Puriss A1000A. Class A amp for serious listening

[anm]

wish people in delhi could audition it. Is it possible to send it by courier? Maybe a few people in delhi can group to pay for the cost of shipping both ways.

 

[akshayjha]

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..

Yup Francis, That would be the A600A

 

[keith_correa]

Hey Akshay - what's behind the name "Puriss? Purity?

 

[akshayjha]

Hey Akshay - what's behind the name "Puriss? Purity?

Hi Keith,

Very Good Question. Firstly do you like the name?

My sixth sense told me that you would be the first to ask this question. hyeah:

I wanted the name to reflect the design objective of the amp which was to have the desired power amplification with

minimum number of stages. Thus a name like "Purist" would have been most appropriate. However purist is just 1

adjective, insufficient to describe an entire character of the amp. Thus, PURISS, which was derived from Purist.

Also, in the chemical domain, Puriss is a term signifying the purest grade.

Regards.
Akshay

 

[anilva]

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

Akshay,

Thanks for taking time to write down the circuitry and components used. Seems quite well thought out. Overall should result in a great product.

Few questions out of interest: Have you checked DC offset shifts and thermal stability. What happens when ambient temperature goes around 35-40 deg centigrade? Did you use any distortion and waveform analyzers to measure the specs of the amp?

Also why do you keep saying capacitance as "memory"?

I am asking these questions since you are planning to commercialize this design.

Cheers.

 

[akshayjha]

Akshay,

Thanks for taking time to write down the circuitry and components used. Seems quite well thought out. Overall should result in a great product.

Few questions out of interest: Have you checked DC offset shifts and thermal stability. What happens when ambient temperature goes around 35-40 deg centigrade? Did you use any distortion and waveform analyzers to measure the specs of the amp?

Also why do you keep saying capacitance as "memory"?

I am asking these questions since you are planning to commercialize this design.

Cheers.

Hi Anil,

I have checked the thermal stability from 15 deg cel to 35 deg cel ambient. The DC o/p offset is set at +80mv with +-15mv variation. The bias current has a tolerance of +-15mv and stays within these limits after 30 mins of operation, which was tested at both the temperature extremes.

The amplifier has also been played continuously for 120 hours straight. and the various readings have been taken from time to time.

The distortion figures were also tested at various temperatures and was observed to be below 1% variation from the specs, typically 0.7%. I have used software analyzers to get the specs.

Well by memory I mean capacitance.

Regards.
Akshay

 

[CLEARCUT]

Captain sir, take one amplifier for south region demo. So that we from the extreme south can audition and order. So that you could support an indian hifi r&d gentleman. I am interested i have also given ad for class a amp. But the audition problem and the distance and its weight is the main problem. More over if its integrated it would be more better. Ofcourse good pre is chanceless. But minimal is the best here avoiding one more power chord and inter connect.

 

[sandip_d]

These are exceptional efforts Akshay. Congratulation. Are you into it full time now? Your amp looked like big brother to my Emotiva XPA-3. I need to save money so sometime I can buy yours.

 

[sandip_d]

These are exceptional efforts Akshay. Congratulations. Are you into it full time now? Your amp looked like big brother to my Emotiva XPA-3. I need to save money so sometime I can buy yours.

 

[akshayjha]

These are exceptional efforts Akshay. Congratulations. Are you into it full time now? Your amp looked like big brother to my Emotiva XPA-3. I need to save money so sometime I can buy yours.

Hey Sandip,

Thanks a million. Every moment spent on the project was heaven for me. Loved every bit of it. Do drop in some time for an audition.

Regards.
AKshay

 

[magma]

nice electronics akshay
tempting:licklips:

 

[square_wave]

Great amp and effort Akshay. Wish I could hear it one day !

 

[murali_n]

Hi akshay,

Congrats on your build .:clapping:
BTW what type/ wattage of speakers do you recommend for this amp. How is its sound signature compared to the present available brands of AB mode operated amps in the market (read Marantz or NAD).

N.Murali

 

[akshayjha]

Hi akshay,

Congrats on your build .:clapping:
BTW what type/ wattage of speakers do you recommend for this amp. How is its sound signature compared to the present available brands of AB mode operated amps in the market (read Marantz or NAD).

N.Murali

Dear Shri Murali,

Speakers capable of handling >30 watts of power should do just fine. The ideal set would be to use large tower speakers to experience the deep controlled bass characteristics of class A. However, the mid and top end response is extremely balanced and unadulterated.

The beauty of a class A amplifier is that rail voltages filtered by the capacitor bank(filter) does not buck during heavy music transients. This is because the amp is on full load at all times irrespective of the presence of an audio signal. Since music is AC, the average load at the o/p power transistors is unchanged over a single cycle (since audio signals are nothing but an infinite set of sine and cosine waves). So if we consider an ideal audio signal, the average AC power dissipation over one cycle would be zero.

That's what makes the sound of a class A amplifier unique. The depth of sound of a Class A amp operating at say 10 watts is much better than a Class AB operating at the same power o/p.

I think it will not be fair for a Class A amp to be compared with Class AB amplifiers. Class A is in a different league altogether. However, the real test would be to do an AB test, keeping all the other variables, constant.

Warm Regards.
Akshay

 

[avidyarthy]

One of the Laws of physics .... least efficient ... heat generating ... yet the 'best' in performance. Thats Class A amplification .....

 

[denom]

Had a demo of Akshay's Puriss Amp today for a decent period of time (1 & 1/2) hrs to be precise & have foll observations:

1) The Amp is H U G E truly a monster!:clapping:
2) Quality of build is really fantastic & does not appear like a run of the mill DIY effort.
3) Can be used without a pre-amp.

To be very honest I felt that the amp is serious overkill but then it was made to a specific requirement of the buyer, nonetheless Akshay has already got plans to build a smaller amp for 'normal use'

Icing on the cake was that Akshay is a very nice person. Glad that he is part of this forum as we can pick his brains on topics related to hi-fi.

Heard my selection of music + some random jazz & hindi tracks from Akshay's collection.
Source was his modded Pioneer DVD Player & DIY Speakers.
Suggest fellow members to call Akshay & get a demo of the amp before its delivered to the owner.

 

[avidyarthy]

Had a demo of Akshay's Puriss Amp today for a decent period of time (1 & 1/2) hrs to be precise & have foll observations:


Heard my selection of music + some random jazz & hindi tracks from Akshay's collection. Source was his modded Pioneer DVD Player & DIY Speakers.

So, whats the outcome of the BOLD? You liked it or to your ears it was so so ... bright or laid back etc etc ..... your opinion ... ??

 

[jls001]

One of the Laws of physics .... least efficient ... heat generating ... yet the 'best' in performance. Thats Class A amplification .....

I guess it is the TANSTAAFL (There ain't no such thing as a free lunch - Wikipedia, the free encyclopedia) principle at work here:lol:.
Joshua

 

[jls001]

3) Can be used without a pre-amp.

Please explain a bit more about this aspect.
Joshua

 

[denom]

So, whats the outcome of the BOLD? You liked it or to your ears it was so so ... bright or laid back etc etc ..... your opinion ... ??

overall sound was good, save for the cymbals which were sounding shrill/distorted & unclean. But then on jazz tracks they sounded just perfect, so maybe his DIY speakers were not meant for my kind of music.

Bass was very Natural, just the way I like it.