+/- 67 Volt for the LME and +/- 56 Volt for the Allfets. 6,3 A, slow blow fuses, placed right after the diodebridge, followed by 30.000 uF capacitors. I modded Velleman k4700 speakerprotection relays (15A/125V ac) like Elliot Sound project 33, so they wouldn't arc.....but this one did! Amp is playing without problems now. Relay is replaced. Maybe I should get better relays.
Just happened to be browsing Connex and saw he still had the obsoleted LME49830 listed in his catalog - don't know how up to date his catalog is, but he might still have a few left in stock.Yes, fingers crossed, the chips are obsolete now and I have 4 amps that use them. You wouldn't have anymore spare by any chance?
Connexelectronic
On a sufficiently revealing system, the degradation to the sound quality caused by speaker protection relays is easily audible.
Once it's been heard there follows a risk vs. benefits decision.
Many opting for years of poorer sound with the small possibility of replacing the bass units.
Maybe bi-wire, or tri-wire, from two, or three, pairs of output terminals per channel, with the relays only in series with the bass.
Relays are fine, these are pretty good, often used for the task G2R-2 12DC | Omron DPDT PCB Mount Non-Latching Relay, 12V dc Coil | Omron
Thanks for the link
Fine for most people yes, especially if the difference from the relays can't be heard, or not enough difference, on the equipment anyway.
However some people, not rich ones necessarily, who have done everything they can to make their system as clear and revealing as it can be, who have listened to each resistor and capacitor, listened to each plug and socket, etc, etc, will leave relays off as use of such items is not even a question.
I had a DC coupled system as clear I could make it and had a failure in the 1990's and did replace the bass units. It's a problem though if they are discontinued drive units on older speakers, but I wasn't willing to audibly downgrade just in case it happened again as the whole point for me was to have the best clarity possible.
The mid and top drive units are protected from DC offset by the capacitors in series with them in the crossover. If you get an excessive as HF noise it can still damage tweeters even with relays present if the protection circuit doesn't switch them off.
I'm just saying, the differences are there if you want them.
Fine for most people yes, especially if the difference from the relays can't be heard, or not enough difference, on the equipment anyway.
However some people, not rich ones necessarily, who have done everything they can to make their system as clear and revealing as it can be, who have listened to each resistor and capacitor, listened to each plug and socket, etc, etc, will leave relays off as use of such items is not even a question.
I had a DC coupled system as clear I could make it and had a failure in the 1990's and did replace the bass units. It's a problem though if they are discontinued drive units on older speakers, but I wasn't willing to audibly downgrade just in case it happened again as the whole point for me was to have the best clarity possible.
The mid and top drive units are protected from DC offset by the capacitors in series with them in the crossover. If you get an excessive as HF noise it can still damage tweeters even with relays present if the protection circuit doesn't switch them off.
I'm just saying, the differences are there if you want them.
I have opened up various relays and applied a lot of Electrolube Highly Conductive Grease and that can make the relays 'transparent' but it had to be so much grease that it would 'strings' across the contacts when open, so they remained conducting.
I added small capacitor and that might help the treble but not the rest.
I made a 16 pole relay, from 4 x 4 pole relays wired together, for mains switching pre transformer, from a protection circuit, but disappointingly was just as big a downgrade as one relay, compared to a captive lead straight onto the Tx.
Again for the mains switching protection, and on / off, and thinking 'this should do it' as it has a liquid contact, I bought one of those mercury relays that industry use to switch high current loads (not for use in portable equipment) (not mercury wetted sold contacts, it's a pool of it that rises up a tube and immerses a central conducting pin). Very expensive, no good at all, just as bad as one relay, maybe worse.
I expect more could, and has, been done to ameliorate the negative sonic effects of relays, but my patience, and budget, expired and it was easiest to simply not use them.
I added small capacitor and that might help the treble but not the rest.
I made a 16 pole relay, from 4 x 4 pole relays wired together, for mains switching pre transformer, from a protection circuit, but disappointingly was just as big a downgrade as one relay, compared to a captive lead straight onto the Tx.
Again for the mains switching protection, and on / off, and thinking 'this should do it' as it has a liquid contact, I bought one of those mercury relays that industry use to switch high current loads (not for use in portable equipment) (not mercury wetted sold contacts, it's a pool of it that rises up a tube and immerses a central conducting pin). Very expensive, no good at all, just as bad as one relay, maybe worse.
I expect more could, and has, been done to ameliorate the negative sonic effects of relays, but my patience, and budget, expired and it was easiest to simply not use them.
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One year later: Now the other channel (!) did start to do the same thing, but only sometimes after switching on. Bam! DC protection comes in. After switching off and on again, the amp plays a whole day without problem. Replaced lme49830 (3 left) and the problem is gone. Amp plays without problem for one month now. So weird.
EDIT - 27/05/2012
The schematic and layout below are incorrect. For the updated information, along with the assembly guide, please see this post:
"The Wire AMP" Class A/AB Power Amplifier based on the LME49830 with Lateral Mosfets
Where can I find the revised layout and in short what's the difference the original and revised schematic?
Thanks.
The schematic and layout below are incorrect. For the updated information, along with the assembly guide, please see this post:
"The Wire AMP" Class A/AB Power Amplifier based on the LME49830 with Lateral Mosfets
Hi Guys,
I finally finished writing up the instructions for the amp assembly, so you can take the time to read them now while we all wait for mosfets to arrive
Any comments, suggestions or corrections are welcome. I tried to cover all the major points, but I am assuming a certain level of skill when it comes to this project.
Also attached is the functional schematic showing the resistor values for an SE circuit. Every part is carefully covered in the assembly document, so please read it thoroughly. If a question is asked here, that is already answered in the instructions, you'll simply get a "Read the instructions" post.
I will be posting all these documents, along with the worksheet and anything else in a build Wiki that should be up in the next few days.
Cheers,
Owen
Where can I find the revised layout and in short what's the difference the original and revised schematic?
Thanks.
I been sucked in to this board, after reading the Ti article and was impressed with the simplicity of an amplifier with just one IC and two output transistors. When I got the boards I realized how badly designed they was, never saw anything like this, and I saw a few in my life (I'm 78). Seemed the Op was in a competition who can make the smallest PCB, this takes the Palm. No clearances what so ever, the ground plane surrounds everything way to close. Even the mounting screws won't clear the designated pads, the input caps, the filter caps and the heatsinks of the LME49830. 3mm holes but even a 2.5mm inhex screw heads would just clear. I populated my board a few years ago, but I was afraid to switch them on. Now last week I hooked them up to a 3X35V supply. One was working ,the other had two shorts. Luckily I didn't need to change any components. The 1kHz TDH is -97dB, I might use them as a good headphone amplifier.