Tube Experts

Chad

Chad

Slender Hobbit
I am getting ready to replace the tubes on my egnater tweaker. It has a tube spot that says it's for the loop. Does that tube have any impact on tone or volume if I never use the loop? I'm not going to worry about replacing that one if it only maters if I use the loop.
 
Probably a recovery stage for the loop. May in fact be in the chain with nothing in the loop - would have look at the schematic to be sure.

I'd replace it just to be thorough; if it's on, it's getting used, even with nothing going through it.
 
wagdog said:
Probably a recovery stage for the loop. May in fact be in the chain with nothing in the loop - would have look at the schematic to be sure.

I'd replace it just to be thorough; if it's on, it's getting used, even with nothing going through it.
Click to expand...
^^^^this. Just put a cheapie JJ in there and be done with it.
 
wagdog said:
Probably a recovery stage for the loop. May in fact be in the chain with nothing in the loop - would have look at the schematic to be sure.

I'd replace it just to be thorough; if it's on, it's getting used, even with nothing going through it.
Click to expand...

The tubes in it are good. I'm just looking to clean the amp up a bit. If it doesn't chance the tone, I'll just throw in something I already have sitting in a box.
 
It can change the gain in the loop. I put a 12ax7 in my loop once because I didn't have a 12au7... it didn't sound bad but it sounded more "pushed" so it works with a little grit or a lot of gain but it wouldn't be crystal clean if you were trying to do that.
 
baimun said:
It can change the gain in the loop. I put a 12ax7 in my loop once because I didn't have a 12au7... it didn't sound bad but it sounded more "pushed" so it works with a little grit or a lot of gain but it wouldn't be crystal clean if you were trying to do that.
Click to expand...

I don't use the loop at all. The amp has the stock tubes in it and am going to replace them. I'm not going to worry with it if it only messes with the tone of the loop. I think I have a couple EHX 12au7s somewhere, maybe I'll just throw one of those in there and get new ones for the other 2 spots.
 
Without a schematic, no one can tell for sure.

The loop tube may just be split between a cathode-follower (send) and gain stage (return) when the loop is used. It may be in the signal at all times, maybe only the gain stage is, maybe neither. I suppose if it works with that tube pulled, it means it is out of the chain when the loop is off.
 
Last edited:
Generally speaking.....power tubes, at least for me get changed about once a year ymmv due to how often and how hard you use the amp. Preamp tubes last much longer. If yours are still working you probably don't really need to change them.
I would definitely install and bias a set of power tubes then, fire up the amp and play it. If it sounds/feels good then leave the preamp tubes in there. Just because they are old(er) doesn't mean a thing.
I swap preamp tubes strictly for tone purposes. All of my preamps are NOS (or used) tubes from the 60's. I only swap if one fails( which has only happened once in my JVM) or I'm looking to change a tonal characteristic.
If it ain't broke.....
 
Well, if I was going to replace the others, I would replace that one too. 12AX7/AT7/AU7/5751 etc series tubes are the cheapest tubes in your amp, so you might save like 10-15 bucks by not swapping it. Not worth the worry of not doing it, I think.

As for the 'loop' issue, 12AX7 tubes are a dual triode tube and therefore can be used to do two different things in an amp. I don't know enough about electronics to say if a loop tube would use both triodes. On several of my amps I have 12AX7 tubes that have two different functions listed, one for each triode of the tube. So, that loop tube might be doing something else as well.
 
Last edited:
Tiltsta said:
Well, if I was going to replace the others, I would replace that one too. 12AX7/AT7/AU7/5751 etc series tubes are the cheapest tubes in your amp, so you might save like 10-15 bucks by not swapping it. Not worth the worry of not doing it, I think.

As for the 'loop' issue, 12AX7 tubes are a dual triode tube and therefore can be used to do two different things in an amp. I don't know enough about electronics to say if a loop tube would use both triodes. On several of my amps I have 12AX7 tubes that have two different functions listed, one for each triode of the tube. So, that loop tube might be doing something else as well.
Click to expand...
It is possible that the 2nd triode of the loop tube could be performing another function.
When I had the JVM one side was the loop and the other was reverb.
 
Ok...just found this:

http://www.egnateramps.com/download/TweakerTubeChart.pdf

Looks like V1 has2 gain stages.
V2 is strictly for loop purposes.
V3 is your phase inverter. Hence the "power amp" labeling.

So if this is me if replace the power tubes,
I would also do some tube rolling in V1. Try whatever you have because they all have different characteristics. (JJ- dark w/ lots of gain, EHX smoother, Svetlanas-brighter etc...)
The next most important 12ax7 is the PI...to me this tube has a greater impact on the "feel" of the amp. Try a Sovtek LPS here-IMO they have a fantastic feel for a new production tube. I actually prefer to have a NOS there if available. They just seem to feel the best (to me anyway).
Now if you decide to swap out V2, most people will put the same tube that they have in V1. Reason being is that you may not want that tube to "color" you're fx running through the loop and rather would prefer it to be tonally similar to your V1 stage.
I know you said you don't use the loop, so this may be a non-issue for you....just wanted to throw that info out there to you.
Let us know what you decide on!!
 
You must log in or register to reply here.
Back
Top