Plenty DIY'ers seem to agree that DC sounds worse...But I have seen quite a few..(like Morgan Jones) explanations why that is...
Something to do with the differential noise on the filament that DC does not take away...
From a layman's point of view then..placing a common mode filter after the DC would give you DC.. that also sounds good.
Like I posted before...I do not have this from firsthand experience..as I have not used DHT'S YET!
.
Plus...are you sure it is really the amp itself..I thought so to after building my latest amp..but then I plugged the CD (Variable output) straight into my amp bypassing the preamp...and was stunned by how little hum there was...)
So it could also be a ground loop in your system..
Hope any of this help..
Good luck..
Something to do with the differential noise on the filament that DC does not take away...
From a layman's point of view then..placing a common mode filter after the DC would give you DC.. that also sounds good.
Like I posted before...I do not have this from firsthand experience..as I have not used DHT'S YET!
.Plus...are you sure it is really the amp itself..I thought so to after building my latest amp..but then I plugged the CD (Variable output) straight into my amp bypassing the preamp...and was stunned by how little hum there was...)
So it could also be a ground loop in your system..
Hope any of this help..
Good luck..
AC DC
Hi guys,
Why not take a look at this thread:
http://www.diyvideo.com/forums/showthread.php?threadid=6082
Cheers,
Frank.
Hi guys,
Why not take a look at this thread:
http://www.diyvideo.com/forums/showthread.php?threadid=6082
Cheers,
Frank.
AC DC
Hello Little Tomato,
How is the 6SN7GTB heated?
If AC pull it out for 30 secs and see if the hum dissapears.
Don't do this for too long since your B+ is going to rise and may take a cap or two out.
Also put the speaker at least 70 cm away from the amp,it's magnetism may upset the iron in your amp.
Cheers,
Hello Little Tomato,
How is the 6SN7GTB heated?
If AC pull it out for 30 secs and see if the hum dissapears.
Don't do this for too long since your B+ is going to rise and may take a cap or two out.
Also put the speaker at least 70 cm away from the amp,it's magnetism may upset the iron in your amp.
Cheers,
HUMBUCKING
Tomatito,
Basically it means you suffer from inductive coupling between those two heaters.
Are they run from the same xformer?
What about the heating of the rectifier?
That should always be run from a separate winding,better still a separate xformer alltogether.
As a last resort: try to run them away from each other taking good care you don't approach any signal carrying wires and push them as close to the chassis. (fix 'em there with a stick-on clip,e.g.)
If that doesn't help try to reorientate your choke with respect to the xformers.
This is hard to crack from a distance but we'll give it a try.
What the efficiency of your speakers anyway?
Do you feel the woofers' membrane slightly trembling to the touch?
Cheers,
Tomatito,
Basically it means you suffer from inductive coupling between those two heaters.
Are they run from the same xformer?
What about the heating of the rectifier?
That should always be run from a separate winding,better still a separate xformer alltogether.
As a last resort: try to run them away from each other taking good care you don't approach any signal carrying wires and push them as close to the chassis. (fix 'em there with a stick-on clip,e.g.)
If that doesn't help try to reorientate your choke with respect to the xformers.
This is hard to crack from a distance but we'll give it a try.
What the efficiency of your speakers anyway?
Do you feel the woofers' membrane slightly trembling to the touch?
Cheers,
Frank,
Yes, they are run from the same transformer. Someone suggested I ground the transformer itself from one of the bolts. Is this a valid suggestion ?
Do you mean separating the heater wires from the 6SN7 ?
The test speaker is a very old Dynaudio with (guessing) no more than 85 db. sensitivity. I don 't feel the membrane trembling.
Thanks for your time and effort
Martin
Yes, they are run from the same transformer. Someone suggested I ground the transformer itself from one of the bolts. Is this a valid suggestion ?
Do you mean separating the heater wires from the 6SN7 ?
The test speaker is a very old Dynaudio with (guessing) no more than 85 db. sensitivity. I don 't feel the membrane trembling.
Thanks for your time and effort
Martin
HUM
Tomatito,
I mean arranging the twisted wires for both heaters (6SN7 +300B) in such a way that their far apart (at least a couple of cm) from each other.
No,you've got a ground already there with the midpoint (loper in Dutch) of your rheostat (like on Steve Benchs' site),don't you?
Sure,that's no good.
You had CRL.
Here's what you can do:disconnect the first cap after the rectifier
and put the R after the cap that was after the choke,then add another cap after that.
What was that first cap?A polyprop?
If so,you better use an elco there.
Good luck,
Tomatito,
I mean arranging the twisted wires for both heaters (6SN7 +300B) in such a way that their far apart (at least a couple of cm) from each other.
No,you've got a ground already there with the midpoint (loper in Dutch) of your rheostat (like on Steve Benchs' site),don't you?
Sure,that's no good.
You had CRL.
Here's what you can do:disconnect the first cap after the rectifier
and put the R after the cap that was after the choke,then add another cap after that.
What was that first cap?A polyprop?
If so,you better use an elco there.
Good luck,
LAST RESORT
Tomatito,
I think you got the hum pretty much under control though,1mV isn't that bad.
One of the tubes is amplifying it a bit although I'm not convinced it really is 50Hz related.
If you have a scope then that should tell the story.
Just try it out you may (I can't guaranty anything here) well take advantage of the better filter properties of the otherwise imperfect elco.
Use the same value (dunno what you put there) and try it out.It higher ESR may give you a bit of voltage drop as well.
Did you use a gridstopper R on the 6SN7?
Cheers,
Tomatito,
I think you got the hum pretty much under control though,1mV isn't that bad.
One of the tubes is amplifying it a bit although I'm not convinced it really is 50Hz related.
If you have a scope then that should tell the story.
Just try it out you may (I can't guaranty anything here) well take advantage of the better filter properties of the otherwise imperfect elco.
Use the same value (dunno what you put there) and try it out.It higher ESR may give you a bit of voltage drop as well.
Did you use a gridstopper R on the 6SN7?
Cheers,
METER.
Tomatito,
I looked at your pic again.
Is the bias current meter permanently monitoring?
If so,you better put a small pushbutton in series with one of the wires so that it will only give a readout when you push it.
Such meters are basically coils,hence inductance etc.
Sorry to interfere with such minor details,not for nothing my buddies call me "the purist".
Cheers,
Tomatito,
I looked at your pic again.
Is the bias current meter permanently monitoring?
If so,you better put a small pushbutton in series with one of the wires so that it will only give a readout when you push it.
Such meters are basically coils,hence inductance etc.
Sorry to interfere with such minor details,not for nothing my buddies call me "the purist".
Cheers,
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