Electronics > Beginners

TL071 distortion - bad amplifier design?

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spec:

--- Quote from: Hero999 on December 16, 2018, 06:56:41 pm ---There are a couple of errors in the annotations:
--- End quote ---
That is a presumption

--- Quote from: Hero999 on December 16, 2018, 06:56:41 pm ---Constant current generator #2 should be current mirror.
--- End quote ---
That would be like calling the the input stage a long tailed pair- not very helpful or informative.
That arrangement of Q10 and Q11 has two functions, which if possible, will be explained. Just a clue: a current mirror is a constant current generator.

--- Quote from: Hero999 on December 16, 2018, 06:56:41 pm ---The voltage to current converter, is mislabeled.
--- End quote ---
Another presumption

--- Quote from: Hero999 on December 16, 2018, 06:56:41 pm ---A voltage to current converter would be a transconductance amplifier i.e. voltage in, current proportional to the input voltage out.  It's really a unity gain buffer or current booster circuit i.e. input voltage = output voltage, with a high input impedance and low output impedance.
--- End quote ---
Incorrect, the output transistor pairs convert an input voltage from the VAS to a current to drive the speaker (V/R).
It is difficult to chose titles for circuit functions, but Current Booster, gives totally the wrong message.
'unity gain current booster' that is a contradiction in terms.

--- Quote from: Hero999 on December 16, 2018, 06:56:41 pm ---I'm aware that the poster knows this and has just worded it poorly.
--- End quote ---
And yet another presumption.

spec:
Just a general note. I was rather hoping that we could have a positive and constructive discussion about the Self Simple Blameless Amplifier (SSBA). And it was my intention to discuss how the circuit works and what it's merits are, rather than grinding on about capacitor selection again and discussing audio power amplifier architecture and frequency stabilization etc, etc.

Also bear in mind that the SSBA is in wide use and has been designed by Douglass Self, no less, so criticism of the design by mere mortals does not make sense, neither does equating the TL071 amp with the SSBA.

By the way, as first mentioned on this thread by Mark Hennessy, read Douglass Self's book, 'Audio Power Amplifier Design Handbook', Edition 6, to get a bit more insight into audio power amplifier design- it is a very interesting read and it also covers circuit design and layout techniques that are applicable to electronics in general.

spec:
AngraMelo

What are your plans now? I suggest at this stage that the way forward is:

[1] Correct/develop the TL071 amp and get it performing as well as possible to the latest mod standard that I posted.
[2] Build a Self Simple Blameless Amplifier (SSBA).

In regard to the actual build of the SSBA you have a few options:

[1] Knife and fork
[2] Your own PCB layout
[3] Stock PCB
[4] Stock SSBA kit
[5] Ready built SSBA

[1] By hand wiring using copper/brass strip/wire for the relevant signal paths, you can make a superb SSBA, but it would involve much work and development
[2] Like [1] above you could produce a superb board, but once again it would involve much work and development. And then you have to have the PCB manufactured.
[3] Last time I looked there were a load of SSBA (or similar) boards on the market.
[4] As [3]
[5] As [3]

I would recommend [5] from a practical point of view, but as you have said that you are in this for the experience, rather than to just have an amplifier, so perhaps [3] or [4] would suit.

By the way you have already got eminently suitable output transistors, or would you like to buy another pair of output transistors for the SSBA?

AngraMelo:

--- Quote from: spec on December 17, 2018, 06:47:47 am ---AngraMelo

What are your plans now? I suggest at this stage that the way forward is:

[1] Correct/develop the TL071 amp and get it performing as well as possible to the latest mod standard that I posted.
[2] Build a Self Simple Blameless Amplifier (SSBA).

In regard to the actual build of the SSBA you have a few options:

[1] Knife and fork
[2] Your own PCB layout
[3] Stock PCB
[4] Stock SSBA kit
[5] Ready built SSBA

[1] By hand wiring using copper/brass strip/wire for the relevant signal paths, you can make a superb SSBA, but it would be a load of work and development
[2] Like [1] above you could produce a superb board, but once again it would involve much work and development. And then you have to have the PCB manufactured.
[3] Last time I looked there were a load of SSBA (or similar) boards on the market.
[4] As [3]
[5] As [3]

I would recommend [5] from a practical point of view, but as you have said that you are in this for the experience, rather than to just have an amplifier, so perhaps [3] or [4] would suit.

By the way you have already got eminently suitable output transistors, or would you like to buy another pair of output transistors for the SSBA?

--- End quote ---

I would like to go for option one!! As I friends says: aim on Mars to hit the Moon! hahahaha
I know it will be a pain in the butt but hey, Im here for the ride! If it proves a challenge to far away from my paygrade lets try option 3/4

Ill send an email to the Signal Transfer Company and see about the shipping fees, they appear to be a Licensed dealer of the boards, if they are not please let me know so I can look for someone who can actually sell them.
They are a bit pricy when doind the currency exchange (around double what I pay for my electrical bill per board not including shipping), so if I could etch them myself it would be awesome!

Also, lets to the TL071!!

spec:

--- Quote from: AngraMelo on December 17, 2018, 07:04:33 am ---
--- Quote from: spec on December 17, 2018, 06:47:47 am ---AngraMelo

What are your plans now? I suggest at this stage that the way forward is:

[1] Correct/develop the TL071 amp and get it performing as well as possible to the latest mod standard that I posted.
[2] Build a Self Simple Blameless Amplifier (SSBA).

In regard to the actual build of the SSBA you have a few options:

[1] Knife and fork
[2] Your own PCB layout
[3] Stock PCB
[4] Stock SSBA kit
[5] Ready built SSBA

[1] By hand wiring using copper/brass strip/wire for the relevant signal paths, you can make a superb SSBA, but it would be a load of work and development
[2] Like [1] above you could produce a superb board, but once again it would involve much work and development. And then you have to have the PCB manufactured.
[3] Last time I looked there were a load of SSBA (or similar) boards on the market.
[4] As [3]
[5] As [3]

I would recommend [5] from a practical point of view, but as you have said that you are in this for the experience, rather than to just have an amplifier, so perhaps [3] or [4] would suit.

By the way you have already got eminently suitable output transistors, or would you like to buy another pair of output transistors for the SSBA?

--- End quote ---

I would like to go for option one!! As I friends says: aim on Mars to hit the Moon! hahahaha
I know it will be a pain in the butt but hey, Im here for the ride! If it proves a challenge to far away from my paygrade lets try option 3/4

Ill send an email to the Signal Transfer Company and see about the shipping fees, they appear to be a Licensed dealer of the boards, if they are not please let me know so I can look for someone who can actually sell them.
They are a bit pricy when doind the currency exchange (around double what I pay for my electrical bill per board not including shipping), so if I could etch them myself it would be awesome!

Also, lets to the TL071!!

--- End quote ---

OK
So it is:
[1] Develop TL071 amp
[2] Separately build the SSBA by knife and fork and, if that is not successful/takes too long, go for a stock PCB.

The PCBs from the Signal Transfer Company are very expensive and postage to Brazil would add significantly to the cost.
The PCBs that I was thinking of are from ebay, and many of the home electronics companies. If I get time, I will try to find some links, and perhaps other members may like to assist here too.

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