Wiring and similar changes are not bad, quite the contrary, but best case will improve fractions of a dB ... if that much.}
Since you are comparing it to a *old* not exactly flat amplifier, and to boot using old middle quality speakers, I suggest you try this instead:
[Fat LM3886 schematic]
Smoothly rising below 160Hz, + 6dB plateau boost between 40 and 80 Hz.
Try it and post results
As a side note, your speakers are at least 20 years old, maybe 30, and foam edges must be rotten by now.
Did you refoam them?
There are replacement kits available and job is "doable" at home just being somewhat careful.
Thanks, I think I have all the components needed so I will try it out when I have time.
Hmm, about the speakers, that might be the case but I have not looked into it enough to know if it's something I can manage and they are my only speakers right now so I wouldn't want to mess them up. I want to go the DIY speakers route after I am satisfied with the amp so maybe after some experience I might try that.
And this is where the light of truth starts to shine on the words of Richard...
The MyRef design improves upon the total PSRR by the the extra psrr brought into the pic by the control opamp.
Also here, stepping up the quality of this control opamp, first of all in the CMRR / PSRR department like in LM318 (poor) - OPA827 (good) OPA828 (very good) >> in my house and opinion brings an incremental step forward..
And yes, bass is simply great with this design. Powerful, full and punchy ~~ almost like the great classic amps out there.
Ps.: and yes, < 13 years ago my 'wow' experience was properly regarding the bass compartment, with the first myref amp with respect to the previous 3875 / 3886 simple amps.
Ciao, George
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The lonely lm3886 has no real psrr issues at low frequencies. At 60hz, it still has 100db of psrr for the - rail and 115 for the + rail. It could be better (it can always be better with audiophiles...) but it certainly won't cause the issue considered by the OP, which is way better explained by the boosted bass of his old amp, as explained by JMFahey.
@isaiahb: sorry that your thread has been kind of derailed by the usual debates and obsessions of this forum. Your wiring and technical execution are more than adequate; just add the bass boost suggested, nothing more is needed.
@isaiahb: sorry that your thread has been kind of derailed by the usual debates and obsessions of this forum. Your wiring and technical execution are more than adequate; just add the bass boost suggested, nothing more is needed.
I was wrong. f < 20 Hz and not 50 Hz.
https://www.akitika.com/GT102.html
Power Output Versus Load Impedance
https://www.stereophile.com/content/akitika-gt-102-power-amplifier-measurements
Maybe the problems come with nominal 4 ohm speakers, with a low/very low minimum impedance and low sensitivity.
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Talking about LM3886, this amp has two, one by channel:
ARCAM FMJ A19
[Polish] https://audio.com.pl/testy/stereo/wzmacniacze-stereo/954-arcam-a19
to English with Google
Incredible bad with this chipamp: SNR-A at 1 watt/8 Ohms: 79 dB
Very bad LM3886 implementation I think.
ARCAM FMJ A19
[Polish] https://audio.com.pl/testy/stereo/wzmacniacze-stereo/954-arcam-a19
to English with Google
Incredible bad with this chipamp: SNR-A at 1 watt/8 Ohms: 79 dB
Very bad LM3886 implementation I think.
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The lm3886 has an internal protection system (more about it in this app note). This will limit the power delivered by a lm3886 into a load. It will mostly affect the low frequencies but not at a set frequency, it's an interaction between level, load, frequency and temperature.
Having the lm3886 properly heatsinked helps but, ultimately, the only workaround to drive low impedance/low sensitivity speakers are paralleled ICs.
Having the lm3886 properly heatsinked helps but, ultimately, the only workaround to drive low impedance/low sensitivity speakers are paralleled ICs.
It's a loosely similar effect as if you compressed the low frequencies only (f.e. sidechained a compressor with a lpf). Resulting in a "flattened" sound (i.e. not "round").
Imho a "loose muscle grip" on bass region describes the situation perfectly. Ymmv?
Not really in my view. With most music and speakers, at normal (including loud) listening levels, it's not active or audible at all. When it kicks in, it has gross distortion (look at the waveforms in the app note).
Btw, this applies even to composite amps as the modxxx or the myref. It's quite different to the psrr issue which, otoh, is really helped by the composite amps higher open loop gain.
Btw, this applies even to composite amps as the modxxx or the myref. It's quite different to the psrr issue which, otoh, is really helped by the composite amps higher open loop gain.
+1
The LM3886 is both one of the most highly built, and most improperly built of all audio ICs. In a proper setup they are very good at what they do. Hearing TomCHRs Modulus amplifiers driving the Linkwitz LXMinis at Burning Amp fest this year was a very rewarding experience, and was probably one of the best solid state setups I have ever heard.
Woofer of 8 Ohms
http://melp242.blogspot.com/2018/06/linkwitz-lxminifirst-impressions.html
http://melp242.blogspot.com/2018/06/linkwitz-lxminifirst-impressions.html
I decided to look for an amplifier in a half-rack width body so I can fit it into my gear rack. The woofer driver of LXmini is rated for 8 Ohm impedance and "long term power handling" for 80 Watts.
The second—full range driver is 4 Ohm and requires less power. So I decided to look for a 4 channel amplifier rated for 100 Watts into 8 Ohms to have some headroom.
But it sounds great so the numbers are just part of the story. The sonic presentation reminds me of my AKSA 55N+.
Trust me, with better SNR it should sound better.
The harmonics graph is very good/clean.
Which speakers and type of music? Wich modern commercial music you do not need to spend a lot of money. With very good records and high DR (dynamic range) the quality demands are greater/much greater.
Just now: Gustav Mahler - Symphony No 4 (1983), Tennstedt & London PO, vinyl -> DR16
this track: DR17 -0.53 dB -24.39 dB B1 3rd Movement- Ruhevoll
The harmonics graph is very good/clean.
Which speakers and type of music? Wich modern commercial music you do not need to spend a lot of money. With very good records and high DR (dynamic range) the quality demands are greater/much greater.
Just now: Gustav Mahler - Symphony No 4 (1983), Tennstedt & London PO, vinyl -> DR16
this track: DR17 -0.53 dB -24.39 dB B1 3rd Movement- Ruhevoll
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Wiring and similar changes are not bad, quite the contrary, but best case will improve fractions of a dB ... if that much.}
Since you are comparing it to a *old* not exactly flat amplifier, and to boot using old middle quality speakers, I suggest you try this instead:
[Fat LM3886 schematic]
Smoothly rising below 160Hz, + 6dB plateau boost between 40 and 80 Hz.
Try it and post results
As a side note, your speakers are at least 20 years old, maybe 30, and foam edges must be rotten by now.
Did you refoam them?
There are replacement kits available and job is "doable" at home just being somewhat careful.
Reporting back after trying this out, it sounds much better now! Bass is there and it's not booming or dominating the higher frequencies. I will give it some time but I guess it will stay like this. So thanks JMFahey for taking the time coming up with a solution and also everyone else for giving their input.
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