2 cnannels for less
Cheers ,
Rens
Zoe_Tsang sells a pair for 50 A$ on the bay and they are good ! I can tell ,using them for more then a year now .
Cheers ,
Rens
And altronics is ****. I ordered a class AB 250 watt amp to actually replace my sub amp that blew up.
In january.
Then silicon chip came out with the CLASSiC-D. Sold!
In january.
Then silicon chip came out with the CLASSiC-D. Sold!
Watch out for high mains voltage!
Have just completed a stereo amplifier based on the Silicon Chip Classic-D boards. However, the +40V 0V -40V transformer that is recommended in the Silicon Chip articles on the Classic-D has proven to be a tad to high if your mains voltage is up a bit. I measured a mains voltage of 251V, and this was producing DC voltages of +62V -62V -- too high for the overvoltage protection in the amplifier. A mains voltage of 251V is still within the aUSTRALIAN legal limits of 230V +10% -6%.
When switched on the Protect LED stayed on and the protection relay remained off. However, when switched off the dropping voltage from the big capacitor bank dropped low enough for the relay to switch on and the music to sound for all of one or two seconds before the voltage dropped too low for the low V protection circuit.
The solution was to remove about 10 windings from the transformer secondaries. In fear and trepidation I unwound the outer insulation from the transformer, and proceeded to unwind the secondary windings. Much to my relief, this proved to be quite straigtforward, and I was able to relace the outer clear plastic insulation without much trouble. The result was not pretty, but it worked!
Have just completed a stereo amplifier based on the Silicon Chip Classic-D boards. However, the +40V 0V -40V transformer that is recommended in the Silicon Chip articles on the Classic-D has proven to be a tad to high if your mains voltage is up a bit. I measured a mains voltage of 251V, and this was producing DC voltages of +62V -62V -- too high for the overvoltage protection in the amplifier. A mains voltage of 251V is still within the aUSTRALIAN legal limits of 230V +10% -6%.
When switched on the Protect LED stayed on and the protection relay remained off. However, when switched off the dropping voltage from the big capacitor bank dropped low enough for the relay to switch on and the music to sound for all of one or two seconds before the voltage dropped too low for the low V protection circuit.
The solution was to remove about 10 windings from the transformer secondaries. In fear and trepidation I unwound the outer insulation from the transformer, and proceeded to unwind the secondary windings. Much to my relief, this proved to be quite straigtforward, and I was able to relace the outer clear plastic insulation without much trouble. The result was not pretty, but it worked!
Have they changed the output filter inductor to a higher current rated one?
Schematic shows 22uH 5A.
250W / 4R peaks at 11A.
Schematic shows 22uH 5A.
250W / 4R peaks at 11A.
No. The parts list has "INDUCTOR 22UH 5A ORO18 18x16x20mm". This is supposed to be a very linear inductor, as it comes after the point in the circuit that is tapped for error feedback into the op amplifier. The only markings on the inductor are "220 Yy". It seems to be a substitution of the original part, which was "EL3363".
The fuses on the power inputs are only 5 Amps. Not sure if that is relevant.
Dug the answer to your question is probably yes and no. I forgot to mention that the holes for the inductor on the Classic-D PC board do not match the inductor supplied. It was necessary to drill the two smaller holes to the same diameter as the 2 larger holes. This shows that the suppied inductor (Jaycar Cat No. EL3364) is different to the original inductor (which was Jaycaqr Cat No. EL3363). Both appear to be 5 Amp inductors, though.
My speakers are 8 Ohms.
My speakers are 8 Ohms.
I have just finished building this beasty of an amp. Damn its amazing!!!
Its in subwoofer mode only for me, but wow. Its tight, clean and amazingly clear. Very impressed!
My rails sit at 57 volts with no load but i am using two bridges.
Its in subwoofer mode only for me, but wow. Its tight, clean and amazingly clear. Very impressed!
My rails sit at 57 volts with no load but i am using two bridges.
An externally hosted image should be here but it was not working when we last tested it.
Impressive image, I see you double up on the toroidal transformers as well.
The four PCB’s stacked together, I assume are soft starters?
What size coil are you use on the filter caps?
The four PCB’s stacked together, I assume are soft starters?
What size coil are you use on the filter caps?
The 4 are actually 5, and thats the LM3875 gainclones that drive my satellites. Good old analog tech 🙂
The twin toroids drive the array of gainclones.
Those filter cap toroids are 220uh. Primarily just to prevent any interference from the class D amp from doing anything nasty anywhere. Do a great job of removing rectifier noise too!
The twin toroids drive the array of gainclones.
Those filter cap toroids are 220uh. Primarily just to prevent any interference from the class D amp from doing anything nasty anywhere. Do a great job of removing rectifier noise too!
Here is my Classic-D stereo amplifier in its current incarnation. It's the first amplifier I have ever built, so please forgive any amaterish manifestations. I intend to encase it in cedar or spotted gum, with a perforated perspex top. There are two big holes in the base under the heat sinks, that I plan to cover with screen-door mesh. The aluminium chassis was made from an old oven tray!
I would welcome any advice regarding the earthing of the channel boards. At present they are earthed via the 0V wire from the power supply, as well as from the chassis to the ground pins near the heat sinks. If I place an ear close to the midrange speakers I can just hear a bit of quiescent 50Hz buzz, but it's vey unobtrusive. The jumpers near the RCA connects are both off, so the RCA shields are now connected to ground via a 10 Ohm resistor However, this seems to make no difference.
It's a different matter if I connect an old Sony Discman to the RCA inuts. The 50Hz buzz becomes very pronounced, but then this Discaman will now only run off a battery eliminator that probably has no ripple supression. No buzz off my iPad Mini, though! I can see I need to upgrade my CD player -- perhaps even build the Silicon Chip "Classic DAC".
I would welcome any advice regarding the earthing of the channel boards. At present they are earthed via the 0V wire from the power supply, as well as from the chassis to the ground pins near the heat sinks. If I place an ear close to the midrange speakers I can just hear a bit of quiescent 50Hz buzz, but it's vey unobtrusive. The jumpers near the RCA connects are both off, so the RCA shields are now connected to ground via a 10 Ohm resistor However, this seems to make no difference.
It's a different matter if I connect an old Sony Discman to the RCA inuts. The 50Hz buzz becomes very pronounced, but then this Discaman will now only run off a battery eliminator that probably has no ripple supression. No buzz off my iPad Mini, though! I can see I need to upgrade my CD player -- perhaps even build the Silicon Chip "Classic DAC".
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The other thing to watch, if you used the amp PSU kit from jaycar, is your main rails, and your AC mains voltage.
The caps are rated at 63 volts, and your rails can get nearly that high with a high input voltage.
Personal experience has a bank of those particular suntan caps start to swell with my old class AB sub amp that ran of the same voltage, and that was with using TWO bridge rectifiers, so i would imagine just using one would increase the voltage a bit more.
I ended up using the suntan 10000uf 80v caps in my class D stage. Just worth it for the extra reliablity, and i have 2 caps per rail, giving me a total of 40000uf of cap in the bank, with 20000 uf before and after the inductors.
I will be getting myself some ferrite beads too, the class D amp runs at 500khz, so is prone to throwing a bit of EMI out.
The caps are rated at 63 volts, and your rails can get nearly that high with a high input voltage.
Personal experience has a bank of those particular suntan caps start to swell with my old class AB sub amp that ran of the same voltage, and that was with using TWO bridge rectifiers, so i would imagine just using one would increase the voltage a bit more.
I ended up using the suntan 10000uf 80v caps in my class D stage. Just worth it for the extra reliablity, and i have 2 caps per rail, giving me a total of 40000uf of cap in the bank, with 20000 uf before and after the inductors.
I will be getting myself some ferrite beads too, the class D amp runs at 500khz, so is prone to throwing a bit of EMI out.
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Thanks for that, Rainwulf. I'll keep an eye on the power capacitors and relace them if needed. For the time being my Classic D amplifier will not be used all that often, although I'm tempted to lug it upstairs and insert it into my home theatre setup! Since removing about 10 windings off the secondaries on my torroid, rhe DC rails have been at +/-55V. The ferrite beads sound like a good idea.
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