Roadster help - Spongy Hum and speaker "thump" - thoughts?

Discussion area for Single, Dual and Trip Rectifers

Moderators: Guitarzan, Grandor, ned, Platypus

Post Reply
BlakemoreMusic
Bottle Rocket
Posts: 20
Joined: Sun Oct 23, 2016 1:51 pm
Location: Nashville, TN
Contact:

Roadster help - Spongy Hum and speaker "thump" - thoughts?

Post by BlakemoreMusic » Sun Nov 13, 2016 12:30 am

Hey friends,

looking for a little guidance. I recently traded for a Roadster from a forum member and I'm learning the quirks of this particular amp and am thinking something may have happened during shipping.
The amp is running JJ EL34L's and Tungsol 12ax7 in V1.

My problem(s)-

-when I switch to Spongy mode, i get a 120Hz hum. It is especially noticeable on channels 3 and 4 as they amplify more gain stages than channels 1 and 2. The hum is there in 1 and 2 as well if I turn up there masters to listen for it. If I turn whichever channel master down all the way, the noise stops. This tells me its in the preamp section, pre-master. In bold mode there is no hum. Spongy there is hum. Preamp tube rolling has not changed the hum at all. Removing the rectifer tubes, changes nothing. Hum is present in all modes and configurations.

-I get 60z hum on channel 4 in both bold or spongy

-channel one has hiss/fizz in the background. Definitely has the campfire sound. Probably a resitor/cap combo going bad

- I get a nice "thump" through my speaker cab when changing channels. I am familiar about the roaster pops, this is different and much lower in frequency. Ive never had a mesa do the "thump" thing before.


Any thoughts or insight are much appreciated.

afu
Mark IV
Posts: 662
Joined: Thu Aug 15, 2013 12:20 am
Location: Tucson, AZ
Contact:

Re: Roadster help - Spongy Hum and speaker "thump" - thought

Post by afu » Tue Nov 15, 2016 7:26 pm

Does it continue to thump after several channel changes? My 3 channel gets deep pops once in awhile from dirty to clean. It's like the mute bus takes a nap for one switch, while someone thumps a mic.

Have you checked the guitar or cable for grounding issues or swapped them out?
2007 3 Channel Dual Recto w/loop mod

My Humble Music Tech Blog:
Dual Rectifier Index

BlakemoreMusic
Bottle Rocket
Posts: 20
Joined: Sun Oct 23, 2016 1:51 pm
Location: Nashville, TN
Contact:

Re: Roadster help - Spongy Hum and speaker "thump" - thought

Post by BlakemoreMusic » Wed Nov 16, 2016 1:07 am

The thump stays consistent through guitar and cable changes.

I've got the amp at a mesa the here in Nashville going through it

bandit2013
Triple Recto
Posts: 3142
Joined: Fri Feb 22, 2013 7:31 am
Location: North Carolina

Re: Roadster help - Spongy Hum and speaker "thump" - thought

Post by bandit2013 » Sun Nov 20, 2016 2:55 pm

I will get a certain amount of noise from the amp but it is typically quiet due to signal level of the noise. I do not use EL-34s with my Roadster. However, I do with the RA100 and that seems more prone to the hum and amp buzz depending on gain setting and what guitar I am using.

Also, have you tried moving the amp to a different room? I have one room that is hard to get noise free as it has floor mounted electrical plates. I can tell were the lines run under the floor easily just in moving my position. Overhead lamps in ceiling also contribute to noise as they are fluorescent type lamps and not tungsten filament types. Also lamps on a dimmer will also create noise levels above typical noise floor from a high gain amp.

If they do not find any issue with the amp, it could be related to outlet voltage or line quality. You may need a power conditioner to eliminate electrical line noise issues with better filtering and isolation along with stable voltage level better suited for tube amp use. If I run the dishwasher in the kitchen, I will hear the motor noises though any of my amps.

BlakemoreMusic
Bottle Rocket
Posts: 20
Joined: Sun Oct 23, 2016 1:51 pm
Location: Nashville, TN
Contact:

Re: Roadster help - Spongy Hum and speaker "thump" - thought

Post by BlakemoreMusic » Mon Nov 21, 2016 12:08 am

I run my amps on a furman voltage regulator which works great. My royal Atlantic is more prone to buzz for sure but not hum (like I was expiriencing with the roadster.)

Got the call back from the tech and here was the synopsis:
had a leaky cap in the channel 1 tonestack casuing the campfire noise, loose tube sockets, bad preamp tubes and a roughed up rectifier were the hum culprits.

I'm looking forward to sitting down with the roadster, fresh tubes, and a clean slate to see what she can do.

Post Reply