RoydRage

Keen Eye there fixr... I knew I should have learned to read as a child!

I was very excited I love this head, and I just drooled at the idea of a little more gain, and meat to the sound... Love that 80-81' Black Sabbath sound (mob rules, and heaven and hell).

Just bought a 79' 2203 off of ebay to get modded, but this AVT would be pretty amazing with some mods...

Thanks,

Royd

rockinr0ll

I was reading on another Marshall forum and somebody there mentioned that disconnecting the reverb on the AVT50 was a good mod. Thought I mentioned it, little was said about it but it sounds like it might give a boost to the signal or something.

Fixr1984

I wounder if they mean to simple unplug the tank or to bypass the reverb circuit on the board.

Do you have a link or remember where you read that?

rockinr0ll

He just unplugged. There is no more information so no need to post.

edit: but here it is anywayz

http://www.marshallampforum.com/foru...&highlight=avt

Could you try it and tell me how it goes? lol. I never really liked the reverb so I keep it low but with the amp being completely dry I don't think I would like that either.

rockinr0ll

fixr1984 do you have any more pics of the inside of the avt50 head? I have always wanted to see where the tube and reverb are located.

Fixr1984

Kinda far away photo...the pink arrow is the tube and the yellow arrow is the connector for the reverb tank.
I dont have a pic of the tank but its mounted on the top of the inside of the cab. If you look in thru the vent in the top you
should be able to see it.

rockinr0ll

You know what, the AVT has a pretty nice layout. I'm kinda shocked that the tube is located on the board though. I always thought the tube would be facing up on top. I noticed you have the older one do you think that the avtx is the exact same or they made some slight changes? Also how easy is the Reverb tank to disconnect and have you tried it yet? And what preamp tube you using?

Thanks man for the pictures! I finally know what it looks like!

Fixr1984

To disconnect the reverb just unplug the connector from the board (yellow arrow in the picture above.) I had played thru the amp with the reverb unplugged but I was testing the mid shift so I honestly cant comment on the effect of not having the reverb. I still have the stock tube in mine, its an Electro Harmonics.

Arcarix

I prefer to leave the reverb on 'cos I use it, especially with a Marshall Vibro-trem pedal for CCR tunes. With the Jensen spkr, the only thing I felt like I was missing for the fender type sounds was the vibrato a lot of their amps come with, but now I'm FINE! Seems like I've got the best of both worlds, anyway, sounds good to me!

Anybody have any thoughts on what tube to use for the pre-amp? Does it make any difference? Any preferences? I replaced the stock 'Marshall VLVE00065 WK45'with a JJ ECC83, and to tell the truth, I really couldn't tell any change in the tone. Any suggestions/opinions are welcome.

shoelace

Well, I've put a Tungsram NOS ECC83 in mine and I can feel the difference The marshall stock tube is quite dry and not that punchy. The Tungsram which I've put in has more character but it is a bit more noisy.

Arcarix

Even with a strat I can deal with a LITTLE noise, (my strat has been copper shielded,single point grounded, grounded backing plates on all PUP's). How much did the Tungsram cost?

Yeh the stock tube is pretty much just not 'there', like there's no real response, maybe 'dynamics' is the word I'm looking for. The JJ ECC83 I'm using now is just about the same it seems like. Replacing the stock spkr helped a lot, I just think the tube is the next major place for improvement.

I love this amp for the wattage (loudness), it's just right for home, maybe a little loud , but works very well in a small venue like bars, loud practice sessions w/drummer, studio is good, great all around amp, even at 60 pounds.

I just feel like there's a lot more this amp can do tonally than what it does in the stock configuration.

Thanks for your thoughts - anyone else?

lukeveess

Hello guys, do you know if it is possible to make the parallel fx loop on avt150h to be serial or to add a switch serial/parallel? if yes, how is it possible? thanks

cairomike

Hi. I'm new to this forum so I hope you might be able to help. I've been asked to service a AVT 50H, but don't have a circuit diagram. On the pre-amp board resistor R58 is showing signs of getting over heated. Measuring it in-situ it appears to be 15K, do you know if that's right?

You mention upgrading some components, which would you recommend for upgrade?

Where can I get a circuit diagram?

Thanks in advance for any help you can give me.

Fixr1984

Looking at my schematic it shows R58 as a 1/2 watt 10ohm resistor. I know this is a problem in these amps. (mine has been changed also) I would put a higher wattage resistor in to keep it from happening again. I believe mine is a 1 watt and it shows signs of getting hot. Send me a PM with your email address and I can send you the schematic.

eon

Wow, what a thread.

Im an owner of an AVT150 Head, and im wondering how these mods would work on that, as well.

Im also very interested in the Parallel to Series mod for this amp, to facilitate the use of a Boss GT-8's 4 Cable Method.

Anyone got any idears?

Fixr1984

I think it is possible they would work on the AVT150 as well. The component locations and possibly values will be diferent. I havn't seen the schematic so I cant verify one way or another.

mystic fred

I recently improved my AVT50 - I sold it and bought a JCM 600

shoelace

feel free to post your mods, cause I believe that many people, including myself, are eager to find out how to improve their gear

Fixr1984

I would also be interested in hearing what you changed in your amp as well. Was it a big improvement? Did it not help and thats why you sold it? My fan is making noise again so i have to open it up again so I wouldnt mind doing a few more mods.

rockinr0ll

= sarcasm

Fixr1984

Wow............its been a long week. When I first read that I took it as he modified the amp and then sold it.

bellarum

You say that you did replace the 1/2 watt with a 1 watt @r58 and now it shows signs of overheating? or it did and now it doesn't? I just replaced the reverb pot that was stripped out on my atv50h and was looking around for signs of over heating on my board and found the orange-ish brown color on the board around r59 and r60. Could this have maybe been caused by the reverb pot being stripped out? r58 looks fine.

Fixr1984

Yes, R58 was burned up and replaced with a 1 watt. The 1 watt resistor is starting to show signs of getting hot. R59 and R60 are part of the power section coming off of the transformer, doubtfull that is a result of the reverb pot. I see on the trace side of my board there is some slight discoloration on those 2 resistors possibly from heat. Do you have a picture of that area of your board?

bellarum

For some reason I didn't take a pic while it was apart. I will break it down again to do so, if it will help you out. The board isn't fried or anything. Just discolored at those points. When you say power section could that have anything to do with running a preamp like a POD XT in the effects loop? Or an EQ in the loop? I did both of those things at one time to sample them. Right now I have a BBE 482i rack mount Sonic maximizer,EH Holy Grail,Boss DD-5 delay in the loop. The reverb tank is unplugged and the knob is set at 4. Amp is running on the clean channel with a Boss NS-2,EH Metal Muff,Boss CE-3, and modded Boss GE-7 in front. With all of those running it sounds like I'm pushing it really hard. It sits on a stock 1960a JCM900 lead.

jfox00

Can anyone post a way to add a mid eq control for the clean channel of a Marshall AVT50H? Thanks.

rockinr0ll

It's all good, just letting you know. BTW have you been doing anymore mods to the AVT?

I also have a very similar rig (sonic maximizer in the loop and Boss in the front), I have had no problems. Chances are you are golden.

I use a 2 band EQ in the rack to get the needed mids. TBH I actually have been scooping the mids recently. On the clean it doesn't sound that great with mids, it actually distorts in a weird way.

Fixr1984

There's another thread about unplugging the reverb and using the reverb controll
to alter the sound. I did that but I am still unsure if i like it without the reverb on a little. I am thinking of making reverb footswitchable.

rockinr0ll

Yeah, I actually mentioned that a few posts back. lol.

VintageTone

Hey im looking for a avt 50 head, cant find one anywhere!!
i heard a very simple mod is to unplug the reverb, from inside
this is surposed to improve the amp

tgifntx

Chunked this in here hoping I'm in the right neck of the woods..? Have an AVT50h and was curious if somebody could tell me what the ideal scenario is or would be as far as cab/head match up in terms of ohm load proficiency. The head states, "minimum of 4ohms", And the cab I'm using is a 16ohm config. Is there an optimal in terms of sound produce where the two would best match up? ie; 8ohm head/8ohm cab or 16ohm head/16ohm cab or even 4ohm/4ohm? How does or would this particular head best perform. Sorry for the long winded question and I thank you for any and all assistance.