Puriss A1000A. Class A amp for serious listening

[akshayjha]

Hello,

I have designed,developed and engineered a new class A amp. The specs are as below:

PURISS A1000A Pure Class A stereo power amplifier tech specs:

1. Power Output: 50 watts continuous from 10Hz to 30000Hz two channels driven into 8 ohms
2. THD at rated power : 0.01%
at 25 watts : 0.005%
at 1 watts : 0.005%
3. IMD (50Hz:7Khz=4:1) : 0.01%
4. Frequency response : 2Hz to 150000Hz
5. Input sensitivity :1V/50Kohms
6. Speaker : 6/8 ohms
7. Damping factor : 60
8. Dimensions (WxHxD) : 23in X 11in X 19in
9. Weight(approx.) : 35 kgs (without packaging)


Other unique features.

1. The design objective for PURISS A1000A was to design a no holds barred pure class A amplifier which has a unique fluid sound with least distortion allowing for long duration of fatigue free music enjoyment. The amplifier, not just meets, but far exceeds its design goals.

2. Another important design requirement was to use a corrosion free chassis and cabinet. The
cabinet is made from stainless steel ensuring wear free and corrosion free performance for
decades even in very demanding environments like coastal areas and beach-fronts. The
front panel is made of anodized aircraft grade aluminum. The markings on the front panel
are laser engraved ensuring perfect and fine finish for decades with no signs of
aging.

3. Speaker terminals are gold plated with facility for banana plugs, spade connectors and
bare wire speaker terminations. The RCA connectors are also gold plated.

4. The amplifier can be used as a mono-block providing 100 watts of pure and clean class A
power, when used with a balanced source.


The amp is available for audition at my place, Andheri, Mumbai.

http://img217.imageshack.us/img217/5859/p1020314x.jpg

http://img517.imageshack.us/img517/2172/p1020296.jpg

http://img33.imageshack.us/img33/2752/p1020315n.jpg

 

[gobble]

good show! But the most important spec is missing in the details ... the price!!

Cheers

 

[Hiten]

wow! looks massive. Is it possible to post pics of inside of the amp ?
Thanks and regards

 

[Vinod.R]

Hi Looks fantastic,

Great design from the outside !!! (Any chance for a peak at the insides)?

And a photo of the back of the unit plus the $$ would be helpful for anybody looking at it

Once more congratulations

Vinod

 

[Kittu]

Great job mate, Whats the cost of building this beauty?

Very nice design :clapping:

 

[maniac_2004]

is this available for sale btw ?

 

[odyssey]

Hi
What is the heat dissipation for each channel? Why is the damping factor so low? you mentioned 6/8 ohm speaker, can it handle much lower impedances?

cheers

 

[anilva]

Great build. Can the circuitry be explained please. How is the design good compared to other Class As.

Cheers

 

[vivek.saikia]

That's a gorgeous amp and to top it all, it is a DIY amp!!! Hat's off to you for designing such an absolute beauty.
As everyone already enquired, how much moolah you spent on it?

 

[spirovious]

Congrats & hope to listen it soon...

 

[fran_elite]

Congrats Akshay, at last your Amp is ready & thanks for the invitation, if possible I will surely visit you.

Now for a more compact version..

 

[akshayjha]

Hi Looks fantastic,

Great design from the outside !!! (Any chance for a peak at the insides)?

And a photo of the back of the unit plus the $$ would be helpful for anybody looking at it

Once more congratulations

Vinod

Heres a pic of the back of the amp. will take a few pics of the innards and post later

 

[akshayjha]

is this available for sale btw ?

Yes the amp is available for purchase. In fact this one is already sold. The amp can be made to order. There can be changes made to the front panel design as per your request. The amp is also available in silver. (working on champagne gold, may be available in champagne gold as well)

 

[akshayjha]

Hi
What is the heat dissipation for each channel? Why is the damping factor so low? you mentioned 6/8 ohm speaker, can it handle much lower impedances?

cheers

Hi,

The power dissipation on each channel is 200watts continuous, which needs a rather 'laaaarge' heat sink. The heatsink is so designed that the maximum temperature of the heatsink would be 70 deg cel at an ambient temp of 27 deg cel. It does have a built in over-heat protection circuitry.

The damping factor is 60 per design, it can be made much higher, however a damping factor of >50 is fairly good to handle any type of speakers and music transients. Apparently, a higher damping factor would need other changes in the design which would alter the sound signature. Also it is worth noting that unless you weld the speakers directly to the amp output posts, a damping factor of >60 will be useless.

The amp is ideally designed for 8 ohms 'nominal' load works equally well at 6 ohms 'nominal' load. It can comfortably handle 2 ohm resistive loads.

Regards.
Akshay

 

[anilva]

Great build. Can the circuitry be explained please. How is the design good compared to other Class As.

Cheers

Can you please respond. What is topology of the circuit?

 

[CLEARCUT]

Quality of the components like pcb capacitors resistors power supply wiring used in the amp ? I come to know even the quality of power transistors are also depict the quality. So come out of yours ideas behind the amplifier. I am asking this bec i myself has given an ad for buying a class a amp.

 

[akshayjha]

Can you please respond. What is topology of the circuit?

Hi Anil,

Sorry for the delayed reply.

The circuit is based on a 2-stage differential push-pull, 2stage darlington, parallel push-pull, direct-coupled OCL(ouput capacitor less) class A operation. The amplifier has no electrolytic capacitors in the signal path. The only capacitors used in the signal path is for i/p DC filtering and they are film capacitors in parallel with 0.1uf polystyrene capacitors.

The first stage is powered by a regulated +-45V supply using a high bandwidth discrete power supply. The final stage is powered by a memory of 132000uF per channel (264000uF in total).

Each channel is powered by a seperate supply by two 1.2KVA toroidal transformers which is more than double of what is required.

The design uses no output coupling capacitors which were commonly used in older class A designs. Puriss A1000A definitely has an edge over capacitor coupled class A designs. The real test is in the listening though.

A lot of care has been taken to prevent start-up currents which are exceptionally high considering the high current requirements at start-up itself. A line filter is built in to prevent line noise from getting to the amp circuitry. A transient current suppressor circuit has been incorporated to limit the start-up current and give the amp a soft-start characteristic. The amp power supply stabilizes in 4 seconds and the outputs kicks in around 8 seconds

The amplifiers are designed to last for decades without any problem, cosmetically as well as performance wise.

Hope that answers your queries.

Warm Regards.
Akshay

 

[akshayjha]

Quality of the components like pcb capacitors resistors power supply wiring used in the amp ? I come to know even the quality of power transistors are also depict the quality. So come out of yours ideas behind the amplifier. I am asking this bec i myself has given an ad for buying a class a amp.

Hi,

The amp uses dual supplies, 1 for each channel. The juice is provided by 2 1.2kva toroidal transformers. Portion of the power supply is regulated and the output has a total memory of 264000 uF.

The PCB is made of 70micron glass epoxy boards 2.4mm thick.

All the 1/4 watt resistors used are Vishay/Dale 1%MFR resistors. Resistors at the output are 0.1% 5W custom-made wirewound resistors. Film capacitors are of very good quality manufactured by ISO9001 registered companies. Electrolytic capacitors are a combination Nichicon/United chemi-con and keltron. (Very high end capacitors can be used as per your requirement). However the ROI is negligible. The main power supply capacitors are a set of 22000uF Nichicon Gold Tune capacitors.

Low voltage dioides are philips. All power stage transistors are Motorola (aka ON semiconductors). The output transistors used are a pair of MJL21193 and 21194 per channel. The input differential uses a high gain Mitsubishi dual transistor (two transistors in a single pack).


Do let me know if you have any doubts. I would be posting a few Pics of the amps innards soon.

Best Regards.
Akshay

 

[captrajesh]

The components used appear to be top notch and the fit and finish looks very good. Hope it sounds equally good. Great work buddy. Keep it up.:thumbsup:

 

[akshayjha]

The components used appear to be top notch and the fit and finish looks very good. Hope it sounds equally good. Great work buddy. Keep it up.:thumbsup:

Thank you sir. Yup listening is the best test.