I recently purchased an x.150 ( circa 2000 build date) for a second audio system. I admired an was curious about the build philosophy of the Pass products and have aways gravitated towards audio electronics with simple and minimal gain stages (and simple crossovers in speakers). To my ears they sound more like music and typically are more dynamic and life-like.
I also happen to own a balanced DAC/Pre (made/distributed by K&K Audio) and though the balanced output would match a Pass Labs amp well.
I have had the amp for a fews days now but have not had much luck with the amps performance in my system. While the amp is quite tonally correct and runs quite - it is dynamically flat and lifeless. If i didn't know better it sounds to me like a 10 watt amp might present and not the rated 150w of this model.
I have tried switching from XLR to RCA inputs ( little difference) . I have tried switching out different speakers ( both of which are 84-86 db small monitor 2 way speakers with very simple crossovers). No luck with either.
When i replace the x.150 with my Naim 250.2 amp ( 70 watts) i regain the dynamic presentation and the small monitor speakers once again sing.
Before i pass this off as an audio experiment gone wrong, or poor matching to my pre-amp - perhaps there is something i am missing? Would the caps beginning to age on the now 15 year old x.150 present like this? Would a bias issue present like this?
Or perhaps these 'x' series amps are just not as dynamic as some of their counterparts and there are not issues with the unit?
My, pre amp's specs are: Output voltage: 2vRMS at 0dBfs;
Output impedance: 350 ohms
Thanks in advance for any advice forum members may have.
Im located in Canada so delivery the manufacture would be a logistical nightmare.
Britshc
I also happen to own a balanced DAC/Pre (made/distributed by K&K Audio) and though the balanced output would match a Pass Labs amp well.
I have had the amp for a fews days now but have not had much luck with the amps performance in my system. While the amp is quite tonally correct and runs quite - it is dynamically flat and lifeless. If i didn't know better it sounds to me like a 10 watt amp might present and not the rated 150w of this model.
I have tried switching from XLR to RCA inputs ( little difference) . I have tried switching out different speakers ( both of which are 84-86 db small monitor 2 way speakers with very simple crossovers). No luck with either.
When i replace the x.150 with my Naim 250.2 amp ( 70 watts) i regain the dynamic presentation and the small monitor speakers once again sing.
Before i pass this off as an audio experiment gone wrong, or poor matching to my pre-amp - perhaps there is something i am missing? Would the caps beginning to age on the now 15 year old x.150 present like this? Would a bias issue present like this?
Or perhaps these 'x' series amps are just not as dynamic as some of their counterparts and there are not issues with the unit?
My, pre amp's specs are: Output voltage: 2vRMS at 0dBfs;
Output impedance: 350 ohms
Thanks in advance for any advice forum members may have.
Im located in Canada so delivery the manufacture would be a logistical nightmare.
Britshc
Hmm, The amplifier cannot reduce dynamics unless it is horribly compressing things. Not heard a modern Naim, but the older stuff was coloured in a way to enhance their famous 'PRAT'. I would listen to it for a week and see how you feel then. Totally possible caps are in need of replacement, but something doesn't feel right.
Zen,
i cannot figure out how to attach images to this website, but the insides look entirely stock and unmolested.
I looked at some prior posts of yours and while i had the lid off did a few measurements with a digital volt meter and got the following readings after the unit had been powered up (fully) for about 30min:
Main board pins: 0.106 for one side and 0.109 for other ( slightly higher than the 0.94 referance)
Right speaker term output: btw 0.218 - 0.224 btw positive and negative; and 2.48 & 2.25 against ground (the housing of the amp)
Left output: 0.0 btw positive and negative; and 0.15 & 0.15 against ground (the housing of the amp).
Not sure how helpful this information is. If you send me an email adr - i will send you pics directly if you like.
Build date seems to be 2001.
i cannot figure out how to attach images to this website, but the insides look entirely stock and unmolested.
I looked at some prior posts of yours and while i had the lid off did a few measurements with a digital volt meter and got the following readings after the unit had been powered up (fully) for about 30min:
Main board pins: 0.106 for one side and 0.109 for other ( slightly higher than the 0.94 referance)
Right speaker term output: btw 0.218 - 0.224 btw positive and negative; and 2.48 & 2.25 against ground (the housing of the amp)
Left output: 0.0 btw positive and negative; and 0.15 & 0.15 against ground (the housing of the amp).
Not sure how helpful this information is. If you send me an email adr - i will send you pics directly if you like.
Build date seems to be 2001.
Bill,
thxs for your reply. It feels like an impedance or component mismatch. Or something about the speaker crossover that is unfriendly to a Pass design. it not a small difference, its striking. I was under the impression that these amps are know for their attack and PRAT.
One item of note. I had to increase the volume on the preamp significantly to achieve the same volume from the speakers. My Naim amp is rated 29db gain. Where the x.150 is 30db gain. So in theory they should be a similar output, no? Im out of my depth here - so bare with me....
thxs for your reply. It feels like an impedance or component mismatch. Or something about the speaker crossover that is unfriendly to a Pass design. it not a small difference, its striking. I was under the impression that these amps are know for their attack and PRAT.
One item of note. I had to increase the volume on the preamp significantly to achieve the same volume from the speakers. My Naim amp is rated 29db gain. Where the x.150 is 30db gain. So in theory they should be a similar output, no? Im out of my depth here - so bare with me....
feel free to toss as many pictures you can on >sasica5@gmail.com<
leave them unshrinked/original size
even better , if you have dropbox or some other way of putting big and plenty pictures on similar server , that would save us e-mailing procedures/limits
regarding hum/buzz and similar nastiness - I understand none of them are present , having X150 in system ?
leave them unshrinked/original size
even better , if you have dropbox or some other way of putting big and plenty pictures on similar server , that would save us e-mailing procedures/limits
regarding hum/buzz and similar nastiness - I understand none of them are present , having X150 in system ?
hm..
I have an x150, should be a thread here about the poor thing. http://www.diyaudio.com/forums/pass-labs/205030-pass-x150-where-does-sit-overall-line-up-5.html
Even before the minor reno I did, it still seemed very happy to drive the few speakers I have to throw at it.
With every speaker it's always been really really nice.
But I don't know what your Naim sounds like..
If you can post pics, the brains trust here should be able to pick out which version it is and advise from there.
At least my fussy memory thinks theres more than one version ?
I have an x150, should be a thread here about the poor thing. http://www.diyaudio.com/forums/pass-labs/205030-pass-x150-where-does-sit-overall-line-up-5.html
Even before the minor reno I did, it still seemed very happy to drive the few speakers I have to throw at it.
With every speaker it's always been really really nice.
But I don't know what your Naim sounds like..
If you can post pics, the brains trust here should be able to pick out which version it is and advise from there.
At least my fussy memory thinks theres more than one version ?
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Zen,
i sent some pics to you via a Drop Box invite. I can add any further pics of any other parts that is helpful if there is not enough detail in the pics i provided.
No noise from the unit. It runs quite ( no hums and no pops). The x.150 seems to just not have much gain, or much capacity to render transient passages of music with any authority.
i sent some pics to you via a Drop Box invite. I can add any further pics of any other parts that is helpful if there is not enough detail in the pics i provided.
No noise from the unit. It runs quite ( no hums and no pops). The x.150 seems to just not have much gain, or much capacity to render transient passages of music with any authority.
while I'm sleeping , you can conduct/repeat simplest test - feed amp with RCA cables (don't forget to put shortie plug in XLR , between pins 1 & 3);
no load , play sine between 300 and 600Hz , volume up to have something as 3-4V at outputs
measure (use DVM at AC , which is good in said freq. range , so no need for scope) what's input voltage ; it's convenient to measure that on XLR pins then , between pin 2 and shortie
my idea is that something is fishy with several links in your system,speaking of prior reference ; KK thing need to be wired on both input and output xformers to have energized full primary(input) and full secondary(output) to avoid garbage around 10Khz ; speaking from experience with their line preamp , which is having exactly same basic electronic arrangement .....
besides that ..... Naim ....... kudos where it belongs ...... but I'm simply not having good thoughts for/about heatsink-less amplifiers
whatever - let start with gain check-up
good night
no load , play sine between 300 and 600Hz , volume up to have something as 3-4V at outputs
measure (use DVM at AC , which is good in said freq. range , so no need for scope) what's input voltage ; it's convenient to measure that on XLR pins then , between pin 2 and shortie
my idea is that something is fishy with several links in your system,speaking of prior reference ; KK thing need to be wired on both input and output xformers to have energized full primary(input) and full secondary(output) to avoid garbage around 10Khz ; speaking from experience with their line preamp , which is having exactly same basic electronic arrangement .....
besides that ..... Naim ....... kudos where it belongs ...... but I'm simply not having good thoughts for/about heatsink-less amplifiers
whatever - let start with gain check-up
good night
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Zen,
thanks for your email. I think i understand the procedure you are suggesting and will take that measurement when i get back home tonight and report back via a PM if that's ok.
i agree that this is an issue with the structure of the K&K line pre (which is exactly the same design as the DAC) and not the amp itself. There is a mismatch. either electrical or just one of synergy. The KK pre is a bit unusual in it's design.
thanks for your email. I think i understand the procedure you are suggesting and will take that measurement when i get back home tonight and report back via a PM if that's ok.
i agree that this is an issue with the structure of the K&K line pre (which is exactly the same design as the DAC) and not the amp itself. There is a mismatch. either electrical or just one of synergy. The KK pre is a bit unusual in it's design.
Dear Zen,
re:
"no load , play sine between 300 and 600Hz , volume up to have something as 3-4V at outputs
measure (use DVM at AC , which is good in said freq. range , so no need for scope) what's input voltage ; it's convenient to measure that on XLR pins then , between pin 2 and shortie "
on a 600 hz sine wave at 3.1 volts AC at the speaker terminals, im getting .09v AC at the input of the amp on both left and right input.
re:
"no load , play sine between 300 and 600Hz , volume up to have something as 3-4V at outputs
measure (use DVM at AC , which is good in said freq. range , so no need for scope) what's input voltage ; it's convenient to measure that on XLR pins then , between pin 2 and shortie "
on a 600 hz sine wave at 3.1 volts AC at the speaker terminals, im getting .09v AC at the input of the amp on both left and right input.
3.1/0.09 = 34,444444444444444444444444444444 V/V , which is pretty much as 30db , which is carved in stone (read- user manual) for your amp
paste here rest of PM you sent me , so I can comment that too
Zen,
as i noted further above and in my PM to you. I measured the main board pins and the speaker outputs against each other and against ground ( the metal frame of the amp i used for ground - perhaps not ideal)
Main board pins: 0.106 for one side and 0.109 for other ( slightly higher than the 0.94 referance spec)
Right speaker term output: btw 0.218 - 0.224 btw positive and negative; and 2.48 & 2.25 against ground (the housing of the amp)
Left output: 0.0 btw positive and negative; and 0.15 & 0.15 against ground (the housing of the amp).
Right channel seems a bit out of balance. Is this within tolerance? Any possibility of a user adjustment or indicative of a hardware issue?
Thxs
as i noted further above and in my PM to you. I measured the main board pins and the speaker outputs against each other and against ground ( the metal frame of the amp i used for ground - perhaps not ideal)
Main board pins: 0.106 for one side and 0.109 for other ( slightly higher than the 0.94 referance spec)
Right speaker term output: btw 0.218 - 0.224 btw positive and negative; and 2.48 & 2.25 against ground (the housing of the amp)
Left output: 0.0 btw positive and negative; and 0.15 & 0.15 against ground (the housing of the amp).
Right channel seems a bit out of balance. Is this within tolerance? Any possibility of a user adjustment or indicative of a hardware issue?
Thxs
there are 3 things nee to be taken care of :
1.Iq - 106mV and 109mV are practically the same (2.8% diff.) and - if your heatsinks aren't too hot in your environment just leave them be ..... diff. to 94mV is measly 10% up anyway
2. differential offset - DC voltage between speaker terminals - ditto OK on left channel (say that 50mV and less is allowed for home amps , either positive (+50mV) or negative (-50mV) , while right channel needs correction
3. absolute offset - DC voltage between any speaker terminal and gnd ; it isn't so critical (say up to 500mV in temp equilibrium ) but if not set properly , it'll chip of one half of voltage amplitude ( take it as one half of output sine shorter than other ....... so clipping sooner than other one ) , while also sliiiiightly influencing linearity on much smaller voltage levels ,below clipping area
so , few preparation steps :
- take 2-5cm wide sticky paper tape , put it all around edge of top plate/cover of amp, to prevent scratching while manipulating with cover ;you can make few loops of tape as handles , to ease pulling it away from amp
-prepare two DVM's - connect one for absolute offset (probes on terminals) , connect second for relative offset (one terminal (any)) and gnd ; case gnd is good enough
-nice ,wide,proper screwdriver for these blue bugger pots ;
now - look at pictures you sent me - I labeled pots on UGS pcbs ( that's all you'll need to fiddle with - leave those at main pcb as is) .
case 2. differential offset - attach DVM's as explained - to one channel , UGS closer to connectors is for left channel , while UGS closer to xformer is for right channel (as written on speaker terminals) .... that speaking of UGS to output terminals correspondence
now - all inputs grounded ; most practical way is to put shorties on XLR's (pins 1 and 3) and on RCA's , so practically pin 2 of XLR is also shorted to gnd ; no dummy load on speaker outputs ;
power up amp , let it cook to temp equilibrium , with top cover in place
open cover , then slowly fiddle in one way (or another - DVM will tell ) with P2 , to decrease existing offset (observing DVM between terminals) in half , no more ; put cover back , let it stabilize
repeat previous step , as many times is needed to achieve decent small offset between terminals
now - case 3.
open cover , then slowly fiddle in one way (or another - DVM will tell ) with P1 , to decrease existing offset (obser4ving DVM between terminal and gnd) in half , no more ; put cover back , let it stabilize
repeat previous step , as many times is needed to achieve decent small offset between terminal and gnd
NB that one setting will slightly influence other one , but you'll repeat it few times iteratively and get done
when done with one channel - move to second one and do all that again
remember that each time put cover back and let stabilize , in between steps
OK , that's it ;
did you had chance to hear amp with some other source/preamp ?
procedure explained above will not bring you Mana from Heaven , but amp will be set as it was from factory ; I believe any discrepancy between previous state of your system and now with X150 in , lies in so called synergy
between system components ...... which is most often then not just fact that one component's flaws are covering for other one's , and vice versa .
now - with X150 in place , you have much more honest and clean amplification (in good meaning ) , so something is fishy - either speakers/room combo , or something upstream ;
remember that X150 deserves/demands no more than , say, 500-600R output impedance of preceding stage , be it attenuator or preamp's gain stage or whatever is closest to X150 input side
1.Iq - 106mV and 109mV are practically the same (2.8% diff.) and - if your heatsinks aren't too hot in your environment just leave them be ..... diff. to 94mV is measly 10% up anyway
2. differential offset - DC voltage between speaker terminals - ditto OK on left channel (say that 50mV and less is allowed for home amps , either positive (+50mV) or negative (-50mV) , while right channel needs correction
3. absolute offset - DC voltage between any speaker terminal and gnd ; it isn't so critical (say up to 500mV in temp equilibrium ) but if not set properly , it'll chip of one half of voltage amplitude ( take it as one half of output sine shorter than other ....... so clipping sooner than other one ) , while also sliiiiightly influencing linearity on much smaller voltage levels ,below clipping area
so , few preparation steps :
- take 2-5cm wide sticky paper tape , put it all around edge of top plate/cover of amp, to prevent scratching while manipulating with cover ;you can make few loops of tape as handles , to ease pulling it away from amp
-prepare two DVM's - connect one for absolute offset (probes on terminals) , connect second for relative offset (one terminal (any)) and gnd ; case gnd is good enough
-nice ,wide,proper screwdriver for these blue bugger pots ;
now - look at pictures you sent me - I labeled pots on UGS pcbs ( that's all you'll need to fiddle with - leave those at main pcb as is) .
case 2. differential offset - attach DVM's as explained - to one channel , UGS closer to connectors is for left channel , while UGS closer to xformer is for right channel (as written on speaker terminals) .... that speaking of UGS to output terminals correspondence
now - all inputs grounded ; most practical way is to put shorties on XLR's (pins 1 and 3) and on RCA's , so practically pin 2 of XLR is also shorted to gnd ; no dummy load on speaker outputs ;
power up amp , let it cook to temp equilibrium , with top cover in place
open cover , then slowly fiddle in one way (or another - DVM will tell ) with P2 , to decrease existing offset (observing DVM between terminals) in half , no more ; put cover back , let it stabilize
repeat previous step , as many times is needed to achieve decent small offset between terminals
now - case 3.
open cover , then slowly fiddle in one way (or another - DVM will tell ) with P1 , to decrease existing offset (obser4ving DVM between terminal and gnd) in half , no more ; put cover back , let it stabilize
repeat previous step , as many times is needed to achieve decent small offset between terminal and gnd
NB that one setting will slightly influence other one , but you'll repeat it few times iteratively and get done
when done with one channel - move to second one and do all that again
remember that each time put cover back and let stabilize , in between steps
OK , that's it ;
did you had chance to hear amp with some other source/preamp ?
procedure explained above will not bring you Mana from Heaven , but amp will be set as it was from factory ; I believe any discrepancy between previous state of your system and now with X150 in , lies in so called synergy
between system components ...... which is most often then not just fact that one component's flaws are covering for other one's , and vice versa .
now - with X150 in place , you have much more honest and clean amplification (in good meaning ) , so something is fishy - either speakers/room combo , or something upstream ;
remember that X150 deserves/demands no more than , say, 500-600R output impedance of preceding stage , be it attenuator or preamp's gain stage or whatever is closest to X150 input side
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I knew it , brainfart .
it needs to be written as :
-prepare two DVM's - connect one for differential offset (probes on terminals) , connect second for absolute offset (one terminal (any)) and gnd ; case gnd is good enough
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