AVT50 acoustic mods/use

Mikeldo · 09-03-2009, 10:04 AM

Has anyone used an AVT50 amp for an acoustic guitar and if you have did you make any modifications? I have a Martin D41 with a fishman pickup and an old Boss GT3 multi-effects pedal.

rockinr0ll · 09-03-2009, 10:08 AM

No sorry, I don't think it would be that great for acoustic because the amp has not that much headroom.

Mikeldo · 09-03-2009, 12:30 PM

That is a good opinion to start with. Thanks! What is headroom and how can I get more out of the amp I have? My amp sounds really good to me right now but I would always be open to improve it.

rockinr0ll · 09-03-2009, 12:45 PM

Headroom is the point before the amp starts to distort. You would have to have the gain on the clean channel around 12 o clock and the volume to liking. You should try to keep the clean channel clean as possible so I would suggest a 12 o clock tone setting for the bass and treble. I would unplug the reverb and use that as a treble booster. Try switching out the preamp tube and putting a lower gain tube in, like a 12AU7. Change out the speakers and put in 75's because those are the cleanest speakers out there. Good cables would help as well. I think that would be a good start. I was just saying I don't think this would be that great of an amp for acoustic guitar but if you must try some of the things I mentioned.

JohnH · 09-03-2009, 05:05 PM

I actually use my DSL401 with my acoustic, on the clean channel of course. I think an AVT could work the same.
What limits it is the speakers, since 12"speakers have nothing to offer about 5kHz, which is where alot of the acoustic zing comes from.

So, what you can do is get one or two piezo tweeters - put them is a seperate small cab and arrange for them to be wired in parallel with your main speakers. No crossover is needed and they are high impedance so they dont affect the Ohms that the amp sees.

Its is best to put a 100Ohm resistor in series with the piezos, and if you use two piezos, try them in series or parallel with each other. I found two piezos in series with the 100Ohms worked best, and they can be pointed apart to spread the sound. A switch is needed to cut them out when you dont want them.

John

Mikeldo · 09-06-2009, 04:36 PM

hey rocknrOLL,
The settings (12 Oclock) worked great!
I lowered my volume to an acceptable level with my old Boss GT3 rear level knob.Why did you choose a 12AU7 tube over the others? You also suggested using "75"s speakers. What are "75"s? My amp has only one 12". Is this the two Piezos that JohnH suggested? Lastly, I turned my reverb all the way down (If I need it I can get it from my effects system) but how do I use it as a treble booster?
Sorry I'm not up on all the small stuff. I just love to play guitar!!

rockinr0ll · 09-06-2009, 05:10 PM

I actually use the 5751 which has lower gain than the standard 12AX7 (thank you Marty).

Check out this site for comparison in gain.

Guitar amp tweak - change the gain factor of your pre-amp

I suggested the lowest gain possible for acoustic guitar.

GT 1275 Celestion speakers are 12" inch speakers with a great high in them that would bring out the acoustic guitar better then many other speakers IMO.

Unplug the reverb from the back of the unit and then use the knob as a boost control.

Hope this is helping you out a little.

Mikeldo · 09-08-2009, 12:13 PM

Wow,
So my amp now has a 12ax7, right?
what type of speaker does it have?
and thanks so much for breaking it down for me!
when I unplug the reverb do i do it at the back of the pot then leave it unplugged and it will give me the boost, or do I need to land the wire someplace else?

rockinr0ll · 09-08-2009, 12:38 PM

The Marshall AVT50 comes stock with 1 12AX7 Marshall preamp tube and the stock speakers should be Celestion voiced speakers aka cheap budget speakers. All I do is unplug the rca wires from the in and out of the reverb tank. I'm pretty sure the depth pot is still running because there is a noticeable increase in brightness when turning the reverb pot.

Mikeldo · 09-08-2009, 08:17 PM

Okay, I have an AVT valvestate2000. I am trying to upload a photo.
where and what is my "pot" and how do I uplug it?
I know I'm not that savvy and thanks for hanging in here with me. Something tells me I'm not the only one....

http://www.marshallforum.com/attachm...1&d=1252455365

rockinr0ll · 09-08-2009, 08:21 PM

Unplug the reverb tank, it's not actually on the amp.

rockinr0ll · 09-08-2009, 08:24 PM

There should be one of these located somewhere in the amp, on mine it is located on the top of the cabinet.

This is what is looks like:

Accutronics Reverb by Sound Enhancement Products, Inc.

Unplug both wires from the "tank" and wrap them up and put them to the side.

The chassis should not be touched.

rockinr0ll · 09-08-2009, 08:32 PM

There is tons of information in the AVT50 mod thread, maybe you should glance at it if you haven't yet.

Mikeldo · 09-09-2009, 09:41 PM

Actually no one seemed too interested.
Thank you again for your patience. You are awesome!
I tried a 12AT7 tube today (I got a chance to borrow one) The tone was a great improvement for my martin. My volume had to be about 2 degrees higher though. I also found the reverb in the enclosed speaker cabinet. I got it unplugged and it made a good bit of change for the better there also. It is a 4 Ohm Celestion 12G50AVY speaker. Does the 50 mean 50 watts? and if so why go with the 75 you mentioned?
I thnk I can borrow a 12AY7 tomorrow...
There may be hope for me yet.
My ears and all my listeners ears thank you!

09-03-2009, 10:04 AM	#1 (permalink)
Mikeldo Junior Member Join Date: Sep 2009 Posts: 7	AVT50 acoustic mods/use Has anyone used an AVT50 amp for an acoustic guitar and if you have did you make any modifications? I have a Martin D41 with a fishman pickup and an old Boss GT3 multi-effects pedal.

09-03-2009, 10:08 AM	#2 (permalink)
rockinr0ll Senior Member Join Date: Feb 2009 Posts: 1,340	Re: AVT50 acoustic mods/use No sorry, I don't think it would be that great for acoustic because the amp has not that much headroom.

09-03-2009, 12:30 PM	#3 (permalink)
Mikeldo Junior Member Join Date: Sep 2009 Posts: 7	Re: AVT50 acoustic mods/use That is a good opinion to start with. Thanks! What is headroom and how can I get more out of the amp I have? My amp sounds really good to me right now but I would always be open to improve it.

09-03-2009, 12:45 PM	#4 (permalink)
rockinr0ll Senior Member Join Date: Feb 2009 Posts: 1,340	Re: AVT50 acoustic mods/use Headroom is the point before the amp starts to distort. You would have to have the gain on the clean channel around 12 o clock and the volume to liking. You should try to keep the clean channel clean as possible so I would suggest a 12 o clock tone setting for the bass and treble. I would unplug the reverb and use that as a treble booster. Try switching out the preamp tube and putting a lower gain tube in, like a 12AU7. Change out the speakers and put in 75's because those are the cleanest speakers out there. Good cables would help as well. I think that would be a good start. I was just saying I don't think this would be that great of an amp for acoustic guitar but if you must try some of the things I mentioned.

09-03-2009, 05:05 PM	#5 (permalink)
JohnH Senior Member Join Date: May 2008 Location: Wollongong NSW Posts: 640	Re: AVT50 acoustic mods/use I actually use my DSL401 with my acoustic, on the clean channel of course. I think an AVT could work the same. What limits it is the speakers, since 12"speakers have nothing to offer about 5kHz, which is where alot of the acoustic zing comes from. So, what you can do is get one or two piezo tweeters - put them is a seperate small cab and arrange for them to be wired in parallel with your main speakers. No crossover is needed and they are high impedance so they dont affect the Ohms that the amp sees. Its is best to put a 100Ohm resistor in series with the piezos, and if you use two piezos, try them in series or parallel with each other. I found two piezos in series with the 100Ohms worked best, and they can be pointed apart to spread the sound. A switch is needed to cut them out when you dont want them. John __________________ DSL401 8412 cab Crate Powerblock 1 x 12 Vintage 30 cab '76 Shergold Masquerader '93 Les Paul Studio '83 Roadstar Last edited by JohnH; 09-04-2009 at 06:29 AM.

09-06-2009, 04:36 PM	#6 (permalink)
Mikeldo Junior Member Join Date: Sep 2009 Posts: 7	Re: AVT50 acoustic mods/use hey rocknrOLL, The settings (12 Oclock) worked great! I lowered my volume to an acceptable level with my old Boss GT3 rear level knob.Why did you choose a 12AU7 tube over the others? You also suggested using "75"s speakers. What are "75"s? My amp has only one 12". Is this the two Piezos that JohnH suggested? Lastly, I turned my reverb all the way down (If I need it I can get it from my effects system) but how do I use it as a treble booster? Sorry I'm not up on all the small stuff. I just love to play guitar!!

09-06-2009, 05:10 PM	#7 (permalink)
rockinr0ll Senior Member Join Date: Feb 2009 Posts: 1,340	Re: AVT50 acoustic mods/use I actually use the 5751 which has lower gain than the standard 12AX7 (thank you Marty). Check out this site for comparison in gain. Guitar amp tweak - change the gain factor of your pre-amp I suggested the lowest gain possible for acoustic guitar. GT 1275 Celestion speakers are 12" inch speakers with a great high in them that would bring out the acoustic guitar better then many other speakers IMO. Unplug the reverb from the back of the unit and then use the knob as a boost control. Hope this is helping you out a little.

09-08-2009, 12:13 PM	#8 (permalink)
Mikeldo Junior Member Join Date: Sep 2009 Posts: 7	Re: AVT50 acoustic mods/use Wow, So my amp now has a 12ax7, right? what type of speaker does it have? and thanks so much for breaking it down for me! when I unplug the reverb do i do it at the back of the pot then leave it unplugged and it will give me the boost, or do I need to land the wire someplace else?

09-08-2009, 12:38 PM	#9 (permalink)
rockinr0ll Senior Member Join Date: Feb 2009 Posts: 1,340	Re: AVT50 acoustic mods/use The Marshall AVT50 comes stock with 1 12AX7 Marshall preamp tube and the stock speakers should be Celestion voiced speakers aka cheap budget speakers. All I do is unplug the rca wires from the in and out of the reverb tank. I'm pretty sure the depth pot is still running because there is a noticeable increase in brightness when turning the reverb pot.

09-08-2009, 08:21 PM	#11 (permalink)
rockinr0ll Senior Member Join Date: Feb 2009 Posts: 1,340	Re: AVT50 acoustic mods/use Unplug the reverb tank, it's not actually on the amp.

09-08-2009, 08:24 PM	#12 (permalink)
rockinr0ll Senior Member Join Date: Feb 2009 Posts: 1,340	Re: AVT50 acoustic mods/use There should be one of these located somewhere in the amp, on mine it is located on the top of the cabinet. This is what is looks like: Accutronics Reverb by Sound Enhancement Products, Inc. Unplug both wires from the "tank" and wrap them up and put them to the side. The chassis should not be touched.

09-08-2009, 08:32 PM	#13 (permalink)
rockinr0ll Senior Member Join Date: Feb 2009 Posts: 1,340	Re: AVT50 acoustic mods/use There is tons of information in the AVT50 mod thread, maybe you should glance at it if you haven't yet.

09-09-2009, 09:41 PM	#14 (permalink)
Mikeldo Junior Member Join Date: Sep 2009 Posts: 7	Re: AVT50 acoustic mods/use Actually no one seemed too interested. Thank you again for your patience. You are awesome! I tried a 12AT7 tube today (I got a chance to borrow one) The tone was a great improvement for my martin. My volume had to be about 2 degrees higher though. I also found the reverb in the enclosed speaker cabinet. I got it unplugged and it made a good bit of change for the better there also. It is a 4 Ohm Celestion 12G50AVY speaker. Does the 50 mean 50 watts? and if so why go with the 75 you mentioned? I thnk I can borrow a 12AY7 tomorrow... There may be hope for me yet. My ears and all my listeners ears thank you!

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode