Budda Twinmaster - Unusual Hum, need help...

dragonfly66

Member
Messages
476
I have a 1996 Budda Twinmaster 2x10 combo. When I turn it on it there is a loud hum when nothing is plugged in. If I plug my guitar into the "Normal" input the amp is quiet with the usual shhhhh sound. If I plug my guitar into the "Hi Gain" input the hum doesn't go away. So really the "Hi Gain" input is unusable.

I'm guessing that when I plug my guitar into the normal input that the guitar cable is grounding the circuit and that is why the hum goes away. The hi gain input is not grounding the circuit (maybe it should) and that is why I still hear the loud hum when plugged into that input.

The filter caps have been replaced on this amp recently in hopes it would remove the hum, but it did not. I thought maybe other tech savvy people would know or other owners of Twinmasters could tell me if this was normal behavior or not. Any help understanding what might be happening is appearciated.

Here is the 1 page manual, http://www.budda.com/resources/twinmaster_manual.pdf.

THE TWINMASTER AMP
BY
BUDDA AMPLIFICATION​

SUGGESTED OPERATING SETTINGS:

Hi Gain/Normal Inputs:
There are two inputs that access different gain structures from the TwinMaster. This particular design circuit is a cascade front end drive circuit, therefore you can only access one input at a time. The Normal input has slightly dininished gain and has a tone reminiscent of an early Fender black face Deluxe. Sweet and smooth, this input is great for power chords, rhythm and slide. The Hi Gain input is designed for maximum distortion and is reminiscent of a hybrid Plexi Marshall/Ac 30 combo.

Bass & Treble Controls:
Depending on whether or not you use single coils or humbuckers, 2x12's, 4x12's, etc., you will find the treble control likes to sit between 12 o'clock and 4 and the bass control between 10 O'clock and 2. Feel free to experiment. There are no rules when finding your tone!

Volume:
This controls the amount of gain for both inputs of the amp. Start by setting this control at around 12 o'clock. Feel the power section start to work with lots of headroom and punch behind your rhythm chords. As you turn the control clockwise you will add gain to your signal for great crunch tones. Fully clockwise offers great crunch and lead tones. Rolling off the volume of your guitars volume pot off between 5 and 7 will clean up the signal without muddying up the tone of your amp. The amp is equipped with capacitors to maximize the clarity and brightness of your signal as you roll off your guitars volume pot. As you turn up the volume incrementally on your guitar, you can essentially go from rhythm, to crunch, to lead drive. This works on both inputs of the amplifier and is considered the "purist" form of
channel switching.

Effects Loop:
This is where you introduce effects into the signal path of your amplifier.To hook up an effect to your amp, take a 1/4" shielded mono cable and run the send of the amp to the input of the effect and run the output of the effect into the return on your amp.

Slave:
The slave out is an identical replication of the signal coming off the speaker outputs of your amp with a padded eq circuit. Feel free to experiment by sending the Slave Out signal to an external stereo power amp feeding a couple of 2x12 or 4x12 extensions for a wall o sound!

Another option is to send the Slave Out signal to a recording console for DI tones to tape, or
send it to a board for a signal feed to the mains for live applications in a club or arena. When slaving make sure that there is always a load on the speaker out of your amp.

* A note of interest is that the power section of this amplifier is an extremely powerful and we recommend using Budda extension cabinets that are fine tuned to the Twinmaster electronics for maximum sonic performance. Some cabinets with minimum baffle space may sound woofy, especially with low wattage speakers.

**Budda also recommends that you wear ear plugs to avoid the serious complications of hearing loss. Budda says; Steer Clear of Bad Ear!
 
Messages
1
id look at the LOW input jack first it may not be shorting to ground when no lead is in it, thus when using the LOW you get a short from the lead, but when using the HI the low still has no short and the hum will remain constant.
 

dragonfly66

Member
Messages
476
Thanks for the suggestions. I did think about changing the tubes, but the amp is not where my extra tubes are, so will try that when I can get them together. I'll check the first input and see what I can see. I have no schematic for this amp and it isn't available from Budda/Peavey.
 

pdf64

Member
Messages
7,937
It may just be dirt on the input switch contact; does plugging a shorted jack plug into the normal input allow the Hi-Gain mode to work correctly?
A shorted jack can just be a guitar with its volume/s turned down.
 

Tone Meister

Member
Messages
3,266
I know this is a long shot, but just for sh**s and giggles, try patching a cable from the FX Send to the FX Return to complete that part of the circuit. I have one of these amps ('95 model) and awhile back it had the very same issue - it appeared to be the inputs jacks during troubleshooting. Turned out the shorting jacks in the FX loops were dirty.

A simple cleaning of those jacks took care of my issue. I hope your issue can be resolved that simply.
 

dragonfly66

Member
Messages
476
Cleaned and burnished guitar inputs and fx loop jacks. Tried patch cable from fx send to fx return.

Still have the hum. Hum still quieted when putting an input into the normal input. So I'll be looking at the wiring around the normal input and what it is connected to.
 
Last edited:

dragonfly66

Member
Messages
476
It is currently at the home of a friend of mine who is an engineer (an actual rocket scientist) who is also a guitar player. He is troubleshooting it. He said it seems there is a grounding issue. I'll report back when he figures it out.
 

Dave B

Exit... Dual Stage Left
Gold Supporting Member
Messages
1,817
I know this is VERY old @dragonfly66 (saw it when I was looking up stuff about older Buddas), but did you get this resolved? I'm assuming you did, but if you didn't, there are two simple things you can try, per Scot from back in the day.

Hope you still have the amp and that it's treating you well...
 

Dave B

Exit... Dual Stage Left
Gold Supporting Member
Messages
1,817
You probably already know this, but here goes anyway from a tubes/amp novice. Other, feel free to chime in.

V1 and V2 are the two two-stage preamp tubes (dual triodes). The 12A* families are split in half electronically and can be accessed separately within a circuit. It's possible that half of V1 is good and the other half is not.
  • Normal Input - uses the 1st half of V1 (V1a) as a singular gain stage.
    • Normal does not use the 2nd half of V1 ( V1b).
  • Hi Gain Input - uses both halves of V1, where V1a feeds into V1b.
  • V2 (both halves) is the phase inverter (PI).
  • You normally can only plug into either Normal or Hi Gain, but not both, to coax music from the TM.
    • You cannot use a standard A/B box to switch between channels (except for the few amps that slipped through and went out the door, where this A/B was possible due to a wiring glitch during assembly).
    • This 'glitch' became a published mod (and I think part of Peavey's revamped Twinmaster circuit), involving the connectivity between the two inputs. Though, the volume discrepancy between the two inputs sharing the singular Volume control was too much to make it functional for most.
...Trials... (Info from Scot S on how he told me [the novice] how to determine if the crackling I was getting at the time was coming from the preamp tubes or the power amp tubes.)
  1. Did you try replacing V1 with a 12AX7, or other preamp tube, that you know functions fine, from another amp?
  2. If that doesn't work, did you try the same with V2? Not sure if the PI would be part of the hum problem, but it could be worth a try?
  3. If you plug your guitar directly into the EFX Return, you are completely bypassing the Twinmaster's preamp. (You'll notice that the amp's Volume, Bass, and Treble will not function.) Try that and see if the hum goes away.
    • If it goes away but didn't when you swapped out V1 and V2 with good tubes, it is something in the preamp circuit. (Maybe it could have something to do with a flaw in that designed, or modified, connectivity between the two inputs?)
  4. Even though based on the symptoms, it doesn't seem like it could be the EL84s or rectifier tube, did you try swapping them out if the above didn't work?
A knowledgeable amp tech should be able to find the source if it still hummed with known good preamp tubes (and power amp and rectifier, too) in it.

Where are you located? If interested, Jeff Bober is still in the amp business outside of Baltimore, and repairs amps, including his older Buddas. You can ship him just the chassis, too. He can be messaged through his East Amplification website to get more details and rates.

Hope this helps. (Looks like in the fine print you go through a London Fuzz - very nice! Mine sound great through my TM. )
 

garret

Member
Messages
1,052
Give Jeff Bober a shout as well. He will respond to your questions. He did when I had an issue with an SD30 version II believe it or not.
 






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