High End Amplifier from Elektor with perfect measurements “Fortissimo 100”

[EXIF68]

Hello forum,

the german electronics magazine Elektor has released an ultra high end power amplifier for all diy electronic hobbyists.
Take a look to this:

Elektor Fortissimo-100 High-End-Verstärker-Kit

Der gefeierte Elektor-Audio-Design-Spezialist Ton Giesberts hat erneut einen phänomenalen Entwurf für eine High-End-Audio-Endstufe veröffentlicht, den Elektor Fortissimo-100. Die Ergebnisse des Verstärkers auf dem Prüfstand forderten die hochwertige Audio Precision-Test Vorrichtung von Elektor...

www.elektor.de

what do you think about this system?
greetings,

Walter

 

[piotrkundu]

I'm looking into building this.

 

[pma]

Looks good. Below is the schematics from the manual.

 

[piotrkundu]

This looks tempting too:
https://www.diyclassd.com/product/nilai500diy-500w-mono-kit/184

New Hypex Nilai500DIY modules )

Is a trigger or audio sense including? Any pop or click on power on/off? More pictures less hyperbole. I can make clicking noises and dogs will run in surprised to see what's happening.

www.audiosciencereview.com

 

[Capitol C]

Looks like a fair amount of work, ie, matching transistors which may or may not help if you don't have enough of them, building an additional regulated power suppl, , then building a second amp for the other channel, putting the whole thing in a box or two. Ends up being expensive and as far as I can tell hasn't been tested by an independent party.

 

[syn08]

A stupid schematic.

- Two differential gain stages + VAS, only to have it shunt frequency compensated (C12). It was shown decades ago that shunt compensation is the worst single (dominat) pole option, and Miller compensation is the best single pole approach. The zeroes introduced by R31, R37, R43 are doing exactly nothing.

- No buffer separating the VAS. A bad idea when it comes to the differential stage loading.

- The servo loop is wrongly designed. C29 introduces a zero in the control loop, that will make a LF response overshoot. Only a non inverting servo could use this zero, to compensate for the native extra pole in the servo.

- Lots of device matchings required, with zero net benefits.

- This thing may deliver with +/-40V supplies at best some 80W into 8ohm load (with reasonable distortions), a far cry from the spec of 94W.

- Absolutely no clipping management to speak of. Expecting nasty rail sticking a overloading, due to the unmanaged high open loop gain.

- And the deal killer: the temperature compensation of the output stage NJL thermaltrak devices won't work properly. The NJL internal diodes are poorly DC and tempco matched with the power transistors, and will either make the whole output stage thermally unstable, or overcompensate, with nasty thermal induced distortions.


One would be much better with a classic Lin topology (aka Blameless). No need to spend money and work on this design abomination.

Shame on Elektor for promoting this junk.

 

[piotrkundu]

Trimodal (Blameless) is on my list https://www.audiosciencereview.com/forum/index.php?threads/power-amplifier.29869/
And so is BC-1 (by Bob Cordell) and I'm actually waiting for newPCB's. Dartzeel Clones (NHB-108).

 

[piotrkundu]

A stupid schematic.

- Two differential gain stages + VAS, only to have it shunt frequency compensated (C12). It was shown decades ago that shunt compensation is the worst single (dominat) pole option, and Miller compensation is the best single pole approach. The zeroes introduced by R31, R37, R43 are doing exactly nothing.

- No buffer separating the VAS. A bad idea when it comes to the differential stage loading.

- The servo loop is wrongly designed. C29 introduces a zero in the control loop, that will make a LF response overshoot. Only a non inverting servo could use this zero, to compensate for the native extra pole in the servo.

- Lots of device matchings required, with zero net benefits.

- This thing may deliver with +/-40V supplies at best some 80W into 8ohm load (with reasonable distortions), a far cry from the spec of 94W.

- Absolutely no clipping management to speak of. Expecting nasty rail sticking a overloading, due to the unmanaged high open loop gain.

- And the deal killer: the temperature compensation of the output stage NJL thermaltrak devices won't work properly. The NJL internal diodes are poorly DC and tempco matched with the power transistors, and will either make the whole output stage thermally unstable, or overcompensate, with nasty thermal induced distortions.


One would be much better with a classic Lin topology (aka Blameless). No need to spend money and work on this design abomination.

Shame on Elektor for promoting this junk.

I'm trying my best to understand the schematics with basic EE skills and asksome questions.
1. The shunt compensation is R43 and C12 to ground. Do you think it will oscilate?
2. Do LM334 act as buffer?
3. Servoloop? So the entire first stage is regulated based on the output and global NFB ? Could you remove everything between R59 and base of T3?
4. Wouldn't the ThermalTrak actually be "piece the resistance" in this design? I mean it could possible be better matched then the other 25 unmatched transistors you get in the kit.

@syn08 It would be super interesting explain in more detail or maybe add your comments or suggestion for improvement in the schematics. Perhaps in a DM?

 

[sarumbear]

Hello forum,

the german electronics magazine Elektor has released an ultra high end power amplifier for all diy electronic hobbyists.
Take a look to this:

Elektor Fortissimo-100 High-End-Verstärker-Kit

Der gefeierte Elektor-Audio-Design-Spezialist Ton Giesberts hat erneut einen phänomenalen Entwurf für eine High-End-Audio-Endstufe veröffentlicht, den Elektor Fortissimo-100. Die Ergebnisse des Verstärkers auf dem Prüfstand forderten die hochwertige Audio Precision-Test Vorrichtung von Elektor...

www.elektor.de

what do you think about this system?
greetings,

Walter

Decent kit but why would you call an amplifier that has distortion at -67dB at 100W as “perfect measurements” when there are amplifiers with much better values reviewed on ASR.

Not to mention that by the time you created a stereo power amplifier you would have spent upwards of €450. For much less money you get twice the power and similar distortion with a Crown XLS 1502.

 

[pma]

Not to mention that by the time you created a stereo power amplifier you would have spent upwards of €450. For much less money you get twice the power and similar distortion with a Crown XLS 1502.

For the DIYer or the hobbyist it is much more interesting and satisfying to build the amplifier himself and a kit is a good way to do it, because a design from scratch needs more knowledge. I completely understand if someone wants to build something and not to buy a second hand product. To me, buying a second hand product would be extremely boring.

 

[piotrkundu]

With the recommended SMPS its another 150 and then encolsure around 200-300 it’s close to €900

 

[syn08]

I'm trying my best to understand the schematics with basic EE skills and asksome questions.
1. The shunt compensation is R43 and C12 to ground. Do you think it will oscilate?
2. Do LM334 act as buffer?
3. Servoloop? So the entire first stage is regulated based on the output and global NFB ? Could you remove everything between R59 and base of T3?
4. Wouldn't the ThermalTrak actually be "piece the resistance" in this design? I mean it could possible be better matched then the other 25 unmatched transistors you get in the kit.

@syn08 It would be super interesting explain in more detail or maybe add your comments or suggestion for improvement in the schematics. Perhaps in a DM?

Based on your questions, you are indeed at the very basic level. You'd be much better attempting to build a simpler and proven amplifier that you could understand. Reading some books on electronics would certainly help to start. Art of Electronics, Self, etc...

 

[piotrkundu]

Based on your questions, you are indeed at the very basic level. You'd be much better attempting to build a simpler and proven amplifier that you could understand. Reading some books on electronics would certainly help to start. Art of Electronics, Self, etc...

Read them all more then once, doesn’t seem to help. Anyone else that can explain?

 

[syn08]

Good luck, I don't have the time and patience to explain and debate at this level. Knowing that a current source (LM334) is not a buffer is a prerequisite for any further discussion. Go to DIYaudio.com, you may find better help there.

 

[Stinius]

Read them all more then once, doesn’t seem to help. Anyone else that can explain?

If you have read the books that syn08 mentions more than once and still dont have a clue, maybe you should buy a TOPPING amplifier.

1. with a 100p shunt C it should not oscillate, but as syn08 says a shunt C is not optimal when it comes to the performance (THD wise) of the amplifier, and the zero that R43 creates is quite meaningless.
2. The LM334 is a adjustable CS (Current Source) and it sets the current in the LED's wich sets the BIAS current in the IPS and "VAS"
3. The servo loop is a DC servo that is meant to keep the DC at the output close to zero and as syn08 says "as it is designed" it is designed wrong.
4. About the TT transistors I copy and paste what syn08 is writing
" And the deal killer: the temperature compensation of the output stage NJL thermaltrak devices won't work properly. The NJL internal diodes are poorly DC and tempco matched with the power transistors, and will either make the whole output stage thermally unstable, or overcompensate, with nasty thermal induced distortions. " and he is absolutally right.

Edit: I see that syn08 recommended diyaudio.com maybe a better place for you to ask fo help.

Stein

 

[gene_stl]

There are much better kits available from Tom Christiansen at Neurochrome. Also Akitika.

The only thing you might learn from building one of these is how to solder and how to do some mechanical assembly.

But it will cost triple what a Crown amp would cost and if the above comments are correct , which I have no reason to doubt, you will spend $1000 and lots of hours on an amp that will have or develop problems. I would get very angry.
I have seen in the 1970s people get similarly angry when their Southwest Technical Products kits didn't meet the advertised specs or failed catastrophically (sometimes taking out spikker systems) which happened frequently. Dyna and Heathkit were much better bets.

 

[piotrkundu]

If you have read the books that syn08 mentions more than once and still don't have a clue, maybe you should buy a TOPPING amplifier.

1. with a 100p shunt C it should not oscillate, but as syn08 says a shunt C is not optimal when it comes to the performance (THD wise) of the amplifier, and the zero that R43 creates is quite meaningless.
2. The LM334 is a adjustable CS (Current Source) and it sets the current in the LED's which sets the BIAS current in the IPS and "VAS"
3. The servo loop is a DC servo that is meant to keep the DC at the output close to zero and as syn08 says "as it is designed" it is designed wrong.
4. About the TT transistors I copy and paste what syn08 is writing
" And the deal killer: the temperature compensation of the output stage NJL thermaltrak devices won't work properly. The NJL internal diodes are poorly DC and tempco matched with the power transistors, and will either make the whole output stage thermally unstable, or overcompensate, with nasty thermal induced distortions. " and he is absolutelly right.

Edit: I see that syn08 recommended diyaudio.com maybe a better place for you to ask for help.

Stein

There more I read the more confused I get and I get as much out of it as reading multiple recipe books more than once. I much rather watch people cook and explain why and how they are treating the ingredients and then try it myself.

1. Audio Power Amplifier by Douglas Self is really good intro, the other 3 books are much more detailed and still the shunt compensation is described as a cap going from collector to the emitter and negative rail in that example and there was no resistor in series either. Visually it's nowhere near that R43 and C12 looks like and I discarded it as "some filtering". At a second glance it connected to T16's collector but not to it's base - so it's really not that obvious to me.

2. All I remember from all these books is that VAS needs a good/perfect current source and it's mostly explained with discrete components, so seeing an IC I was wondering if that would compensate for the missing buffer stage.

3. The DC servo loop is on the input stage and I've never seen that before. I've seen it output stages due to nonlinearities between PNP and NPN transistors in combination with thermal drift between the two. I haven't put any energy into DC servos since there is a lot of negative comments about DC servos in amps. I felt that I would never need one.

4. First time I've ever seen ThermalTrak and until now I didn't know such a device existed, let alone what impact it has on amps.

There are threads on diyaudio already:

Elektor Fortissimo-100

Did anyone check out the recent article in Elektor Electronics? There's a class A/B amp, very low noise, discrete and through hole design. https://www.elektormagazine.com/labs/fortissimo-100 To my eyes it looks kind of interesting. Symmetrical and pleasing to the eye. I can't judge the design...

www.diyaudio.com

I need comments about "100W power amp. elektor april 1982"

I need comments about "100W power amp. elektor april 1982" Someone built it for sell he change the power transistor to new one maybe for improvement. I had listen to it. Its sound better than gainclone! I need comments.

www.diyaudio.com

PS. I've built two Amp Camp Amps monoblocks so far and soldering skills are decent (always have been) and I'm looking for next DIY project. I have commercial amps, not sure I want to spend more money there. I don't think there many analog guys alive in my city and the few people I know in hardware are mostly into digital design and there is limited milage out of pure theory and books. Nevertheless this kit seems like a lot of hustle and most people seems to have had problems with it. It's been around since 1982, but a few people seem to like it.

I strongly doubt anything commercial (in the $1000 range) is going to be much better/different than wiring up some Hypex modules into an enclosure don't you think?

 

[SIY]

I strongly doubt anything commercial (in the $1000 range) is going to be much better/different than wiring up some Hypex modules into an enclosure don't you think?

Likely not even as good. The days of conventional linear amplification are over, and these are as much nostalgia pieces as tube amps. Intellectually interesting- Self and Cordell are excellent reads and can bring a lot of insight- but the maturation of switching amps has been creative destruction in the Schumpeter sense.

Most grumbling comes from people who have spent a professional lifetime gaining competence and expertise in old fashioned technologies and suddenly find their knowledge to be obsolete.

 

[piotrkundu]

I have had my ass handed to me few times by ”seniors” and it’s (hard) learning experience. I ask if he/she is right OR can I learn and improve. Most times I’ve learned and improved and retrospect realized that I was doing pretty good in the first place. Sometimes I gained their respect and we got on just fine while everybody else wanted to stay as far away as possible from that person. I try to appreciate their skill and knowledge and disregard everything else. Sometimes I handed their ass right back at them, but too old for that now. I’m a hobbyist with a dayjob, not Linkwitz or Baxandall.

 

[pma]

Likely not even as good. The days of conventional linear amplification are over, and these are as much nostalgia pieces as tube amps. Intellectually interesting- Self and Cordell are excellent reads and can bring a lot of insight- but the maturation of switching amps has been creative destruction in the Schumpeter sense.

Most grumbling comes from people who have spent a professional lifetime gaining competence and expertise in old fashioned technologies and suddenly find their knowledge to be obsolete.

And that‘s why the linear Benchmark AHB-2 still measures better than any matured switching amp, right? And free from the ultrasound garbage.

BTW, I designed and built my PWM based switching system for optoelectronic fibre transmission of analog signals in 1982, that is 40 years ago. It solved the nonlinearity of the transmitter opto diode and variable attenuation of fibre cables and connectors. Good for such purposes, with BW much higher than audio and extended down to DC. Audio amplifiers could dream about such BW. However, for audio purposes, linear circuits are still better with better parameters than switching amps.