Krill - The little amp that might...

[mlloyd1]

these meetings (and the discounted cds, of course) were a major reason i enjoyed going to ces when it used to be in the midwest.

ah, the good ole days ...

sigh,
mlloyd1

...
We have met three times at CES. You were a very friendly and open person who spent a great deal of time talking and explaining things. I can't say that about everyone I met there.

 

[Steve Dunlap]

these meetings (and the discounted cds, of course) were a major reason i enjoyed going to ces when it used to be in the midwest.

ah, the good ole days ...

sigh,
mlloyd1

I do miss my visit to Chicago every year. It was a pretty easy drive when I lived in St. Louis. Really in Alton Ill., but no one would know where that is. Our house was 19 miles from the arch so I call it St Louis.

 

[Nelson Pass]

I am also glad you don't keep your designs private. You were one of the people I worried about inevertantly copping when I designed my circuit. Being able to read all your patents and publications was a great relief.

In his monumental biography of Richard Feynmann, Gleick writes that
Feynmann often did original work without publishing, which was a
danger to later scientists who would embark upon a problem and later
discover that Feynmann had previously solved it, signed the guest book,
and moved on.

Worse, his solution was typically more elegant and general. To add
insult to injury, the problem did not rise to the level that Feynmann
considered publishable.

I find myself reinventing other people's ideas constantly, and it does
introduce a little humility.

 

[Lumba Ogir]

Nelson,
such a nice person you are.

 

[mlloyd1]

interesting ...

i became a displaced ee from telecom last year and have "kinda" moved from plainfield, il to st louis!
hey, i know where alton is!


btw, i'm enjoying your krill development, but only reading for now. i have no toys down here with me; not even my soldering iron.

mlloyd1

... when I lived in St. Louis. Really in Alton Ill., but no one would know where that is ...

 

[Samuel Jayaraj]

I find myself reinventing other people's ideas constantly, and it does introduce a little humility.

Or was that to read, I find other people constantly reinventing my ideas....?

God Bless You Nelson.

 

[Nelson Pass]

such a nice person you are.

I said a little humility. Not nearly as much as you imagine.

 

[Lumba Ogir]

Nelson,
no misunderstanding, besides I have much more evidence.

 

[scott wurcer]

26dB? For some reason I thought it was 27.84 dB. Also, my amp is not a triple Darlington biased at high current. You are correct about the noise however.

Since the triple has been brought up so many times, lets look at how my amp performs current wise at low impedance. First, we make the assumption that the current sources providing dive to the output Darlington are set at 10mA as shown. The second assumption is that an amp driving a low impedance load at near maximum current will warm up above ambient temperature. Now look at the spec sheets for the transistors I show on the BOM. That 10mA translates into a maximum output current of 100A, give or take an amp. I really don't expect that from a 16A transistor. Even taking into account beta droop on the output transistor (shouldn't be a problem for the driver) you can easily destroy the transistor before the non triple output stage "chokes" for lack of current.

The exact number was not important, I just rounded off a typical PA value. The lack of short circuit protection is a typical "feature" of many amps, I would assume there is a fuse somewhere.

 

[c2cthomas]

I would assume there is a fuse somewhere.

Hmmmmm........ Speaker coil????

 

[megajocke]

That's an expensive fuse

 

[scott wurcer]

Hi Bob,
I'm struggling with what appears to be a suspension of reality in this thread. I look at Steve's output stage and can see how the output devices can be reverse biased (switched off) in normal operation. Can you?

Also, do you have any objective understanding of why his saturated transistor bias scheme ought to improve linearity?

Brian

I was hoping to find out if the distortion trim "knows" if the load is 8 Ohms or 4 Ohms. I have no way to build or simulate this so I am waiting patiently for the builders to finish.

 

[c2cthomas]

That's an expensive fuse

Good to have a couple of these on hand!

 

[Steve Dunlap]

The exact number was not important, I just rounded off a typical PA value. The lack of short circuit protection is a typical "feature" of many amps, I would assume there is a fuse somewhere.

I realize you have not been following this thread from the beginning. Yes there is a fuse. I address the protection issue some time back. I stated that a fuse and thermal shutdown must be incorporated into the schematic. If there are other considerations to meet local codes, they must be incorporated also.

So far, the amps seem to survive a short circuit with only a blown AC fuse. I do not recommend that as a test on any amp, but it does happen.

 

[Steve Dunlap]

I was hoping to find out if the distortion trim "knows" if the load is 8 Ohms or 4 Ohms. I have no way to build or simulate this so I am waiting patiently for the builders to finish.

The distortion null would normally be set with a load that reflects the expected load while in use. If the expected load is unknown (not likely for the DIY crowd) set the null at rated power at 8 ohms. If you listen to mostly frequencies in the 20KHz range then use 20K as the input frequency.

You could set the distortion at full power at 4 ohms if you prefer. The difference in the performance will be very minor.

If you are asking "Is the distortion the same at all load impedances at all power levels at all frequencies", the answer is no. It does change, but not much.

I have no idea how many of the current builders have access to any type of distortion analyzer so I don't know what they will report. c2cthomas does, but that is here in my shop so the results would be suspect to some anyway.

 

[troystg]

I got a distortion analyzer from MR. Erath when he passed away a few months back. If anyone is in the Louisiana area you are welcome to use it.

 

[scott wurcer]

c2cthomas does, but that is here in my shop so the results would be suspect to some anyway.

That's fine with me. I would be happy with simple Vin-Vout plots of the output buffer vs load.

 

[stinius]

I was hoping to find out if the distortion trim "knows" if the load is 8 Ohms or 4 Ohms. I have no way to build or simulate this so I am waiting patiently for the builders to finish.

Hi Scott
I have done some simulations of the circuit, at 20 Hz 100 Hz 1 kHz 10 kHz and 50 kHz into 2 Ohm, 4 Ohm and 8 Ohm. I did the simulation of the whole circuit, the front end and the output stage.

I did the simulation with 5V output (to compare it with the Ayre, I think it was Glen that posted the Ayre THD at 5V output), and on almost full power 49W out. The 49W output power I have only simulated into 8 Ohm (so far)

I can email you the results, if you send me an email, I don’t think it is possible to attach a file when emailing from the forum.

I don’t want to post the results here, because every time I post something it’s a certain person that makes insulting comments.

Cheers
Stinius

 

[AndrewT]

I don’t want to post the results here, because every time I post something it’s a certain person that makes insulting comments.

I have reported this post with the following comments.

Hi,
why should this Member be intimidated by others? If this bullying is countenanced by the Moderating team, then we need a new Moderating team.
regards
Andrew T.

 

[Nelson Pass]

I was hoping to find out if the distortion trim "knows" if the load is 8 Ohms or 4 Ohms. I have no way to build or simulate this so I am waiting patiently for the builders to finish.

By the looks of it, it responds to current, so I doubt the null would
have a lot to do with impedance per se.