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]

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]

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]

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]

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]

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]

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.