Tubes!

I have never changed a tube, so I have no real idea what I am doing. I've read "about" tubes, the various types, how to make them, and all kinds of stuff. But I still could use some kind of feedback if anyone had some input.

My tone quest is something between Slash and Santana. Playing Blues, Classic and Alt mostly. I think subconsciously I want to put a less British tone on the amp, but I guess that would be defeating the design.

I'm looking at a 50 watt Jet City JCA50H. These amps (all the JC line really) are a little shrill with oem tubes. A lot of people change them out, then swear by the amps, so I want to give it a try.

Preamp
The amp has drive. So much drive! I normally have the gain on 2 and it's plenty. So, I'm thinking of changing some or all of the 5 preamp tubes from 12AX7 to something with less gain like the 12AT7 or 12AU7.

The preamp effect as it is is a smooth overdrive, not very crunchy. I'd like to get more crunchability.

Power Amp
6L6's in it now. Probably keep those, but replace with some better quality. I had tossed around the idea of putting in 6V6's because I don't need the volume. Anyone have any comment on this? I haven't found much info on people reducing amp's output.

I am aware of biasing and getting a matched tube set. I know for perfection, we would get the amp re-biased, but a matched set should be pretty tolerable, right? I just go into L&M and pick up a box o' tubes?

Appreciate anyone's thoughts. Thanks!

Originally Posted by: Razbo
Preamp
The amp has drive. So much drive! I normally have the gain on 2 and it's plenty. So, I'm thinking of changing some or all of the 5 preamp tubes from 12AX7 to something with less gain like the 12AT7 or 12AU7.

The preamp effect as it is is a smooth overdrive, not very crunchy. I'd like to get more crunchability.
[/quote]
I'm not aware of a higher gain tube preamp tube than the 12ax7. I'm a bit confused though. You said that you have more than enough gain and you run your gain on 2, yet you want more crunch. Well, wouldn't you just turn your gain up more?

Also, something I read and makes a lot of sense. Put power hungry (less sensitive) speakers in your cab. They push your power tubes harder thus cause more breakup.

Originally Posted by: Razbo
Power Amp
6L6's in it now. Probably keep those, but replace with some better quality. I had tossed around the idea of putting in 6V6's because I don't need the volume. Anyone have any comment on this? I haven't found much info on people reducing amp's output.

I've heard of folks removing a power tube, or two depending on how many you have. Will have to read up on 6V6 tubes. My 100w head is rather loud.

Have you considered an attenuator? I just purchased one from Weber Speakers. It's being built now. Hope to have it in the next week or so.


[QUOTE=Razbo]
I am aware of biasing and getting a matched tube set. I know for perfection, we would get the amp re-biased, but a matched set should be pretty tolerable, right? I just go into L&M and pick up a box o' tubes?

I've read several times that matched tubes on preamps is total bogus BS. That it's not necessary, that only the power amp tubes benefit from this.

Originally Posted by: RickBlackerI'm not aware of a higher gain tube preamp tube than the 12ax7. I'm a bit confused though. You said that you have more than enough gain and you run your gain on 2, yet you want more crunch. Well, wouldn't you just turn your gain up more?[/quote]
Yeah, I want to reduce the amount of available gain. Well, that's not necessarily true, I just have 60 or 70% I'm not using. It seemed matching capacity to requirement would be a good thing. Plus I think it would "open up" the drive channel, making it more crunchy.

Like a Jimmy Page sound would be more crunchy. Later day Santana would be more creamy. (...imo)

[Edit]Just thought of an analogy: Think of screen resolution. HD res gives you teeny tiny pixels for super smooth edges and definition. That's Smooth. A low resolution screen gives you sawtoothing and roughness. That's crunch.

...Maybe :D

Originally Posted by: RickBlacker
Also, something I read and makes a lot of sense. Put power hungry (less sensitive) speakers in your cab. They push your power tubes harder thus cause more breakup. [/quote]
This is as much an experiment with tubes as anything. That's a good idea, but would really only manifest when you were pushing the volume anyway, right?

Originally Posted by: RickBlacker
I've heard of folks removing a power tube, or two depending on how many you have. Will have to read up on 6V6 tubes. My 100w head is rather loud.

They are supposed to produce about half the output wattage. Maybe something for you to consider if your amp is really loud. Supposed to be interchangeable from what I've read, but probably confirm your plate voltage and the tube are compatible.

[QUOTE=RickBlacker]
Have you considered an attenuator? I just purchased one from Weber Speakers. It's being built now. Hope to have it in the next week or so.

Sweet! I'm going to see what the tubes do. They will change voicing and so I'm curious to see.

[QUOTE=RickBlacker]
I've read several times that matched tubes on preamps is total bogus BS. That it's not necessary, that only the power amp tubes benefit from this.

That's true. Supposedly you can mix and match power tube types (and this is actually a common practice), and even leave tubes out entirely.

I kind of don't understand what's the big dif with output tubes, but I don't want to challenge that one; I'll stick to matched sets. My friend has the JC 100 watt head and put a matched set in without amp biasing. His rig sounded awesome.

Originally Posted by: RazboI kind of don't understand what's the big dif with output tubes, but I don't want to challenge that one; I'll stick to matched sets. My friend has the JC 100 watt head and put a matched set in without amp biasing. His rig sounded awesome.

If i understand correctly, it has to do with biasing your tubes. You want the voltages to be the same so that you can bias them.

Originally Posted by: RazboI've read "about" tubes, the various types, how to make them, and all kinds of stuff. But I still could use some kind of feedback if anyone had some input.

I'd search The Gear Page first. For example I searched it for "setting amp bias jet city", and got this:

http://www.thegearpage.net/board/showthread.php?t=662492

Santana's "signature tone" is the Mesa Boogie Mark 1 with it's "smooth gain". The best qualitative description I've heard is: Marshall drive is harsh on the surface with a warm, thick core. Conversely, Mesa drive is warm on the surface with the harshness in it's core. Anyway, if that's what you are after, why not try a Mesa Boogie?

http://www.mesaboogie.com/Reviews/ToneQuest-LoneStar/ToneQuest-Mark1-LSReview.htm

Possible issues regarding tubes & biasing: Does the amp in question have a fixed or adjustable bias? Do the replacement tubes require different pin wiring on the chasis?

Regarding different pre-amp tubes:
http://music-electronics-forum.com/t8863/

Regarding different power tubes:
http://www.thegearpage.net/board/showthread.php?t=317598

I think the most important thing is to define your goal as precisely as possible, then do experimenting. Hope this helps! Have fun tone chasing.

Originally Posted by: CSchlegel
I think the most important thing is to define your goal as precisely as possible, then do experimenting. Hope this helps! Have fun tone chasing.

You guys and your goals! :p It's the journey, not the destination :D

The Gear Page linked to a biasing demo which led to me checking out a lot of YouTube vids. Lots of great stuff in easy to digest media clips. Thanks!

So, I did not do the clever things I'd been thinking with AU's of 6V6's. I went with a matched pair of JJ 6L6GC's and five of the JJ ECC83S preamp tubes which included a graded and balanced ECC83S in the phase inverter. I did business with Eurotubes whom I found excellent to deal with: knowledgeable AND informative, fast delivery, and excellent prices.

Visually comparing the JJ's to the Chinese brand tubes, even *I* could see a big difference in quality. Where the Chinese tubes had steel rods, the JJ's had copper and were just beefier looking inside.

I cleaned the sockets, replaced the tubes and set the bias (which is amazingly simple to do; I don't know why the techs keep people so scared, but I guess that's just a form of marketing lol).

It took me an hour, but would be closer to 15 minutes next time. My chassis was over balanced and would not stand on end or edge, so I spent time leaning it, making sure nothing touched anything. I'm still not sure if it would have been safe to just let the transformer lean on something. ...And why they don't put the bias adjustment on the top side of the chassis in the first place, I do not understand. :p

Results: Definitely a smoother, warmer sound. I didn't really understand the term "brittle sound" before, but I do now that it is gone! :) Only a couple hours on the tubes yet, so the final tone is yet to be determined after they burn in some. Definitely worth doing as it cost me less than $100 for 7 tubes, the probe, and a muiltimeter (the leads for the probe would not fit mine).

Right on! :)

Originally Posted by: RazboI went with a matched pair of JJ 6L6GC's and five of the JJ ECC83S preamp tubes which included a graded and balanced ECC83S in the phase inverter. I did business with Eurotubes whom I found excellent to deal with: knowledgeable AND informative, fast delivery, and excellent prices.
[/quote]
Sounds good. I know guys that swear by this or that various 12AX7. With a zillion to choose from it's not easy! Glad you found a solution you are happy with.
[QUOTE=Razbo]My chassis was over balanced and would not stand on end or edge, so I spent time leaning it, making sure nothing touched anything. ...And why they don't put the bias adjustment on the top side of the chassis in the first place, I do not understand. :p

It's always interesting when you have to work on something. You find out very quickly how well the designers considered problems like maintenance.

I hope you enjoy your smoother, warmer, non-brittle tone!

Originally Posted by: CSchlegel
I hope you enjoy your smoother, warmer, non-brittle tone!

It is still a work in progess, but it's getting close. I find the Treble and Middle tone controls overlap way too much and I can't really define mids the way I want, so I picked up a MXR 108 EQ to try in the fx loop.

My first idea was to change the pots, but this will give me some tone shaping I wouldn't have had anyway. Or may be a waste of time. That's all part of the fun!

I seem to have fallen victim of this whole tone-seeking thing. :rolleyes:

Ok, so the tubes have about 25-30 hours on them now (I use a different amp in the house). The EQ settings were quite wavy at first to get my ears happy, with a big drop in settings around the 2 - 4 k mark. I noticed lately the EQ has gotten flatter and flatter as the tubes darken and I tweak. I think I will pull the EQ again and see.

Man, guitar is the best thing ever for people that need to be doing stuff all the time! :)

Originally Posted by: RazboOk, so the tubes have about 25-30 hours on them now (I use a different amp in the house). The EQ settings were quite wavy at first to get my ears happy, with a big drop in settings around the 2 - 4 k mark.[/quote]
Careful, there! Between 2-4KHz is prime punchy sonic "real estate". That's the way to get a guitar to stand out in a mix of a full band. It's ironic that so many guitarists try to kill this range with the mid-scoop. That area of the spectrum is exactly where the classic bark & punch of R&R guitar sits.

I understand that the new tubes may be too much in that range until they burn in a little bit, though. You even mentioned you are already gradually tweaking the EQ flatter.

Don't forget how much milage you can get from the tone knobs on the amp, too. Not to mention the volume & tone on the guitar!
[QUOTE=Razbo]Man, guitar is the best thing ever for people that need to be doing stuff all the time! :)

+ 1,000,000 to that. :)

Originally Posted by: CSchlegelCareful, there! Between 2-4KHz is prime punchy sonic "real estate". That's the way to get a guitar to stand out in a mix of a full band. It's ironic that so many guitarists try to kill this range with the mid-scoop. That area of the spectrum is exactly where the classic bark & punch of R&R guitar sits.

No worries there! There was a massive spike right there in that frequency range. So last night I pulled the EQ, and that spike is gone. I have to run mids about half, treble is still set way low.

I don't scoop because I find some notes fade and lose their edge when I solo certain notes on certain keys or ocataves. (This statement makes sense to me if not to you :) ) Don't know if it's just my imagination, but I feel like I'm reducing my sound by scooping. It's not what I'm looking for, anyway. :)

Jet City amps are just plain awesome. I have the 50 watt combo and I replaced the preamp tube with a JJ in V1, and a 1960 RCA Grey plate and left the rest stock - It toned down the treble and the RCA in the second position seems to give it a little more punch.
I also have the 20 watt head and that thing rips! I put a JJ in V1 RCA Grey plate in V2 and the V3 stock - some times a 12AT7 works great as an inverter before the power amp section because of the transduction - I did this in my Mark 4 and it made a difference in keeping the bass articulate.
Rolling Tubes is a lot of fun!!

http://www.youtube.com/watch?v=0marWEdsk6k - link to my JCA20H Demo.

All the best,
Joe Pinnavaia
www.guitarlessonsbuffalony.com

I almost bought the 20 but I got the 50 for the channels and the loop. They didn't have those options on the 20's at first, but have several mods available now, I think. For the price, these amps rock.