circuit analysis
Per, thanks for sending me the August 98 article. The input stage looks like a standard complementary diff amp, except that the emitters are coupled trough R6 and C8. I guess this allows the active side to draw extra current from the inactive side, so maximum current into the VAF stage is not limited by the tail current. This is somewhat similar but probably not as effective as the Analog Devices Quad Core, see: http://www.analog.com/technology/amplifiersLinear/training/tutorialsSeminarMaterial.html, go to figure 1.9 of Chapter 1 by Walt Kester.
The VAF stage consists of complementary current sources T9 and T12, which looks straightforward enough. If T10 and T11 had constant voltage sources on their bases, they would constitute cascode transistors. However, their input is generated by T13 and T14. These in turn, receive some of the output current from the differential input stage. I lack the original 97 article and I am a little too slow today to understand what this part of the circuit does. Can anybody give me a hint?
Thanks,
Eric
Per, thanks for sending me the August 98 article. The input stage looks like a standard complementary diff amp, except that the emitters are coupled trough R6 and C8. I guess this allows the active side to draw extra current from the inactive side, so maximum current into the VAF stage is not limited by the tail current. This is somewhat similar but probably not as effective as the Analog Devices Quad Core, see: http://www.analog.com/technology/amplifiersLinear/training/tutorialsSeminarMaterial.html, go to figure 1.9 of Chapter 1 by Walt Kester.
The VAF stage consists of complementary current sources T9 and T12, which looks straightforward enough. If T10 and T11 had constant voltage sources on their bases, they would constitute cascode transistors. However, their input is generated by T13 and T14. These in turn, receive some of the output current from the differential input stage. I lack the original 97 article and I am a little too slow today to understand what this part of the circuit does. Can anybody give me a hint?
Thanks,
Eric
Not exactly. The point in a diff amp (with or without degeneration resitors) where the emitters are joined is the common reference of the two inputs. Having it insulated from any capracious capacitance might make sense. Besides, degeneration resistors are typically 10 - 100 R whereas the CCS series resistors should be >> 1 k if voltage swing permits.
Regards,
Eric
Regards,
Eric
Craig,
If you send me a PM with your address I can put a copy of the article in the post to you.
So 20th Century, I know...
Alex
stochino-ultra fast pwr amp
Dear Smithy666,
Searching for the original Stochino article: Ultra Fast, Low Distortion Pwr Amp, EW&WW Aprill 1997, I found your offer to diy member Craig 405, that you have it and that you can scan it and send it to him via e-mail.
If you are still able to scan it, I will appriciate you very much, if you can send full article to me, as I am very interesting in Stochino's works.
Note that I already have the following Stochino's articles:
- Fast, Clean and Powerfull (the follow-up for the above article), EW Aug. 1998; pages 633 - 638,
- Audio Design leaps forward, EW&WW Oct 1994, pages 818 - 827,
- Non-slewing Audio Pwr Amp, EW March 1996, pages 256 - 259.
I can send you the above articles if you have not or need them.
Thank you in advance.
Best regards,
Bane (Branko Nojkovic), Belgrade, Serbia, e-mail address: b.nojkovic@gmail.com
Dear Smithy666,
Searching for the original Stochino article: Ultra Fast, Low Distortion Pwr Amp, EW&WW Aprill 1997, I found your offer to diy member Craig 405, that you have it and that you can scan it and send it to him via e-mail.
If you are still able to scan it, I will appriciate you very much, if you can send full article to me, as I am very interesting in Stochino's works.
Note that I already have the following Stochino's articles:
- Fast, Clean and Powerfull (the follow-up for the above article), EW Aug. 1998; pages 633 - 638,
- Audio Design leaps forward, EW&WW Oct 1994, pages 818 - 827,
- Non-slewing Audio Pwr Amp, EW March 1996, pages 256 - 259.
I can send you the above articles if you have not or need them.
Thank you in advance.
Best regards,
Bane (Branko Nojkovic), Belgrade, Serbia, e-mail address: b.nojkovic@gmail.com
stochino-ultra fast pwr amp
Dear Smithy666,
Searching for the original Stochino article: Ultra Fast, Low Distortion Pwr Amp, EW&WW Aprill 1997, I found your offer to diy member Craig 405, that you have it and that you can scan it and send it to him via e-mail.
If you are still able to scan it, I will appriciate you very much, if you can send full article to me, as I am very interesting in Stochino's works.
Note that I already have the following Stochino's articles:
- Fast, Clean and Powerfull (the follow-up for the above article), EW Aug. 1998; pages 633 - 638,
- Audio Design leaps forward, EW&WW Oct 1994, pages 818 - 827,
- Non-slewing Audio Pwr Amp, EW March 1996, pages 256 - 259.
I can send you the above articles if you have not or need them.
Thank you in advance.
Best regards,
Bane (Branko Nojkovic), Belgrade, Serbia, e-mail address: b.nojkovic@gmail.com
Dear Smithy666,
Searching for the original Stochino article: Ultra Fast, Low Distortion Pwr Amp, EW&WW Aprill 1997, I found your offer to diy member Craig 405, that you have it and that you can scan it and send it to him via e-mail.
If you are still able to scan it, I will appriciate you very much, if you can send full article to me, as I am very interesting in Stochino's works.
Note that I already have the following Stochino's articles:
- Fast, Clean and Powerfull (the follow-up for the above article), EW Aug. 1998; pages 633 - 638,
- Audio Design leaps forward, EW&WW Oct 1994, pages 818 - 827,
- Non-slewing Audio Pwr Amp, EW March 1996, pages 256 - 259.
I can send you the above articles if you have not or need them.
Thank you in advance.
Best regards,
Bane (Branko Nojkovic), Belgrade, Serbia, e-mail address: b.nojkovic@gmail.com
Yesterday I started a research on the Stochino designs, particularly because they are using IRFP mosfets outputs, which are much more affordable than other types.
So I loaded the schematic into LTSPice and simulated it.
The results are promising, with reasonably low THD. Biased the amp for 150mA, which seems to be the recommended setting.
The only changes I did was the LP cap at the input, from 1000p to 470p, and the 3v9 zener for a 4v9 one, because I couldn't find a 3v9 model. The amp simmed well with those zeners, so I think they might not be critical. Correct me if I'm wrong.
The DC offset is a bit high, at 84mV, but I don't know what to trim to lower it. I tried with the 200R resistor between the LTPs, but I'm not sure.
What I expected to be better was the square wave response, but I got quite rounded edges that I didn't get on other designs.
As several years have passed for this thread, maybe someone can say what happened to the amps and else.
Is there any commercial amp using Stochino designs?
So I loaded the schematic into LTSPice and simulated it.
The results are promising, with reasonably low THD. Biased the amp for 150mA, which seems to be the recommended setting.
The only changes I did was the LP cap at the input, from 1000p to 470p, and the 3v9 zener for a 4v9 one, because I couldn't find a 3v9 model. The amp simmed well with those zeners, so I think they might not be critical. Correct me if I'm wrong.
The DC offset is a bit high, at 84mV, but I don't know what to trim to lower it. I tried with the 200R resistor between the LTPs, but I'm not sure.
What I expected to be better was the square wave response, but I got quite rounded edges that I didn't get on other designs.
As several years have passed for this thread, maybe someone can say what happened to the amps and else.
Is there any commercial amp using Stochino designs?
With the original circuit and parts values I found the offset was quite a lot lower than that, and I would be surprised to see a measurement as high as yours. You could try playing with the parameters of the transistors in your simulator.
The most straightforward way to reduce the DC offset is to replace the input transistors with parts with higher current gain, and match the PNP-NPN devices closely. In one of my amps I replaced the existing input pairs with reasonably well-matched 2SA970 and 2SC2240 low-noise transistors, and this reduced the offset to around 5mV in one channel. I think I must have made a mistake with the transistor substitution in the other channel, as this actually increased the offset, but I didn't get round to fixing the fault.
I stopped using the Stochino amplifiers after a while, as I didn't really enjoy the treble quality in the longer term. I went back to my EL84 valve amps, and eventually I gave the Stochinos to Bill.
That surprises me, as the original article (if I recall correctly) quoted a bandwidth of a MHz or so, so you should get nice clean square waves, particularly at low power.
Alex
The problem with matching on the Stochino is that they are NPN and PNP. I could try simulating with MAT02 and MAT 03, and see what happens. Perhaps someone tried a DC servo with it.
The treble being tiring by a mismatch between tweeters and amp, or the output MOSFETs having that specific sound.
I'm not so sure the BW is completely related to the square wave shapes.
On sim, the Stochino is 6dB down at 1MHz.
This sim model I have now seems more accurate and stable now. I also changed the bias system, so as not have any doubts on the TL431 Stochino used.
If I remember correctly, I bought enough of each to get the Hfe quite close between NPN and PNP.
Perhaps the latter, since I was using speakers with the revealing but quite benign ScanSpeak D2905/9300 soft dome. The amps reminded me of my impressions listening to big Krells on a couple of occasions few years ago - detailed, but a bit "over-lit".
Alex
Hi,
In regards to Giovanni Stochino articles, does anyone have the article from Electronics World & Wireless World, October 1995 :
Stochino, G, "Ultra-fast Amplifier", EW, October 1995, pp.835-841.
I have some of the magazines after 1996, and some are on the internet, except for this particular issue.
If anyone has access to the article,or the magazine, would it be possible to scan in and e-mail to myself - would be very grateful.
Thanks and regards,
Shadders.
In regards to Giovanni Stochino articles, does anyone have the article from Electronics World & Wireless World, October 1995 :
Stochino, G, "Ultra-fast Amplifier", EW, October 1995, pp.835-841.
I have some of the magazines after 1996, and some are on the internet, except for this particular issue.
If anyone has access to the article,or the magazine, would it be possible to scan in and e-mail to myself - would be very grateful.
Thanks and regards,
Shadders.
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