ALEPH P1.7 CAP values/mods - diyAudio
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Old 10th October 2003, 02:50 PM   #1
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Default ALEPH P1.7 CAP values/mods

Hi all

I am in the process of sourcing components to build an Aleph P1.7 Clone

One of the significant costs is the capacitors used in the output legs of the circuit, namely C10-13 and C14-16. each is noted as 10uF.

I am trying to use WIMA MKP4’s for each of these
The 3 caps in the output are paralleled to equate to 30uF

Unfortunately these are rather costly at approx $10 AUS each..

My question is this, what would happen if I used 1 off 10uF cap instead of 3 off to each +ve & -ve leg?

Would the LF roll off rise by a factor of 3? (quoted in spec’s as being down 3dB at 1Hz) to 3Hz??

Am i missing something?

Pardon my ignorance

Regards and thanks in advance
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Old 10th October 2003, 07:46 PM   #2
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The original circuit used 10 uF at the outputs, and I
think it worked fine. The 3 Hz figure presumes loading
something along the line of 5 Kohm, so if you load it with
a higher value, you can go lower in frequency.
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Old 10th October 2003, 08:35 PM   #3
Jaac is offline Jaac  Netherlands
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hi there iám also building a aleph p 1.7 i've designed a board that let me play with the valeu of that output cap currently i'am using two wima mkp4 10uF parallel maybe i will make this 30 uF in the futere if i can here the difference

gr jaac uit TUK
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Old 11th October 2003, 01:43 AM   #4
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Nelson

Thanks for your very prompt reply!
Your response leaves little issue for discussion!- I'll just plough on forward!

BTW have you had any chance to mull over the following thread?

http://www.diyaudio.com/forums/showt...994#post235994

This posting by Mark Finnis relates to an alternative way of achieving a simplified volume control for the P1.7's that he and I will be building concurrently.

many thanks again, your kind efforts on this forum are effectively allowing me to achieve the equivalent in HiFi terms of the Sports car I can't afford to buy to battle my mid-life crisis.

"My regards to you and anyone else you might happen to bump into" Quote- Elwood P. Dowd.
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Old 26th January 2005, 01:48 AM   #5
Stabist is offline Stabist  Slovenia
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Mr. Nelson - so I guess - if matching AP with A5 with 10Kohm SE input and 25Kohm balanced input - 10uF will be more than enough - and so no need to parallel three of them?? Thanks!
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Old 26th January 2005, 01:59 AM   #6
Gaucho is offline Gaucho  Canada
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Quote:
10uF will be more than enough - and so no need to parallel three of them?? Thanks!
1/(2PiRC)=cut off freq (-3dB)

1/(2Pi*10k*10E-6)=1.59Hz

10uF should be lots, unless you perhaps require deeper bass!
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Old 26th January 2005, 02:09 AM   #7
Stabist is offline Stabist  Slovenia
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Quote:
Originally posted by Gaucho


1/(2PiRC)=cut off freq (-3dB)

1/(2Pi*10k*10E-6)=1.59Hz

10uF should be lots, unless you perhaps require deeper bass!

Hehe - you now - it's never too deep
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Old 26th January 2005, 05:56 AM   #8
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Default 1.7 output capacitors

Hi all......

For the Aleph 1.7 output capacitor that is consisting of 3 x 10uF, not only for the purpose of lower frequency, but I guess more the 'sense of body' since the output volume control acts as a load to the pre-amp circuit.... The lowest the volume, the lower resistence, the more output is loaded.

You could test it with 30uF single caps and then parallel 3 x 10uF and feel this effect.... I have my own experiments and the experience told me so...

Just bear in mind, never use 'too big' output caps, since the sound just like when you use a graphic equalizer with V frequencies setting. Very un-natural and metallic on its high frequency...

I hope this will help you, and See you, guys....
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Old 26th January 2005, 08:41 AM   #9
JEKYLL is offline JEKYLL  France
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George, if you want to save money, maybe would it be possible to use a 1 µF capacitor for the inputs like in the first ALEPH P.
But I'm not sure.
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Old 26th January 2005, 01:53 PM   #10
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Default what about the volume control

Quote:
Originally posted by Gaucho


1/(2PiRC)=cut off freq (-3dB)

1/(2Pi*10k*10E-6)=1.59Hz

10uF should be lots, unless you perhaps require deeper bass!
The volume control shown for the P1.7 is also connected to ground. Not knowing the microcontroller details, I can't know the resistance for sure. However, it seems reasonable that the volume control could, for some volume levels, be as low as a 250 ohm load.

In that case the cutoff frequency (-3dB) is

1/(2Pi*250*30E-6) = 21 Hz

That is pretty high.

If you use a 5k or 10k pot instead, then you have no problem.

Jeremy
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