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Old 30th July 2009, 08:52 PM   #571
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John and Bob did you use the LT1166 with MOSFET or BJT OPS?
Anyway I donít see the point in continuing to discuss that chip.

OTOH I think that Bob has a good point in his post when it comes to high biased amps and also the use of TT transistors.
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Old 30th July 2009, 09:15 PM   #572
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John,

output BJTs
more=better?
any limits?
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Old 30th July 2009, 09:37 PM   #573
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Quote:
Originally posted by stinius
John and Bob did you use the LT1166 with MOSFET or BJT OPS?
Anyway I donít see the point in continuing to discuss that chip.

OTOH I think that Bob has a good point in his post when it comes to high biased amps and also the use of TT transistors.

Hi Stinius,

I used it in a MOSFET amplifier experiment about three years ago.

Its too bad that the Linear Tech guys did not put a little more thought into alternative ways to use the chip. I'm pretty sure I'm not the only one who had success with it, but I did have to give it a lot of thought and sweat some details. I was fortunate enough to get my hands on a SPICE file of it and somewhat reverse engineer a schematic out of it that gave me some insight.

The LT1166 can also be used with BJT output stages where there is enough bias spread to bias it. I think a Locanthi T circuit is probably compatibe with it. Additional artificial spread can always be added.

One key to using the LT1166 is to just use it as a shunt bias spreader, just like a Vbe multiplier, but one that acts dynamically.

Another key is to use special sauce when compensating the amplifier with Miller compensation around the VAS.

The third is to properly compensate the LT1166 itself.

These do not require many components at all.

Cheers,
Bob
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Old 30th July 2009, 09:58 PM   #574
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Quote:
Originally posted by myhrrhleine

output BJTs
more=better?
any limits?
More devices=more base charges + higher Icbo.

Think of expected peak currents and beta droop. That's it.
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Old 30th July 2009, 11:27 PM   #575
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That is ALL I did Bob, considering consultations with the LT App engineer and Walt Jung. Design your own stuff, please.
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Old 30th July 2009, 11:45 PM   #576
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Quote:
Originally posted by Bob Cordell

I used it in a MOSFET amplifier experiment about three years ago.

I was fortunate enough to get my hands on a SPICE file of it and somewhat reverse engineer a schematic out of it that gave me some insight.
Did it myself, about the same time, with bipolars:

http://www.diyaudio.com/forums/attac...amp=1168801187

Wow, I thought I was the first one reverse engineering the LT1166, to the device level:

http://www.diyaudio.com/forums/showt...40#post1485140

Anyway, even if I don't know how the THS spec sounds, I'm pretty sure I could meet it using LT1166.
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Old 31st July 2009, 07:34 PM   #577
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Quote:
Originally posted by john curl
That is ALL I did Bob, considering consultations with the LT App engineer and Walt Jung. Design your own stuff, please.

John,

Let be more clear. You should not diss the part if you did not do your homework. Just looking at the data sheet and app note and giving up on the part is not what "a real engineer" would do.

I'm pulling your chain here because you like to use the "real engineer" language on others.

Cheers,
Bob
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Old 1st August 2009, 04:14 PM   #578
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Bob, you have me at a disadvantage. I can barely see, and the stress of using the computer for more than a few minutes at a time, threatens to tear my retina for a 3'rd time. It is impractical for me, therefore, to go into some 'dialogue' with you at this time on the 1166. However, I found a few notes, from 1996, that I will put up, IF anyone can locate SY, or put it up themselves. It might at least, show something useful.
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Old 1st August 2009, 04:41 PM   #579
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John, if SY is unavailable, I can host anything you want to put up. No prob.

jd
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Old 1st August 2009, 05:21 PM   #580
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Quote:
Originally posted by john curl
Bob, you have me at a disadvantage. I can barely see, and the stress of using the computer for more than a few minutes at a time, threatens to tear my retina for a 3'rd time. It is impractical for me, therefore, to go into some 'dialogue' with you at this time on the 1166. However, I found a few notes, from 1996, that I will put up, IF anyone can locate SY, or put it up themselves. It might at least, show something useful.

Hi John,

I'm really sorry to hear about your problems with your eyes. I'm no youngster, either. Nor is my wife. I just spent over a week in NYC with her for some surgery she needed. It's Hell to get old, but the alternative is worse.

Anything that you feel comfortable contributing on the LT1166 is welcome. I have been trying to contribute on the LT1166 in a positive and educational way. Bear in mind that there are others on this thread who can contribute both their positive and negative experiences with the LT1166. All I ask of you is that you contribute in a technically positive way if you contribute, rather than in a way that is rude or demeaning of the contributions of others.

Making the best use of the LT1166 is not straightforward. It is a very clever device, but the datasheet and app notes do not do justice to it. This is understandable to some extent, because the focus of the LT engineers was probably more on the benefit of eliminating the bias pot that on highest sound quality. I had to work very hard to harness the 1166 in the way that I wanted to.

Here is an analogy. The ThermalTrak transistors are a wonderful device, nearly game-changing in some ways. Yet the Onsemi folks did not do a good enough job on the spec sheet and app notes to make them optimally useful to achieve their best potential. Charles feely admits that he had to workj very hard to make good use of them. Yet he did not criticize the devices as bad because it required a lot of effort to get them right.

For this reason, other designers should not feel bad that they did not get the greatest results from the 1166. Maybe they spent their many hours on getting good results in a different way.

Get better,
Bob
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