I use the same tubes. I cant comment yet, the high freq. tone makes the whole tone harsh at the moment so will have to find the problem first....
Annoying noise....
I have isolated the annoying noise I get from the phono the input is shorted to ground so I have no idea where is it coming from...WIFI???
I have added the sound file in ZIP....
View attachment noise-EO-phono.zip
I have isolated the annoying noise I get from the phono the input is shorted to ground so I have no idea where is it coming from...WIFI???
I have added the sound file in ZIP....
View attachment noise-EO-phono.zip
I don't know either. Looking at it quick and dirty in foobar2000, the high frequency noise appears about 3kHz with some additional near 5kHz. The level is equal in both left and right and runs -30 to -35 dB.
The fact that it is in both channels suggests it is not a single tube or single component in the signal path. Could you measure the power supplies to see if the noise is in them?
If it is airborne RF noise, you might take your cell phone and wave it near to the circuit. I have often had cell phone generate a noise similar to that on other circuits, especially when the cover is off the enclosure.
Anyone else have suggestions for tracing this?
The fact that it is in both channels suggests it is not a single tube or single component in the signal path. Could you measure the power supplies to see if the noise is in them?
If it is airborne RF noise, you might take your cell phone and wave it near to the circuit. I have often had cell phone generate a noise similar to that on other circuits, especially when the cover is off the enclosure.
Anyone else have suggestions for tracing this?
Thank you for your feedback...I am also puzzling, on scope I get mix of noise ranging to 2 mhz and I have encloused the amp in an aluminium enclosure. It looks like the noise is less intensive when cartridge is connected or inputs shorted to ground. I will check the psu...
Guys, I think I found the problem in B- power supply so I changed the RAW filter but after power up R54 this is the 8.2K resitor on the B+ regulator began to cook....so I turned it down and cant find the problem! The B- supply work I get -13.5V. The heater is working just the B+ is collepsing! I hope the JFETs arent dead! Any idea?
I think I have some sort of ringig of the B- regulator LM337 Its peaking from 30hz-2.5khz-12khz...So what to do? I changed the output cap fron 220uf to 470uf no effect. Any ideas? The noise produced by lm337 is 6-7mV RMS this is the noise I measure at the output also...
Not sure what to recommend.
When you say that you changed the output cap from 220 uF to 470 uF with no effect, are you referring to C24 in the schematic below? If so, you might try the same change at C23 instead. From my experience, the cap at the adjust terminal is important for controlling ripple.
Also, not a likely thing, but check that the polarity of these electrolytics is correct with the plus terminal to ground. It could form a leak current in the wrong polarity and the schematic isn't very specific about marking polarity.
Does the noise look like a sine, indicating ripple? It is possible that there is a faulty component that is breaking down or leaking somehow. D9, D19, and the LM337 would be the next things to try replacing.
Good luck with this. Hunting down noises is never much fun.
Jac
When you say that you changed the output cap from 220 uF to 470 uF with no effect, are you referring to C24 in the schematic below? If so, you might try the same change at C23 instead. From my experience, the cap at the adjust terminal is important for controlling ripple.
Also, not a likely thing, but check that the polarity of these electrolytics is correct with the plus terminal to ground. It could form a leak current in the wrong polarity and the schematic isn't very specific about marking polarity.
Does the noise look like a sine, indicating ripple? It is possible that there is a faulty component that is breaking down or leaking somehow. D9, D19, and the LM337 would be the next things to try replacing.
Good luck with this. Hunting down noises is never much fun.
Jac
I would advise to tackle these issues separately to avoid going around in circles. Power up just one of the regulators, the B+ OR the B-, and report what happens.
Jan
Jan
Yes Its sine wave 2-3mV...When connected to speakers there is hum on both channels on the LEFT a little more than on RIGHT. The hum is not constant it depends on volume control.On scope it is coming from B- supply. hmmmm
I disconnected the B+ and the hum is coming from B-. Its 2-3mV mixed freq. humming on speakers when the volume control is turned more 1/2 turns I can hear it near the speakers.
I must correct myself after I tested the new installed C22 I replaced the 1nF caps with 220uF as my raw psu is 1 meter apart from the amp stage the regulator has no ringing but the Hum I get from the speakers is constant in both speakers just slightly more on left! A ground loop? I am using the graounding shematic SY proppsed.
The 220 uF replacement of C22 might be part of your problem. The datasheet for the LM337 recommends a 1 uF tantalum cap for distances longer than about 100mm from the RAW supply filter cap. But a jump to a 220 uF electrolytic is pretty big and may not be better. The internal LM337 circuit is somewhat complex, so it isn't easy to estimate what might happen, but perhaps something in the 1 to 2.2 uF range might be worth a try. I would also consider a parallel 1 nF cap to address higher frequencies.
For what it is worth, my RAW supply is almost 1 meter from the regulator and I am using only the 1 nF recommended by SY. If yours is ringing with the 1 nF, there might be something else going on.
For what it is worth, my RAW supply is almost 1 meter from the regulator and I am using only the 1 nF recommended by SY. If yours is ringing with the 1 nF, there might be something else going on.
Think. If it varies with the volume control, what does that tell you about is origin?
If you put your scope directly across the last elco on the B- supply, directly at the elco, what do you see?
Jan
Was looking for a phono pre for my MM an i stumbled onto Sy's HMN MC pre and after messaging him on a MM version of HMN he suggested the Equal Opportunity pre.
I really like the design and would build it in a heart beat.
The only problem is the availability of the LSJ74 jfets wich are out of stock everywhere. Does anyone know of any substitutes? Any recommendations would be very welcome.
I really like the design and would build it in a heart beat.
The only problem is the availability of the LSJ74 jfets wich are out of stock everywhere. Does anyone know of any substitutes? Any recommendations would be very welcome.
Hi all together , an new post in an old thread.......since 4 years now.
It`s also about 4 years ago since i first read SY article in the Linear Audio Vol. about this unique phono preamp.
And now i am a bit proud to pesent my version of this great sounding amp. I build my device in this 4 year period an now i am satisfied with the results and like to show some pics. I designed my own single layer PCBs ( 2 stages on each PCB + one for the powersupply ). The transformer and the choke too are from Toroidy, costum made in Poland, nice looking and for a fair price. I also made some mesurements as you can see in the pics down below. The mesurement results are not as good as SY described in Linear Audio but the amp sounds really great, no hum an low noise at all. I modified my Ortofon Super OM30 for symetrical wiring and changed the RCA Jacks on my turntable for a Tiny XLR connector because of the small space in the back of my PRO-Ject turntable. The tubes are old and used ones from a 70`s oscilloscope, but with good emission. The rest of the circuit is pretty much 1:1 what SY published in the LA Volumes.
All in all a real nice preamp, thanks to Stuart Yaniger an all the people here in the DIY Audio forum who told me the way to build "The Equal Opportunity".
with kind regards from Germany........Matze
It`s also about 4 years ago since i first read SY article in the Linear Audio Vol. about this unique phono preamp.
And now i am a bit proud to pesent my version of this great sounding amp. I build my device in this 4 year period an now i am satisfied with the results and like to show some pics. I designed my own single layer PCBs ( 2 stages on each PCB + one for the powersupply ). The transformer and the choke too are from Toroidy, costum made in Poland, nice looking and for a fair price. I also made some mesurements as you can see in the pics down below. The mesurement results are not as good as SY described in Linear Audio but the amp sounds really great, no hum an low noise at all. I modified my Ortofon Super OM30 for symetrical wiring and changed the RCA Jacks on my turntable for a Tiny XLR connector because of the small space in the back of my PRO-Ject turntable. The tubes are old and used ones from a 70`s oscilloscope, but with good emission. The rest of the circuit is pretty much 1:1 what SY published in the LA Volumes.
All in all a real nice preamp, thanks to Stuart Yaniger an all the people here in the DIY Audio forum who told me the way to build "The Equal Opportunity".
with kind regards from Germany........Matze
