New DIY amp - Nelson Pass design

[anilva]

Folks,

I have recently completed my higher power variant of Nelson Pass F5 Class 'A' amplifier. This is a slightly modified design in terms of having Toshiba MOSFETs instead of IR/Vishay MOSFETs. and also has 2 pairs per channel instead of 1 pair of MOSFETs in the original design.

This means beefier power supply, much larger heat-sinks and all other associated stuff.

While still a 50W amp, can drive lower impedance speakers better and has much tighter power delivery.

The caps are Nippon Chemicon 60000 uF per supply rail powered by a 600VA toroid.

The amp sounds fantastic with extreme detail and imaging.

Attached are the pictures:







Planning to get the casing powder coated and heat-sinks anodized after stabilizing the amp for few months.

Cheers.

 

[Rajiv]

Hi Anil,


The amp is looking great.

I must make a trip to B'lore to listen to all your new projects.

What plans for the Altec 515B?

Regards
Rajiv

 

[Bluu]

Good job Anil! Any chance of getting a demo sometime?

 

[CANDUU]

Congrats anil,u are a marathon diy'er.....

 

[kanwar]

Congrats Anil,

Nicely done aluminum chassis


Cheers,
Kanwar

 

[350650]

The amplifier looks awesome and pretty clean work on the aluminium chasis really looks beautiful . It would look more beautiful after getting powder coated. :clapping:

 

[ukjeyaraj]

Nice looking amp.

I like your flooring too.

 

[grubyhalo]

nice looking amp.

I like your flooring too.

+1 !

 

[gobble]

Is the Chassis DIY or DIO?

Just when I was planning not to build one, in comes the temptation ... :licklips:

Cheers

 

[captrajesh]

Great work Anilva, keep it up

 

[anilva]

Thanks folks for all your kind comments. IMO if one has the required skills and commitment, there is nothing like building a F5. It is head and shoulders above most of the commercial designs, barring very few expensive and esoteric designs. Mr. Pass has put 'high end' audio within the reach of a DIYer by his contributions. Hats off to that man!

Unfortunately my schedule does not permit me to offer demos to a lot of you, but once in a while, when I have time, I am most willing to let people listen to the amp. I strongly encourage people to build F5. It is not difficult, as long as one follows some simple guidelines. Anyone interested in knowing more about building this in the Indian context, please PM me.

Cheers.

 

[Anil kumar]

Great work, congrats.....



Anil

 

[prem]

Hi Anilva


Congrats. What kind of a preamp is suggested with the F5?

 

[madbullram]

very very neat looking amp, doesnt look like a DIY. Would like to hear this with a passive pre

 

[jls001]

Beautiful amp. I am sure it would sing real sweet. The current issue of AVMax lists this amp in its amp section and the price is not trivial.

Where do you source the parts - active as well as passive (like cabinet, PCBs, heatsinks, connectors)?

And the final damage before powder coating and anodising?

Would love to attempt it if it's not too challenging and too costly.
Joshua

 

[prem]

Hi Madbullram


Am not sure how a passive pre would sound with the F5. The F5 has a gain of only 15 db. Srajan of 6 Moons feels you need an active pre with the F5. Srajan is extremely well versed with the First Watt amps.

 

[anilva]

Most of the passive components are available in the local market - heatsinks, toroids, components etc. Active components are available from eBay. PCB is available from Peter Daniel in Canada or from the Diyaudio.com store. Chassis is tricky. Best bet is magma (who is on this forum) or import it from modu or few other sources in Hongkong.

Ideal preamp for F5 is Nelson Pass B1 (buffer preamp - no gain) or Bride of Zen (which has gain). Of course can be mated to a whole host of low noise high performance preamps.

Cheers.

 

[prem]

Hi Anilva

Since B1 has no gain and F5 has only 15 db gain as per their site, would that be enough. I generally thought you need 20-24 db gain.

 

[anilva]

Hi Anilva

Since B1 has no gain and F5 has only 15 db gain as per their site, would that be enough. I generally thought you need 20-24 db gain.

My personal preference is BOZ, but many are happy with B1 using a hi output dac/cd. Also one needs to look at high to mid efficiency speakers when using a F5 instead of very low efficiency speakers. I personally use a high efficiency fostex full range and higher efficiency Altecs.

 

[prem]

Thanks Anilva. I have high efficiency speakers. So am good on that front. Will look at the BOZ.