one of my employees was reading the pass article about this amp that is made from i don't recall how many small J fet
so he said to my why not do the same with bjt transitors ore make one that has 10X BD139 +10X BD 140 for outputs
anyone thinks that this is an idea worth looking at ?
so he said to my why not do the same with bjt transitors ore make one that has 10X BD139 +10X BD 140 for outputs
anyone thinks that this is an idea worth looking at ?
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This has been discussed before, I can't remember where - but somebody did build something on the forum and said they really liked the results.
I think modern BJT power transistors are very good - not sure it's worth the effort to make massively parallel small power BJTs.
For JFETs there aren't many power devices available.
I think modern BJT power transistors are very good - not sure it's worth the effort to make massively parallel small power BJTs.
For JFETs there aren't many power devices available.
quick look on the net i couldn't find much about the article ...it could be nice if you had some more info
Thanks
sakis
Thanks
sakis
i had no trouble finding the Pass article ...still it seems that i cannot find the Jan Didden article
Paralelling those small BD's works very well but carefully matching is needed. And this is a serious effort. TO220 devices are better from POV of cooling than TO126's.
"MJE200/210, cascoded with 2N3773 IIRC ..."
Ah, the author speaks!
You are of course correct, the MJE200/210 being 65Mhz/5A devices.
"TO220 devices are better from POV of cooling than TO126's. "
The real heat is handled by the 2N3773s.
Ah, the author speaks!
You are of course correct, the MJE200/210 being 65Mhz/5A devices.
"TO220 devices are better from POV of cooling than TO126's. "
The real heat is handled by the 2N3773s.
Wasn't there a thread somewhere that someone had used a bunch of to-92 transistors for outputs? Headphone amp maybe?
Hfe=100 at 2A.
With say, five devices in parallel it would be good for 200W/4Ω with a cascode (as per janneman).
With say, five devices in parallel it would be good for 200W/4Ω with a cascode (as per janneman).
Comparing to modern output devices I honestly dont see any benefits in going this route, its more complex and honestly it doent sound good. Even Nelso Pass has says he wouldnt go this route for outputstages as for some reason they dont sound good. Spec wise the difference is minimal and sometimes worse off using these parraleled parts depending on the devices used.
As for drivers Id say there is to be gained, OnSemi drivers like mje15033 and compliment are slow and have high parasitic capacatances, doubling two lesser IC capable transistors to achieved same power levels but much higher Ft, lower capacitance and better hfe linearity is not difficult to find.
As for drivers Id say there is to be gained, OnSemi drivers like mje15033 and compliment are slow and have high parasitic capacatances, doubling two lesser IC capable transistors to achieved same power levels but much higher Ft, lower capacitance and better hfe linearity is not difficult to find.
In quantity they are less than $0.13 each. I like the idea of five in parallel for a 25A 65Mhz device.
So Pass doesn't like a cascode output stage now?
Why do some of his recent designs use cascodes then (Lovoltec FET)?
So Pass doesn't like a cascode output stage now?
Why do some of his recent designs use cascodes then (Lovoltec FET)?
$.013 + the price of the cascode devices needed and offcourse the emitter resistors for current sharing + increased board space. How about single 30A 60Mhz device (MG6332) ??
Nelson own words in his forum although it was about the times he was designing conventional class AB amps like seen from threshold.
Nelson own words in his forum although it was about the times he was designing conventional class AB amps like seen from threshold.
I was under the impression that as one increases the number of output devices in a follower type output stage that the distortion decreases - as per Krell, I think that was part of the discussion on that amp?
Will the output Z decrease, assuming a similar device but lower in power all being in parallel as compared to a single device?
_-_-bear
Will the output Z decrease, assuming a similar device but lower in power all being in parallel as compared to a single device?
_-_-bear
I find it very important, that in designs with GNFB, output stage would be fastest compared to all previous stage. However, looking at datasheets, one finds that output transistors, on contrary to this requirement, are the slowest among all.
So, it has a strong reason, looking towards RF output transistors, like 500-1000MHz ones.
There are a lot of RF ones, but they are usually quite expensive, around 50USD price tag.
I have managed to get some tenths of russian kp958a (equivalent of Motorola MRF650) 40V 130W 10A Cob=130pF), could offer hFE matched pairs for 20USD per pcs. Static hFE span at 1A is from 30 to 60. Good driver transistors to them are 400MHz Sanyo 2SC3953.
Semelab MG6332
$6+ in 100 lot.
Gain and Ft drop like a rock above 9A, but it does have 200W SOA at 100V (25°C).
$6+ in 100 lot.
Gain and Ft drop like a rock above 9A, but it does have 200W SOA at 100V (25°C).
Choosing between MRF650 and MG6332 , one will choose between various design philosophies and even between various life styles.
Few days ago a friend of mine came to me with new CD disk, that he bought recently during his trip to US.
We were listening at rather high loudness (room is 6,5x5,5x3m, 89dB speakers), and he was curious what average power we are listening at. I have measured varying level of RMS voltage on speaker terminals, but anyway we were below 1W. Rated amp power was 10W (SE class A). And he started to ask, why people buy 400W amps. I assumed, that they do it because of belonging to different life style, they use to play music during parties, near swimming pool, etc. In this case requirements to the system are nothing in common with listening to audiophile recordings.
Few days ago a friend of mine came to me with new CD disk, that he bought recently during his trip to US.
We were listening at rather high loudness (room is 6,5x5,5x3m, 89dB speakers), and he was curious what average power we are listening at. I have measured varying level of RMS voltage on speaker terminals, but anyway we were below 1W. Rated amp power was 10W (SE class A). And he started to ask, why people buy 400W amps. I assumed, that they do it because of belonging to different life style, they use to play music during parties, near swimming pool, etc. In this case requirements to the system are nothing in common with listening to audiophile recordings.
i usualy listen much louder if i´m alone in the room , if i have a friend over even if we arent talking it´s unconfortable to listen louder.
I had a technics amp rated 45w , the equalizer setting i used took 50% of the power away , still it was enough , so i believe 20w is more than enough .
I had a technics amp rated 45w , the equalizer setting i used took 50% of the power away , still it was enough , so i believe 20w is more than enough .
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