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Messages - skey
« on: April 29, 2008, 10:33:59 AM »
Thank you Teemuk!
I've only just skimmed the book but appreciate the history you give. The detail you give in this area isn't something I've seen in other books. It's very interesting.
I would comment that some phrases could be insulting to some readers, for example:
"However, this is against false beliefs and information
spread by a vast number of people who have little idea of what they are talking about."
If you have proof and measurements then I think it's fine to present the evidence, but no need to polarize some readers who may think otherwise.
Also, technology changes very quickly, DSP/modeling are catching up to anything real. Your opinions at the time of writing the book may soon be changing. Keep an open mind. Software approaches may seem complicated, but as they grow more common they gain acceptance.
I hope to get a chance to really read it in a few months.
« on: November 28, 2006, 06:30:55 PM »
Thanks for the feedback
Can you post the spice model?
Here's a spice model of an amp that closely matches the tube amp in the patent:http://duncanamps.com/zips/el34_push_pull.zip
If you raise the input voltage to say 2v you will see something very close to diagram 3F.
At think the point is that class-ab tube amp overdriven migrates to class-b type output.
Interestingly, at http://tech.groups.yahoo.com/group/LTspice/
there is a schematic of a preamp that does crossover distortion as well as clipping:
Files/Examples/Apps/Audio Distortion Preamp for Electric Guitar
« on: November 28, 2006, 10:37:00 AM »
Here's an interesting Peavey patent. http://www.freepatentsonline.com/5524055.html
"... Thus, the output tubes 16 and 18 become over biased beyond class-B and at severe output clipping significant crossover distortion is generated as well. Consequently, at overload, the output signal of tube amplifier 10 will be clipped at the peaks. However, it will not be as "dirty" as a typical solid state power amplifier operating under the same conditions, because a large portion of the overloaded output waveform is forced or compressed into the severe crossover distortion region. To a musician, such a waveform is much more musical in nature and "cleaner" (i.e., less harsh) than a solid state amplifier at overload. Due to the compression (i.e., distortion near the zero crossover), the actual peak output clipping is reduced and is far more tolerable than that of the solid state amplifier. This phenomenon is thus, tube power amplifier compression."
There's circuit schematics that simulate this type of compression.
I commonly see diodes for clipping, but never anything for adding crossover distortion, and the effects it has on clipping.
« on: June 14, 2006, 11:36:54 PM »
Neither of the above heatsinks above seem to take advantage of thermal airflow.
Sometimes smaller is better if it's less bulky. Is there any convenient way to figure out a useful minimal size you'd need?
« on: May 05, 2006, 04:46:51 PM »
I recall reading about a Bob Carver Challenge in that he had found similar results.
Hard to find current information on this challenge.
« on: May 02, 2006, 07:17:34 PM »
I ran across these:http://www.oliveaudio.com/index.php?page=1
Click on the "ULCA" link.
They are from Lars Clausen who started www.LCaudio.dk
but is no longer with them.
The ULCA3 - Single ended Class-A looks like a lot of fun and ultra-simple and potentially a great sounding amp.
« on: May 01, 2006, 12:39:46 AM »
Teemuk - this is great information and a couple of very interesting surprises!
I was expecting more out of the modern design.
« on: April 24, 2006, 01:22:54 AM »
Wow - that link is a good find. That whole site is great. Thanks!
« on: April 16, 2006, 11:32:48 PM »
Maybe the difference in complexity is just what measures different between amps? Listening there's really not much of a difference. I know I have good and bad amps all over my house and cars. In the end I tune out any sound the amp contributes and just listen to the music.
On tube sound. Yes any clean amp can reproduce a tube sound. Just play a recording or mic a tube amp. But what makes that tube amp sound in the first place?
All articles on what makes "tube" sound always show a sine wave, and squashing during clipping on the sine wave.
for example: http://www.paia.com/tubesnd.htm
It just doesn't seem complete.
Hitting a string on a guitar is a complex waveform with harmonics. More so on a bass guitar with round wounds.
As mentioned elsewhere, with a clean amp, when the fundamental clips, the clipping itself doesn't really add that much more harmonic content. Instead what happens is the fundamental compresses as it can't get any louder, and the high frequency harmonics of the input signal grow stronger and stronger as they haven't clipped yet. This unbalance might be characteristic SS harshness.
Why would a tube be better? I just have gut feeling it has to do with roll-off of the high frequency as it approaches clipping.
Maybe - there's usually transformers in tube power amp circuits, this might help in roll off of the highs.
Maybe it's the tube itself, when it approaches clipping for a class-a preamp, on one side of the waveform there's build up of electrons, on the other end there's starvation of electrons. I have a feeling that at one of these extremes, high frequency can't pass. Like at the high end of the curve, maybe a high abundance of electrons doesn't let as much highs through. Or during starvation - high frequencies can't pass, so it may be adding to the roll-off. I haven't been able to find frequency response curves of a tube amp as it approaches and goes into clipping. I don't have a tube amp to measure, and I don't know how to simulate one.
I've seen that a mosfet amp can be made with the exact same squashing behavior of a sine wave as a tube amp, but I don't think it's going to be the same HF roll-off with a complex waveform at clipping.
« on: April 14, 2006, 02:53:19 PM »
I would be very interested to see the results of your listening tests, but what will the subjects be listening to?
I think it would vary if they listened to an electric guitar straight in, verses music.
For music, at reasonable levels I highly doubt there will be much of a difference.
For guitar, a clean transparent amp would probably give the "sterile" sound as really that what comes out of a e-guitar. The cheap amp my sound better as it will give some colorization to the guitar.
On the other hand, if you had a processed guitar signal going in, then I'd say you want a transparent amp so you don't add any extra colorization than what you put in.
All just guessing, it'll be interesting to see the results of the tests.
« on: April 12, 2006, 01:35:04 PM »
If we're talking LM3886 chipamps, clipping those will sound horrible period. ...
This is the generalization I'm trying to avoid here. The article points out one reason why an amp may sound bad at clipping, and it's not due to the clipping. It's due to the high frequency component of the input signal gaining unproportionate DBs.
Clipping harmonics are very small compared to the high frequency components of the input signal.
« on: April 12, 2006, 01:23:34 PM »
For oddball ideas take a look at the mini-itx site:http://www.mini-itx.com/projects/sparc/
I've been looking in thrift shops for one of those old stylish toasters. I was going to have the power supply toroid sticking out like a bagel. And put some red LEDs or that neon wire stuff in so it'd look like it's toasting.
This stuff can be a lot of fun.
« on: April 12, 2006, 11:57:35 AM »
Thanks Teemuk - youve taken it 400x more than I can at my pace.
I'm not up on the spice tools, and manipulating wave files.
I'm just very happy the whole idea wasn't shot down because I missed something.
I was going to try some wire experiments. Mainly at first doing the grain-of-wheat lamp trick on the output to feedback to a ldr on treble control in the preamp. This probably won't be fast enough, so maybe switch to some LEDs. Trying to keep it simple if possible. Maybe not ideal but at least a little benefit.
« on: April 12, 2006, 01:52:43 AM »
Take a read at this: http://www.rane.com/pdf/old/note128.pdf
Limiting can be used to prevent clipping, but this doesn't get the maximum drive out of the amp. Lows usually cause the clipping. During bass clipping the high frequency of the input signal has not clipped and thus is still allow to gain DB's. The lows compress far before the highs ever do.
I'm thinking the key to squeezing out the maximum from a lower wattage SS amp is to allow the lows to clip, but when they do start to compress the highs. In other words instead of limiting the whole signal just limit the highs. The amp will still clip and add "some" high frequency content, but as much as people believe.
This just might be the key to squeezing out the most from a small SS amp.
« on: March 31, 2006, 06:30:14 PM »
Nice! These are truly classy.
Well except for the the flower pot
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