A carbon filament light bulb runs so hot it emits light.
It outlasts even tungsten filament bulbs, not by a few percent, but by a decade or more.
Carbon is used in arc lamps and in DIY home brazer kits because it does not melt.
It outlasts even tungsten filament bulbs, not by a few percent, but by a decade or more.
Carbon is used in arc lamps and in DIY home brazer kits because it does not melt.
I've decided to use a Jim's audio board instead of buying the yuanjing pre-built one. It's going together well but I'm missing a few parts like the LM3886 and the 8.5mm pitch terminal blocks for the speakers and transformer which I can not seem to find anywhere.
Is this a suitable transformer for this amp?
Buy Toroid Transformers Toroidal transformer,225VA 2x30V o/p Nuvotem 0225P1-2-030 online from RS for next day delivery.
picture of amp here.
Is this a suitable transformer for this amp?
Buy Toroid Transformers Toroidal transformer,225VA 2x30V o/p Nuvotem 0225P1-2-030 online from RS for next day delivery.
picture of amp here.
An externally hosted image should be here but it was not working when we last tested it.
30-0-30 is pushing it, that'll give you 42V rails when rectified, I'd go for something around 25-0-25.
Just for you to know, I did buy this kit, based on Mauro Penasa's design, in its last parts version, and I have been using it for seven months now.
Classic lines LM3886 dual-channel +LM318 AMP/ DIY | eBay
I must say I was worried, both about the parts quality and mainly about the audio quality. Audio quality is excellent, so I would recommend it as a real Mauro Penasa clone.
Classic lines LM3886 dual-channel +LM318 AMP/ DIY | eBay
I must say I was worried, both about the parts quality and mainly about the audio quality. Audio quality is excellent, so I would recommend it as a real Mauro Penasa clone.
Thanks for your reply I was thinking the same thing too did not think an extra 2 volts would matter that much. Its says 28v GND 28v on the bottom of the board I'm guessing this must be a absolute maximum. It may run a bit cooler on 25v.
Haz,
are you stating AC voltage or DC voltage?
The 3886 can operate at <=42Vdc-0-42Vdc or stated as +-42Vdc or 84Vdc
This allows one to use upto 28Vac-0-28Vac transformer.
All transformers of lower voltage are OK, if using 8ohms or higher speaker impedance.
are you stating AC voltage or DC voltage?
The 3886 can operate at <=42Vdc-0-42Vdc or stated as +-42Vdc or 84Vdc
This allows one to use upto 28Vac-0-28Vac transformer.
All transformers of lower voltage are OK, if using 8ohms or higher speaker impedance.
Look at the 3886 datasheet and app notes.
You will find, when you follow the design process, that 230:28+28Vac gives too high a supply voltage for 6ohms speaker load.
You will find, when you follow the design process, that 230:28+28Vac gives too high a supply voltage for 6ohms speaker load.
Hi, ive completed the amp and it sounds very good!! no complains at all really. The bass is a little flat and dull but I'm only using a 80 VA 2 x 25 transformer with 4700uf filter caps so that could be why. But I'm only using my test speaker not my main ones that have more bass but don't trust the amp enough to use them without further testing!!
The amp is also very quiet when I turn the input all the way up only very minor hiss and hum can be herd.
Looks kinda funny with that huge heatsink but that is for only for testing purposes. My drill tap bit broke when trying to tap the second hole that why there is only one screw in the there.
I'm going to buy a larger transformer maybe a 320VA I think it will benefit from it, and may upgrade the filter caps to 10,000uf . Ive already tried replacing one of the NE5532 with the Burr-brown op-amp from my cmoy project. But its too soon to see if it makes a different. But ive only listened to it at very low volumes as its late at night. My first impression is that it has.
The amp is also very quiet when I turn the input all the way up only very minor hiss and hum can be herd.
Looks kinda funny with that huge heatsink but that is for only for testing purposes. My drill tap bit broke when trying to tap the second hole that why there is only one screw in the there.
I'm going to buy a larger transformer maybe a 320VA I think it will benefit from it, and may upgrade the filter caps to 10,000uf . Ive already tried replacing one of the NE5532 with the Burr-brown op-amp from my cmoy project. But its too soon to see if it makes a different. But ive only listened to it at very low volumes as its late at night. My first impression is that it has.
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Is it possible to see a schematic for that amp? Perhaps we could hint why bass is flat and dull.
I do remember when we carried out some tests with a friend with two 3886 amps, one with 4700uF on each leg in the supply and the other with 1000uF. The one with less capacitance had better bass detailing than the larger one. The highs and mids were also better. The other one seemed to have more bass.
The original gainclone seemed to need a zobel if you used larger capacitors in order to get more bass and still have a better bass, but that also seemed a matter of taste.
Maybe that's what's happening on your case.
It might also be a question of letting the parts burn in.
I do remember when we carried out some tests with a friend with two 3886 amps, one with 4700uF on each leg in the supply and the other with 1000uF. The one with less capacitance had better bass detailing than the larger one. The highs and mids were also better. The other one seemed to have more bass.
The original gainclone seemed to need a zobel if you used larger capacitors in order to get more bass and still have a better bass, but that also seemed a matter of taste.
Maybe that's what's happening on your case.
It might also be a question of letting the parts burn in.
Here's the schematic for the amp. You don't think the lack of bass is due to the small power supply used? I have some Nichicon 10000uf caps I got the other day so I could try them to maybe increase the bass. The highs and mids on the amp at normal listening volumes are too much. I could not listen to it that long.
Hi Haz, Have you contacted Stanton Tin at Jim's Audio directly? He really knows what he is doing and makes himself fully available for product support for all customers. Try sending an email if you haven't done so already.
Yeah that guy really knows his stuff!! I've contact him many times, I don't like to nag him too much. I like to post here for different opinions, suggestions and to share ideas.
From what I see, there shouldn't be any major problem with the amp.
You won't get more bass quality just by adding more capacitors. You already seem to have 10000uF/63v on the supply, though the schematic does not show the terminals for the power amp, which should be before the 22K resistors. Can you check on that?
Some critical points, that might affect audio quality:
1) Signal path capacitors. Those 2.2uF caps should be film types, though I think those are the large Russian types on your board, right?
2) Unnecessary buffer. The second stage of the preamp is unnecessary and should be bypassed, with a wire or using the 1K resistor to go from pin 1 to pin 7.
3) Feedback capacitors. The NFB caps on the 5532 (10uF/25v) and 3886 (22uF/50v) should be good quality types.
4) LP caps. Check that those 100pF caps in parallel with 22K are good quality types. Polystyrene or silver mica.
Look for CFM suggestions for using a zobel on the supply.
You won't get more bass quality just by adding more capacitors. You already seem to have 10000uF/63v on the supply, though the schematic does not show the terminals for the power amp, which should be before the 22K resistors. Can you check on that?
Some critical points, that might affect audio quality:
1) Signal path capacitors. Those 2.2uF caps should be film types, though I think those are the large Russian types on your board, right?
2) Unnecessary buffer. The second stage of the preamp is unnecessary and should be bypassed, with a wire or using the 1K resistor to go from pin 1 to pin 7.
3) Feedback capacitors. The NFB caps on the 5532 (10uF/25v) and 3886 (22uF/50v) should be good quality types.
4) LP caps. Check that those 100pF caps in parallel with 22K are good quality types. Polystyrene or silver mica.
Look for CFM suggestions for using a zobel on the supply.
Thanks for the reply.
It seems the problem was with the crappy speaker I was using for testing, I've connected my good ones and now the amp has plenty of bass and the mids and highs have settled down to a nice level.
It's impressive how cheap this thing is how much power and sound quality it can produce. I want to build another without the buffer with a better power supply more capacitance and bigger transformer!!
It seems the problem was with the crappy speaker I was using for testing, I've connected my good ones and now the amp has plenty of bass and the mids and highs have settled down to a nice level.
It's impressive how cheap this thing is how much power and sound quality it can produce. I want to build another without the buffer with a better power supply more capacitance and bigger transformer!!
There appears to be an error in the schematic in post #474. The 470r resistors that go to the regulators should connect to the other side of the 22k resistors.
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