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Old 26th March 2010, 07:32 PM   #61
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Is the 3886 a split die design? Was thinking there is the whole input section up to the drivers and then the power transistor on an adjacent die. Is that wrong or right and does that make it a hybrid or an IC?
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Old 26th March 2010, 11:19 PM   #62
tomchr is offline tomchr  United States
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Originally Posted by sumaudioguy View Post
Is the 3886 a split die design? Was thinking there is the whole input section up to the drivers and then the power transistor on an adjacent die.
I highly doubt that. National has the technology to make large power devices. That's just a matter of putting a whole bunch of smaller devices in parallel. While, packaging multiple dice in one package is certainly possible, it's much more expensive than packaging a single die. So I would imagine that the LM3886 is a single die. The only reason they'd go with a multi-die approach would be if there was a significant performance gain to be had by doing so AND the customers were willing to pay for that performance gain.

Unless you can get the information out of National directly, the only way to find out for sure is to take an LM3886 apart -- or get one x-rayed...

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Old 26th March 2010, 11:24 PM   #63
a.wayne is offline a.wayne  United States
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Originally Posted by analog_sa Click the image to open in full size.
"In my limited experience - extremely speaker dependent, especially in bass and dynamics. Don't quite see how adding hundreds of db extra open loop gain can really correct for this - there just seems to be insufficient current from single chips."

Feedback makes an amplifier more linear. More feedback is more linear. Also having the amp stable with that much feedback makes it drive bad loads a lot better. I use no compensation at all on the output like an inductor or RC snubber to calm the amp from oscillation. It is like big rock stable. It also means the dominant pole gets moved out to a very high frequency so out of band signals do not cause foldback distortion of the worst kind. Comparing the very well built straight 3886 to the "high gain composite amp" version on the bench and in listening test was not even fair. One sounds like the typical halfway decent amp the the other sounds like music and forget the amp part.

Also the extra gain means higher damping at all frequencies which translates directly into more control over the transducers. This reduces the effects you mention of the speakers making the difference. This damping also makes the amp run hotter because it is absorbing more back EMF from the voice coil.

As far as current I am not certain what you mean. The 3886 with a good supply will put out 11 amps which translates into an easy 7.5 amps RMS so that is 450 watts into 8 ohms and 225 into 4 if it could swing the voltage. That is plenty of current. So much current that I run 2 3886 balanced output to increase the voltage swing making 160 watt amps out of a pair of them (32 volt supplies) which takes less than 5 amps RMS into 8 ohms.

Further I run the very same amp on 15 volts and drive loads down to half an ohm. Most amps puke at that kind of load but this is the easy way to do it. It will direct drive a ribbon just fine if the power supply voltage is set appropriately.

This explains everything you could not see so I hope now you can "see."
Hmmm, interesting to hear your drive a ribbon direct theory , I'm all ears on that one, if a chip amp can really drive 200-300 watts @ 1 ohm ..

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Old 26th March 2010, 11:44 PM   #64
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Well i did listen to the Bel Canto for the first time on the maggies 2 nights ago , unfortunately we did not get to compare it to the krell ( it died ) nor the Threshold ( never lugged it along , will do this weekend ) but those before me who heard the krell , thought the Bel Canto ran rings around it .


I must say , the combination was pretty good, very dynamic , open and full sounding. There were issues , Bass, muddy , not enuff air around instruments and it tended to get noisy sounding ( harshness) on complex passages, blending instruments together etc.

On single instruments , small ensembles for eg. the sound had a purity to it that was really unexpected to me from a chip amp and there was some audible compression on dynamic passages, apart from that it did acquit itself very admirably. Those that heard the Krell felt it excelled over the chip amp with dynamics and the bass, but overall and unanimously they all preferred the Bel Canto over the Krell.....

For me it was an unexpected pleasant afternoon and can't wait to hear the differences when compared to the Threshold, I'm now a believer that the chip amp can be made to sound good, as it did appear to me that the Bel canto lacked a suitable power supply and while there were issues it is well worth keeping an eye on VS discrete and it did not idle at 12 amps like the Krell.


Speaker : Magnapan MG1.6
Pre-amp : Audio Research ( solid state )
Amp : Bel Canto 300 Mono's /Krell KSA 200
CD Player : Sony

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Old 27th March 2010, 12:45 AM   #65
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ever tried an actual BLIND test?
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Old 27th March 2010, 02:26 AM   #66
a.wayne is offline a.wayne  United States
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A deaf person could hear the difference and after 40 yrs at this, not necessary anymore , the results would have been the same, plus I'm nearly blind, well my optician thinks so.
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Old 27th March 2010, 02:43 AM   #67
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Hmmm, interesting to hear your drive a ribbon direct theory , I'm all ears on that one, if a chip amp can really drive 200-300 watts @ 1 ohm ..

The 3886 is limited to about 7.5 amps RMS which translates into about 55 watts into 1 ohm. Not so much power but then will the ribbon really take that kind of power? I don't know. Just have to try it.

There is a discrete amp sitting here I use on the bench but that is off subject. Watts/Load: 120/8 200/4 375/2 575/1 1030/0.5 Maybe this is like what you want?
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Old 27th March 2010, 04:17 AM   #68
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blind tests are constantly proven to NOT give the same results as when people see the equipment regardless of their age.
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Old 27th March 2010, 04:56 AM   #69
a.wayne is offline a.wayne  United States
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Originally Posted by sumaudioguy View Post
The 3886 is limited to about 7.5 amps RMS which translates into about 55 watts into 1 ohm. Not so much power but then will the ribbon really take that kind of power? I don't know. Just have to try it.

There is a discrete amp sitting here I use on the bench but that is off subject. Watts/Load: 120/8 200/4 375/2 575/1 1030/0.5 Maybe this is like what you want?
I wantie , wantie want ....... tell me more , interesting it current limits very early and yet can still drive a 1 ohm load, anymore details , i know off topic , but i'm very interested and would like to take a look and yes the ribbons will need a lot more than 50 watts, i currently pop 10 amps fuses ( speaker side) from time to time, when i do get carried away with the sound ...

Couldn't you parallel enuff chips to increase the power ? I know 7 amps would not be enuff i had to go to a 10 amp from a 8 amp fuse to stop blowing the fuses.

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Originally Posted by thetube0a3 View Post
blind tests are constantly proven to NOT give the same results as when people see the equipment regardless of their age.
Hello the tube,

Well that would be "people " who can't evaluate what they hear so they have to see . A double blind test would not have made a difference, I can hear the difference between amplifiers, et al .

Last edited by a.wayne; 27th March 2010 at 04:59 AM.
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Old 27th March 2010, 07:35 AM   #70
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Originally Posted by sumaudioguy View Post
Feedback makes an amplifier more linear. More feedback is more linear.
************************************************** ***
Also the extra gain means higher damping at all frequencies which translates directly into more control over the transducers.
*************************************************
As far as current I am not certain what you mean.


I can certainly see that more OLG and more feedback translates into lower harmonic distortion. Does this in any way correlate to better sound? THD is pretty low in chip amps anyway. Are you eager to follow into the footsteps of Jap designers from the seventies?

Damping factor? Can you give a numerical example? Are you using superconductors for your speaker cables?

As far as the current goes i have no objection to the datasheet rating but why do these amps fail completely with some speakers? SPike protection?
I have two sets of speakers which play with less stress, more dynamics and better bass when powered from a 15W tube amp than a 68W chipamp with a monster PS.
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