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Adding Sag to an Artisan 15

souljunkie

Member
Messages
15
I have an Artisan 15 and although I really like the tone of this amp I don't like it when it breaks up. I find the distortion to be stiff and harsh. It's unpleasant to me whether it's the amp turned up and distorting or with an overdrive pedal pushing the amp. I changed the speaker for a Red Fang. This softened the attack slightly and improved the overall tone IMO. I would like the amp to have more sag (sponginess, brownness). The amp is hand wired and I would think would be easy to mod. Is it possible to add sag or should I just start shopping for a new amp?
 

Lullabies

Member
Messages
2,054
you could turn up the bass or EQ pedal some bass frequencies up and mids. That's what I do. I turn the bass up on tighter amps and put up the mids to clear it up a bit
 

wyatt

Member
Messages
4,168
I have an Artisan 15 and although I really like the tone of this amp I don't like it when it breaks up. I find the distortion to be stiff and harsh. It's unpleasant to me whether it's the amp turned up and distorting or with an overdrive pedal pushing the amp. I changed the speaker for a Red Fang. This softened the attack slightly and improved the overall tone IMO. I would like the amp to have more sag (sponginess, brownness). The amp is hand wired and I would think would be easy to mod. Is it possible to add sag or should I just start shopping for a new amp?
That's not really sag you are talking about. Sag is about the volume dropping at the moment of attack on the note. Plenty of amps with zero sag (Tweed Champ, Marshall Plexi's, etc.) are looser feeling with big, thick, unfocused, smooth overdrive without harshness and they have zero sag.

There are lots of factors that could be a play, from amp voicing to PI design to voltage. It's always possible to mod, but I think you probably want a different amp. If you do want sag and lower plate voltages (which would help with stiffness as the cost of volume and headroom), you would achieve it by adding additional resistance on the B+ voltage supply.
 

la noise

Senior Member
Messages
21,156
How about modding it so that a Tube Rectifier replaces the solid state rectifier??
 

Blue Strat

Member
Messages
30,226
How about modding it so that a Tube Rectifier replaces the solid state rectifier??
If the SS rectifier is "hardwired" this isn't a simple job. Weber used to make a "copper cap" (solid state, tube rectifier simulator) that could be wired internally. That would do the job. Still not trivial unless an experienced person is doing the work.
 

souljunkie

Member
Messages
15
The Artisan 15 actually has a tube rectifier. It is an EZ81. I've read this is one of the stiffer tube rectifiers.
 

la noise

Senior Member
Messages
21,156
I am sure Blue Strat can hook you up with a more appropriate tube.... that will give
you a better feel. In fact, I was checking out some of his NOS Rectifier Tubes last
night myself. :aok
 

Blue Strat

Member
Messages
30,226
The Artisan 15 actually has a tube rectifier. It is an EZ81. I've read this is one of the stiffer tube rectifiers.

Not sure about the stiffness factor (that's NOT what she said! :D) but there are no known subs for the EZ81. If sag is REALLY what the OP desires then an internal resistor could be added.
 

la noise

Senior Member
Messages
21,156
Can different brands, or NOS, Rectifier tubes of the same type, offer a different "feel," Mike. Or are all EZ81's... or 5AR4's, for that matter, created equal in terms of sag and squish?
 

souljunkie

Member
Messages
15
Blue Strat are able to elaborate on adding a resistor? Is there 12AX7 tubes for the PI position that would loosen the amp? I've read the way an amp distorts is determined by how the PI tube breaks down.
 

Gemini2

Member
Messages
1,701
My advice is you're really not going to change it.

I owned that amp and sold it to a buddy. After tweaking till the cows come home we both came to the conclusion the amp has some tonal characteristics you can not dial out including a retube, change speaker, etc.

The amp is designed to be played loud and for the bass and overall sound to hold together when cranked. It will always sound "stiff" at lower volumes.

The sweet spot I found was the 2nd channel @ 5 watts with the tone knob around eleven o'clock. Btw, it's loud enough to gig at that setting.

It's actually a really nice sounding, made (Korea) amp once you settle down and understand it. It's def boutique quality to boot.
 

Gearopenia

Silver Supporting Member
Messages
2,367
We are talking about sag. But above Wyatt stated not appropriate term.
I have been looking to ask this question.
Please indulge and enlighten me.

If sag is a drop in volume, what is that sounds where the note when picked hard collapses on itself?
The best example I can come up with is the intro to electric gypsy by Andy Timmons. ( http://www.youtube.com/watch?v=MXCcGgaeX1I
Andy Timmons - Electric Gypsy )
What is that phenomena called?
 

souljunkie

Member
Messages
15
I was hoping to rid the amp of it's harshness. The overall tone is really good. It's Korean but it's built like a tank and handwired. It's very loud for 15 watts. I gig with it all the time and can rarely turn it up past 9:00 before the sound man starts complaining. I run both channels at the same time. I bought a variable voltage regulator for it but I haven't installed it until I decide if I'm keeping the amp.

I guess the Andy Timmons clip is what I'm talking about. I don't want that much sponginess or whatever the proper term is but I have none right now.
 

wyatt

Member
Messages
4,168
It's impossible to make a fair or accurate suggestion without seeing a schematic, and I couldn't find a complete schematic with a fast Google search (I found part of one!).

But, in my quick Google search for the schematic, I spotted a noticeable trend in describing the amp..."bright and harsh." Typically, the two are related, a tight and bright amp is more likely to have an unpleasant harshness when overdriven.
 

Masco

Member
Messages
125
Have you tried an EZ80 rectifier instead of the EZ81?
You could easily modify that amp to be more like the AC-15 if you want to go there. Lower main filter caps from 47uF to 22-32uf and bypass the tone control for each channel. The EF86 channel is way different from Vox, it has NFB.
I know it has a crude 5w setting(switches in a large resistance on one of the EL84 grid leaks shutting one side down), but power scaling that amp would be fun. It looks like you could do almost anything to get the tone you want from one of these, a good solid HW platform to work on you just need to find the right person.
 

Blue Strat

Member
Messages
30,226
Have you tried an EZ80 rectifier instead of the EZ81?
If memory serves (and it often doesn't...) those two tubes have a different number of pins so can't be used in the same socket.

OP: An internal high-ish power resistor (10-20 watts depending on what resistance value does what you want) can be installed in series with the cathode (output) of the rectifier. If any of this doesn't make sense you'll need a pro to help you with this.
 

Blue Strat

Member
Messages
30,226
I understand it somewhat but would have a tech do mods so I don't kill myself or screw up the amp. This is a schematic I found online.

http://www.el34world.com/Forum/inde...72&action=dlattach;topic=11923.0;attach=24873

On another thread somebody recommended lowering the value of the filter caps on the screen grids of the power tubes. Does this look like a solution on this amp and what would be a good value to drop to? What are the drawbacks?

That might help. Going to half the stock value is a good first step but there's no predicting what amount with work for you. Drawback is that at some point you'll start getting ghost notes on low notes.
 

Masco

Member
Messages
125
If memory serves (and it often doesn't...) those two tubes have a different number of pins so can't be used in the same socket.

OP: An internal high-ish power resistor (10-20 watts depending on what resistance value does what you want) can be installed in series with the cathode (output) of the rectifier. If any of this doesn't make sense you'll need a pro to help you with this.
Both have 9 pin mini's and are interchangeable.

To OP: After posting yesterday on this thread, I went to my buddies house and played his Artisan 15 w/ my tele. It's a loud 15 watts! And shrill. Had to keep the tone control fully CCW on both channels. Playing at higher volumes, say above halfway, yelds a fatter tone. It's not a bad sounding amp, just bright and tight. Methinks it's better suited for Gibsons, but it has potential for some personal tweaks. One easy thing you could do is disconnect the tone control and find a suitable coupling cap for your needs before the volume pot. The stock 22nF might work for you.
 

souljunkie

Member
Messages
15
It is a loud amp. That's why I bought the variable voltage regulator kit so I could play it at the sweet spot at lower volumes. I'll install it if I choose to keep the amp. I don't care for the tone when I switch to the 5 watt mode so I always have it at 15 watts. I've attached a gut shot. It looks easy to work on.

http://www.performing-musician.com/pm/oct08/images/BlackstarArtisan_03_15tagboard.jpg

Looking at the schematic is the cap on the screen grid the 470u/ 63v going to pin 3 of the power tube?

Masco are you recommending changing the main caps to lower values to make it more like an AC15?
 






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