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"PINNACLE AB200" - Class AB DIY Amplifier with thermal track transistors NJL3281D & NJL1302D

sadik

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Hi Friends,

I am sharing my new built Class AB amplifier with ThermalTrak transistors. These circuit and PCB is designed by our Forum Member Mr. @Aniket It was a very slow built & took almost a year to complete it, as i was busy with other projects.

We have named this Amplifier "PINNACLE AB200". There are in total 5 PCBs manufactured. Three kits will be built and remaining two will be in spare.

Specifications are as under.
Power : 250 Watts @ 4 Ohms, 150W @ 8 Ohms, continuous average power output, both channels driven
Dynamic unclipped power output : 165W, 320W, 600W into 8,4,2 ohms
THD: <0.005% 20-20000Hz, @ 200W into 4 ohms, 0.0006%, 1kHz @ 50W into 4 ohms
Frequency response: 5Hz-300kHz (-3dB)
Signal to noise ratio: 115dB
Damping factor: >500, 20-500Hz @ 8 ohms
Slew Rate: 95V/us
Sensitivity: 0.9V rms for rated power
Transformer Rating : 40-0-40 V AC / 600 VA
Total Capacitance Bank : 60,000uf(min) for both channels.

For Any other details Mr. @Aniket will join in as he is the designer of this Amplifier & I am only the assembler. My knowledge is very limited i may not able to answer all questions.

Both the channels including power supply bank and speaker protection kit is on single board which makes wiring very less.


Enjoy the below Pics.

Photo of PCB










Finally Testing & The Amp is singing.




Face Plate is yet to be made. I will upload final external photos once i finish with the face plate.

As far as my reviews are concern, It is the second most best sounding Amplifier from all my built till date. (First is my Class A Amplifier Jean Hiraga Super 30).

I cannot define its sound just by words, because defining by words will not do the justice to its sound signature one has to hear it and decide by themself. I really thank Aniket for this wonderful design of Amplifier. & I would also thank Mr. Harjindersingh (he is not on our forum) who took gave us these transistors (without any charges) to make this amplifier.

Sadik
 
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rsponline

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Well done Sadik bhai.

Having single board design looks very clean. Minor suggestion will be routing those three wires from side of board.


One question. What changes will be needed if we just need 45 wpc at 8 ohm max ?
 

tcpip

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Is this a stereo PCB? I'm guessing yes. Very nice. Two pairs of OPS devices per channel, to help drive more difficult loads. Does it have on-board speaker protection? I'm guessing yes, because I think there are two relays on the two sides of the board. I think it's a good idea to add speaker protection to any amp PCB design -- why keep it separate?

Will you be sharing the circuit?
 

Kannan

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Is speaker protection really necessary and does it impact sound quality?
I am not tech savvy, so just asking to clarify.

I have used quite a few amps, and some without protection circuits. Both my two current amps based on Nelson Pass designs do not have protection circuits either and just produce a mild pop-up on switching off.

@sadik Nice and simple sadik bhai, especially moving on from your mostrous Hiragas :)
 

sadik

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Well done Sadik bhai.

Having single board design looks very clean. Minor suggestion will be routing those three wires from side of board.


One question. What changes will be needed if we just need 45 wpc at 8 ohm max ?
Suggessions are welcomed. The amplifier is still open so i can change the layout of wiring. & for second question i don't have answer. @Aniket will join in to reply that.

Is this a stereo PCB? I'm guessing yes. Very nice. Two pairs of OPS devices per channel, to help drive more difficult loads. Does it have on-board speaker protection? I'm guessing yes, because I think there are two relays on the two sides of the board. I think it's a good idea to add speaker protection to any amp PCB design -- why keep it separate?

Will you be sharing the circuit?
The complete amplifier design and layout is done by @Aniket. Your all guesses are correct. This circuit is not for sharing some things are better to keep with our self. but who knows about future, i may sell the complete amplifier to a good buyer.

Is speaker protection really necessary and does it impact sound quality?
I am not tech savvy, so just asking to clarify.

I have used quite a few amps, and some without protection circuits. Both my two current amps based on Nelson Pass designs do not have protection circuits either and just produce a mild pop-up on switching off.
Yes speaker protection is must. If something happens with the amplifier it will protect your speakers from blowing out. And No Bro I am not moving away from Hiraga, wait for 6-8 months there will be a bigger Monster than i have at present. The Heatsinks alone weight 18 Kg & Power Bank capacitors weight is 7 Kg. I am getting the parts slow and steadily.
 

Kannan

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Yes speaker protection is must. If something happens with the amplifier it will protect your speakers from blowing out
Most amps come with the protection. But I find that some leading amp designers do not use them at all.
 

tcpip

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Is speaker protection really necessary and does it impact sound quality?
If done right, it does not impact sound quality at all. (But then that's true of the amp itself. If done wrong, so many things in the amp impact sound quality.) And it's a good idea to have it in case your speakers are the kind which may get damaged.

One thing they protect the speaker from is the power-on thump. This can definitely damage tweeters if you're driving an active load directly from amp to tweeter without any crossover in between. (My Darbari is an active design.) Even in conventional setups, some tweeters may get damaged. This damage may not happen overnight, but over twenty or fifty turn-on thumps. I have seen tweeters blowing in expensive, high quality speakers after 5 or 10 years of usage, and I've suspected that it may be due to slow degradation caused by such thumps. (Of course, it's almost impossible to find an expensive commercial amp which does not have speaker protection modules at its output, so I don't know where the thump came from.)

Second: if an amp's OPS devices blow, then the full DC power rail level voltage will come to the speaker output and will definitely damage speakers. The typical speaker protection circuit has DC detection ability, and instantaneously disconnects the speaker if there is DC at the output. If this is not done, the DC will destroy the woofer. (Tweeters have high pass filters which block DC.) Once again, this won't affect sound quality at all.

People can go for a decade, two decades, without any accident like this where their speaker protection circuit has to kick in. I agree. But it only needs to happen once for your expensive million-rupee speakers to get fried. This is like seatbelts. People who have suffered will refuse to travel without seatbelts.

I have used quite a few amps, and some without protection circuits. Both my two current amps based on Nelson Pass designs do not have protection circuits either and just produce a mild pop-up on switching off.
Nelson Pass believes in minimalist designs, and completely discards any kind of protection circuits anywhere. He caters to the extremist hobby and fanatic crowd. He's a very knowledgeable and talented designer. But his rejection of protection circuits is not based on them not being useful. His rejection is based on a kind of idealistic focus on minimalistic design. For instance, some of his amp designs have much more distortion than an entry level Marantz or Cambridge Audio amp, because his minimalist designs do not incorporate distortion minimization features and components. His fans like the sound of his amps. So it is clear that his design goals are different.

I, who have maybe only a tiny fraction of his knowledge and maturity, have a belief which has guided me well: "Everything should be made as simple as possible, but no simpler." It is the "but no simpler" which is the key difference between the perspective of pragmatic engineers like me and that of idealist designers like Nelson Pass.

I am a fan and student of Douglas Self, Bob Cordell, John Curl and the late Randy Slone. They have built some of the greatest and most respected audio gear sold worldwide. They would add protection circuits to all their designs. It's seat belts. It makes sense.
 
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Kannan

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@tcpip brilliantly explained, but in a simple and articulate layman terms. Should I say minimalistic, but pragmatic as well :).
Thank you for the time taken to write the long note.
 

yugaaa

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The heatsink does not look adequate enough , unless you are going to use forced cooling .
 

sadik

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The heatsink does not look adequate enough , unless you are going to use forced cooling .
Its class AB. I have run test it for continious 4 hours. No abnormal heating. I now need to just add soft start. And face plate is still pending.
 

yugaaa

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Its class AB. I have run test it for continious 4 hours. No abnormal heating. I now need to just add soft start. And face plate is still pending.
How is the amp bias setting done ? I am surprised that the heatsink is good enough . Probably at low volumes it might not be that hot , but it should heat up quite a bit at good listening volumes .
 

tcpip

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The heatsink does not look adequate enough , unless you are going to use forced cooling .
In fact, to my eyes, the heatsink looks big enough for even a modest powered Class A. :)
 

sadik

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How is the amp bias setting done ? I am surprised that the heatsink is good enough . Probably at low volumes it might not be that hot , but it should heat up quite a bit at good listening volumes .
The Amp is Biased in Class AB. The Size of Heatsink is 300mm End to end, Fin length is 82 mm & Total Height is 100 mm. Its the ideal size for this Amp.

In fact, to my eyes, the heatsink looks big enough for even a modest powered Class A. :)
I have used this same size heatsink for Jean Hiraga 8 watt (one each for each channel)
 

Aniket

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Is this a stereo PCB? I'm guessing yes. Very nice. Two pairs of OPS devices per channel, to help drive more difficult loads. Does it have on-board speaker protection? I'm guessing yes, because I think there are two relays on the two sides of the board. I think it's a good idea to add speaker protection to any amp PCB design -- why keep it separate?

Will you be sharing the circuit?
Yes, there is speaker protection on the board.
The circuit, it is basically a fully symmetrical amp design, starting from input to the output stage, its a mirror image of the +ve half to the -ve half.

Is speaker protection really necessary and does it impact sound quality?
I am not tech savvy, so just asking to clarify.

I have used quite a few amps, and some without protection circuits. Both my two current amps based on Nelson Pass designs do not have protection circuits either and just produce a mild pop-up on switching off.

@sadik Nice and simple sadik bhai, especially moving on from your mostrous Hiragas :)
I find no harm in adding speaker protection to any amplifier. It wont change the sound neither will deteriorate it. In simple terms, it is easier and cheaper to fix an amp rather than a burned speaker. That does't mean any amp which has protection is underbuilt or poor. its just that its better to prevent than to cure. Rest tcpip has explained very well.

How is the amp bias setting done ? I am surprised that the heatsink is good enough . Probably at low volumes it might not be that hot , but it should heat up quite a bit at good listening volumes .
Bias setting is done by setting the quiescent current of the output stage. generally done by setting a certain voltage drop across the resistors in the output stage. depends on topology of the amp how much is required to eliminate crossover distortion.

Regrading the heat, The heatsink is quite substantial, they look small in pic, but is quite big. big enough for a 200W+ per channel amp.


Regards,
Aniket
 

yogibear

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How does it compares in sonic impressions to Anikets DD amp ?

Any impressions to report ?
 

sadik

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How does it compares in sonic impressions to Anikets DD amp ?

Any impressions to report ?
I cannot compare the sonics between these 2 Amplifiers. Both are Legends in their own region.

The only thing I can compare is the Power factor, PINNACLE AB200 is 250 watt per channel amplifier, 250 watts is enough power to drive any kind of speakers. Sound is very clean even on higher volumes. I think below specifications may give you idea.

Specifications of PINNACLE AB 200.
Power : 250 Watts @ 4 Ohms, 150W @ 8 Ohms, continuous average power output, both channels driven
Dynamic unclipped power output : 165W, 320W, 600W into 8,4,2 ohms
THD: <0.005% 20-20000Hz, @ 200W into 4 ohms, 0.0006%, 1kHz @ 50W into 4 ohms
Frequency response: 5Hz-300kHz (-3dB)
Signal to noise ratio: 115dB
Damping factor: >500, 20-500Hz @ 8 ohms
Slew Rate: 95V/us
Sensitivity: 0.9V rms for rated power.

This amplifier was specially designed for our needs & @Aniket has made it possible to reach our goal. I am really thankful to @Aniket for this wonderful Amplifier.

Sadik
 
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