Need to add gain to a Laney GH100L

[kka]

Hello folks,

I'm new here and this is my first post. I'm helping out a friend with a GH100L. He wants to add more gain to the Drive channel. Can anyone give me some hints please? Schematics attached.

Thank you for your help.

[Chuck H]

Really??? I'm pretty sure I could get all the cat swinging harmonic mayhem from that amp the way it is. What kind on guitar is the guy playing? Does it have a humbucker in the bridge?

Increasing gain in this amp may cause stability problems. But... You could try changing R13 to 1.5k with a 2.2uf cap parallel (use an electrolytic with the + end on the cathode). And change C9 to 1n. Change R10 to 220k. If the amp squeals uncontrolably remember that I warned you.

[Jazz P Bass]

Use a pedal.
Mod, mod, mod, mod.
Mod, mod, mod, mod.
Mod, mod, mod.
Mod, mod, mod
Reminds me of kids tinkering with there cars.

[kka]

Thanks for the reply and help, Chuck H. My friend uses Humbuckers in the bridge. He wants more sustain and punch. I will try your suggestions and see what happens. I will also be looking at the installed tubes when I get the amp. A new tube type in addition on minor mods might help as well.

Mr. Jazz P Bass, I understand your suggestion and concern. First of all it is fun to tinker with cars to see what you can get out of them and it keeps us off the street while doing so.
The pedal is an option, however the amp has a Drive channel switch, so I would to combine switching the pedal and the ch switch at the same time. Also, some folks just don't like to have anything in between guitar and amp. If the mods don't do the job a pedal might be the only option. ;-)

[Jazz P Bass]

Mod away.
I was just funnin ya.

[tedmich]

absolutely everyone puts pedals upstream on this amp if you want a modern high gain out of these amps without blowing out your eardrums. Zintolo over at sloclone has a bunch of recommended mods but I am unsure if they'll do what you want.

They include jumping C6 and adding a parallel cap across R11 (470pF) which removes fuzziness (high cut) as well as transforming V1b from R3/C3 to (a higher gain/deeper boost) 1.5k/1uF and the unlabeled coupling cap from 22nF to 47nF to pass more bass.

these mods can all be done by adding parallel piggy backed components as the parallel R become smaller and the parallel C become bigger.

Joey at Sloclone plays a modded GH100L as his main amp but has been somewhat cagey about what he's actually done (it is his business after all)

[kka]

absolutely everyone puts pedals upstream on this amp if you want a modern high gain out of these amps without blowing out your eardrums. Zintolo over at sloclone has a bunch of recommended mods but I am unsure if they'll do what you want.

They include jumping C6 and adding a parallel cap across R11 (470pF) which removes fuzziness (high cut) as well as transforming V1b from R3/C3 to (a higher gain/deeper boost) 1.5k/1uF and the unlabeled coupling cap from 22nF to 47nF to pass more bass.

these mods can all be done by adding parallel piggy backed components as the parallel R become smaller and the parallel C become bigger.

Joey at Sloclone plays a modded GH100L as his main amp but has been somewhat cagey about what he's actually done (it is his business after all)

Thanks for your input, much appreciated. Not everyone puts pedals in front of their amps. Just think of all the Diezel users which includes me. Diezel amps like VH4, Herbert, Hagen and Einstein have endless sustain in the high gain channels, no need for pedals. We are trying to go that route with the GH100L.

I will research about the Sloclone mod. Thanks for that hint. ;-)

[tedmich]

Thanks for your input, much appreciated. Not everyone puts pedals in front of their amps. Just think of all the Diezel users which includes me. Diezel amps like VH4, Herbert, Hagen and Einstein have endless sustain in the high gain channels, no need for pedals. We are trying to go that route with the GH100L.

I will research about the Sloclone mod. Thanks for that hint. ;-)

I am allergic to pedals And you needn't go with a +$2k amp to get pedal less gain (many can't go this route). An older PV ULTRA+, xxx and 6505+ will all rage sans pedals. IME its the Marshall guys who want the tone without the ear splitting volume who have to use pedals; Marshall stack bedroom amp type scenarios.

[Steve Conner]

Decreasing/bypassing R13 seems like an easy and worthwhile mod.

A more involved mod would be to rewire V3a from a cathode follower to a gain stage. The Diezel and Peavey amps probably have one more gain stage than the Laney.

Any time you increase gain, watch out for instability! The manufacturer will have tested stability, but only at the gain the amp was designed for.

I don't have a problem with pedals. To my ear, a boost pedal in front of a tube amp does about the same as an extra gain stage in the amp. Sometimes this kind of overdrive can sound a bit trashy and farty played alone, but when you tromp on it at a gig, it does the business.

[Gtr_tech]

I'd look to the "v2a" stage if it were me. Play with different values of cathode resistors. Maybe try a 4.7k and see what happens. If that dog don't hunt, you could bring it down all the way to 1k. Adding a small value bypass cap will boost gain even more especially in the mids and up area.

Or....maybe just put a 10k trimpot in series with a 1k. Then you can dial it around until you get it to where you need it. Then just note the value and replace it with the nearest value to the pot setting + the 1k series resistor.

[olddawg]

A lot of sustain is in the instrument itself and your hands. It also depends on your definition of sustain. I would suggest trying a compressor. I like the Rocktron. It is not difficult to get sustain out of high gain 100 watt amps dimed and boosted. The problem comes at club levels when the big amps are turned down, then people saturate their preamps. Fizz, fizz. Sometimes the better option is just to use a smaller amp into the big cab and OD the shit out of it. I would suggest a Bad Monkey and a Rat for an inexpensive solution.

[Gtr_tech]

My guess is they're goin' for gained out metal stuff, so they wouldn't like the sound of a small amp dimed anyway. Whever you hear the words "more gain", its safe to say they're try'n ta get to Panteratown...

[Chuck H]

My guess is they're goin' for gained out metal stuff, so they wouldn't like the sound of a small amp dimed anyway. Whever you hear the words "more gain", its safe to say they're try'n ta get to Panteratown...

And there should be enough gain available from that preamp to get close. Some adjustment might do it. But even then it's not enough gain. For some players there isn't enough gain. An amp I build is very similar to a TW Express type design. With a similar amount of gain as the TW Express clips you hear on line. I was at a customer/friends house when a young metal guitar player stopped in. My guy wanted to show off his custom amp. The kid played it and basically said "Eh. It's good for vintage stuff. If you ever build a high gain amp I'd love to try it though."

I've actually considered designing a preamp that will take whatever you put into it and turn it into a square wave. Maybe some controls to add assymetry or some dip and overshoot. Maybe even adjustable crossover distortion and sag. Sort of like high gain analog modeling but able to render a perfect square wave if one wished. Could be the new sound!?!

[tedmich]

Yah many of these young'ns are in heaven the first time they try a SS square wave filter amp/pedal. The rap on the GH100L is its "fizzy" and the remedy for this seems to be CRANK IT UP, which deafens you unless you are onstage and/or using an attenuator. A couple guys pointed out that C9 is shown (in error) as 22nF on the early page but a correct value (470pF) in the later page of the file. Some mod this cap to be switchable between 470-220pF and then switch it in/out or to ground to modify the amps high end response. Many Marshall mods work on these amps too; guess why?

[kka]

Thank you very much everyone for all the valuable input! I'm going to get to work when I get the amp dropped off and see what can be done with the ideas y'all mentioned. Much appreciated.