Though its a really tedious and fiddly work to file down the leads of 50 resistors from 0.6 to 0.5mm
Hi Mark,
IMO it should be possible to diy enhance the diameter of the holes (using a suitable bit) when there is only one track that connects to the hole. One track above the PCB and one track under the PCB both connected to the same hole would not allow that, as the electrical connection between under and above the PCB could be interrupted.
Best regards
rephil
Yes if you drill out the hole to increase it, you lose continuity between the top track and the bottom track.
However if you solder the component's lead on both sides of the PCB you will regain continuity........not exactly a perfect solution.
It's imperative that PCB designs allow for option components.
However if you solder the component's lead on both sides of the PCB you will regain continuity........not exactly a perfect solution.
It's imperative that PCB designs allow for option components.
Though its a really tedious and fiddly work to file down the leads of 50 resistors from 0.6 to 0.5mm
Or you could just use 0.25W resistors as it's ment to. Much less work.
Though its a really tedious and fiddly work to file down the leads of 50 resistors from 0.6 to 0.5mm
Use a lathe
!Best regards!
They seem much harder to source these days. Pity, I liked them, but now I have oven, stencil frame, stock of 0805 resistors and caps...
No, the capacitor seems very little voltage as its normally very low impedance compared to the rest of the feedback network. However if the amp fails shorted to the rail, then the capacitor would see full supply voltage, so often you see some diode clamping circuit around the capacitor to protect it (a couple of LEDs do the job nicely as well as indicating the fault). This avoid using a physically large cap.
I have never built a stereo amplifier before, only the Objective O2 headphone amplifier. I now have the option to buy a kit with two HB amp boards, power supply board, softstart board, speaker protection board, one 800VA 2x40V toroid transformer, one 20VA 24V toroid transformer, and a Modushop Dissipante chassi for 2500SEK (around 265usd). Is that a fair price? Does anybody have an estimate for what the parts for the circuit boards will cost me? $150? $300? $400?
That's a good deal! The supplies and chassis is where the money goes. Parts for the amplifier boards themselves are cheap, around $100 depending on what parts you choose. Caps for the supplies can add up though. Prices climb quickly once you go above 63V. You would need to go with 80V caps with a 40VAC transformer.
If I decide to build this I would go with high quality parts too so I know that I get the most out of it. Is it $100 per channel or in total? How about power supply board, softstart, and speaker protection?
I might have another transformer option, but I don't know its ratings. It's in a S.A.T Amplifix stereo amplifier I have where the left channel is dead and I don't know how to troubleshoot it so I might just scrap it for parts. It's a very big and heavy lump of metal though. Would it be better to use a transformer with lower voltage or higher voltage?
I might have another transformer option, but I don't know its ratings. It's in a S.A.T Amplifix stereo amplifier I have where the left channel is dead and I don't know how to troubleshoot it so I might just scrap it for parts. It's a very big and heavy lump of metal though. Would it be better to use a transformer with lower voltage or higher voltage?
The output devices are the only real money on the amplifier boards. $100 will easily build both with good quality parts. You can spend 10x that on boutique junk that doesn't fit but it won't sound any better and will be hard to cure all the extra noises they cause.
The voltage of the transformer depends on what you are planning to drive with the amp. 40V is at the higher end of what you should run with 4 ohm speakers, but with 8 ohm speakers you can go even higher.
The power supply isn't a section of the amp where one should try to go cheap. This is where all of the power of the amplifier comes from. If the supply is saggy your bass response will suffer. Most tweeters work better with some extra voltage available too.
The voltage of the transformer depends on what you are planning to drive with the amp. 40V is at the higher end of what you should run with 4 ohm speakers, but with 8 ohm speakers you can go even higher.
The power supply isn't a section of the amp where one should try to go cheap. This is where all of the power of the amplifier comes from. If the supply is saggy your bass response will suffer. Most tweeters work better with some extra voltage available too.
Alright! My current speakers are two-ways with two Morel CAW638 woofers and a CAT408 tweeter. I think they can be seen as ~3.5 ohm speakers if I remember correctly.
I just had a look at the power supply bill of materials and looked up prices for the caps on Mouser. The cheapest we're around €12 each (Kemet, good or crap?), the Nichicon were like €50 each, and I need 8 of them, right? Or is it 16 for two channels?
I just had a look at the power supply bill of materials and looked up prices for the caps on Mouser. The cheapest we're around €12 each (Kemet, good or crap?), the Nichicon were like €50 each, and I need 8 of them, right? Or is it 16 for two channels?
Supply caps should be around $10 each for 80V. You need 4 per channel normally. LLS1K103MELC Nichicon | Mouser Canada
Kemet is good for ceramic. NPO/COG or silver mica (Cornell Dubilier) for in the audio path, X7R for decoupling. For film caps most prefer MKP caps, Wima, Epcos, Panasonic.... Nichicon and Panasonic are good choices for electrolytic. United Chemicon are good stuff but they are hit or miss if they will actually fit, data sheets and supplier provided dimensions are very inaccurate.
If you like it loud, double die output devices are money well spent for 4 ohm speakers. MJL4302/4281 have better current handling than standard transistors.
Kemet is good for ceramic. NPO/COG or silver mica (Cornell Dubilier) for in the audio path, X7R for decoupling. For film caps most prefer MKP caps, Wima, Epcos, Panasonic.... Nichicon and Panasonic are good choices for electrolytic. United Chemicon are good stuff but they are hit or miss if they will actually fit, data sheets and supplier provided dimensions are very inaccurate.
If you like it loud, double die output devices are money well spent for 4 ohm speakers. MJL4302/4281 have better current handling than standard transistors.
A weakish supply just limits the maximum output level before clipping by a small factor (maybe around 1dB), it doesn't change the frequency response as the sag is power dependent, not frequency dependent. Gaining 1dB by doubling the cost of a supply to make it super stiff isn't worth doing IMO, since you can just go with a slightly higher power and voltage supply to gain 1dB more economically.
You can spend all that extra money making an amp with 2 or 3dB extra output in fact, despite sagginess. I'd suggest putting the money where the most benefit will come if you can, low hanging fruit first.
However a supply must be upto the task asked of it without overheating or popping fuses, so under-spec'ing it is worse than over-spec'ing.
And there are some other considerations like the overall efficiency of the amp, which can place requirements on the supply voltage regulation.
And how might that happen? The only benefit I see is slightly higher headroom, which if you don't need it means no benefit to the tweeters. Good amps keep linear upto the point of clipping, so the drivers have no knowledge of the supply voltage unless it clips.
A low quality amp that gets less linear with higher output levels / lower supply voltage means you should spend that extra money first on improving the amp design, not increasing the supply voltage - its distorting, fix that first.
In short consider the overall performance and overall cost when designing the supply, everything is a trade-off ultimately.