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MEGA_amp 29th December 2003 06:23 AM

questions on aleph 2 parts
 
I just recently received my aleph 2 PCBs from Kristijan.

Going over his parts list I have a few questions:
The R values for the main board are listed, is there a general wattage rating for the resistors i'm looking for, for the main PCB components? I saw somewhere that all resistors are rated at 25W unless otherwise noted.

per Kristijan's schematic:

1. R1=4,75 K?

is this 4 watts 75,000 ohms? 4.75 K? his notation is confusing me

2. D1-D5= zener 9,1 V

9.1 V? wattage?

3. What voltage is recommended for the caps on the main PCB?
C1=1 nf
C2-C4=220 uf
C5=10 pf
C6=1 nf

4. what will yield the best sound? Bulk Metal Foil, Thin Film, Metal Film. Or is the type non-important?

5. Do any resistors require tolerances of 1%?


Thanks in advance
John

elizard 29th December 2003 06:36 AM

Re: questions on aleph 2 parts
 
Quote:

Originally posted by MEGA-amp
Going over his parts list I have a few questions:
The R values for the main board are listed, is there a general wattage rating for the resistors i'm looking for, for the main PCB components? I saw somewhere that all resistors are rated at 25W unless otherwise noted.

that's 0.25W (1/4Watt) .. 25watt is a slight overkill :)


Quote:

Originally posted by MEGA-amp

per Kristijan's schematic:

1. R1=4,75 K?

is this 4 watts 75,000 ohms? 4.75 K? his notation is confusing me

That's 4.75Kohms
the ',' in europe is used as a '.' in US/Canada is generally

Quote:

Originally posted by MEGA-amp

2. D1-D5= zener 9,1 V

9.1 V? wattage?

this is my guess only, but i'm guessing its just a standard zener diode, so whatever wattage they are

The rest of the questions I don't have an answer to, except one last one.
I don't think any resistors REQUIRE a 1% tolerance, however if you can afford 1% resistors i think you'll be graced with a (possibly ever so) slightly better amp.

edit: you can refer to http://www.passlabs.com/pdf/aleph/a2srv0.pdf for more info of course

another edit: the only resitor's wattage you need be concerned about are the 0.47ohm and the 1ohm ones, those i believe are 5watt wirewounds if i'm not mistaken.

BobEllis 29th December 2003 01:10 PM

Re: Re: questions on aleph 2 parts
 
Quote:

Originally posted by elizard

the only resitor's wattage you need be concerned about are the 0.47ohm and the 1ohm ones, those i believe are 5watt wirewounds if i'm not mistaken.

THE RESISTOR POLICE ARE COMING TO GET YOU, ELIZARD! BAR THE DOORS! :D

Some say that you should use thick film resistors here, but I plan to use cement wirewounds. Maybe when I have silly money I'll try something exotic, but for now I'll worry about choosing the best sounding transistors.

As for capacitor voltage ratings, I'd go slightly above the rail to rail voltage for the 220uf (eg. 25 volt rails, rating > 50 V) for teh others the dc potential across them is small, so virtually anything will do.

moe29 29th December 2003 01:15 PM

the lowest values you'll be able to find for the small caps will be
well within tolerences (1nf, 10pf) The 220uf cap = 50v (Digikey part# P5572-ND)

Zeners = 1watt (Digikey part# 1N4739ACT-ND)
NTC (for power supply inrush limiting) KC006L-ND
10PF cap 399-1806-1-ND
.001uF P4785-ND

(i'm sure there are better sounding parts that could be substitued
for the above, but you can get all these at one place, and they work!)

m.

moe29 29th December 2003 01:34 PM

:) as for the resistors:

3 watt parts, use the Panasonics from Digikey
.47ohm P0.47W-3BK-ND
1ohm P1.0W-3BK-ND

1/4 watt parts Yageo 1% Metal Films will do fine, Digikey also

jewilson 29th December 2003 03:38 PM

Parts
 
The 220uf cap should be a Black Gate

The resistors should be RN60D Dale/Vishay metal flim. www.mouser.com

Panasonics from Digikey have ferrous metal lead, So don't use any resistors that can be picked up with a magnet.

The 10pf cap should be a Mica type.

moe29 29th December 2003 04:35 PM

...i think i need a LearJet.
 
the only Black Gate cap i see on Percy Audio that fits would be a
220uF 160V NH for 29.95 USD a piece. Times 6 for stereo Aleph 2
would be $180.00 ..... YIKES!!! :bigeyes:

or are you just talking their Standard Polarized line, which would
be 220uF 50V for $6.95 USD for $42.00 total.

You can get 10 of the Panasonics i posted for $4.10 USD.

I'd try them first and see how things sound.

Pass Labs uses the same Panasonic resistors in their Amps, they
can't be that bad.

the above caps and resistros sound great in my Aleph 2's.

...go figure.

trigon 30th December 2003 06:09 PM

I have used BlackGate FK 220uF 25V for my Aleph 4 and with 50V rail voltage I have measured 16V on bootstrap and the others are not that critical they can be 6.3 if you want, but I have used all 220uf 25V FK BlackGate

Hope this help

Trigon

jewilson 30th December 2003 07:58 PM

Seeing how that this cap on the inverting balanced input, I would not use just any old cap there Moe. However, the 220uf for the bias could be a Panasonic, itís not that important since it not in the signal path. If the PCB had room I would use and Black Gate and parallel with a Polypropylene 2uf on the input only.

I just hate to use parts that know I will remove later, just cost more time and money.

moe29 30th December 2003 10:44 PM

Jim,

C5 is the cap you are saying should be Black Gate right?

what you're saying makes since - and i'm not saying that Black Gates
don't make any difference sound wise... Just hard to reccomend
them for a first time build. (i'm assuming this, becuase of the
questions from the original post)

I guess i'm just always for getting the circuit built first, and then
doing upgrades later.


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