Help with AOR 100 mod

[MattT]

Another thing...compare the series 1 and series 2...maybe the series 2 came about because they needed to trim some fizzies from the series 1. It might be that just modding it to a series 2 is all it needs.

[rockon1]

Does yours have that 68k grid stopper on the grid of the second stage? If not, adding it might help. Put it right on the socket.

The 100K across the pot just changes the pot value to...whatever the full pot resistance is in parallel with a 100k resistor. So if it's a 100k resistor and a 100k pot...now the pot is effectively 50k. Check to see what the value of the pot is...maybe just removing that resistor (if it is indeed in parallel with the pot...i.e. across it's outer lugs) will get you closer to what you want.

Another thing to help with fizzies is to put a cap across (in parallel with) the plate resistor of the third stage. Start with .001uF...you could go much higher to .01uF or so or go down to 500pF but below 500pF or so you won't likely hear much if any difference.

If you want to try removing those 470pF caps in those treble peaking circuits I would start at the tail end of the preamp and work towards the input. Go one at a time...and listen to the whole tone not just the fizzies (it's easy to get misdirected because you're so focused on getting rid of the fizzy stuff that you can castrate the whole tone). Having that high-end early in the preamp is usually a good thing for high-gain. Typically with high-gain you want to cut bass early and cut treble late in the circuit. But if you remove all those 470pF caps I think you'll find that the high-mids got castrated (you will lose some gain too). So also experiment with smaller values, like 390pF, or whatever. These will reduce the high-mids (which too much of can sound harsh and be fatiguing on the ears) but not nearly as much as removing the cap altogether. You can also try a 390pF in the tone stack instead of the 470pF treble cap...that will also reduce high-mids but won't affect the fizzies.

Another way to trim fizzies is a treble bleed circuit after the tone stack. From the 'top' lug of the Master Volume connect a .001uF to .005uF cap in series with a 500k pot (or trimmer) to ground...it's just a very simple treble (or tone) control. Dial it in to where you like it and then measure the resistance of the pot and use a resistor of that approx. value...or just leave the pot/trimmer in there so you can tweek later. Look at a Dual Rectifier Red channel 'Presence' circuit right after the tone stack...similar to that.

Hope that helps. Laneys are supposedly quite good sounding amps even though they are relatively inexpensive...they're like production rodded-Marshalls.

Wow-lot of good info! Thanks Matt! I thought of removing that resistor across the pot but honestly didnt know what it would do lol! Seeing as a higher value seems to be the way to go I may give the simpest mod a try first. I dont see that resistor on any of the schematics Ive dug up either so pehaps it was a mod. Anyhow youve given me a lot to work with,thanks again , Bob

[rockon1]

So I took the resistor off the pot. Seems like an improvement but more so with the AOR channel off. A bit fatter. With the AOR activated its still raspy,buzzy,fizzy and seems to almost overload the preamp if things are set to high. Im not sure what if anything has been done to the amp and much of what Id like to do is still beyond my scope. I have to say though with the AOR off it sounds like a JCM 800 style single channel amp and pretty nice. Would be nice to tame the AOR and have switchable gains(AOR on /off) but for now I'll have to use it as a single channel amp. Thanks Bob

[rockon1]

Also bumped up the input grid resistor to 470k. Really simple mod that took a good bit of buzzy-ness off the distortion. Bob

[rockon1]

The saga continues...lol! I realised today the amp sounds great-but only when Im using the FX loop! Its still pretty fizzy otherwise. Im wondering should I mod the amp to sound good without the FX loop being used? And if I do will it sound too dark when I use the loop? FWIW I always have my pedalboard plugged into the loop. Thoughts? Bob

[hamfist]

The saga continues...lol! I realised today the amp sounds great-but only when Im using the FX loop! Its still pretty fizzy otherwise. Im wondering should I mod the amp to sound good without the FX loop being used? And if I do will it sound too dark when I use the loop? FWIW I always have my pedalboard plugged into the loop. Thoughts? Bob

SOunds like you've pretty much got your answer, already. If it sounds great using the loop, and you always use the loop then ...... always use the loop. Don't change anything. Great tone is a difficult thing to achieve, and is a mixture of so many factors so once you've got it, don't fiddle too much !

If you ever want to use it without effects in the loop then use a jumper cable (long or short - whichever sounds the best) in the loop.

[rockon1]

SOunds like you've pretty much got your answer, already. If it sounds great using the loop, and you always use the loop then ...... always use the loop. Don't change anything. Great tone is a difficult thing to achieve, and is a mixture of so many factors so once you've got it, don't fiddle too much !

If you ever want to use it without effects in the loop then use a jumper cable (long or short - whichever sounds the best) in the loop.

I guessI did! Just seems weird not to be able to run it without the loop. Im funny like that -even though I never run a completely dry amp. I found a long not so good cable in the loop works well too to shave off the highs! lol!
Ive got a feeling though I may use the amp to learn more though. Thanks Bob

[Gtr_tech]

I completely redesigned/rebuilt an AOR 50w for a guy about a year back. It was a *big* job, but it came out sounding real nice. Just getting the signal gnd off the chassis helps alot to reduce noise. I ended up using some Molex style male pins inserted into the pcb and ran bus wire across them to create a new gnd bus. I'll do this on Mar$halls as well.

[rockon1]

I completely redesigned/rebuilt an AOR 50w for a guy about a year back. It was a *big* job, but it came out sounding real nice. Just getting the signal gnd off the chassis helps alot to reduce noise. I ended up using some Molex style male pins inserted into the pcb and ran bus wire across them to create a new gnd bus. I'll do this on Mar$halls as well.

Interesting. Ive read a lot of guys complain about noise issues. I dont consider mine to be any noisier than most high gain amps. Its a fizz monster without the 30 feet of cable in the loop and a few stomp boxes though. That said if I crank it up -even with nothing in the loop- the fizz goes away as the amp starts cooking. Probably a good canidate for an attenuator. Might borrow my friends THD.
To bad my board isnt marked. Makes mods with my novice skills more difficult. Of coarse it makes me learn more too that way! Bob

[Gtr_tech]

Right.....I thought it really sounded like @$$ with so much high end and just a nasty overdrive character. I redid the front end with only 3 gain stages and it quieted down and had a nice OD.

Yea the pcb ain't marked so ya gotta trace everything and hope the schematic you have matches it. I think I went through about 3 different ones before I got one that was even close and even then it wasn't exactly the same.

They're built pretty shitty.....crap lead dress an' all. They need help....but they're stilll a fairly decent buy on the used market.....for now.

[rockon1]

Right.....I thought it really sounded like @$$ with so much high end and just a nasty overdrive character. I redid the front end with only 3 gain stages and it quieted down and had a nice OD.

Yea the pcb ain't marked so ya gotta trace everything and hope the schematic you have matches it. I think I went through about 3 different ones before I got one that was even close and even then it wasn't exactly the same.

They're built pretty shitty.....crap lead dress an' all. They need help....but they're stilll a fairly decent buy on the used market.....for now.

Does make you wonder what they were thinking when they designed it. It is a MV amp and should sound decent at lower volumes. Bob

[Gtr_tech]

Heh.....there's a lot of amps that come through here for repair and make me wonder who actually thinks it sounds good. MV amps typically sound thin at low volumes and don't start to really "happen" until you open them up some, but there are exceptions.

[rockon1]

Update:....You know I couldnt leave well enough alone!

I decided to try a treble bleed circuit after the tone stack. All I did was hook up a 500K pot with a .001uf cap as Matt suggested from the center lug of the MV to ground. Next thing you know the MV isnt workingat all and it like its fully on. Hmmmm. I disconnect the mod and -same thing!. I remember something like this happening before and I couldnt figure out what it was. I looked around making sure no stray strands of wire werent shorting things out. Didnt see anything. Anyhow I sprayed the pots with contact cleaner andnothing. After a few looks I noticed a bit of noise then the MV started working again. Even stranger it the amp sounds smoother,less fizzy for no apparent reason! If it would stay like this it would be great.Even sounds good with nothing in the loop now. Unfortunately I dont know why. Im thinking the MV pot is messed up? I'd replace it but not sure what value it is. 100K 500K? Audio? Linear? Is there makings on the pot I can use to determine this? Thanks and HAPPY NEW YEAR EVERYBODY! Bob

[hamfist]

Hmmmm, strange things going on indeed with your amp.

Your MV pot should say on it somewhere what value it is, but you may need to remove it to see. It should be an Audio (log) taper. If it doesn't say what value pot it is on it, then you can always remove it and measure it with your DMM, of course.

Looking at the schematics linked to earlier in this thread, it looks like Laney like to use 100K pots for their MV's in this series. Always best to check though !

[rockon1]

Hmmmm, strange things going on indeed with your amp.

Your MV pot should say on it somewhere what value it is, but you may need to remove it to see. It should be an Audio (log) taper. If it doesn't say what value pot it is on it, then you can always remove it and measure it with your DMM, of course.

Looking at the schematics linked to earlier in this thread, it looks like Laney like to use 100K pots for their MV's in this series. Always best to check though !

Sounded worked great all yesterday. I'll have a look if it is I think I'll buy it and maybe a larger value to experiment with. Thanks Bob