Aleph P1.7 first pictures

[acaudio]

Hi,
my first aleph plays music

Greetings
Adam

 

[acaudio]

more pics

 

[acaudio]

next picture

 

[Duck-Twacy]

Very nice.

What PCBs are you using?

Still pondering wether I will make me an Aleph pre or buy me a secondhand X2.5 one day

 

[acaudio]

The PCB´s are my own design, made for the wima mkp4 10µF capacitors. Size 160x100mm single-sided.
Power supply are 100x75mm (2x 60V) with 80VA transformer.

thx
Adam

 

[jleaman]

nice work .. Keep it up : O )

 

[MikeW]

Nice boards. What do you have planned for the housing?

 

[acaudio]

19" housing with a sanded aluminium surface and steinless steel buttons will be nice, but this is a long way...

thx
Adam

 

[Jean]

Very nice, how does it sound ? Do you have other preamps you can compare this to side by side ?

 

[acaudio]

I listened so far with direct connection CD to my power amp (selfmade like Thel), see my homepage http://www.acaudio.de (under construction). I will compare this with another preamps when the relay volume control works. With headphones sounds smooth and sweetly but these have only 75 ohms impedance.

thx
Adam

 

[acaudio]

problem with relay volume control

Hi,
the relay volume control like aleph p1.0 (with adc0804) works.

Problem:
between step 32 (relay 1-5 on, relay 6 off) and 33 (relay 6 on, 1-5 off) gives it pop noise. Only with signal.
anybody an idea?

thx
adam

 

[Holger Barske]

You have already found the reason for the problem:
This happens when all te relays are switching at once - this generates a very short "level step".
One proven method to get rid of that requires the presence of a "mute relay" on the output and some additional circuitry (microcontroller to be preferred): just switch the mute relay on just before the volume control makes "the evil step". If you play a little with the delay times, you might get this solution working without audible effects.

 

[acaudio]

Hello Holger,
thanks for your replay. How is your new LP?
I would like to do this without microcontroller.
I have already by parallel connection of a 1k resistor at the exit of the circuit a clear improvement reached. The gain is a little lower, but it works good.


I like this Aleph sound, i have today removed the input capacitor from the power amp , it sounds very good with much more detail and dry bass...

Now i need a housing.

greetings

Adam

 

[acaudio]

Files

I uploaded the layout an my website.
For first the pre- and supply pcb.
http://www.acaudio.de/aleph_p17_supply_bottom.pdf
http://www.acaudio.de/aleph_p17_supply_top.pdf
http://www.acaudio.de/aleph_p17_bottom
http://www.acaudio.de/aleph_p17_top.pdf
http://www.acaudio.de/aleph_p17_overview.pdf
http://www.acaudio.de/aleph_p17_supply_overview.pdf

Critical comments are welcome.

thx
Adam

 

[Stabist]

Great looking AP!

Btw - the "bottom" (3rd one) pdf is not working (at least in my case )

How exactely did you do your PCB?? Are they milled?

Btw - your amplifier - how hot does it get - and do you find the copper plates with transistors mounted on it as a good solution or not??

 

[Zen Mod]

Re: problem with relay volume control

Hi,
the relay volume control like aleph p1.0 (with adc0804) works.

Problem:
between step 32 (relay 1-5 on, relay 6 off) and 33 (relay 6 on, 1-5 off) gives it pop noise. Only with signal.
anybody an idea?

thx
adam

try with elco in paralel with some relay coil;
that will give ya small delay
mebbe it will work

 

[acaudio]

Great looking AP!

Btw - the "bottom" (3rd one) pdf is not working (at least in my case )

How exactely did you do your PCB?? Are they milled?

Btw - your amplifier - how hot does it get - and do you find the copper plates with transistors mounted on it as a good solution or not??

uups

http://www.acaudio.de/aleph_p17_bottom.pdf

/Adam

 

[acaudio]

...How exactely did you do your PCB?? Are they milled?

Btw - your amplifier - how hot does it get - and do you find the copper plates with transistors mounted on it as a good solution or not?? [/B]

The pcbs are Bungard FR4 singlesided.

The photoplots are printed on transparece paper with laser printer. Exposed with UV light and developed with NaOH. Pcbs is normally atched at 50°C witch sodium-per-sulfate .Then drilled and afterwards still times full-laminar exposed and developed with NaOH.
For last soldermask painted (Contact).

The Fets runs hot, aprox. 70°C without heatsinking, 65° with. With copperplate these are optimal thermal coupled. A simple thermal coupling in pair isn´t available then this layout is nearly point-symmetric, so are all coupled, both channels an one copper plate. and this looks pretty. I like copper then this is nearly double thermal conductive as aluminium.

sorry for my bad english

/adam

 

[acaudio]

Re: Re: problem with relay volume control

...If you play a little with the delay times, you might get this solution working without audible effects. [/B]

This works GOOD!
Danke Holger!

...try with elco in paralel with some relay coil;
that will give ya small delay
mebbe it will work

The relay coil has 320OHM/2=160Ohm -> For delay aprox.0,1s you need a capacitor ~625µF and have almost short by off->on switsching.

I added a 1µ capacitor at basis, and this works pretty.
The resistor parallel to output is now removed.

thx
Adam

 

[Clarkcr]

Where is the universal ground? Doesn't the circuit need a ground?

Nice looking setup.

C