My Aleph p1.7 sounds wonderful !

[zei]

So.. I just tested my aleph P 1.7 with boards from veteran.

Sound is full, rich, bass is better, overall it is just smooth and i could,nt be happier!

Thanx Mr. Pass and thanx Damian (Veteran) who made the PCB,s.

The only "fancy" parts i have used is BG N Caps.
Volume control is an ALPS Blue Velvet 10k on the output.

Everything is mounted in a shoebox (for now)



So only one question.. the Fet,s are getting very warm.. do they need a heatsink?

I have a small heatsink on the PSU but not on the amp boards..

Best regards and thanx for this extraordinary forum!

Joakim

[zei]

Ok so a small heatsink i wise i guess..

However, i thought that i could place a 10k pot on the output ( wich a have) But searching a bit i came across something Nelson Pass wrote..

[QUOTE]There a three places you can put variable resistance in an
Aleph P to alter the gain

1) You can place a dual potentiometer on the inputs as a
voltage divider. (dual pot required for 1 channel balanced)

A good value for this is 10K to 25K

2) You can place a single potentiometer between the Source
pins of the Mosfets, where a good value is about 1 Kohm.

3) You can place a dual potentiometer as a resistive load at
the outputs (again 1 dual for each channel) to load the
current-source output, and here a good value is about 1 Kohm.


It seams i hade it all wrong.. even though it realy sounds good now,, What do i gain if connecting the pot on the input instead.?

/Joakim

[zei]

Anyone has any input in this matter?



/J

[kmj]

2) You can place a single potentiometer between the Source
pins of the Mosfets, where a good value is about 1 Kohm.

And thus one dual pot for both channels? Between the sourcepin och which mosfet exactly?

[heyj]

I suggest you to put your 10k pot on the input.
10k pot on output would make the output impendence of the P1.7 preamp to be almost 10k , which is a little bit high.
If you move your 10k pot to input, the output impendence will change to about 100. This low output impendence was low enough to drive all amp.

[flg]

1)Can't say to much about this. It probably is the standard configuration for volume controls but I havent tried it. It will mess with your source impedance so that must be considered. It may also mess with the input impedance and capacitance causing a rolloff so that needs consideration also...

2) Between the source pins of the gain transistors, is what I have been doing. A 1K maybe 2-5K is about all that's usefull in my circuit. It is not exactly N.P.s 1.7 per'se. It also does not go to minimum audio out, it only changes gain in a reasonable range. You need a mute button also if you want silence from it... It has been commented by several people that this method introduces more distortion. I find this to be true also. I don't want to quote numbers but, the distortion differnces are from, unmeasureable to barely measureable at resonable input/output levels. It depends on the needed gain and on the abssolute output level you need. 1-3 Volts is pretty damn good. If you don't want to spend the money this is the easiest cheapest solution...

3)The dual pot on the output is the original configuration, other than the type of "pot" used . It has a small advantage in that it reduces everything level-wise, including the noise of your 1.7 circuit. The input Z of your next stage is important but your gain setting and average listening level should be considered also, as with option 1) and may be taylored for the most often listened to level, with lowest gain and distortion... Hope that helped...

[zei]

I guess i just move my pot to the input instead

/Z

[Gooch]

Any pictures


Dave

[zei]

Not much but here goes...



another

[kmj]

hehe, Zei! Why don't you post the beautiful casing? It's a work of art rarely seen these days.