Hello
1. Can we use R3 = 0.22 or 0.25 ohm with Evo RevA Mod or it's too low value? I found some sources for this values. Unfortunately values like 0.3-0.47 are hard to buy for me.
2. Is it safe for Fremen edition amp to power speakers through long speaker wires (~10-12m each) without output RL-filter as in original lm3886 datasheet?
1. Can we use R3 = 0.22 or 0.25 ohm with Evo RevA Mod or it's too low value? I found some sources for this values. Unfortunately values like 0.3-0.47 are hard to buy for me.
2. Is it safe for Fremen edition amp to power speakers through long speaker wires (~10-12m each) without output RL-filter as in original lm3886 datasheet?
I would greatly appreciate some technical advice. There was a power surge here (created by my electric water heater!) which flashed my lights and silenced one channel of my preamplifier. It, or the preamp failing, also damaged one of my monoblocks. Now all I hear with no input is a very loud buzz through the speaker. The LED lights, relay clicks, and I measure only 7MV dc at the outputs, but there is no music, only a loud noise which almost sounds like there is no ground. I do not detect any physical damage. Can anyone suggest where to begin testing the circuit?
Peace,
Tom E
Peace,
Tom E
seven megavolts! No wonder something blew!
Since its one channel out only you can start comparing the two channels. However something like a signal injector and or tracer can be invaluable for figuring out where the signal gets lost. Or a 'scope of course.
Since its one channel out only you can start comparing the two channels. However something like a signal injector and or tracer can be invaluable for figuring out where the signal gets lost. Or a 'scope of course.
Tom,
It is intriguing, so to say.. The relay clicking, and Your measurement of the 7mV output offset would indicate that the composite feedback loop works (for sure in DC). It means all the active elements need to be OK..
On the other hand, there is no ground reference to the input signal (buzz)
All this would signal an R11 gone.. but in that case, typically, a strong DC offset is the result.. Maybe it's not totally gone, just got an elevated value (like from 1ohm to some dozen kohm..) .??
though.. this still would not exclude some of the input signal filtering through..🤔
It is intriguing, so to say.. The relay clicking, and Your measurement of the 7mV output offset would indicate that the composite feedback loop works (for sure in DC). It means all the active elements need to be OK..
On the other hand, there is no ground reference to the input signal (buzz)
All this would signal an R11 gone.. but in that case, typically, a strong DC offset is the result.. Maybe it's not totally gone, just got an elevated value (like from 1ohm to some dozen kohm..) .??
though.. this still would not exclude some of the input signal filtering through..🤔
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Interested in this - so what is the best combination to date that drops the last hint of grit and gain? My thoughts on this:Just to add some observations. In my original query about the value of C32 for my OPA828 build, @Joseph K intimated that with the damping resistor mod fitted 150pF would still be a valid value. I went ahead with the recommended 68pF, I then added the compensation damping 1K resistor which definitely dropped a veil in the presentation but there was still a hint of grit and grain in the 2-4kHz presence region, not surprising as it's something I've always heard in virtually all solid state amps. Only valves get those micro tonal shades in sibilants and cymbals absolutely right in my experience. Joseph's insight got under my skin, so I swapped out the 68pF for 150pF and nearly all of that grit and grain vanished. OK, I swapped a polystyrene for an AMCH and I am just a tinkerer but I do believe Joseph is on to something here.
What voltage is LM318 supplied with? Has anyone tried separately powering it with a v.good linear or ultracap supply? I may well end up adopting OPA828 as suggested.
Finally, I've had very good experience with the SALIGNY Power GaN - Expensive, but it does seem to introduce any hash - I do think going offboard for the rectifier would help.
Should read ‘doesn’t seem to introduce any hash’Finally, I've had very good experience with the SALIGNY Power GaN - Expensive, but it does seem to introduce any hash - I do think going offboard for the rectifier would help.
‘doesn’t seem to introduce any hash’
I should hope not for £349 Euro!!! More than my amp cost to build
I should hope not for £349 Euro!!! More than my amp cost to build

checkInterested in this - so what is the best combination to date that drops the last hint of grit and gain? My thoughts on this:
What voltage is LM318 supplied with? Has anyone tried separately powering it with a v.good linear or ultracap supply? I may well end up adopting OPA828 as suggested.
checkFinally, I've had very good experience with the SALIGNY Power GaN - Expensive, but it does seem to introduce any hash - I do think going offboard for the rectifier would help.
the amp that I am using now - applies these. And some. 🙂
But, does it de-valuate this little gem of amplifier? Far from it, it still shines on it's own right..🙂
What voltage is LM318 supplied with? Has anyone tried separately powering it with a v.good linear or ultracap supply? I may well end up adopting OPA828 as suggested.
I have a build where i changed opamp (opa827) psus for ti tps7a very low noise linear ones. There is some increase in sq, but not as much as i expected.
But the amp i implemented that way was already very good sounding, without any harsh and with much grint, thanks to Dario and Joseph K higher quality suggested mods (caps, resistors, opamps, etc...)
P. S. In that build i use hexfred diodes, the best i know with a "normal" price. I am a first time/first models saligny user, they are very good but to be honest i found the best results in valve circuits psus
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Posted a while back about failed amp. Found R11 to be almost broken. Replaced with new resistor, now amp works fine. Thanks again for your help.
Have you a link for aliexpress pcb? ThanksMany thank Ciao, I learned more from you! 🙂 I just simple think oscilloscope probe have 9M Ohm will be safe anywhere.
How to reduce dc output voltage. Last time, I have used My-Ref version pcb (Aliexpess) only have 3.7mV dc output.
Hello everyone,
for whom interested I've updated the build guide with latest recommendations, some revisions and, for italian builders an italian translation is now available.
You'll find those here, as usual.
for whom interested I've updated the build guide with latest recommendations, some revisions and, for italian builders an italian translation is now available.
You'll find those here, as usual.
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