Help with AOR 100 mod

[rockon1]

Heres the mod-

"A very simple MOD to the AOR100 is to simply remove R6 and R7 100K resistors and replace with a single 470K. Replace VR-1 100K POT with a 1 MEG POT, if you cannot find a replacement push/pull you can add a toggle on the front or back panel."

Ive circled what I believe is the VR1.(Also located a replacement 1 meg push/pull pot.) Its the Pre amp volume one with pull to activate the AOR gain. Cant seem to ID the 100K R6 and R7 resistors. Any help with this mod would be greatly appreciated. Bob

[rockon1]

Bigger picture.

[hamfist]

Bob,
I can't see any 100K (brown/black/yellow) resistors on that whole board.

[rockon1]

Originally Posted by hamfist

Bob,
I can't see any 100K (brown/black/yellow) resistors on that whole board.

Thanks for looking. This amp is a diamond in the rough IMO. If I could only figure out how to polish it! The extra gain stages are just to sizzly and it seems like this mod would be perfect-if it fit! Bob

[MattT]

I can't see any 100K (brown/black/yellow) resistors on that whole board.

I was thinking that every blue resistor in that pic was 100K.

EDIT: Do you have the schematic from Schematic Heaven? It has the R6/R7 designations but I can't really see the traces well enough to see which ones they are. I think that blue 100K towards the preamp end of the board (the one in the center of the board...not the one towards V1 that has a cap right next to it) is one of them but I can't see the second one.

EDIT 2: The second 100K might be the one mounted on the pot itself. But to be honest that resistor looks like it's in parallel with the pot...doesn't look right to me (I'm not familair with this amp...just going by the schematic and your pics and I don't see any reason to have a 100k resistor mounted on the pot).

[rockon1]

Originally Posted by MattT

I was thinking that every blue resistor in that pic was 100K.

EDIT: Do you have the schematic from Schematic Heaven? It has the R6/R7 designations but I can't really see the traces well enough to see which ones they are. I think that blue 100K towards the preamp end of the board (the one in the center of the board...not the one towards V1 that has a cap right next to it) is one of them but I can't see the second one.

EDIT 2: The second 100K might be the one mounted on the pot itself. But to be honest that resistor looks like it's in parallel with the pot...doesn't look right to me (I'm not familair with this amp...just going by the schematic and your pics and I don't see any reason to have a 100k resistor mounted on the pot).

I found the AOR 100 series II schematic but this isnt a series two.That resistor on the pot is attached to the two outer tabs on the pot.I found a schematic for an A100H. Written on the inspection tag on the side of the amp it says Type: 100H Unfortunately this schematic isnt legible.If theres anything you can think of to reduce the fizzy ultra high gain on the "AOR" channel Id certainly appreciate it! Bob

[rockon1]

Im thinking perhaps the AOR(not series II)50 schematic might be more helpful? It would bve much easier if my board was marked and I knew what i was doing! Bob

http://www.schematicheaven.com/newamps/laney_aor50.pdf

[rockon1]

OK digging some more. Evidently this mod is for an AOR100 series II. Following the same idea does anybody have any ideas how to calm down the over the top fizzy gain on my A100H(series I)? Heres a link to the series II> The two resistors are right off the AOR VR1 in series.

http://www.bnv-gz.de/~ooehmann/schem...0_Series_2.pdf

[hamfist]

Originally Posted by MattT

I was thinking that every blue resistor in that pic was 100K.

THat's so strange. My eyes completely missed all the blue resistors on the board. I only looked at the brown ones ! My wife will also tell you that I can miss things right before my eyes !

[hamfist]

Originally Posted by rockon1

OK digging some more. Evidently this mod is for an AOR100 series II. Following the same idea does anybody have any ideas how to calm down the over the top fizzy gain on my A100H(series I)? Heres a link to the series II> The two resistors are right off the AOR VR1 in series.

http://www.bnv-gz.de/~ooehmann/schem...0_Series_2.pdf

I see them.
Looking at that schematic, there are two treble-peaking 470K/470pF pairs (R13/C7 and R18/C10). Removing the cap, and replacing the 470K with a plain old 68K resistor would calm down the fizzies. This could be done on one or both pairs. You would just have to experiment to see where it might sound best.
However, it would also obviously affect the tone from the low gain input as well, as both pairs are after that.
There may well be better options though. I'm just playing at this stuff really. Hopefully someone else will chip in.

[rockon1]

Originally Posted by hamfist

I see them.
Looking at that schematic, there are two treble-peaking 470K/470pF pairs (R13/C7 and R18/C10). Removing the cap, and replacing the 470K with a plain old 68K resistor would calm down the fizzies. This could be done on one or both pairs. You would just have to experiment to see where it might sound best.
However, it would also obviously affect the tone from the low gain input as well, as both pairs are after that.
There may well be better options though. I'm just playing at this stuff really. Hopefully someone else will chip in.

Hamfist-thats off the series II schematic? I imagine the same would apply to my series I. Wish I could read the A100H schematic above its a terrible copy. Im looking at the AOR 50 schematic now as it looks similar to my A100H. Could I apply the original mod the the VR1 and seeing as theres only 1 100K resistor swap pot for a 1 meg and resistor for a 470K. Also what wattage?

Couple more questions? Could I just experiment with the value of this resistor/cap not not replace the pot?

What is the purpose of having a 100K resistor across the pot as seen in the picture I posted. Im wondering if someone added it? Thanks much,Bob

Heres the AOR 50 schematic. It seems closer to my A100H


Thanks again Bob

[hamfist]

Most of your questions are beyond my level of knowledge Bob. Hopefully someone else with "the knowledge" will join the conversation.

I'm sure it would be safe enough to play around with the values of the R5 resistor and the gain pot. A half watt resistor would be plenty.

I do notice the C5/R12 treble peaking circuit in your latest AOR50 schem. That might be worth swapping for a single 68K.

Sorry I can't be of more help.

[rockon1]

Originally Posted by hamfist

Most of your questions are beyond my level of knowledge Bob. Hopefully someone else with "the knowledge" will join the conversation.

I'm sure it would be safe enough to play around with the values of the R5 resistor and the gain pot. A half watt resistor would be plenty.

I do notice the C5/R12 treble peaking circuit in your latest AOR50 schem. That might be worth swapping for a single 68K.

Sorry I can't be of more help.

Thats OK I really appreciate the help youve already given. I feel this amp has a lot of potential. Right now it only sounds good when its really cranked up and the saturated power section smooths things out. Thanks Bob

[rockon1]

Hmmmmm. I wonder what will happen if I decrease the plate load resistors on the V1 or V2?. anybody?
Bob

[MattT]

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.

[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]

Originally Posted by MattT

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]

Originally Posted by 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

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]

Originally Posted by hamfist

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]

Originally Posted by 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.

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]

Originally Posted by 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.

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]

Originally Posted by 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 !

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

[capncrunch]

Originally Posted by 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

Mine does that too. I think thats because the loop is a poor design that it accidentally adds some resistance that rolls off some top end. I put a passive loop in a 2204 and it does the same thing to it. Kind of improves the lower volume tone a bit. Incidentally there is a mod for the 2204/03 where you install a 100K or larger resistor between the volume pot and the PI to knock down some buzzy high end. I wonder if that would work on an AOR?

Oh, and BTW, does anyone know how to tighten up the lows in the AOR amps? My AOR sounds great on the upper strings but, the E and A strings really get muddy.

Thanks

[rockon1]

Originally Posted by capncrunch

Mine does that too. I think thats because the loop is a poor design that it accidentally adds some resistance that rolls off some top end. I put a passive loop in a 2204 and it does the same thing to it. Kind of improves the lower volume tone a bit. Incidentally there is a mod for the 2204/03 where you install a 100K or larger resistor between the volume pot and the PI to knock down some buzzy high end. I wonder if that would work on an AOR?

Oh, and BTW, does anyone know how to tighten up the lows in the AOR amps? My AOR sounds great on the upper strings but, the E and A strings really get muddy.

Thanks

Ive come to realise its an amp that just sounds "right" when its loud whether theres something in the loop or not. at lower volumes something in the loop definately helps cut the high fizz. The bass response on mine seems good-just dont engage the boost at lower master volumes or the windows will blow out! Ive never heard an amp capable of so much bass!
Ive developed a problem with mine though. For the first minute or two after I turn it on the volume is full on with no response from the MV. After that it works fine. Im wondering if its just a bad pot or something else. Bob

[capncrunch]

Rockon1: Yeah, I don't know a lot about amps and stuff but, that does sound as though you've got a bad pot.

I can't play with the volume very high in my band. Probably the wrong amp for me.
I'm going to try to run an EQ in the loop at lower volume levels with the bass boost off to see if I can dial in a more definitive low end. Seems like with the boost off there is now lowend at all and with the bass boost on it gets too muddy and undefined.

[rockon1]

Originally Posted by capncrunch

Rockon1: Yeah, I don't know a lot about amps and stuff but, that does sound as though you've got a bad pot.

I can't play with the volume very high in my band. Probably the wrong amp for me.
I'm going to try to run an EQ in the loop at lower volume levels with the bass boost off to see if I can dial in a more definitive low end. Seems like with the boost off there is now lowend at all and with the bass boost on it gets too muddy and undefined.

It really depends how you use the amp. Its a bit tricky. If you dont use the AOR channel then yeah you cant pull the bass boost out(unless you turn it up). If your using the AOR channel then you can turn down the pre volume 1 and turn up the master to 4-5 and the bass boost isnt as extreme. Of coarse you will have a tough time balancing the volumes between channels like this. An attenuator cutting just a few db's off would be great.FWIW- The amp kicks a** with the AOR off and both pre gains up and all the (TMB)boosts on. Of coarse you need to push the volume to at least 5 on the master or its too bassy. Im going to borrow a friends THD hotplate to mess with it with. Bob

[CRU JONES]

The AOR looks alot like the Ampeg VTL50/100 series of amps designed by Lee Jackson(!). I have a buddy with the vtl50 and it is very kickass! You should check those schematics out for some comparisons.

Also, Matt's idea with grid stoppers is a very good one. try bigger values than 68k, 220k, 330k, or even 470k. The grid stoppers create a RC rolloff with the interelectrode capacitances. They will kill the fuzzyness bigtime.