Quick and dirty Mega Boost?

[rogb]

Hi
Having got my #183 preamp running well thanks to some invaluable help here, I'm going to lend it to a friend who is an amazing rock blues player. He likes lots of gain so I thought I'd try and convert the PAB to Mega so he doesn't reach for the pedal board.

It's likely he'll play the preamp through his massive Marshall 9100 power amp.

Is there an easier way to sampleMega boost without full rewire of tonestack to BM values and rewiring the relay?

This is my TS and relay setup as per #183. Any ideas or tips would be welcome. Thanks

Screenshot_20230616_162425_Gallery.jpg

[rogb]

I did try this suggestion by dimitris but I couldn't get it to work, maybe because my relay is not wired like BM.

"Edit:just saw that mojotom has already suggested the same thing)
You can try the bluesmaster pab padded with a resistor,i find it usefull especially with a strat and it will not alter your tonestack in any way.
It's easy to implement it too.You have to disconnect the bass tail resistor from ground and solder it to the
mid pot's lug that connects to ground.
Replace mid pot's ground connection with a resistor (try a value between 68k-220k or a trimmer) and use the pab relay to short-unshort this resistor."

[rootz]

The only way to do a quick and dirty mega boost is disconnecting the grounds on the bass and mid pot, thus lifting the entire tone stack.

Don't think that is what you should want though. It gives a disproportional huge boost of the low end. No experience first hand, but I suspect it will turn your OD to pure mud.

There is one other simple trick for much more gain though (apart from FET on a foot switch). The usual trigger trimmer in 183 is 100k. Try replacing that with 250k, 500k or even 1 meg. I believe #94 had a very large trimmer there and that is a really rainy amp! Much simpler than rewiring your PAB relay to mega boost. In #94 I can run the trimmer up to 1/3, or 330k to ground without the OD going to mush. I usually keep it lower though. You will lose a bit of crispness though, but at the same time can keep the bright switch on in OD. There are some tradeoffs. But hey, aren't those always present?

[rogb]

Hi and thanks for the response. I have the trimmer on the rear panel and yes I can dial up lots of gain with that. Trouble is it can get a little fizzy too.
I'm really after goosing up the PAB so on Clean it will be more Mega too. Also that way in OD you can reduce the OD trim a little and minimise any fizz.
Hope this makes sense.
But I will disconnect both grounds and see how it sounds, thanks

[WhopperPlate]

Hi and thanks for the response. I have the trimmer on the rear panel and yes I can dial up lots of gain with that. Trouble is it can get a little fizzy too.
I'm really after goosing up the PAB so on Clean it will be more Mega too. Also that way in OD you can reduce the OD trim a little and minimise any fizz.
Hope this makes sense.
But I will disconnect both grounds and see how it sounds, thanks

I think you missed rootz point . Changing the actual value of the trimmer is what he is referencing, not simply turning the trimmer up . What value is your trimmer? 100k correct ? Increase this value for more gain

[erwin_ve]

The reason for a Bluesmaster having a Megaboost is because the tonestack is dumping a lot of signal to ground.
The difference in signal between, straight from Tonestack and PAB is Mega. (Some call it over the top).

The Skyliner tonestack is different from the Bluesmaster and doesn't dump as much signal to ground. Thats why the difference in signal between straight from tonestack and PAB is less.

The 68k you mentioned in your opening post actually diminishes the effect of the PAB as it is dumping more signal to ground opposed to the 22M.

The effect of the 22m resistors is almost as big as losing the ground connection from the tonestack. So I'm not sure if you can get it any bigger at that specific point.

Maybe apply something similar to the Volume pot.
A switchable resistor between the ground and the volume pot. Something like 68k?

[rootz]

Hi and thanks for the response. I have the trimmer on the rear panel and yes I can dial up lots of gain with that. Trouble is it can get a little fizzy too.
I'm really after goosing up the PAB so on Clean it will be more Mega too. Also that way in OD you can reduce the OD trim a little and minimise any fizz.
Hope this makes sense.
But I will disconnect both grounds and see how it sounds, thanks

I think you missed rootz point . Changing the actual value of the trimmer is what he is referencing, not simply turning the trimmer up . What value is your trimmer? 100k correct ? Increase this value for more gain

That was my point indeed, but I have to admit, I did not ask which value is there now.

Going to 500k there gives approximately an 8 Db boost across the whole frequency band, apart from the high end obviously (Miller effect).

But disconnecting two ground and changing a trimmer are both simple enough to do and reverse. I do think Erwin has a good point: especially in the high end there isn’t that much signal lost to begin with.

[rogb]

Hi and thanks for the response. I have the trimmer on the rear panel and yes I can dial up lots of gain with that. Trouble is it can get a little fizzy too.
I'm really after goosing up the PAB so on Clean it will be more Mega too. Also that way in OD you can reduce the OD trim a little and minimise any fizz.
Hope this makes sense.
But I will disconnect both grounds and see how it sounds, thanks

I think you missed rootz point . Changing the actual value of the trimmer is what he is referencing, not simply turning the trimmer up . What value is your trimmer? 100k correct ? Increase this value for more gain

Yes I have 100k, but I'll sub in a 250k and see how that goes. Pretty sure I've done all that before on other D type amps and ended up back at original values.
I am more interested in raising the PAB effect on both Clean/OD, that's my goal.

[rogb]

The reason for a Bluesmaster having a Megaboost is because the tonestack is dumping a lot of signal to ground.
The difference in signal between, straight from Tonestack and PAB is Mega. (Some call it over the top).

The Skyliner tonestack is different from the Bluesmaster and doesn't dump as much signal to ground. Thats why the difference in signal between straight from tonestack and PAB is less.

The 68k you mentioned in your opening post actually diminishes the effect of the PAB as it is dumping more signal to ground opposed to the 22M.

The effect of the 22m resistors is almost as big as losing the ground connection from the tonestack. So I'm not sure if you can get it any bigger at that specific point.

Maybe apply something similar to the Volume pot.
A switchable resistor between the ground and the volume pot. Something like 68k?

Thank you for that clear explanation of BM v Skyliner. I have barely looked at BM, having built HRM, #102, 2nd Gen Hybrid and #183.
When I wanted more PAB, I saw Mega and thought yes that's for me!
I'll give the Volume ground a go when I find a 68k.

[rogb]

Hi and thanks for the response. I have the trimmer on the rear panel and yes I can dial up lots of gain with that. Trouble is it can get a little fizzy too.
I'm really after goosing up the PAB so on Clean it will be more Mega too. Also that way in OD you can reduce the OD trim a little and minimise any fizz.
Hope this makes sense.
But I will disconnect both grounds and see how it sounds, thanks

I think you missed rootz point . Changing the actual value of the trimmer is what he is referencing, not simply turning the trimmer up . What value is your trimmer? 100k correct ? Increase this value for more gain

That was my point indeed, but I have to admit, I did not ask which value is there now.

Going to 500k there gives approximately an 8 Db boost across the whole frequency band, apart from the high end obviously (Miller effect).

But disconnecting two ground and changing a trimmer are both simple enough to do and reverse. I do think Erwin has a good point: especially in the high end there isn’t that much signal lost to begin with.

Thanks I appreciate your input here. I'll go 250K as there is plenty of gain already.

As a Strat player primarily, more fatness on PAB would be great, but nobody wants boomy bass I think.

[rogb]

Well after trying every which way to Sunday to increase the PAB level, I must report with some shame that I had wired up the relay incorrectly.

I noticed that I had very little tone control so with layout in hand, I checked from bass pot right through to Volume pot. I found I had mistakenly wired direct to the bass cap when I built it.
Having rewired correctly to the relay I have restored a much better T M B range and the PAB certainly does enough in Clean and OD.

I did also try as advised a 500k OD trimmer but as the sweet spot seems to be 70-80k, I went back to the 100k. Now there is more than enough gain.

Thanks to all that tried to help, but the rabbit hole was of my own creation

[rootz]

Thanks for reporting back and good that you found an issue in your amp! I can imagine the big trimmer being a bit much with 250k drive and volume pots in OD.

[rogb]

Hi
Having got my #183 preamp running well thanks to some invaluable help here, I'm going to lend it to a friend who is an amazing rock blues player. He likes lots of gain so I thought I'd try and convert the PAB to Mega so he doesn't reach for the pedal board.

It's likely he'll play the preamp through his massive Marshall 9100 power amp.

Is there an easier way to sampleMega boost without full rewire of tonestack to BM values and rewiring the relay?

This is my TS and relay setup as per #183. Any ideas or tips would be welcome. Thanks

Screenshot_20230616_162425_Gallery.jpg

I got a chance to put the preamp through its paces this afternoon. It was way better than I ever remember. Nothing planned just a quick loop on the Flashback for the clean and my phone.
Don't worry you won't have to hear my noodling

[WhopperPlate]

Great job . My ears are not complaining