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Old 6th February 2006, 06:17 AM   #1
Hastur is offline Hastur  United States
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Default Resistors in Aleph-X

I have a quick question for all the experts out there. I just took part in the new Aleph-X compact group buy (thanks Bruno), and was wondering which resistors in the schematic for the boards are the "money" resistors. I am looking to make some really nice amps and plan on using Caddock and Holco resistors and am wondering where I can get away with the Holcos without mucking up the sound too much. Doing a full board with only Caddocks is too spendy for me.

Any who, here is the schematic.
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Old 6th February 2006, 02:54 PM   #2
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I'm not sure where you got that schematic, but there are at least two errors in it. The variable resistor in the front end current souce is off by several orders of magnitude. It should be 200 Ohms, not 50k.
R103 should be 330, not 360.
If you build the circuit as shown in that schematic, it won't set up properly and you'll get really, really frustrated. Then there'll be this long thread about trouble shooting an Aleph-X wherein no one can figure out why the thing won't bias.
There may be more problems, but I'm short on time.
Incidentally, I used Vishay/Dale for the signal resistors and Caddock for the Source resistors. Panasonic "blue" for the output-to-ground resistors. If you want to use Holco, Caddock, Vishay, et. al. it suits me just fine. The circuit will be happy as a clam.
Never figured out why it is that clams are supposed to be so happy, but who am I to question them?

Grey
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Old 6th February 2006, 05:45 PM   #3
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Makes me wonder where that schematic came from. I have seen it around but I can not remember where. Some of the component designations are different.
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Old 6th February 2006, 09:52 PM   #4
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Hi all,

that is the schematic I posted on the Aleph-X PCB group buy thread.
It is directly taken from KK's Site and I've just redrawn it to create the PCB.
Now, the value of VR101 is wrong (my BIG mistake! ), it really must be 200 Ohms, as Grey pointed out. I apologise for this mistake.

As for R103, the value of 360 Ohms is exactly the same as on the original schematic I mentioned above. I do not know if it makes too much of a difference with Grey's original value of 330 Ohms.
With VR101 set to 0, the equivalent value of the parallel of R103 and R104 is 203.85 Ohms with R103=360 and 193.875 with R103=330 Ohms.
With VR101 set to 200 Ohms, the equivalent total resistance is respectively 255.53 and 249.1 Ohms.

I leave to the experts (I'm not one) to judge whether it's preferrable to set R103 to 330 Ohms or to leave it as it is. As far as I know, several Aleph-X have been already built following this schematic and they work...

Cheers,

Bruno

P.S.: I'm going to post this message also in the Aleph-X Group Buy Thread, just to keep the relevant information all together.
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Old 6th February 2006, 10:55 PM   #5
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If the output stages won't bias right, you'll know where to start trouble shooting.
The question I have is how many people are trying to build the circuit with bogus schematics?

Grey
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Old 6th February 2006, 10:58 PM   #6
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The "bogus schematic" has been corrected (at least regarding VR101): Corrected Schematic

Bruno
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Old 6th February 2006, 11:05 PM   #7
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I thought it might be useful to repost Grey's original project at this point.
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Old 7th February 2006, 10:58 AM   #8
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Maybe it would have been better to post the schematic from the Wiki? (Hifizen´s)
This one is without the feedback resistors and a few other mods were made too.

William
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Old 7th February 2006, 11:18 AM   #9
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Hi all,

just to clarify things: the schematic I posted in The Aleph-X PCB Group Buy Thread is neither Grey's nor Hifizen's.
The schematic is taken from KK's Site and I' ve just redrawn it with Eagle, in order to create the PCB. I made a mistake (value of VR101), which was pointed out first of all in the Groupbuy thread and then here by Grey. The mistake is now corrected.
The reason why I chose this version of the schematic is that it was already used in a previous PCB group buy (Kari's) and, to my understanding, several people built their Aleph-X according to it without trouble.

Cheers,

Bruno
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