I just bought an SVT 2 Pro- it went into fault, so since i bought used from L&M the service is great = they replaced all but 1 pretube and put in a set of barely used 6550s free of charge (even thought it was a used purchase) sounds better than it did before going into fault, but there is a very loud buzz now.
They are attempting to determine the cause but i was hoping by sharing symptoms here i might get some valuable insight on what to check (they are not sure where to go next with it to ID- and are offering money back refund, but id rather keep it by far if i can id and correct the issue) here are the details:
After it went into fault, they replaced all the power 6550s which removed the fault light and "no sound" issue, but left a very significant buzz.
They then replaced most of the preamp tubes:
5 @ 12AX7's
2 @ 12AU7's
- leaving only 1 12AU7 - either a preamp or likely a drive tube given their service ticket noted "replaced all worn preamp tubes" based on it testing well.
It reduced the buzz / hum greatly but there is still a very significant buzz/hum from the amp when in ON mode (as soon as you come out of stand by, and disappears as soon as back to stand by)
The buzz gets increasingly worse as the master volume is moved from 0 - up ward (but not really effected by increases to gain or any EQ settings) and is not reduced/removed when mute is on (i.e. something in the post Gain & EQ section of the amp?)
There is still a sizable "pop" (physical - you can hear and feel it inside the head (if you rest your hand on top of it) when going from stand by mode to "ON" mode - it seems to occur most (but not all) of the time but is not heard through the speaker. As
I love the amp, They are hard to find around here, and it was at a great price, now with new tubes .... so it sounds really great and am looking for any options to check try before having to return it and move on.
yes the buzz is very loud - far above what you would expect from any amp. I checked against my 2001 SVT cl with older tubes in it, Hartke LH1000, Markbass T800 and SA 450's - and they are all virtually silent when compared to this SVT 2-Pro when tested on same power circuit and cab)
The amp is still much quieter than the SVT CL, but not as quiet as originally before all this work was done.
the buzz is even more evident from the Slave and preamp outs (signal from each is weak/unusable with a far more pronounced buzz, the preamp out is worse than the slave out)
the balanced out is also very noisy with poor signal in pre mode, & 0 signal all noise in post mode. I did not try to adjust the level of this output screw.
the "power amp in" signal is clean & strong (when feeding to it from another amp/preamp source) and the buzz does not appear to get louder as the volume is increased via this input (only stays same as when amp is on, out of stand by mode, and master at 0). I have also uploaded an attachment of symptoms leading to the original entry into fault mode which resulted in they went thru retubing most of the amp
