Puriss A1000A. Class A amp for serious listening

[kanwar]

Kanwar, I am moving (have moved) all your posts and related posts to a different thread. These posts were seriously derailing this thread.
Cheers

My Mistake....!!!

Sorry to all guys, if i had unintentionally hurt anyone here.


Kanwar

 

[kanwar]

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.


Warm Regards.
Akshay

Hi Akshay,

Congrats on Puriss endeavour

Wanted to ask some questions regarding your design.

1: Why did you choose 2stage darlington instead of 3stage darlington [Triple Emitter Follower], IMHO it gives more current gain and loads the VAS much less, thus enables more resolution and nice drive capability in driving low impedance loads.


2. Since class A loads the powersupply constantly with high idle current, it might would have been beneficial to use a balanced bridge output which doubles the slewrate and gives more room for output device SOA for the same power output by lowering the rail voltage , thereby keeping the devices well under the second breakdown region. Also the second order harmonic cancellation in bridge output is much higher plus an added bonus of using single polarity supply, if the design permits.

regards,
Kanwar

 

[akshayjha]

Hi Akshay,

Congrats on Puriss endeavour

Wanted to ask some questions regarding your design.

1: Why did you choose 2stage darlington instead of 3stage darlington [Triple Emitter Follower], IMHO it gives more current gain and loads the VAS much less, thus enables more resolution and nice drive capability in driving low impedance loads.


2. Since class A loads the powersupply constantly with high idle current, it might would have been beneficial to use a balanced bridge output which doubles the slewrate and gives more room for output device SOA for the same power output by lowering the rail voltage , thereby keeping the devices well under the second breakdown region. Also the second order harmonic cancellation in bridge output is much higher plus an added bonus of using single polarity supply, if the design permits.

regards,
Kanwar

1. The no of stages would reduce the bandwidth considerably. As mentioned earlier the objective of the design to get a gain of 26db in the minimum no. of stages.

2. Balanced bridge would make the selection of output transistors fairly critical. Moreover the purpose of class A would be defeated altogether as the entire cycle would be divided over more transistors. Slew rate of many tube amplifiers is way low than solid state amps. Its debatable if that is the cause of the smooth tube-like sound people love. The output transistors are safely in SOA as it is, it may have been a concern if I were using the MJE150xx series instead of MJE2119x transistors. Single polarity again may require o/p capacitors filtering the DC voltage, subject to design.

Cheers.
Akshay

 

[kanwar]

Thanks very much for the reply Akshay

Btw: A bridge output design never has any capacitors at its output because the both nodes of bridge float at same VCC/2 potential and thus DC offset is negligible.


Cheers,
Kanwar

 

[akshayjha]

Thanks very much for the reply Akshay

Btw: A bridge output design never has any capacitors at its output because the both nodes of bridge float at same VCC/2 potential and thus DC offset is negligible.


Cheers,
Kanwar

Ok, so in effect , instead of a +-80V rail you would use a 160V supply, is that right. Comes to the same thing, dont you agree..

Cheers.

 

[kanwar]

Ok, so in effect , instead of a +-80V rail you would use a 160V supply, is that right. Comes to the same thing, dont you agree..

Cheers.

Yes, 160V single supply bridge would give +80V with respect to GND at both nodes of output and speaker will see theoretically zero voltage difference between both output nodes because 80-80=0, In practical, there will be small offset of millivolts say 50 to 10mV would remain or so, hence no capacitor is needed.

But for same power in a given impedance the rail voltage requirement in the bridge would be halved, so a single supply 80V is enough in that case.


Cheers,
Kanwar

 

[vivek.saikia]

Hmm.....I am loving the direction in which this thread is going on now. It is feeling like revisiting my electronics classes during BE

 

[kanwar]

Hello Akshay,

Any new updates ???


Cheers,
Kanwar

 

[akshayjha]

Hello Akshay,

Any new updates ???


Cheers,
Kanwar

Hi Kanwar,

A matching preamp for the power is almost ready. Would take a few months to be ready with the final unit.

Regards.
Akshay

 

[entsurgeon]

Is audition possible in mumbai this mth end?
Of amp?

 

[akshayjha]

Is audition possible in mumbai this mth end?
Of amp?

Yes the Power amp is available for auditioning in Mumbai this month end.

Regards.
Akshay

 

[mukum]

Hi Akshay,

What is the cost of PURISS A1000A ?

 

[mpw]

akshay,

the A1000A looks good. will try and drop in one of these days. also look forward to the
A600 and do update us on the pre amp you referred to which you were custom - making for the Puriss.

Congratulations for your enthusiasm and effort.

best regards,
mpw

 

[akshayjha]

The P1000A and P600A pre amp would be ready by september end. P1000A would have a phono input with option to select the cartridge load. The P600A would have no phono inputs. each pre amp has an overall gain of 17db. would post the details once the project is complete

 

[Viki]

I was at Akshay's place yesterday, and had a chance to see the Puriss. Guys, this thing is a MONSTER. Unfortunately, I couldn't hear it, but I will be going back soon, and hope to hear it when I do.

Akshay is a very nice guy, and I also enjoyed having a little chat with his father.

I wish you the best in further developing the Amp, Akshay, and look forward to hearing it.

Viki

 

[abhijitnath]

Any updates on the preamp, Akshay?

 

[spirovious]

When will Home edition be coming?

 

[vktarun]

Hi to every one, as this is my first post

Akshay,

whether Puriss A1000A can be paired with Magnepan MG-12 placed in hall size of 11ft by 20ft for stereo application ?
Magnepan MG-12 has a sensitivity of 86db (practically 83db) with a resistive load of 4Ohms (practically goes down to 3Ohms)

Further I have carefully gone through all the posts in this thread but could not found any information on pricing. Most probably it has not been disclosed yet!!

Regards,
Vipin

 

[anm]

vktarun - you can also look at NAD C375 - review here - Stereophile Reviews C375BEE C565BEE - NAD Electronics

 

[vktarun]

Anm thanks for your reply!

Regarding NAD C375 Specification: It say 150 watts rms in 4 ohms or 8 ohms. I mean how they achieve that? may be the impedence sensing circuitry reduces the rail voltage supplied to the Power Amp unit.

Can you provide some insight?

Experts always say that the amp that can doubble(approx.) its power in 4ohms load (in comparasion to 8ohms) is best for maggies or in general also.

Further I find MG-12 a little bit bright (personal view). So usually adjust Treble by -2db for general listening. Experts define Newer NAD models as bright one. However I have never auditioned MG-12 with NAD wish to do someday.
Thanks in advance for further sugession.

Vipin