Aleph-X builder's thread.

[eapavant]

The bc550c are in correctly. It also seems like I have all the correct resistor values, unless I have two of the same resistors marked wrong. Can I take out r7, r8 and q3? It should work with out them? Or am I wrong?

 

[Netlist]

R7, R8 and Q3 can be removed.
Apply a signal and check with the scope on both sides of both feedback resistors. (52 and R52).

/Hugo

 

[eapavant]

Thanks Netlist. I will check with scope and report back.

 

[Nixie]

Is it possible to speed up initial warmup time? I don't want to have to wait more than a couple minutes for the amp to reach a stable operating point. What about running extra high bias for the first minute or two to heat up the output devices and heatsink?

 

[jleaman]

Is it possible to speed up initial warmup time? I don't want to have to wait more than a couple minutes for the amp to reach a stable operating point. What about running extra high bias for the first minute or two to heat up the output devices and heatsink?

Sure.. go buy a heat gun and heat the heat sinks your self. Kinda pointless.. why are you so much in a rush ?

 

[Babowana]

Is it possible to speed up initial warmup time? I don't want to have to wait more than a couple minutes for the amp to reach a stable operating point. What about running extra high bias for the first minute or two to heat up the output devices and heatsink?

For example, my Zen V5 needs half an hour to one hour depending on room temp, in reaching to the warm operation (within +/- 50mV offset) from the cold (abt 300mV offset).

During this period, I'm not able to distiguish musical sound difference at home listening.
Just nice sound all the way . . .

 

[eapavant]

R7, R8 and Q3 can be removed.
Apply a signal and check with the scope on both sides of both feedback resistors. (52 and R52).

/Hugo

Thanks for the help Hugo. I now have a working amp. One of my feedback resistors was bad, it some how failed open. I don't know if I did it when I folded the leads or what. I pulled it out and replaced it and now it is settling down. I will let it warm up and see where Vdc is at. Now off to the second channel. Thanks for the help!

 

[Nixie]

I take it there's no output inductor?

 

[wuffwaff]

Hi,

no, ´s not needed to keep it stable.

William

 

[Nixie]

But my question was about regulated power supply for Aleph X - did someone try it ? How did it affect the sound ?

I built a higher-powered version of http://mrevil.pwp.blueyonder.co.uk/amp/amp4/sub/psu2.shtml
It's a capacitor multiplier instead of fixed voltage reference so you can have a minimum voltage drop in the regulator without worrying about mains variation.
However, I haven't listened to it as I've yet to order the bulk metal foil resistors I intend to put on the Aleph-X boards. I just finished my masters and I'm looking for a job now, so it may take some time...

 

[juma]

Thanks Nixie,
that's something I had in mind but I already have some LT1083s left and it would be a shame to let them go to waste. They are LDO (Vin-Vout @7.5A is only 1.5 V) and they have very positive influence on the sound of AB class amps.
I wonder how will it be in the case of Aleph X?
In any case, when I build it I'll let you know.

 

[james watt]

Hi!

I am Robert. I have built the aleph-x according Greys original schematic, but using 17,5V rails and bias 5A. The output devices are IRFP044N. All IRF9610, IRFP044N and the 0.22ohm resistors, left and rigth channel, are mounted on the same aluminum block, which is watercooled.
I have matched all transistors within 10mV, but the DC ground to output offset will not go lower than about 5V. Now I changed R23 to a 500ohm pot. When I go down to 350ohm on R23 (R25 still at 390ohm) DC to ground offset is <3V and output- to output+ <100mV. The amp is playing music, without signal its quiet. The aluminium block goes up to 65°C.
Now some questions to the forum:
Will this modification have impact on the overall performance?
What is the recommended minimum of the bias difference between Q2/Q11?
Is more important to have same voltage across R23/R25 or same current?

I have attached a picture showing one channel completed.

 

[Netlist]

The interesting PCB etching discussion has been split off here

/Hugo

 

[Nixie]

Originally posted by Netlist
split off

I find the email subscriptions don't transfer when a thread gets split, and manually resubscribing is necessary. I find that very annoying, as I've not always noticed when a thread has been split in cases of large posting volume.

 

[Netlist]

Indeed, and the best we can do is notify as I did above.

/Hugo

 

[Nixie]

I'd have thought the best thing you could do is fix the bug in the forum software. I'm sure it will be very small trouble, and will save far more to the rest of us.

 

[tenderland]

Aleph x heat sink

I am building the Aleph x low power version and have a concern concerning the heatsink. With 4 power mosfets /ch each dissipates 34w. With a desired heatsink temperature of 50C a and an ambient temp of 22C I have a thermal resitance of .82 C/W
For 1 device. I can use a 6 “ tall 5 3/8 wide heat sink per device.(thermal resistance = .71) Does this sound accurate?


Thanks
J

 

[wuffwaff]

Hi,

yes sounds good.

William

 

[Emeric]

Hi ,

I've some questions about the Aleph-X:

1- What is the gain of the amps ?
i think I've read it, it depends of resistors but i'm not shure.

2- Is it necesserary to have a good power supply if the amps
are connected to mid-range and tweeters loudspeakers ?
When i say good power supply i think : CRCRC or CLCLC with big value for C.

3 - Is a 36mV ondulation of the rail voltage or to mutch ?

4- What mode input work the best ? Balanced or unblanced ? Is it
the similar ?

Sorry for my bad english
I try to learn it.

Thanks for your answers

 

[wuffwaff]

Hi,

1. 20-26dB depending on the resistors
2. CLC should be sufficient, CRC is also possible. Just keep the ripple low enough (see 3.) or the bias down wich should also be possible when used for mid and highs.
3. 36mV ripple is OK
4. balanced

William