These question may very well be left for the factory but since this is Saturday and my Aleph P arrived last night I thought I would start here.
I purchased a Aleph P serial #003 and upon first listen there was noise almost like a ground loop or improperly grounded circuit. No hum. Also I was getting two sources playing at once. I pulled the top and found the two wires that would I believe to connect to the center pins of the RCA's right next in line from the output jacks off and hanging (damn FEDEX). One other wierd thing is that someone apparently wanted two sets of outputs so they wired jumpers from the output jacks to the same center pins of the input jacks that had the wires that came off. *** That is why I had two sources playing at once. **** I will fix this.
The only manual for the P on the pass website is for the revised version and some changes were made.
This preamp has way too much gain for me, too much to be able to be use. The later revision has changes made to the Master volume control to allow it to be set in a number of positions (5 normal and 5 positions that are -12db down.) Then the separate right and left controls do the fine tuning. My preamp has a more conventional ladder volume control. The separate volume controls for L & R are a 1K conductive plastic pot.
If I need more attenuation can I use a higher value pot in its place, or add a resistor in line?
Walt
I purchased a Aleph P serial #003 and upon first listen there was noise almost like a ground loop or improperly grounded circuit. No hum. Also I was getting two sources playing at once. I pulled the top and found the two wires that would I believe to connect to the center pins of the RCA's right next in line from the output jacks off and hanging (damn FEDEX). One other wierd thing is that someone apparently wanted two sets of outputs so they wired jumpers from the output jacks to the same center pins of the input jacks that had the wires that came off. *** That is why I had two sources playing at once. **** I will fix this.
The only manual for the P on the pass website is for the revised version and some changes were made.
This preamp has way too much gain for me, too much to be able to be use. The later revision has changes made to the Master volume control to allow it to be set in a number of positions (5 normal and 5 positions that are -12db down.) Then the separate right and left controls do the fine tuning. My preamp has a more conventional ladder volume control. The separate volume controls for L & R are a 1K conductive plastic pot.
If I need more attenuation can I use a higher value pot in its place, or add a resistor in line?
Walt
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I have been on the phone with the techs at Pass. The more I look at my copy of the P it does not match what became the first production units. I asked about increasing the value of R115 or changing the pots to 1.5K or 2.0K units they indicated that higher resistance would allow higher noise. They offered a better way would be to jumper a 1k resistor across two 750 ohm 3 Watt resistors except I cannot find any 750 ohm 3 watt resistors. Do not know how to copy the pdf to here.
Every schematic I have seen is loaded with 1uf and 10uf caps and none here. I am not sure if this preamp is cap coupled unless it uses one of those large 1000uf caps. This may have been one of the original prototypes.
Any idea the location of resistor R115? Should it be one of the 3 watt resistors?
Here is a the ad where I bought the preamp. It has a pic of the inside. Clicky to expand the pics.
Pass Labs Aleph P Preamp Non remote version - Audio Asylum Trader
Every schematic I have seen is loaded with 1uf and 10uf caps and none here. I am not sure if this preamp is cap coupled unless it uses one of those large 1000uf caps. This may have been one of the original prototypes.
Any idea the location of resistor R115? Should it be one of the 3 watt resistors?
Here is a the ad where I bought the preamp. It has a pic of the inside. Clicky to expand the pics.
Pass Labs Aleph P Preamp Non remote version - Audio Asylum Trader
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there must be some miscommunication - I can't see how increasing amount of source degeneration can increase noise
however , it seems that is early specimen (Ser. No. 003) , mosfets (IRF240) as active elements and bipolars (MJE) in PSU reg role
it's probably time for Papa to chime in ....... but - if schematic is in any way similar to one we have , you can make this :
look at picture I attached , and two red arrows ; desolder one red wire from right pot , solder 1K resistor (small one of 250mW is good enough ) to pot lug , solder wire to free end of resistor .
do the same on other pot with white wire
regarding output caps ..... I'm not seeing any other than big honking electrolytics ...... but that's separate issue ( bypass them or not , recap entire thingie or not)
however , it seems that is early specimen (Ser. No. 003) , mosfets (IRF240) as active elements and bipolars (MJE) in PSU reg role
it's probably time for Papa to chime in ....... but - if schematic is in any way similar to one we have , you can make this :
look at picture I attached , and two red arrows ; desolder one red wire from right pot , solder 1K resistor (small one of 250mW is good enough ) to pot lug , solder wire to free end of resistor .
do the same on other pot with white wire
regarding output caps ..... I'm not seeing any other than big honking electrolytics ...... but that's separate issue ( bypass them or not , recap entire thingie or not)
Attachments
Much appreciated, I wondered about just adding resistance along the same method as you just described. One other choice is buying a 2K honeywell pot to replace the 1K pot. The resistor to the left of the pot wires must be R115. In your and the pass labs techs schematic that resistor is 475 ohm I believe. On mine it is 211 ohm. I am thinking of replacing it with another Dale 1/4 watt resistor I have lying around that is 681 ohm. Not sure on the calc but suspect that should get me -5db and thats in the ballpark.
The preamp sounds fantastic. May be the single best piece of audio equipment I have ever owned. I am slowly putting together a Tubelab TSE single ended amp built for 45 output tubes and hoping the pairing works out well. I am listening to it through a pair of PP 6V6 amps from Mapletree and I am blown away how good those amps sound with this preamp. All of a sudden I have bass, deep articulate and tunefull bass. I can hear everything but no grain or harshness.
Thanks for all your attention.
The preamp sounds fantastic. May be the single best piece of audio equipment I have ever owned. I am slowly putting together a Tubelab TSE single ended amp built for 45 output tubes and hoping the pairing works out well. I am listening to it through a pair of PP 6V6 amps from Mapletree and I am blown away how good those amps sound with this preamp. All of a sudden I have bass, deep articulate and tunefull bass. I can hear everything but no grain or harshness.
Thanks for all your attention.
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