Has anybody tried building Stochino fast amplifier ?

Suman Dachepalli

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Hi,

Iam trying to build an amplifier came across Stochino amplifier (attached circuit, improvised version and related documentation).

Want to know if anyone has tried this earlier, if so how is the sound signature and overall performance.

Also DIY gurus kindly analyze the circuit and suggest if this is worth giving a try with your expertise.

Thanks in Advance.

Regards,
Suman
 

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  • Stochino fast amplifier design.pdf
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  • Stochino fast amplifier design-Improving the Ultra-fast Audio Amp (A).pdf
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IndianEars

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Giovanni Stochino's design is well known.

A Word of Caution when building an Ultra Fast amplifier... The Layout of components and even the wiring is Critical. Poor layout can cause the amplifier to oscillate, which could blow the amp or connected speakers or Both !
 

HormusPeston

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I tried building one in the 1990s from the magazine article I found at the British Council Library in Calcutta. I was young and foolhardy. Completed it. Blew up the output mosfets (twice!) and filled the room with the aroma of burnt PCB. Couldn't diagnose the problem. I salvaged what parts and pride I had left, and built a JLH instead. Thirty years later (now old and foolhardy) I wouldn't recommend building this design unless (1) you have the skills to design a PCB for a circuit that can handle high currents, and (2) you can afford to purchase a handful of transistors, first to match them and then destroy the matched pair while troubleshooting the amplifier during set up.
That shouldn't stop you! Good luck and a very happy New Year to you.
Cheers!
~hp
 

IndianEars

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Which JLH did you build ? I was a BIG Fan of John Linsley Hood, and built some of his designs starting with the Class A ....
 

Suman Dachepalli

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Which JLH did you build ? I was a BIG Fan of John Linsley Hood, and built some of his designs starting with the Class A ....
Never tried JLH builds, kindly let me know if you have any good suggestions.

Also I prefer class AB due to size and complex of large heatsinks on class A
 
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sachu888

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Never tried JLH builds, kindly let me know if you have any good suggestions.

Also I prefer class AB due to size and complex of large heatsinks on class A
Class AB can be sound very good. I have listened and built variety of Class A and Class AB amps, so I have a fairly good idea.

Regards
Sachin
 

IndianEars

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Never tried JLH builds, kindly let me know if you have any good suggestions.

Also I prefer class AB due to size and complex of large heatsinks on class A
JLH Designs are all Dated by today's preferences.

They all used high feedback (except the Class A design that was a low gain design).

Also all JLH designs rolled off the HF beyond the audible band, as JLH felt they provided a better sound and amplifier stability, when built by DIY guys.

You may want to look at other more modern designs to build.

If you are Not an Expert at building DIY amps, I would STRONGLY recommended that you build amps that have a ready made, tested PCB available for you. This will of course restrict many designs.

Also if you think DIY will save you money, think again, and factor in the fact that a DIY amp will have little resale value .....
 

IndianEars

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Class AB can be sound very good. I have listened and built variety of Class A and Class AB amps, so I have a fairly good idea.

Regards
Sachin
I fully agree with you, sachu888.

Also "Class A' has become marketing (or bragging) hype for power amps.... Most designs and implementations here on this forum (and often elsewhere) are Class A only for the first few watts... They are infact High Bias Class AB amps. ( High Bias Class AB often yields HIGHER Distortion than optimum bias Class AB.

As an example any design claiming 100 Watts, Class A into 8 Ohms & 4 Ohms is likely to be false. The Bias Current required to deliver 100 Watts into 4 Ohms in Class A is inordinately large....

100 Watts Class A into a 4 Ohm load will require a Bias / standing current of 7 Ampere, that too into a simple resistive load. Real world speakers with Reactive loads will require even more Class A Current !

The JLH 10 Watt Class A design from Wireless World is recommended reading for those who want to learn / understand the basics Class A Power amp design. There is an Excellent site dedicated ONLY to this design.

Do not miss reading the followup content, in addition to the original article of April 1969 is Wireless World.
 

IndianEars

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The Most simple, straightforward MOSFET Amplir design was the classic HITACHI MOSFET Audio Power Amplifier. It delivered more than 100 Watts into 8 ohms, and really got MOSFETS into audio power Amplifiers. It uses Lateral power MOSFETS.

Erno Borbely's 60 Watt (Lateral) Mosfet design also took this a step further with a Dual Differential input stage.

Theree are pros & Cons to using MOSFETs v/s bipolar transistors. What aspect has got u interested in constructing a MOSFET design ?
 

IndianEars

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MINIMUM CLASS A POWER AMPLIFIER BIAS CURRENT REQUIRED

For clarity & quick reference, I have created a table listing the MINIMUM bias current in a Class A Audio Power Amplifier for 4 Ohm & 8 Ohm RESISTIVE speaker loads. Real World Speakers are Never Resistive, so will require even higher currents.

(Incidentally, this is also the MINIMUM current that a Class AB amplifier needs to deliver into 4 / 8 ohm speakers.)


4 OHM SPEAKER
8 OHM SPEAKER
1 Watt
0.7 Amperes​
0.5 Amperes​
5 Watt
1.6 Amperes​
1.1 Amperes​
10 Watt
2.2 Amperes​
1.57 Amperes​
20 Watt
3.1 Amperes​
2.2 Amperes​
50 Watt
4.95 Amperes​
3.5 Amperes​
100 Watt
7 Amperes​
4.95 Amperes


As an example, a Class A power amplifier biased at 1.3 Amperes will deliver (in Class A) a little less than 5 Watts into 4 Ohms!



Note: The Average (RMS) Speaker current required to develop the required power is calculated with the simple formula:

Power = I x I x R Where
P = Power in Watts
I = RMS Current in Amperes
R = Speaker Impedance


The DC current required to generate the Average / RMS AC current into the speakers is 1.4 ( i.e. Square Root of 2) times higher.

Hence to generate 2 amperes AC Current into the speaker, 2.8 Amperes of DC current is required in the Amplifier's Power Transistors.
 

Suman Dachepalli

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MINIMUM CLASS A POWER AMPLIFIER BIAS CURRENT REQUIRED

For clarity & quick reference, I have created a table listing the MINIMUM bias current in a Class A Audio Power Amplifier for 4 Ohm & 8 Ohm RESISTIVE speaker loads. Real World Speakers are Never Resistive, so will require even higher currents.

(Incidentally, this is also the MINIMUM current that a Class AB amplifier needs to deliver into 4 / 8 ohm speakers.)


4 OHM SPEAKER
8 OHM SPEAKER
1 Watt
0.7 Amperes​
0.5 Amperes​
5 Watt
1.6 Amperes​
1.1 Amperes​
10 Watt
2.2 Amperes​
1.57 Amperes​
20 Watt
3.1 Amperes​
2.2 Amperes​
50 Watt
4.95 Amperes​
3.5 Amperes​
100 Watt
7 Amperes​
4.95 Amperes​


As an example, a Class A power amplifier biased at 1.3 Amperes will deliver (in Class A) a little less than 5 Watts into 4 Ohms!



Note: The Average (RMS) Speaker current required to develop the required power is calculated with the simple formula:

Power = I x I x R Where
P = Power in Watts
I = RMS Current in Amperes
R = Speaker Impedance


The DC current required to generate the Average / RMS AC current into the speakers is 1.4 ( i.e. Square Root of 2) times higher.

Hence to generate 2 amperes AC Current into the speaker, 2.8 Amperes of DC current is required in the Amplifier's Power Transistors.
Superb thanks for valuable inputs.
 

HormusPeston

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I built the updated JLH that came out in the mid nineties with a regulated power supply. The link provided by IndianEars has the schematics. Note that Class A designs (including the JLH, Hiraga and others) are best suited to very efficient speakers (90dB/W or better) if one wants to keep the quiescent current at sensible levels while providing an acceptable gain, i.e., for an amplifier that is loud enough, but not hot enough to fry eggs. I cannot stress this point enough to youngsters who like to give their speakers a guard of honour from TO-3 devices. These amps run hot. I still the have the amplifier lying somewhere and when I last checked it many years ago, it still worked and sounded just as nice as when it was first turned on. Class A designs are relatively easy to troubleshoot, which is useful for a beginner. I would suggest going through Rod Elliot's website before you decide which circuit to build.
Best of luck with your project.
Cheers,
~hp
 

nn_in

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The Most simple, straightforward MOSFET Amplir design was the classic HITACHI MOSFET Audio Power Amplifier. It delivered more than 100 Watts into 8 ohms, and really got MOSFETS into audio power Amplifiers. It uses Lateral power MOSFETS.

Erno Borbely's 60 Watt (Lateral) Mosfet design also took this a step further with a Dual Differential input stage.

Theree are pros & Cons to using MOSFETs v/s bipolar transistors. What aspect has got u interested in constructing a MOSFET design ?
Also refer to Randy Slone's designs
 

nn_in

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Thanks, nn_in

Can you please share a link ?
There are books available https://www.amazon.in/G-Randy-Slone/e/B000APG19O/ref=dp_byline_cont_pop_ebooks_1
http://ledeaudio.com/product-category/audio-kits/g-randy-slone/ kits

Note that errors/corrections need to be culled out of the diyaudio forums
 

IndianEars

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There are books available https://www.amazon.in/G-Randy-Slone/e/B000APG19O/ref=dp_byline_cont_pop_ebooks_1
http://ledeaudio.com/product-category/audio-kits/g-randy-slone/ kits

Note that errors/corrections need to be culled out of the diyaudio forums
Many
THANKS :)

I have just downloaded it.
 
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