DIY F5 pure class A power amp(Nelson Pass design)

[brainf]

Joey, the PASS B1 board was ordered from HK, the mundorf caps came from audio amplified. Casing came from Loi Lazaro. Other details I'd let Leslie to fill in the gap. Thanks

Slight correction - the MCaps were bought in Malaysia (Octave Electronics), along with the RCA sockets used Dale resistors and Panasonic FCs from Farnell, JFETs from Spin Electronics. I forget exactly where I got the other stuff - some of them from my parts box, Raon and Alexan Megamall (I tend to pick stuff up whenever I think I'll be needing something for some future project... I don't think I'm alone in this madness... )

cheers!

[tony]

I don't think I'm alone in this madness...

indeed you are not......

there are lots of case modding gurus over at tipidpc.com in case you mant costumised plexiglass casings.....

[JoeyGS]

Thanks Leslie.

Most of Nelson Pass' projects are geared towards achieving tube sound with all SS topology and with as much as less parts (less is more). And likwise you eliminate the problem on the tube maintenance.

Hi Endrik and Leslie,

Congrats. I heard that B1 really sounds tubey

Would you mind telling us what parts were used?

Regards,
JoeyGS

Hi JoeyGS,

From Tony's insights on the circuit topology and characteristics of the JFETs in his posts above that's not surprising at all.

FWIW I used Mundorf MCaps (those white ones with red lettering) and Dale resistors for the critical components directly on the signal path; JFETs were matched pairs; PSU caps were Panasonic FCs; Volume pot is an Alps; and all internal wiring is single-core SCC.

The choice of components used are the distilled experience from previous DIY projects so no guesswork in this project.

Hope this helps!
leslie

[tony]

From Tony's insights on the circuit topology and characteristics of the JFETs in his posts above that's not surprising at all.

i suppose you can mimic this circuit using bipolars at higher currents for greater transconductance, but it will be harder to copy the simple elegance that the jfet and the triode tubes offer....

you need at least 3 bipolars to mimic this circuit...

[brainf]

I don't think I'm alone in this madness...

indeed you are not......

there are lots of case modding gurus over at tipidpc.com in case you mant costumised plexiglass casings.....

Hehe - no I'm the kind who stocks/hoards up on components (for some *future* project). Have so many in my parts bin already still waiting patiently for their "turn". Unfortunately I'm really bad with casings and a chicken around power tools.

I do admire the work of those who have the time, artistic talent and patience though. "Case" in point was this B1 project (Pun intended). Doc took care of the all the aesthetic aspects, and a darn good job he did at it too!

[endrik35]

Sir JoeyGS, here are pics of the innards of the B1 preamp for your consumption

[Tjaderman]

Heard this B1 performed, a real Nelson Pass signature!

For those who like tube pre -amp but afraid of its tube replacements/maintenance, this is for you!

Congratz, Doc Endrik!

[endrik35]

Thanks Brader SamTellig, este Brader Cal. Binuksan ko kanina ng makita mo yung bituka. Parang gusto ko pa ng vetsin eh!

[JoeyGS]

Thanks endrik for the photos. This gives me motivation to pursue the B1 project in the future

Regards,
JoeyGS

Sir JoeyGS, here are pics of the innards of the B1 preamp for your consumption

[Tjaderman]

Thanks Brader SamTellig, este Brader Cal. Binuksan ko kanina ng makita mo yung bituka. Parang gusto ko pa ng vetsin eh!

Ikaw talaga , Sir John!! May pa- Sam sam ka pa dyan! hahahha .....Ayos na yan,dok! Galing ng B1 mo!

[endrik35]

Me and Les wants to impart a Zen spirit to this pre-amp. I bought a rubber wood the other day, painted it with maple varnish and burned some portions to achieve a "bird's eye" maple effect.Then I attached it to the sides of the B1. I found this interesting thread in pDVD, Sir dBinu made a Nelson Pass First watt F5 Class A power amp. According to sir sBinu, the amp cost around 25k to build. Hopefully, it will be our next project. I think the F5 will mate well with the B1.

Here's the link to the F5 thread:
http://www.pinoydvd.com/index.php/topic,129241.0.html

B1 pics with handle:

[brainf]

Wow, I'm amazed at your artwork Doc! A far cry from what the prototype looked like!

I'm sure the extra weight and material helps in damping the casing too. Looking forward to our next listening session!

[Tjaderman]

Nice one, Doc!

[endrik35]

Leslie(BrainF), I'm astounded by the SQ of your Salas shunt regulated power supply. Really made a difference imho. A co-member in Lenco heaven posted pics of his shunt regulated PS for the b1 and it seems that its all included in the circuit board for the preamp. This is a pic of ejfud's shunt regulated b1 preamp for your perusal. It seems that the trappo is included in one box and he used 2 aluminum panels to separate it from the preamp section. . .



I think it's possible if we can get a larger aluminum casing

[6a3fan]

Are the jfets 2SK170 available locally in Raon?

[kabubi]

what does it do?

[tony]

^afaik, newport electronics have them.....you have to buy several pieces and try to match Idss....

[brainf]

Are the jfets 2SK170 available locally in Raon?

You can also get them from Spin Electronics in Mandaluyong.

For the shunt portion matching is not required (but for the buffer stage, yes).

cheers!

[tony]

what does it do?

the diyaudio seems to be down at the moment....

the Salas shunt regulator is highly acclaimed by diy'ers as a very quiet regulator, it is a regulator using CCS mosfet trannie as series pass, and another CCS shunt pass.....does not need a lot of capacitors at the output...

[brainf]

what does it do?

The shunt regulator provides a clean power supply rail which the B1 buffer seems to like very much