Marshall AVT50 Mods

Peter · 03-13-2008, 09:35 PM

I came up with some great modifications for my AVT50 amp:
1. The obvious mod: add a second speaker jack.
2. Installed a clean channel midrange control.
3. Increased preamp tube gain by around 25% (switched).
4. Installed a 6 position mid shift switch on the Overdrive channel with the stock midrange frequency, and 5 others [a great mod in any amp].
5. I reinforced some key components in the amp with higher wattage and voltage components (cheap insurance).

The fatter tones from the mid shift switch along with the extra tube drive really really brought the amp to life. The amp sounds 100% way better, and I didn't even drive the tube nearly as hot as in other tube amps. The clean channel tube sound really rocks on full gain, and rolls off at lower gains. Very impressive improvements. I am also working on an optoelectronically controlled footswitch for Lead Boost and Scoop. Anybody out there interested in Kits? I am interested in producing them.

PETER THE TONE DOCTOR

Peter · 05-06-2008, 11:59 AM

I can't understand why nobody has responded to this post - I took a really good amp, and significantly improved it. Another technician/guitar player I know who only plays tube amps made this comment to me when I was demonstrating the clean channel to him yesterday : "You would be hard pressed to tell it from a tube amp now". Wake up people. These mods rock.

PETER THE TONE DOCTOR

Peter · 06-05-2008, 03:03 PM

UPDATE: I made my tube boost mod footswitchable! Works great, with silent switching, and LED! Go from stock sound to tube boost. Works great!

PETER THE TONE DOCTOR

wolf1419 · 06-05-2008, 04:21 PM

Quote:

Originally Posted by Peter

I can't understand why nobody has responded to this post - I took a really good amp, and significantly improved it. Another technician/guitar player I know who only plays tube amps made this comment to me when I was demonstrating the clean channel to him yesterday : "You would be hard pressed to tell it from a tube amp now". Wake up people. These mods rock.

PETER THE TONE DOCTOR

I found this to be exciting!! Great work!! It's just that most of us "regular guys" without electronics knowledge wouldn't know how, or would be afraid to attempt these mods, so that's probably why everyone's so quiet. We don't understand how to accomplish major feats like that.

I have a Marshall Mode Four MF350 that is similar technology(tube/hybrid) and I have a quick "pop/crack/thump"(spike) sound on powerup(no standby like tube amps), and I can't even figure that out. Marshall support hasn't been able to help. I have 2 of these and they both do it, but it's sometimes softer, sometimes harder sounding. Other than this the amps are excellent sounding-many tones can be tweaked from this beast. Do you have any clues on the spike, or is it just a solid state thing??

Peter · 06-06-2008, 01:32 PM

Thanks so very much for your response. I am looking into the pop thing. I believe a friend of mine (also a tech) may have the answer to this one. As for the mods, I am working on a kit that you can take to your tech, or if you are a hobbyist with some basic knowledge of soldering and electronics components, you can install yourself. I plan to supply detailed instructions, and provide as much support as I can. Cheers!

PETER THE TONE DOCTOR

Peter · 06-07-2008, 07:53 AM

Quote:

Originally Posted by wolf1419

I have a Marshall Mode Four MF350 that is similar technology(tube/hybrid) and I have a quick "pop/crack/thump"(spike) sound on powerup(no standby like tube amps), and I can't even figure that out. Marshall support hasn't been able to help. I have 2 of these and they both do it, but it's sometimes softer, sometimes harder sounding. Other than this the amps are excellent sounding-many tones can be tweaked from this beast. Do you have any clues on the spike, or is it just a solid state thing??

Hey wolf, apparently, the popping is an inherent problem in solid-state amps. The problem is that when you first start the amps, capacitors in the circuitry are in a discharged state, and they pop when power is applied to them. I tried two solid-state Yorkville Sound amps I own, and they both pop, albeit not too loudly, until they have been on for maybe 20 or 30 seconds, then you can turn them on, and since the caps are then fully charged, they don't pop. My Marshall AVT50 amp, on the other hand, has a power module (the main amplifier chip, which is connected directly to the speaker), that has a built-in standy feature, which delays output for a few seconds when it is powered up, so that the amp's capacitors don't pop audibly (great feature). Tube amps don't have this problem, because the power tubes don't amplify until they are heated up, during which time you are on standby anyways, so you don't ever hear any pop. Most amps with a solid state power amp come on right away, and therefore pop. Nothing much you can do about it. Do you like my explanation?

PETER THE TONE DOCTOR

wolf1419 · 06-07-2008, 05:27 PM

Quote:

Originally Posted by Peter

Hey wolf, apparently, the popping is an inherent problem in solid-state amps. The problem is that when you first start the amps, capacitors in the circuitry are in a discharged state, and they pop when power is applied to them. I tried two solid-state Yorkville Sound amps I own, and they both pop, albeit not too loudly, until they have been on for maybe 20 or 30 seconds, then you can turn them on, and since the caps are then fully charged, they don't pop. My Marshall AVT50 amp, on the other hand, has a power module (the main amplifier chip, which is connected directly to the speaker), that has a built-in standy feature, which delays output for a few seconds when it is powered up, so that the amp's capacitors don't pop audibly (great feature). Tube amps don't have this problem, because the power tubes don't amplify until they are heated up, during which time you are on standby anyways, so you don't ever hear any pop. Most amps with a solid state power amp come on right away, and therefore pop. Nothing much you can do about it. Do you like my explanation?

PETER THE TONE DOCTOR

Peter, thank you sooo much. It makes sense and I was wondering why both amps did it to varying degrees, a little different each time. These are also 350 watt amps, tube preamps, so maybe just a little more brutal with the startup than some smaller amps. That's a better answer than I got from Marshall. I'm just wondering why no one else has mentioned it, since it seems a little odd to me. Thanks again, and if you hear anything else about this please don't hesitate to add to it.

Peter · 06-08-2008, 12:15 PM

Quote:

Originally Posted by wolf1419

Peter, thank you sooo much. It makes sense and I was wondering why both amps did it to varying degrees, a little different each time. These are also 350 watt amps, tube preamps, so maybe just a little more brutal with the startup than some smaller amps. That's a better answer than I got from Marshall. I'm just wondering why no one else has mentioned it, since it seems a little odd to me. Thanks again, and if you hear anything else about this please don't hesitate to add to it.

Glad I could help.

perkristian876 · 06-14-2008, 02:26 PM

How about some pictures? looks like a great mod. Easy to perform?

Peter · 06-20-2008, 11:32 AM

Seems easy to me. A certain level of skill is required anytime you modify an amp that has circuit boards though. I am working on producing a kit, with detailed instructions, and all the necessary parts and wiring. Cost will be at issue, as I put $60 worth of parts into mine, but the kits will be simpler of necessity. I truly feel I made a $500 amp into a $1000 amp though; it has found powerful identity and flexibility through the footswitched boost on both channels, and the mid-shift on the dirty channel. Very usable, with 4 distinct voices. I may mod a few of these amps, and sell them on ebay to get the ball rolling... These amps are going to become very popular, I believe. Currently, I need to start producing circuit boards, because I don't think project boards will do much for my reputation, even if they are only 1.5"x1.5". I will keep you posted...

UnChained! · 06-27-2008, 07:38 AM

Hello Peter, I've been watching this thread for a couple months now and finally decided to join the forum. I have an AVT50H with both AVT412A & B cabs. I truely love the flexibility as it supports the varying types of music I play. However, I've always thought that there could be just a little more... Then I saw this thread! The only real changes I've made were to the cabs. I removed all of the stock Celestions and replaced the with 8ohm Emi Legend V12's and Legend GB12's in an X pattern. Seemed to remove what I always thought of as "harshness" especially in the OD channel.

Your mods are very interesting to me. Please keep us posted. I have limited experience fiddling with electronics of this nature, but would be willing to try if simple enough.

Thanks for the info so far. Looking forward to more.

Chip

Peter · 07-10-2008, 02:17 PM

Sorry everybody, I am in and out of town all summer. I take my amp with me, and it has been great! It really blows away the stock amp by a mile (and I loved it even before I made the changes). I plan to add mid-shift to the clean channel next (already have parts), and add a 120V AC power outlet for accessories. I am also considering adding a master volume (attenuator), so that you can adjust both channels for balance between clean and dirty (turned up to the max) with the existing controls, then adjust the overall volume of both channels without messing up the balance between the channels. When I finally work everything out, you will all hear about it. I hope many people will be interested. Many of these mods will work in other amps. Here are some photos, as someone on this thread requested. The black knob above the CH2 mid control is the CH2 mid shift (I plan to replace the black knob with a Marshall knob, as soon as I have obtained one). The toggle switch above the channel switch on the front panel does the same job as the footswitch I added, and will not be a part of the final kit, as it is redundant, and makes everything harder to install. The knob on the back is the clean channel mid. I plan to locate the clean channel mid-shift knob next to the clean channel mid control on my amp. All of the controls can be mounted on the back panel, for those of you that prefer not to drill holes in the front (I prefer front panel access, and don't care about drilling holes in the front panel). Please offer me your suggestions and comments if you have any. Have your say as to how it should be done. Cheers, all!

PETER THE TONE DOCTOR

coldsteal2 · 07-10-2008, 05:32 PM

COOL, this is the first time i have seen this thread

Peter · 07-11-2008, 07:59 PM

Quote:

Originally Posted by coldsteal2

COOL, this is the first time i have seen this thread

Hey, Cliff! I'm listening to some of your originals... Wish we could jam! I'm all the way up in Toronto, Canada, lol... Keep rocking!

DragonSarc · 07-13-2008, 04:14 AM

question what does the preamp tube do? i kinda figured that (like the jcm 900 has 3 preamp tube) is it 1 for clean which is V1 and 2 is for the OD on V2 and the 3rd is the phase inverter which balance the pre amps or all the preamp tube works on both clean and OD?

amplifier · 07-13-2008, 06:12 PM

Quote:

Originally Posted by DragonSarc

question what does the preamp tube do? i kinda figured that (like the jcm 900 has 3 preamp tube) is it 1 for clean which is V1 and 2 is for the OD on V2 and the 3rd is the phase inverter which balance the pre amps or all the preamp tube works on both clean and OD?

All the tubes are working at the same time regardless of what channel you're on. With your 900 the V1 and V2 would mostly affect your gain and tone. The phase inverter drives the current into your poweramp section. When you order tubes for your phase inverter make sure you order one with balanced triodes. The other 2 don't need to be balanced.

DragonSarc · 07-14-2008, 02:47 AM

Quote:

Originally Posted by amplifier

All the tubes are working at the same time regardless of what channel you're on. With your 900 the V1 and V2 would mostly affect your gain and tone. The phase inverter drives the current into your poweramp section. When you order tubes for your phase inverter make sure you order one with balanced triodes. The other 2 don't need to be balanced.

thanks for the reply amp - so basicaly the more preamp you have the more gain you get? like the DSL/TSL amp has 4 preamp tube and has more gain than the 900 is that right?

amplifier · 07-14-2008, 09:56 PM

Quote:

Originally Posted by DragonSarc

thanks for the reply amp - so basicaly the more preamp you have the more gain you get? like the DSL/TSL amp has 4 preamp tube and has more gain than the 900 is that right?

Woops I can't believe I almost forgot the effects loop, that's got it's own tube which your 900 has. It's probably V1=gain, V2= effects loop, V3= phase inverter. Sometimes the last preamp tube controls the effects/loop, and sometimes the phase inverter, it depends on the model but that should give you a good idea of how it works. I'm not exactly sure how it's set up on the 900's but Coldsteal will probably know.

If the extra tubes are part of the gain stage than yes more tubes = more gain but more gain doesn't equal better tone!

CapnCrunch · 07-16-2008, 01:03 PM

Peter,
I have 3 AVT50H heads (VS2000). I love em! I was thinking about replacing the pre-amp tube with a Groove Tube (GT has a nice Mullard 12ax7 re-issue - or else I may go wth their GT-ECC83) - There is quite a waiting list for the Mullard re-issues!

Do you think I'll notice a difference in performance if I do this? Or should I hang on to my cash?

I love the fact that YOU have taken an interest in this model. My third head is "blown". (I run 2 half-stacks in stereo - the third is a backup head). I turned it on with the volume way up.........now..it turns on, but I get a faint, fuzzy output signal through my cabinet (I tested with another cab to make sure it wasn't the speakers).

I'd like to play Frankenstein with it now that there are mods (thanks to you!) but I'm like most folks and can just swap pre-amp tubes at best.

Thanks for your time,
CapnCrunch

Arcarix · 07-20-2008, 12:46 PM

Hi Peter,
Thank you! Someone has finally seen the potential in this amp! This is something I have been waiting for. These are the exact mods I want!
I have the exact same amp and am interested in your kit. These are the exact same mod's I would have made on my own. I am very experienced in working on amps ( Twin Reverb especially)and would have no probs doing this. Have you considered just selling wiring diagrams? Personally, I would prefer a kit that includes all the parts as sourcing the parts is sometime an insurmountable prob.

Peter · 07-21-2008, 07:58 AM

Quite right, Amplifier: the way the tube works in the AVT50 is on both channels. The pre-amp feeds into the tube. On channel 1, the tube is fed a clean signal, which overdrives the tube's input when the gain is up. With my mods, channel 1 gets some serious tube crunch on full gain. Channel 2 is like having a built-in distortion pedal in the preamp before the tube.

CapNCrunch, finding the right tube for you is pure trial and error. I tried over 15 tubes, and most sounded average, and some sounded flat. I am lucky for my old made-in-holland Rogers tube, which crunches, but still sounds sweet. I found I do like the Sovtek 12ax7wb tube, which is not expensive.

Thanks for your input, Arcarix. You are right about the parts; I get some of them from surplus. A complete kit, as well as a web-site are on the horizon. Thanks very much for your interest.
Cheers!

skyryder1212 · 07-21-2008, 01:22 PM

I just picked up one of these used, and am interested in the mod kit. Any idea of pricing and availability. Any youtube or sound files?

Thanks.

Peter · 07-24-2008, 12:13 PM

Quote:

Originally Posted by skyryder1212

I just picked up one of these used, and am interested in the mod kit. Any idea of pricing and availability. Any youtube or sound files?

Thanks.

I am working on a limited run of the circuit boards. I just bought the laser printer, special print paper, etching chemicals, and a copper board needed for the project. I am drawing up a circuit board right now (I did mine using a project board). I will put up an update ASAP. Thanks for your interest.

PETER

AA703 · 07-25-2008, 05:17 PM

I am interested in the mod kit also.

Andypandapedal · 07-28-2008, 08:55 AM

This is awesome stuff!
My AVT50 just got put on the bench, I may wait for the kit now!
Very COOL!

skyryder1212 · 08-03-2008, 04:26 PM

There is a Service Bulletin out on the AVT150's that recommends installing a couple of Xener diodes on the input......does any one know if that also applies to the 50's? I do get a lot of buzz on the distortion channel...

Peter · 08-10-2008, 10:34 AM

Quote:

Originally Posted by skyryder1212

There is a Service Bulletin out on the AVT150's that recommends installing a couple of Xener diodes on the input......does any one know if that also applies to the 50's? I do get a lot of buzz on the distortion channel...

Are those diodes supposed to go to the +- 15v supply? If so, the AVT50 already has them. They just limit the signal going into the first op-amp so the signal doesn't exceed the op-amp's maximum input rating.

PETER

Peter · 08-10-2008, 10:48 AM

Re: Mod Kits

I have never made circuit boards before. I am waiting for a friend to supply me with some pyrex containers to handle the acid for etching the boards. I already have the chemicals, the copper boards (I got some really good old ones with lots of copper on them from surplus), special transfer paper, laser printer, and the circuit board designs. Once I have a run of circuit boards successfully made, I will dish out for the more expensive parts, and put out the kits. Initially, for the first run, I will customize the kits for what each person wants, and I will ask for some feedback, to help me standardize the kits.

I have also been building a web site where I will be showcasing my mods. There will be a new forum on my site, to talk about, and help develop mods. You will all be invited to join me there. Thanks for your patience and encouragement, all.

If anyone want to email me directly, my email address is octopussy@ca.inter.net

PETER

SlickTop · 08-10-2008, 11:33 AM

Hello all, i'm new here. Just got a new JVM410h w/ 1936 2x12 Cab.

I'm confused as to which speaker output/input jack to use. Below are the options i have.

Amp Head Outputs: 1x4 ohms* 2x8 ohms*1x8 ohms*2x16 ohms*1x16 ohms.

Cab Inputs: Right input 16 ohms___Left input 16 ohms or Mono input 8 ohms.

Mark me confused, i'm new to the Marshall lifestyle....Please Help!

Peter · 08-11-2008, 09:03 AM

Quote:

Originally Posted by SlickTop

Hello all, i'm new here. Just got a new JVM410h w/ 1936 2x12 Cab.

I'm confused as to which speaker output/input jack to use. Below are the options i have.

Amp Head Outputs: 1x4 ohms* 2x8 ohms*1x8 ohms*2x16 ohms*1x16 ohms.

Cab Inputs: Right input 16 ohms___Left input 16 ohms or Mono input 8 ohms.

Mark me confused, i'm new to the Marshall lifestyle....Please Help!

Amp Head Outputs: 1x8 ohms
Cab Inputs: Mono input 8 ohms

03-13-2008, 09:35 PM	#1 (permalink)
Peter Member Join Date: Mar 2008 Location: Toronto, ON, Canada Posts: 60	Marshall AVT50 Mods I came up with some great modifications for my AVT50 amp: 1. The obvious mod: add a second speaker jack. 2. Installed a clean channel midrange control. 3. Increased preamp tube gain by around 25% (switched). 4. Installed a 6 position mid shift switch on the Overdrive channel with the stock midrange frequency, and 5 others [a great mod in any amp]. 5. I reinforced some key components in the amp with higher wattage and voltage components (cheap insurance). The fatter tones from the mid shift switch along with the extra tube drive really really brought the amp to life. The amp sounds 100% way better, and I didn't even drive the tube nearly as hot as in other tube amps. The clean channel tube sound really rocks on full gain, and rolls off at lower gains. Very impressive improvements. I am also working on an optoelectronically controlled footswitch for Lead Boost and Scoop. Anybody out there interested in Kits? I am interested in producing them. PETER THE TONE DOCTOR Last edited by Peter; 03-16-2008 at 10:49 AM.

05-06-2008, 11:59 AM	#2 (permalink)
Peter Member Join Date: Mar 2008 Location: Toronto, ON, Canada Posts: 60	Re: Marshall AVT50 Mods I can't understand why nobody has responded to this post - I took a really good amp, and significantly improved it. Another technician/guitar player I know who only plays tube amps made this comment to me when I was demonstrating the clean channel to him yesterday : "You would be hard pressed to tell it from a tube amp now". Wake up people. These mods rock. PETER THE TONE DOCTOR

06-05-2008, 03:03 PM	#3 (permalink)
Peter Member Join Date: Mar 2008 Location: Toronto, ON, Canada Posts: 60	Re: Marshall AVT50 Mods UPDATE: I made my tube boost mod footswitchable! Works great, with silent switching, and LED! Go from stock sound to tube boost. Works great! PETER THE TONE DOCTOR

06-06-2008, 01:32 PM	#5 (permalink)
Peter Member Join Date: Mar 2008 Location: Toronto, ON, Canada Posts: 60	Re: Marshall AVT50 Mods and POP sound Thanks so very much for your response. I am looking into the pop thing. I believe a friend of mine (also a tech) may have the answer to this one. As for the mods, I am working on a kit that you can take to your tech, or if you are a hobbyist with some basic knowledge of soldering and electronics components, you can install yourself. I plan to supply detailed instructions, and provide as much support as I can. Cheers! PETER THE TONE DOCTOR

06-14-2008, 02:26 PM	#9 (permalink)
perkristian876 Junior Member Join Date: Jun 2008 Posts: 2	Re: Marshall AVT50 Mods How about some pictures? looks like a great mod. Easy to perform?

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06-20-2008, 11:32 AM	#10 (permalink)
Peter Member Join Date: Mar 2008 Location: Toronto, ON, Canada Posts: 60	Re: Marshall AVT50 Mods Seems easy to me. A certain level of skill is required anytime you modify an amp that has circuit boards though. I am working on producing a kit, with detailed instructions, and all the necessary parts and wiring. Cost will be at issue, as I put $60 worth of parts into mine, but the kits will be simpler of necessity. I truly feel I made a $500 amp into a $1000 amp though; it has found powerful identity and flexibility through the footswitched boost on both channels, and the mid-shift on the dirty channel. Very usable, with 4 distinct voices. I may mod a few of these amps, and sell them on ebay to get the ball rolling... These amps are going to become very popular, I believe. Currently, I need to start producing circuit boards, because I don't think project boards will do much for my reputation, even if they are only 1.5"x1.5". I will keep you posted...

06-27-2008, 07:38 AM	#11 (permalink)
UnChained! Junior Member Join Date: Jun 2008 Location: Ann Arbor, MI Posts: 3	Re: Marshall AVT50 Mods Hello Peter, I've been watching this thread for a couple months now and finally decided to join the forum. I have an AVT50H with both AVT412A & B cabs. I truely love the flexibility as it supports the varying types of music I play. However, I've always thought that there could be just a little more... Then I saw this thread! The only real changes I've made were to the cabs. I removed all of the stock Celestions and replaced the with 8ohm Emi Legend V12's and Legend GB12's in an X pattern. Seemed to remove what I always thought of as "harshness" especially in the OD channel. Your mods are very interesting to me. Please keep us posted. I have limited experience fiddling with electronics of this nature, but would be willing to try if simple enough. Thanks for the info so far. Looking forward to more. Chip

07-10-2008, 05:32 PM	#13 (permalink)
coldsteal2 Senior Member Join Date: Sep 2007 Location: Chico, CA Posts: 1,674	Re: Marshall AVT50 Mods COOL, this is the first time i have seen this thread __________________ Playing Marshall's since 1969 Marshall Vintage Modern 2266 Marshall JCM-800 2203 Marshall JCM-900 4100 Marshall 900 1960A Heritage G12H's and G12M's Marshall DSL-401 V-30 Marshall AVT-50 combo V-30 Orange Rockerverb 50 Orange cab V-30 Gibson Les Paul, Les Paul Jr, 4 Fender Strats, 4 Fender basses

07-13-2008, 04:14 AM	#15 (permalink)
DragonSarc Senior Member Join Date: Jun 2008 Location: San Leandro, CA Posts: 546	Re: Marshall AVT50 Mods question what does the preamp tube do? i kinda figured that (like the jcm 900 has 3 preamp tube) is it 1 for clean which is V1 and 2 is for the OD on V2 and the 3rd is the phase inverter which balance the pre amps or all the preamp tube works on both clean and OD?

07-16-2008, 01:03 PM	#19 (permalink)
CapnCrunch Junior Member Join Date: Jul 2008 Location: Cincinnati, OH Posts: 1	Re: Marshall AVT50 Mods Peter, I have 3 AVT50H heads (VS2000). I love em! I was thinking about replacing the pre-amp tube with a Groove Tube (GT has a nice Mullard 12ax7 re-issue - or else I may go wth their GT-ECC83) - There is quite a waiting list for the Mullard re-issues! Do you think I'll notice a difference in performance if I do this? Or should I hang on to my cash? I love the fact that YOU have taken an interest in this model. My third head is "blown". (I run 2 half-stacks in stereo - the third is a backup head). I turned it on with the volume way up.........now..it turns on, but I get a faint, fuzzy output signal through my cabinet (I tested with another cab to make sure it wasn't the speakers). I'd like to play Frankenstein with it now that there are mods (thanks to you!) but I'm like most folks and can just swap pre-amp tubes at best. Thanks for your time, CapnCrunch Last edited by CapnCrunch; 07-16-2008 at 06:26 PM.

07-20-2008, 12:46 PM	#20 (permalink)
Arcarix Junior Member Join Date: Jul 2008 Posts: 13	Re: Marshall AVT50 Mods Hi Peter, Thank you! Someone has finally seen the potential in this amp! This is something I have been waiting for. These are the exact mods I want! I have the exact same amp and am interested in your kit. These are the exact same mod's I would have made on my own. I am very experienced in working on amps ( Twin Reverb especially)and would have no probs doing this. Have you considered just selling wiring diagrams? Personally, I would prefer a kit that includes all the parts as sourcing the parts is sometime an insurmountable prob.

07-21-2008, 07:58 AM	#21 (permalink)
Peter Member Join Date: Mar 2008 Location: Toronto, ON, Canada Posts: 60	Re: Marshall AVT50 Mods Quite right, Amplifier: the way the tube works in the AVT50 is on both channels. The pre-amp feeds into the tube. On channel 1, the tube is fed a clean signal, which overdrives the tube's input when the gain is up. With my mods, channel 1 gets some serious tube crunch on full gain. Channel 2 is like having a built-in distortion pedal in the preamp before the tube. CapNCrunch, finding the right tube for you is pure trial and error. I tried over 15 tubes, and most sounded average, and some sounded flat. I am lucky for my old made-in-holland Rogers tube, which crunches, but still sounds sweet. I found I do like the Sovtek 12ax7wb tube, which is not expensive. Thanks for your input, Arcarix. You are right about the parts; I get some of them from surplus. A complete kit, as well as a web-site are on the horizon. Thanks very much for your interest. Cheers!

07-21-2008, 01:22 PM	#22 (permalink)
skyryder1212 Junior Member Join Date: Jul 2008 Posts: 2	Re: Marshall AVT50 Mods I just picked up one of these used, and am interested in the mod kit. Any idea of pricing and availability. Any youtube or sound files? Thanks.

07-25-2008, 05:17 PM	#24 (permalink)
AA703 Junior Member Join Date: Jul 2008 Posts: 1	Re: Marshall AVT50 Mods I am interested in the mod kit also.

07-28-2008, 08:55 AM	#25 (permalink)
Andypandapedal Junior Member Join Date: Jan 2008 Location: Hollywood Florida Posts: 8	Re: Marshall AVT50 Mods This is awesome stuff! My AVT50 just got put on the bench, I may wait for the kit now! Very COOL!

08-03-2008, 04:26 PM	#26 (permalink)
skyryder1212 Junior Member Join Date: Jul 2008 Posts: 2	Re: Marshall AVT50 Mods There is a Service Bulletin out on the AVT150's that recommends installing a couple of Xener diodes on the input......does any one know if that also applies to the 50's? I do get a lot of buzz on the distortion channel...

08-10-2008, 10:48 AM	#28 (permalink)
Peter Member Join Date: Mar 2008 Location: Toronto, ON, Canada Posts: 60	Re: Marshall AVT50 Mods Re: Mod Kits I have never made circuit boards before. I am waiting for a friend to supply me with some pyrex containers to handle the acid for etching the boards. I already have the chemicals, the copper boards (I got some really good old ones with lots of copper on them from surplus), special transfer paper, laser printer, and the circuit board designs. Once I have a run of circuit boards successfully made, I will dish out for the more expensive parts, and put out the kits. Initially, for the first run, I will customize the kits for what each person wants, and I will ask for some feedback, to help me standardize the kits. I have also been building a web site where I will be showcasing my mods. There will be a new forum on my site, to talk about, and help develop mods. You will all be invited to join me there. Thanks for your patience and encouragement, all. If anyone want to email me directly, my email address is octopussy@ca.inter.net PETER

08-10-2008, 11:33 AM	#29 (permalink)
SlickTop Junior Member Join Date: Aug 2008 Location: Fort Wayne, In Posts: 4	Need Help With JVM410H Hello all, i'm new here. Just got a new JVM410h w/ 1936 2x12 Cab. I'm confused as to which speaker output/input jack to use. Below are the options i have. Amp Head Outputs: 1x4 ohms* 2x8 ohms1x8 ohms2x16 ohms*1x16 ohms. Cab Inputs: Right input 16 ohms___Left input 16 ohms or Mono input 8 ohms. Mark me confused, i'm new to the Marshall lifestyle....Please Help!

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