS initiative and contain a new environmentally friendly goo, and; therefore, old performance data does not apply to new production capacitor.

The K50 kit uses 220u amplifier board power caps, actual center-point figure is 330u, and for "laid back" we could use 470u.
I would guess to use the 270u Panasonic FC if the speakers need a clarity boost or the 470u if the speakers are forwards when driven by solid state amplifiers. Aligning for system symmetry means making choices that suit the given models of speakers. To avoid excess shipping charge I'd buy 2 pair 270u and 2 pair 470u and several different models of 100u and some 150u examples too; and, that way the money goes towards useful parts instead of the postman.
What's the 4.7uf used for?
Component selection for this is touchy. It is an audiophile power filtering to "uncongest" the midrange (by removing noise) so that loud playback can be more pleasant, with slightly higher resolution and slightly decreased blare. The Mallory Cornell SEK 250v 4.7u is good for this. Other alternatives include polyester speaker crossover caps in the range of 2u2 to 4u7, and RCR filters as well. I would suggest the known good model from Cornell because it is easy, it works and it is just a few cents. Because of publishing the measurements for proof, Cornell is the industry leader when it comes to power purpose caps, especially smoothing caps used for getting rid of noise.
Just arrived (no, didn't read the 12 pages of posts) but curious: Why do you add unnecessary output capacitors in series with the speaker?. Besides showing them as polarized in post #111. Wiring them in antiparallel will not turn them into bipolars. In post #114 you attribute no polarity to them, maybe hinting you'll use bipolars there. I wonder where you will find 1000uF bipolars but even more what's the perceived advantage of adding them there. Plus, as I said before, you don't need them, that split supply amp has 0V DC at the output. And a polarized electrolytic is not happy at all (as in exploding with a loud bang) with AC across its terminals.
Lausar has plans to use a quickly made chip amplifier to rock the house with costly, rare, classic speakers that were made for current drive, and he also has rails fuses and twin-smps split rail power, both of which may cause rail asymmetry hazards. Output caps prevent destruction of the irreplaceable speakers. Perfect.
And when the size is chosen well, the caps also facilitate some current drive slightly before roll-off and bass/headroom management suited to small amplifiers, so that rocking the house succeeds. A live test with my circa 1962 Pioneer coaxials worked nicely.

Single rail amplifiers commonly use polar caps at output and their output is the same AC audio as a split rail amp. Any cap durable enough for power supply use will also withstand output cap use. For the past several years, all of my amplifiers have output caps, no failures and no exceptions. THANK YOU for causing me to look at Mouser for the big bipolars. Antiparallel (for undistorted signal symmetry and zero treble distortion) will work just fine with radial Bi-polar caps too by using the pin length as an indicator. Bi-polar is more likely to survive a worst case accident. The Nichicon ES has a reputation for low loss and bass slam. I like this idea!
Aluminum Electrolytic Capacitors | Mouser
Really cool! Those big green Nichicon ES should work perfectly for his output caps. Thanks again! :D :D
AFAIK the Gainclone idea is to build a very simple very flat and clean "piece of wire with amplification" , and big electrolytics in series with the speaker do not exactly fulfill that task, at all.
A "gainclone" actually refers to a 47 labs "gaincard" clone with a National Semiconductor Overture chip. My apologies for having misused the term back in 2008. There's no gainclone on this thread. LM1875 isn't an Overture, doesn't have the spike system and doesn't have adequate protection. This thread has a chip amplifier, just like a discrete amp except for the rather flimsy miniature output devices of a chip. The failure mode is to output one full rail's worth of DC offset, so personally I find it quite responsible to use output caps as protection. . . or at the very least, that's an excellent excuse to install really rockin bass extension.
 
Last edited:
Another way to do output caps is series 2200u's (makes 1100u bipolar) or series 3300u's (makes 1650u bipolar). And then parallel those things for lower loss and the bigger capacitance value you want. You can do higher voltage large value bipolar caps this way. The method can usually survive worst case accidents. It is also popular for increasing bass slam of subwoofers.
 
My local has the LM1875 chips in stock for about $5 a pop... I am tempted to throw one of these together. Can the circuit at the beginning of the thread be made to run on batteries? Say a 12v? is there a circuit you would suggest?

As well, your input cap comment, I am assuming the value will dictate the bass roll off? If so, what cap value would net a 40hz roll off?

Is it safe to try this on a 6ohm speaker? I have a few, but one I know is 6ohms.
 
Dear mortron.
*If* you are forced to run on batteries, the "simple 5 pin chip" solution is the original one, which gave birth to all others, specifically designed for car radios and such: TDA2003
Download its datasheet and build the example shown there.
They even suggest a PCB.
With just 12V it will beat more modern, fancier amps, simply because it was optimized that way.
And it happily runs down to 2 ohms loads, all day long :D
Not too loud but, hey, you only have 12V available anyway.;)
 
My local has the LM1875 chips in stock for about $5 a pop... I am tempted to throw one of these together. Can the circuit at the beginning of the thread be made to run on batteries? Say a 12v? is there a circuit you would suggest? As well, your input cap comment, I am assuming the value will dictate the bass roll off? If so, what cap value would net a 40hz roll off? Is it safe to try this on a 6ohm speaker? I have a few, but one I know is 6ohms.
You might want to try the LM1875 datasheet's single rail schematic example. Or maybe not? Considering the low 12vdc power would have LM1875 at 4 watts max and clipping madly, let me suggest these alternatives: http://www.diyaudio.com/forums/chip-amps/158644-12v-dc-gainclone-3.html#post3260469
 
You might want to try the LM1875 datasheet's single rail schematic example. Or maybe not? Considering the low 12vdc power would have LM1875 at 4 watts max and clipping madly, let me suggest these alternatives: http://www.diyaudio.com/forums/chip-amps/158644-12v-dc-gainclone-3.html#post3260469

Thanks Daniel... I am looking over this list and its overwhelming. Is there one you would recommend to me that would sound nice? I am looking to keep it efficient, but am hoping to get about 15-25W per channel at least if possible.

Do you suggest simply building the circuit on the datasheet for whichever chip selected? Part of the reason I liked this one, was its simplicity and low cost. Thanks again.
 
am hoping to get about 15-25W per channel at least if possible.
Not enough voltage available, no matter what you use.
You *may* use a bridged power amp for 16W RMS into 4 ohms.
I commercially make portable Guitar amps, using either 2xTDA2003 bridged (in fact I have one of them on my bench right now, fed from a small 12V Alarm battery) or bridged TDA2005 which is the same, inside a single chip.
There are more modern ones, I mention these because I have built tons of them in the last 30 years (or more) and have all the extra stuff (PCBs, front panel sikscreens, transformers, etc.) already well worked out.
Plus, as the Brazilians say: "Não se mexe com time ganhador" = "You don't mess with a winning Team"
We're talking Football here ("Soccer" in USA)
 
Thanks Daniel... I am looking over this list and its overwhelming. Is there one you would recommend to me that would sound nice? I am looking to keep it efficient, but am hoping to get about 15-25W per channel at least if possible.
That voltage is too low, so that makes a complication.
12v power and 15 or more watts to 8 ohm speaker?
Maybe these:
TDA1560Q
TDA1562Q
About 8 watts to 8 ohms Class AB, but instead of clipping, they proceed to make Much more power in Class H mode.
That's about as easy as it gets, considering the lack of voltage.
 
That voltage is too low, so that makes a complication.
12v power and 15 or more watts to 8 ohm speaker?
Maybe these:
TDA1560Q
TDA1562Q
About 8 watts to 8 ohms Class AB, but instead of clipping, they proceed to make Much more power in Class H mode.
That's about as easy as it gets, considering the lack of voltage.

Ok, I actually take it back... I forget that there isn't full use of the watts in my amps now, as I pad the inputs... I'm a dummy. I guess most music is only using a few watts constant, the rest is for peaks?

So at 12v, is it reasonable to expect 5-10 watts? If so, is there a chip that is well suited? I will go through the list and start reading more.

As for circuits, is the one on the data sheet the recommended build?
 
Yes, check the options.
And datasheet examples, specially in chipamps, work quite well.
Can be improved, of course (the whole of DIYaudio is specifically dedicated to such tasks ;) ), but are not a bad point to start, at all.
Just curious about the 12V limitation: is is a car/boat installation or similar?
 
"off the grid"
Mmmmhhh, interesting.
In that case squeeze every single drop of energy.
A single TDA2003, run straight from a 12V SLA Battery, provides enough power to enjoy music, with minimal requirements.
No, not *loud* but enjoyable, about what a TV plugged into a Hi Fi cabinet can give.
Same amp bridged, provides 16W into 4 ohms or around 10W into 8, not bad.
I suggest you build one, get a kit somewhere, and actually test it.
You may be surprised.
And if not enough, I think you'll need to get some car type amp, with built in switching converters to get higher rail voltages, because with only 12V, the limits are those stated earlier.
But first build a simple kit and try it.
There are more modern chips, even Class D, of course. But 12V is 12V.
 
Class D would be more efficient, right? You can get a $15 amp board assembled and delivered based on TA2024 that would work. They sound decent, play reasonably high volumes, run off of almost no power. I think mine is running on a pretty minimal 12v wallwart originally from a wireless router, driving my Mark Audio full range bookshelf speakers (6 ohms, I believe). Search ebay for 'ta2024' and Google search for 'tripath sla battery' for more context.
 
To have the best of both, you can use Bi-Amp this way:
TA2024 to run a high efficiency, 91db or better woofer, and a passive crossover.
Made for portable Class AB chip to run the tweeter.
In this case, when the bass amp clips, the tweeter does not.

When your battery runs down, you'll get some crunchy bass, but your treble will stay clean.
 
Last edited:
Excellent idea.
Couldn'ty agree more. ;)
So much so, that I have been using it in a ton or my "Callejero" (Street Musician) Amps:
Bridged TDA2005 into an 8" or 10" woofer plus biamped TDA2003 into a 4 ohm LeSon Tweeter.:D
Loud and clean !!:p
The cabinet includes an SLA 12V 7AH battery and the intelligent charger:
730279368_0f6b0bbff9_z.jpg

730279342_5b605a7758_z.jpg

The unmarked knob between both channels is an extra volume/attenuator for the high frequency amp.
The LeSon tweeter is very loud and can be overpowering.
 
Hello Dan
I have been reading for a while now about the LM1875s and they sound as a nice prospect for my next project.
My concern is that my speakers (Montana EP Signature) are 4ohms and 92db (based on the EPS2 specs that I expect to be similar).
I was thinking to remove the bridges (which I would expect to make them easier to drive?) and biamp them (4 monos for 2 speakers).
Do you have any suggestions?
Should I look for a parallel arrangement instead?
Thanks in advance