Fender Bassman LTD
Hi Skip,
I wonder if you, David or anyone else can answer the following questions for me please.
In general when using a '59 Bassman LTD for harmonica and a JT30 with CM element, is it better to use a 5AR4/GZ34 or 5U4G rectifier tube?
Are their any major advantages/disadvantages to using either?
Also if you fit a 5U4G do you need to re-bias the amp or can it just be swapped straight out?
I currently have mine set up with V1 = 12AY7, V2 = 12AX7, V3 = 12AX7, 2 X 6L6GC , GZ34.
I have run both and they work fine and sound good without changing the bias... but it's good to ask Skip just in case! The 5U4 will have more sag. I also recommend you try your "V3 = 12AX7" as "V3 = 12AU7," you may like the change.
Thanks for the info David. I'll have to try a 5U4G. I know that Gary Primich used a 5U4G in his Bassman.
Your recommendation to change "V3 = 12AU7" is one I have heard of a few times. I'll be sure to give that a go as well.
Hello Kingley -
If your amp is currently running a GZ-34, it is fine to switch to a 5U4 without worrying about bias. I think that you will find only a small difference in the tone unless you are playing really loud. Preamp tube swapping will make a far greater change. Remember, tube swapping is really about making an amp easier to play. All this talk about vast "improvements" in tone from various tubes is kinda crazy to me, but it makes sense for two groups of people: players who are hoping a different tube will somehow make their tone better, and tube dealers who want to sell you more tubes!
Skip Simmons
Thanks for the info Skip.
My only reason for considering the 5U4G was the sag is supposed to be greater. Which is supposedly a good thing in a harp amp?
The only preamp swap I have made is to V1 which I changed from 12AX7 to a 12AY7.
My belief (I'm probably totally wrong on this though!) is that swapping out preamp tubes just means you can turn the amp up higher on the volume control before feedback by using lower value tubes. It doesn't really greatly affect tone per se. As tone is ultimately generated by the player not the amp. This is why two people never sound the same (have the same tone) through the same amp. Tube swapping for lower value tubes merely allows for more onstage volume (headroom before feedback).
Am I right in thinking this?
It's really about achieving a more distorted tone at a lower volume.
If you turn your stage amp to the desired volume without tube changes you'll find it to be clean, so you turn it up more to get the tubes burnin' and achieve a tone closer to what you're looking for (more distorted and greater bass response)... but now you're so loud that you're having feedback issues.
When changing your tubes to lower gain tubes you're making the amp work harder to achieve the same volume, the result being the desired affect of more distortion and greater bass response. The outcome is that you don't have to turn the amp up as much as you did before to achieve a nice tone.
ALWAYS keep in mind that in general, a more distorted amp/mic will make you more prone to feedback. It's a fact that a cleaner amp will allow you to play louder and be heard more easily (not so bassy... which is hard to hear... no cut). This is why harp amp manufacturers spend so much time/money/grief developing an amp that can be both distorted and loud... a VERY challenging proposition. With all this said... if you ever have issues with hearing yourself on the bandstand, use a cleaner mic or up the tubes to higher gain (keep those old tubes! ;-)
That's my 5 cents! And yes, you're right, it is in the player... but there's nothin' like playing through a great rig! ;-)
Thanks for all the great info David (and Skip of course). It's worth way more than 5 cents that's for sure!
I have a practice on Tuesday with one band and a gig with another band next Saturday so I'm going to try out your suggestion of a 12AU7 in V3.
Hello Kingley- Sag CAN be a good thing for harp at times, but my point is that at low to medium volumes, you won't be getting ANY real sag from either rectifier. The sag effect won't kick in until you are cranking the amp close to it's maximum.
Preamp tube swaps? DB has a good explanation. It DOES affect both gain AND tone, but all that matters is getting a sound that works for you. It is easy to spend a lot of time messing with tubes instead of practicing, and every pro would tell you that some rooms make your "pet" tone just disappear. That's when it pays to have experience with manipulating your tone "on the fly" through technique and the actual tone controls of the amp. Getting a good sound going in different rooms is tough, even for the best players, and experience is the key.
Skip Simmons
Thanks Skip.
David, I tried your suggestion of a 12AU7 in V3 last night at a rehearsal. Very nice sound indeed! A lot darker and warmer to my ear.
Thanks for the great tip! :-)
Oops sorry!
The 6L6's I'm running are GE not GC I think. They are the stock Groove Tube 6L6's that Fender use in the Bassman LTD.