Lets have it the Class A way

[pranavkumar]

After a few months of research, i was able to find almost every component the Nelson Pass F5 requires, in India. :clapping:
The Input stage JFETs where the only things that weren't available here. So i was left with no choice but to order them.

I decided not to design a PCB and went further with point-to-point assembly.

all components are the best available here in Delhi, resistors are all 1% except for the CFRs used for the feedback loop and the source resistors for the power stage.

I plan to build two separate PSUs for both channels. Since i'll be doing that, scaling the down the PSU caps to 10000uF seems reasonable.
Waiting for the transformers and capacitors.

I also plan to go DIY for the casing !

Stay Tuned !!

Meanwhile, here are some pictures

Yep, Thats my study

The Input stage is done !

DONE !

Biasing probes hooked up!

 

[kanwar]

Nice discrete DIY, Pranav...!!!

 

[pranavkumar]

Nice discrete DIY, Pranav...!!!

Thank you

 

[ukjeyaraj]

Very nice looking DIY. Clean and tidy. Best wishes.

 

[anilva]

I will be watching this thread for progress.

 

[baswamin]

Pranav,

I am inexperienced, pardon my simple question. Is 10,000uF too low for Class A operation?

Thanks
Balaji

 

[gobble]

Do you mean to say you sopurced audiophile grade caps and resistors in India or just those meeting the specs? Watch out for fakes..

--G0bble

 

[sachu888]

Nicely done Pranav,waiting for complete build.We have seen your DIY speakers,so this must be good looking

Regards,
Sachin

 

[pranavkumar]

Pranav,

I am inexperienced, pardon my simple question. Is 10,000uF too low for Class A operation?

Thanks
Balaji

The caps in the PSU serve two purposes,
1. AC Ripple reduction and
2. Providing a surge power bank, whenever there is massive speaker excursion, the driver might draw 50-60Amps but for a very very small duration. We all know, no Power supply can provide 50amps of current (too much to ask for). Hence we introduce these banks to provide this surge current.

as far as if 10,000uF is enough, i guess it would be... Nelson pass used a bank of 15,000uF for two channels, where as i plan to use a bank of 10,000uF per channel. I guess it'll be enough.


Oh its, possible that you assumed a single 10,000uF cap. No No. There will be 4 caps per rail. accounting to about 40,000uF per Channel.

What do you have in mind ?

 

[pranavkumar]

Do you mean to say you sopurced audiophile grade caps and resistors in India or just those meeting the specs? Watch out for fakes..

--G0bble

Hi

well, they are not given the "audio grade" label. but they are the best available. I know.. Fakes are common.
All components are the exact same as the schematic mentions. Only, that they are procured from India, Delhi to be precise.

 

[pranavkumar]

Nicely done Pranav,waiting for complete build.We have seen your DIY speakers,so this must be good looking

Regards,
Sachin

Thanks Sachin !

The complete build could take a few weeks. I plan to build Book Shelves for this amp as well. A package Deal, if you may.
The amp should be ready soon.

 

[linuxguru]

well, they are not given the "audio grade" label. but they are the best available. I know.. Fakes are common.
All components are the exact same as the schematic mentions. Only, that they are procured from India, Delhi to be precise.

I'd suggest replacing the large grey Metal-Oxide Resistors with Indian-made Watts brand CFRs, available in 2W rating. The MORs have magnetic (steel) leads, while the Watts CFRs have non-magnetic (tin-plated Cu) leads and sound better at most locations. Even better would be Dale CMF65, if you can get them in the required value.

 

[pranavkumar]

I'd suggest replacing the large grey Metal-Oxide Resistors with Indian-made Watts brand CFRs, available in 2W rating. The MORs have magnetic (steel) leads, while the Watts CFRs have non-magnetic (tin-plated Cu) leads and sound better at most locations. Even better would be Dale CMF65, if you can get them in the required value.

Yes, thanks for the input!
impossible to get CMF65 here in india, i guess.

I'll try and swap those resistors.

 

[denom]

Originally Posted by baswamin View Post
Pranav,

I am inexperienced, pardon my simple question. Is 10,000uF too low for Class A operation?

Thanks
Balaji

The caps in the PSU serve two purposes,
1. AC Ripple reduction and
2. Providing a surge power bank, whenever there is massive speaker excursion, the driver might draw 50-60Amps but for a very very small duration. We all know, no Power supply can provide 50amps of current (too much to ask for). Hence we introduce these banks to provide this surge current.

as far as if 10,000uF is enough, i guess it would be... Nelson pass used a bank of 15,000uF for two channels, where as i plan to use a bank of 10,000uF per channel. I guess it'll be enough.


Oh its, possible that you assumed a single 10,000uF cap. No No. There will be 4 caps per rail. accounting to about 40,000uF per Channel.

What do you have in mind ?

Hi Pranav,

Looks like all are enjoying 1 of the favorite flavours of the DIY Sweeties - Guru Nelson Pass ji's famous class A amps
Enjoy the taste err amp

My question to you regarding your above response:

By driver i will assume you are saying about speakers connected as load to the amplifier. How come a speaker can draw 50-60A of current from the amplifier which is rated less than 100W? What kind of condition is this?
Kindly enlighten for our benefit pls.

Tks

 

[kaushik]

Some on also trying similar curry .. but slightly different way .
Pass F5 is well respected , however the unit gets very hot (heard few places)
so bulky heatsinks.

 

[trittya]

:clapping::clapping::licklips:hyeah:
Way to go, FM PranavKumar. Very neat and effective DIY there.
Also, now, you won't have to worry about the "Dilli ki sardee" (Delhi winter) in your listening room.
Keep them coming, my friend.

 

[pranavkumar]

My question to you regarding your above response:

By driver i will assume you are saying about speakers connected as load to the amplifier. How come a speaker can draw 50-60A of current from the amplifier which is rated less than 100W? What kind of condition is this?
Kindly enlighten for our benefit pls.

Tks

Yes, Nelson jee has made given us a few things to play with

yes, the speakers is what i mean.
To think of it mathematically now.. 50Amps maybe too much for the F5.

100W is the Continuous or the RMS power rating to an amplifier. But harmonically speaking.. there are spikes considering the fact that music has no single amplitude level over time. Transients.
Due to the small impedance of the speakers, there are current requirements which a 6Amps continuous PSU cannot supply. Because these spikes are very very short lived.. the capacitors are at rescue. They discharge charges as per the requirement and charge back up in no time.

you might have heard the difference between the low frequencies if you increase the effective capacitance in a PSU.

i might be wrong, am i ?

 

[pranavkumar]

:clapping::clapping::licklips:hyeah:
Way to go, FM PranavKumar. very neat and effective DIY there.
Now, you won't have to worry about the "Dilli ki sardee" (Delhi winter) in your listening room.
Keep them coming, my friend.

Oh yes, i didnt think of that
saves you the running cost of a heater ! and we get excellent quality amplification alongside :clapping:

 

[pranavkumar]

Some on also trying similar curry .. but slightly different way .
Pass F5 is well respected , however the unit gets very hot (heard few places)
so bulky heatsinks.

Indeed they do get really hot !
yup, i might just put a Cooler Master CPU fan at the outside to shoo away all the heat !

 

[trittya]

Yes, Nelson jee has made given us a few things to play with

yes, the speakers is what i mean.
To think of it mathematically now.. 50Amps maybe too much for the F5.

100W is the Continuous or the RMS power rating to an amplifier. But harmonically speaking.. there are spikes considering the fact that music has no single amplitude level over time. Transients.
Due to the small impedance of the speakers, there are current requirements which a 6Amps continuous PSU cannot supply. Because these spikes are very very short lived.. the capacitors are at rescue. They discharge charges as per the requirement and charge back up in no time.

you might have heard the difference between the low frequencies if you increase the effective capacitance in a PSU.

i might be wrong, am i ?

Certainly makes sense to me. But then, what do I know?