Hi everyone,
I have read the other threads regarding this preamp, unfortunately (perhaps) I had already bought and assembled the amp. They look great, but I am not fully happy with the sound yet. My full setup includes a ProJect Debut Carbon TT, left and right channel BHL Deluxe phono stages powered by the BHL power supply, then a modified K-502 powering Klipsch RP-160M's.
In general the system is awesome, this is for my work office, so the 5W per channel the power amp is pushing in triode mode is perfect. I have a 3.5mm jack aux input that feeds right to the power amp so I can switch between records, and an auxiliary device.
There is a toriodal transformer hiding behind the power board iron on the left that powers the pre-amp power supply.
Here is a look at the guts.
and a top view:
OK, so I feel like the pre-amp is giving me distortion and it just doesn't sound as good as I feel it should. I am hoping you all can help me with some recommendations. Right now I have R4 set at 22.1Kohm and R5 set at 100ohm.
Anything I can do?
I big thank you in advance!
I have read the other threads regarding this preamp, unfortunately (perhaps) I had already bought and assembled the amp. They look great, but I am not fully happy with the sound yet. My full setup includes a ProJect Debut Carbon TT, left and right channel BHL Deluxe phono stages powered by the BHL power supply, then a modified K-502 powering Klipsch RP-160M's.
In general the system is awesome, this is for my work office, so the 5W per channel the power amp is pushing in triode mode is perfect. I have a 3.5mm jack aux input that feeds right to the power amp so I can switch between records, and an auxiliary device.
There is a toriodal transformer hiding behind the power board iron on the left that powers the pre-amp power supply.
Here is a look at the guts.
and a top view:
OK, so I feel like the pre-amp is giving me distortion and it just doesn't sound as good as I feel it should. I am hoping you all can help me with some recommendations. Right now I have R4 set at 22.1Kohm and R5 set at 100ohm.
Anything I can do?
I big thank you in advance!
Maybe if I describe my symptoms better it will help. I have two main issues that I believe are coming from the preamp. The first is buzzing. When I have needle up, and TT turning, if I crank the volume I get a very audible hum. Second, is with some records I get weird distortion on some recordings.
My only thought, is that my grounding is not idea??? But I don't think that would affect distortion much would it?
My grounding scheme brings every ground point into a single ground screw that mounts the left output transformer to the plinth. I tried to route the ground wires away from singal wires, but maybe not good enough? The ground plane is all the green wires in the above photo.
Suggestions welcome! Thanks!
My only thought, is that my grounding is not idea??? But I don't think that would affect distortion much would it?
My grounding scheme brings every ground point into a single ground screw that mounts the left output transformer to the plinth. I tried to route the ground wires away from singal wires, but maybe not good enough? The ground plane is all the green wires in the above photo.
Suggestions welcome! Thanks!
Sounds like general RFI could be my problem, huh? I didn't think that effect would be so noticeable. I will definitely find some time to fool around with moving stuff around.
This is not a kid friendly piece of kit... I recognize that.
The noise does not change relative to the arm position, the hum is the same no matter the position.
This is not a kid friendly piece of kit... I recognize that.
The noise does not change relative to the arm position, the hum is the same no matter the position.
keep the arm up and turn on the motor, move the arm toward the spindle...if the noise gets louder it's from the motor. Sorry, I should have told you the motor needs to be on.
Bottom line is the BHL kit is pretty sensitive to PSU noise...that's why it;s probably better to run it off batteries. But having all that PC stuff and the tube amp in no enclosure so close is not helping at all. I'd shut the PC down and see if it makes a difference. Also, I'd try batteries to see if that helps...
Could be a grounding issue though.
Bottom line is the BHL kit is pretty sensitive to PSU noise...that's why it;s probably better to run it off batteries. But having all that PC stuff and the tube amp in no enclosure so close is not helping at all. I'd shut the PC down and see if it makes a difference. Also, I'd try batteries to see if that helps...
Could be a grounding issue though.
Another thing...your ground is not connected to safety earth (3rd pin on the wall outlet), unless you are in a country with no safety ground like Japan. I can't emphasize how dangerous this is, especially with the way you have it set up with no chassis, etc. all it takes as for one wire to touch the volume pot or a component failure to make ground live and you could die. You could touch your metal tonearm and be dead. Seriously.
The 3rd wire on your incoming ac should be connected to ground. Preferably with something to break the connection until energized like an ntc or cap and resistor. Google it.
The 3rd wire on your incoming ac should be connected to ground. Preferably with something to break the connection until energized like an ntc or cap and resistor. Google it.
100ohm in R5+
If you have a MM 50dB its 47kOhm in R4 and 3kOhm in R5
If you have an MC 70dB it´s the other way around, 3kOhm in R4 and 47kOhm in R5.
But then you have to find what value your MC wants just solder it at the back of the input RCA´s normally 100 Ohm
I dont know where you got the 100 Ohm from at R5 if you read the manual its resistor values from 50-70dB and you should keep the two values to 50 kOhm added together.
Dont worry i have built 4 of these and this is what i came up with as the best solution.
If you want 60db it´s 35K in R4 and 15 in R5
Hope this helps.
Greetings from sweden
If you have a MM 50dB its 47kOhm in R4 and 3kOhm in R5
If you have an MC 70dB it´s the other way around, 3kOhm in R4 and 47kOhm in R5.
But then you have to find what value your MC wants just solder it at the back of the input RCA´s normally 100 Ohm
I dont know where you got the 100 Ohm from at R5 if you read the manual its resistor values from 50-70dB and you should keep the two values to 50 kOhm added together.
Dont worry i have built 4 of these and this is what i came up with as the best solution.
If you want 60db it´s 35K in R4 and 15 in R5
Hope this helps.
Greetings from sweden
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