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Traynor Dynabass 400 Combo Pre Amp Tube Change.

BaronVonBlurple

BaronVonBlurple

Mar 12, 2023
37
79
Canada
#1
I have the combo amp and cab and Im looking into changing out my pre amp tube. I also want to check if the tube has gone microphonic. I seem to be getting wimpy or no drive. I can see that the tube is illuminated.

I assume on taking out the front screws and sliding it out. From there, is it simply taking off the cover and getting to the tube? I believe I have read that the tube is on the second level pcb board. Any other Dynabass 400 users have you swapped out yours?

Also, recommendations for a gritty, bright, tube replacement. I was just thinking on getting the JJ.

20240107_105849

20240107_105849

 
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#2
That amp is designed to use a modern tube. So the JJ will work fine... There's no real point in throwing anything old or exotic in there. I find it hard to believe the tube would be microphonic, but I guess it's possible. It might be loose, though. Have you confirmed that the FET side is very clean? It should be.

Regarding the tube, see this service manual and page "24" that basically spells out what you should be putting in there and why:
Traynor DYNABASS 400 - MANUAL SERVICE Service Manual (Page 24 of 25) | ManualsLib

On those I often find the push buttons on the panel to get sticky, or sometimes failing to make good contact. You can usually wiggle the head of the switch with your fingertip to "clean" the contact.
 
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#3
I like JJ tubes, but not for "bright and gritty". I associate those characteristics with the Sovtek 12AX7WC. If you can find a Sino/Shuguang 12AX7B you could try that also, but I've found those Sinos vary all over the place quality-wise. They also compress like crazy, which may or may not appeal to you.
 
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#4
The local big Music store (Long and Mcquade) have Mesa Boogie tubes readily available. Most everything else would have to be ordered.

I was hoping to bring someone out of the woodwork who has replaced one in the Dynabass amps. To give me some kind of roadmap on extracting it and replacing it. As I am a neophyte in the Bass world, I was looking for the guidance of a more skilled hand. Also, maybe I have too high expectations for the growl I hope to achieve with just driving this amp. Again, I was hoping someone who has used or owns this amp, could shed some light on just how much dirt I should be hearing.

Yes it has a distortion button and yes it has a wet / dry mix knob. All very nice. However, the distortion sounds horrible and a mess. Not the Geddy Lee Moving Pictures growl I want to achieve. With just tube pre amp, it is getting close, but still out of reach.

I did triple check the button to make sure it is engaging....and it is, but dialing up the gain is not giving more dirt. It seems to only get to a certain point and thats it, just more volume.

That being said, if and when I do it, I will post here in this post the nudies when it happens.
 
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#7
BaronVonBlurple said:
Yup, I agree with you.

Im still trying to find my tone with it and get acclimatized. In the meantime, I practice and research.
Click to expand...

Tube differences in general are very subtle, and you have a 50% chance of going the wrong way anyhow. Not all tube changes yield positive results.
 
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#8
Did I just blow the pre amp tube?

Im playing today with the amp's volume in the sweet spot. Not crazy loud, but vibrating the vibratable things kinda loud.

Tube pre amp engaged.
Drive at noon.
Master at setting 3
Eq's mostly flat with touch of bass boost, and low mid boost.
Plugged into the passive input with pretty hot pickups.

Then....POP!

No more sound.

Disengage the tube and go to solid state....sound is back.
Tube is still lit up.
Re engage tube pre amp.
No sound.
Tube is still lit up.

Im thinking I will have to change the tube anyways now.
 
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#11
BaronVonBlurple said:
Did I just blow the pre amp tube?

Im playing today with the amp's volume in the sweet spot. Not crazy loud, but vibrating the vibratable things kinda loud.

Tube pre amp engaged.
Drive at noon.
Master at setting 3
Eq's mostly flat with touch of bass boost, and low mid boost.
Plugged into the passive input with pretty hot pickups.

Then....POP!

No more sound.

Disengage the tube and go to solid state....sound is back.
Tube is still lit up.
Re engage tube pre amp.
No sound.
Tube is still lit up.

Im thinking I will have to change the tube anyways now.
Click to expand...


I bet the switch that goes from Tube to Solid State is failing. So many of that model I've seen had something wrong with one of those tiny, imprecise push-on-off switches. I find the Mute button tends to fail, but if someone had been "exercising" the tube/ss switch, I could see the contacts losing strength and becoming intermittent.

Turn off the amp and push that button in and out for about a minute... then power back up and see if the tube channel is working.
 
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#13
frankie5string said:
I bet the switch that goes from Tube to Solid State is failing. So many of that model I've seen had something wrong with one of those tiny, imprecise push-on-off switches. I find the Mute button tends to fail, but if someone had been "exercising" the tube/ss switch, I could see the contacts losing strength and becoming intermittent.

Turn off the amp and push that button in and out for about a minute... then power back up and see if the tube channel is working.
Click to expand...

I fiddled with it and still no sound.

Do you think that is serviceable? The local Long and Mcquade should have seen a few of these on their workbench...no?
 
#15
frankie5string said:
I bet the switch that goes from Tube to Solid State is failing. So many of that model I've seen had something wrong with one of those tiny, imprecise push-on-off switches. I find the Mute button tends to fail, but if someone had been "exercising" the tube/ss switch, I could see the contacts losing strength and becoming intermittent.

Turn off the amp and push that button in and out for about a minute... then power back up and see if the tube channel is working.
Click to expand...
I had the same problem with 2 used heads I found @ Long and Mcquade . It wouldn't operate in the tube setting, Chances are its the tube/ss switch and not the tube . I sent them both back and got a Traynor YBA 100.. hope you get it sorted out .
 
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#17
Update

After discussing with a L&M Service rep, their tech recommended I try changing the tube before bringing it in to be serviced. So I picked up a 50 Canadian dollar Mesa Boogie 12AX7 tube, and jumped into this adventure. Against @agedhorse words of wisdom.

So glad I did because, low and behold it was the tube. It wasnt the easiest to get at thats for sure on these combo amps. But I took a few pics for future references if any other Dynabass 400 users want to change their pre amp tube.

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1000006317


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I ended up taking off the front face plate, which was completely unnecessary. I was a little bamboozled on how to slide the amp out of the cabinet.

Stay funky Bros!
 
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