Aleph-X builder's thread.

Mark A. Gulbrandsen said:
I am in the process of populating my first pcb and have a few questions about the board and component choice.


1. Is there any sonic difference between using the IRF9610 or the ZVP3310A devices? I have both so could go either way there.

2. What is the purose of the R48 and R49 position which is shown as a 0 ohm jumper in both locations? Why put space for a resistor if there is only a jumper there?

3. Is a half watt metal film for R-21 ok? Grey called for a 3 watt resistor in this location....

4. What is a good value to start at for C7,8,9,10 ? I don't want to oscillate when I run it up the first time....

5. I assume that it is ok to use the IRFP240 device in leiu of the 044?

Note that I am building this first unit to get used to and learn about this design. Its going to be built exactly as it is on the diagram.

Thanks in advance for any input you might shed on these questions.

Mark


Hi Mark, Let me answer some of your questions:

1. I haven't done that much testing yet. The ZVP3310A was suggested by another member as an improvement, and since it was easy to add a stuffing option for it, I did so (actually, grataku put it into the original layout). I built my prototype rev0.9 channel using it (with a small TO-92 clip-on heatsink) and it sounds fine. Using the Zetex part also left more 9610's to match pairs from.

2. R48 and R49 are indeed jumpers, though the option is there to add resistors if you like. R48 would basically function to soak up some excess voltage and reduce power dissipation in the current source FET (especially for higher rail voltages), and provide some measure of series parasitic capacitance reduction / isolation. You will have to balance this against the reduced DC voltage across the current source FET (think linearity), and decide for yourself how much resistance you want there. Starting with just a jumper is a perfectly fine choice though. R49 is there to allow some flexibility in wiring the input ground... you can jumper it or add some isolation resistance if you like. Again, your choice, and will depend on factors unique to your implementation.

3. Half watt should be fine, or you can just jumper it (I jumpered mine). R21 normally doesn't do anything... the only time it really matters is when the gate protection zeners D2-D5 are conducting. You've made me wonder, though, why Grey used 3W. Hmm.... can't remember... don't want to go digging through that mammoth thread... ;)

4. C7-C10 are at this point just vestigial footprints. I haven't heard of anyone needing to use them, so you can confidently omit them without harm, especially if you're sticking to the basic design without any drastic alterations. Of course, you should still check for oscillations anyway. I could have removed them from the board, but that would have driven up the order cost by incurring an NRE tooling charge.

5. 240 is fine. I believe numerous people have already built with those.

The most valuable piece of advice I have for you is match, match, match. The most important parts to match are: Q5<->Q7 (critical), Q2<->Q11, R6<->R41 (yes, you should try to match these... use a current source and a voltmeter to find their value), and R23<->R25. For other component hints, download the info package (there's a link to it from the order wiki), and read the notes in the BOM spreadsheet.



edit by pinkmouse: I have moved this over from the PCB thread as it is more relevant here, but be aware that the question this answers is not above, but below! ;)
 
Ok, I'll be first in line and move this post over here where it belongs.....

I am in the process of populating my first pcb and have a few questions about the board and component choice.


1. Is there any sonic difference between using the IRF9610 or the ZVP3310A devices? I have both so could go either way there.

2. What is the purose of the R48 and R49 position which is shown as a 0 ohm jumper in both locations? Why put space for a resistor if there is only a jumper there?

3. Is a half watt metal film for R-21 ok? Grey called for a 3 watt resistor in this location....

4. What is a good value to start at for C7,8,9,10 ? I don't want to oscillate when I run it up the first time....

5. I assume that it is ok to use the IRFP240 device in leiu of the 044?

Note that I am building this first unit to get used to and learn about this design. Its going to be built exactly as it is on the diagram.

Thanks in advance for any input you might shed on these questions.

Mark
 
I am also wondering how many will be built in the end.But with over a thousand boards out there I estimate conservatively that if half those that ordered are serious then we have about 100 people that intend to build it in the near future.To be even more conservative I think about 40-50 Aleph-x's are going to be made at least.
 
XLR Input Pin Numbering Conflict

Please note that the XLR pin numbering on the schematic is contrary to most XLR pin conventions.

For proffesional gear the pin out is as follows:

Pin 1: Ground or Sheild
Pin 2: High, +, or Non-inverting
Pin 3: Low, -, or Inverting

Some consumer equipment might be wired to a different convention.

Double check your source equipment to match up by signals not pin numbers.

Aud_Mot

Ps Chad great job all around. Best $5.00 I have ever spent.
 
Cost of Aleph-X

Hi all,

Have got a few boards and am contemplating jumping into this amp building stuff but am not quite sure what the range of cost to build. How much does the aleph x cost to build per channel?

If you are building multiple channels can you share power supplies or do you need to do it per channel?

Thanks for any help.
 
Voltage and bias?

Most of the AX built are low voltage (15-20) high current (6-10). The First Watt is going to have 24 volt rails for a ten to fifteen watt amp.
There must be a reason for the higher rails. Should these be built using 25 volt rails with 3-6 amp bias?:confused:
 
Re: XLR Input Pin Numbering Conflict

Aud_Mot said:
Please note that the XLR pin numbering on the schematic is contrary to most XLR pin conventions.

For proffesional gear the pin out is as follows:

Pin 1: Ground or Sheild
Pin 2: High, +, or Non-inverting
Pin 3: Low, -, or Inverting

Some consumer equipment might be wired to a different convention.

Double check your source equipment to match up by signals not pin numbers.



A non-issue really that was discussed before but alas the schematic was never modified.
Just keep in mind that the actual receptacle should be connected in the usual manner. It is pretty clear why the board end needs to be the way it is.
 
Re: Voltage and bias?

MikeW said:
Most of the AX built are low voltage (15-20) high current (6-10). The First Watt is going to have 24 volt rails for a ten to fifteen watt amp.
There must be a reason for the higher rails. Should these be built using 25 volt rails with 3-6 amp bias?:confused:


I do remember that Mr. Pass once told, long ago, that he would not go below 25V...or was it 20V...

I will use 20-25V and 4 A for my version, 8 mosfet per canal...

Regards
Josip
 
Member
Joined 2003
Paid Member
Thanks Chad and everybody for makng the x boards possible. In the process of building mine with 22.3V Rails and 10 amp bias. In the process of building power supply and chassis now and am very interested in other peoples opinion about the options. Read the thread but by the time I was finished forgot half no 90% of what I read. I guess I will start from the beginning

Regards Scott
 
Questions on Aleph-X

Hello,

this is my first DIY audio project in almost 20 years. My soldering iron is already hot... Some questions:

- Is somebody planning to sell matched FETs?

- Is it a good idea to replace D1 with 1N938 (reference diode 9 Volt with very low temperature gradient)? It is rated with 500 mW but only 7.5 mA. Although in its data sheet this current is rated as max. current, I assume that it is meant as max. current with guaranteed temperature stability (how else would you get 500 mW?) When exceeding this current, temperature stability should still be much better than compared to standard zeners. Or does the diode break with more than 7.5 mA?

- Which type of power resistors would you use?

- I have not found the transistor MPSA18 so far in Germany. By which European type can it be replaced without affecting sound quality and the original resistor values?

- Is there any benefit in using a rectifier bridge for each of the supply voltages vs. using only one bridge delivering both supply voltages?

- I am aiming at a CLC filter in my power supply. Which choke manufacturers should I look for?

P.S.: Nelson, thank you very much for everything!!! I understand that you love a bottle of good red wine from France. I am living in a wine producing region and will try to convince you that there are also very good German red wines. To all others: wouldn't this be a subject for a group buy in favor of Nelson? ;)
 
Re: Questions on Aleph-X

bertram said:
Hello,

this is my first DIY audio project in almost 20 years. My soldering iron is already hot... Some questions:

- Is somebody planning to sell matched FETs?

- Is it a good idea to replace D1 with 1N938 (reference diode 9 Volt with very low temperature gradient)? It is rated with 500 mW but only 7.5 mA. Although in its data sheet this current is rated as max. current, I assume that it is meant as max. current with guaranteed temperature stability (how else would you get 500 mW?) When exceeding this current, temperature stability should still be much better than compared to standard zeners. Or does the diode break with more than 7.5 mA?

- Which type of power resistors would you use?

- I have not found the transistor MPSA18 so far in Germany. By which European type can it be replaced without affecting sound quality and the original resistor values?

- Is there any benefit in using a rectifier bridge for each of the supply voltages vs. using only one bridge delivering both supply voltages?

- I am aiming at a CLC filter in my power supply. Which choke manufacturers should I look for?

P.S.: Nelson, thank you very much for everything!!! I understand that you love a bottle of good red wine from France. I am living in a wine producing region and will try to convince you that there are also very good German red wines. To all others: wouldn't this be a subject for a group buy in favor of Nelson? ;)

-here in the Netherlands is a small company which sells mathed fets (www.specmail.nl), don't know if they deliver to places outside Holland

-D1, don't know a std zener works fine for me

-I used intertechnik mox4 (www.intertechnik.de) 4watt 2% and availible in 0.22 ohm

-I use a single bridge, but double bridge will give lower noise.

-for choke's I urge you to look at what intertechnik have to offer, you'r looking for air-core coils. I use a CRC filter, because power resistors are cheaper ... :).
 
Transformer Discount

Hello,

I too will be constructing an Aleph X in the very near future. I'm finishing up an A40. I have contacted Avel Lindberg and one of their distributors in an effort to get them to set up a "special code" ..... if you will whereby one could call them and place an order for an off shelf Toroidal Transformer that meets the requirements of your specific project. They accept credit cards, and will ship out of the US to approved countries. I would also be glad to contact Mouser, DigiKey, and other suppliers and attempt to make the same arrangements if there is enough interest. I'm looking into heatsinks also. There is real purchase power in the masses I'll keep you posted.
 
My post about transformers...

...is in the Aleph-Xorder discussion. I got a quote from Plitron. Perhaps we would get a discount from them too with an account number like you have suggested. What transformer is the one people would want to use. Quantity discounts would be based upon ordering the same transformer no doubt.