Modding an amp for more gain.

[somedude]

As a bit of background, I have an Orange AD140 that I really like the tone of but I'm finding it a little lacking in the gain department. It's not that I'm a gain-head by any means, but I like to have a certain level of saturation/sustain available it's falling short. I've tried various stomp boxes and I don't like how they all change the tone, particularly they way they emphasize the pick attack and make the strings sound stiff.

Anyway, long story short I'm now considering adding another gain stage and I'd like to know what all is involved in this kind of mod? The AD140 has two channels, each of which has it's own separate preamp (each channel has it's own V1 and PI). I would only want to mod one channel.

[rockon1]

Hit the front end with a clean boost. My cheapo Seymour Duncan pickup booster doesnt color the sound and realyy pushes an amp into OD. Bob

[epluribus]

Before you add a gain stage, have you looked into changing the existing ones a bit? Personally, I've had terrific luck by tweaking plate voltages, bias (natch), and plate load resistors. Bypass caps are another great tool for gain structuring. I've done several variants of all these things to all the gain stages in my little bench-top guinea-pig amp, and the impact on gain structure, saturation, feel, and dynamics is huge. Not to mention S/N, detail and tone...

--Ray

[jjasilli]

Ditto to all the above. It's not clear if you want more gain, or just earlier break-up. If you want to avoid pedals, then epluribus has a solution.

[donnyjaguar]

I agree with Rockon. I have a DOD tube screamer that when you turn the overdrive all the way down becomes basically a high-gain preamplifier. The level can then be used to supply the appropriate drive to the amplifier.

That said, you can often modify the voltage amplifiers for more gain but the tone is likely to change and I don't think that's your goal.

DJ

[epluribus]

Originally Posted by donnyjaguar

I agree with Rockon. I have a DOD tube screamer that when you turn the overdrive all the way down becomes basically a high-gain preamplifier. The level can then be used to supply the appropriate drive to the amplifier.

That said, you can often modify the voltage amplifiers for more gain but the tone is likely to change and I don't think that's your goal.

DJ

Hey DJ, I agree with both you and Rockon, a clean boost is just too easy a way to go if you want to spank the front end. Much easier than rewiring in any event, not to mention far more flexible, gain and EQ-wise. Jm2c, I use a comp to do that, a Humphrey Audio modded Boss CS-3. The really cool part of doing this is that you can kind of preview what an added gain stage will do for you if end up deciding to put the amp under the knife.

Oh yeah, one mo' thang...the tube screamer trick--isn't that what SRV actually used his for? That seems to be the prevailing conventional wisdom on the web, and we all know what a wonderfully reliable source web CW is.

Originally Posted by jjsilli

Ditto to all the above. It's not clear if you want more gain, or just earlier break-up. If you want to avoid pedals, then epluribus has a solution.

Ha! I got one right! I'm postin' this on the fridge! :BEER

--Ray

[stratotone]

Can change plate resistors on the preamp, add cathode bypass caps on preamp stages that lack them, or change values of cathode resistors. That'll add more gain.

Pete

[HipKitty]

Originally Posted by epluribus

Before you add a gain stage, have you looked into changing the existing ones a bit? Personally, I've had terrific luck by tweaking plate voltages, bias (natch), and plate load resistors. Bypass caps are another great tool for gain structuring. I've done several variants of all these things to all the gain stages in my little bench-top guinea-pig amp, and the impact on gain structure, saturation, feel, and dynamics is huge. Not to mention S/N, detail and tone...

--Ray

+1 to this experimentation. You'd truly be surprised at how much gain/distortion you can get out of just 1 1/2 out of a pair of 12ax7a's let me check into the schematic and see what can be done....

[HipKitty]

Maybe this can be of some help:

http://users.telenet.be/orangefg/orange_mods.htm

[somedude]

Originally Posted by HipKitty

Maybe this can be of some help:

http://users.telenet.be/orangefg/orange_mods.htm

I found these on that site;

http://users.telenet.be/orangefg/OFG...Cmainboard.pdf
http://users.telenet.be/orangefg/OFG...mainboard2.pdf
http://users.telenet.be/orangefg/OFG...frontpanel.pdf

But I'm afraid I'm not experienced with amps to actually understand what does what.

[stvnscott]

You can increase the overdrive in the amp without adding actual gain (or at least not much), which can lead to noise or instability. Start by replacing the preamp cathode resistors with 820R. This will make each gain stage clip more easily.

[WaltC]

If you've not looked inside a new AD140C Orange lately, it's not a place you'd want to send an unsuspecting amateur. PC-board mounted tube sockets, surface mounted pc-board 1/4w resistors, coupling caps and jumper wires connecting differing parts of the pc-board. Very little correspondence between the schematic and the physical layout of the circuit board. No published layout diagrams, and (finally <G>) the above listed schematics are the Trace Elliot developed ones, not necessarily the same (is several instances I know they're not the same, the AD30HC and combo models) as the shipped Orange Amp schematics. I don't have my Orange schematics here at home (I'm an auth. Orange service "center" <G>), but adding a quality clean boost or relatively transparent OD pedal (Any of the Xotics, AC, RC or BB, G2D Cream Tone, etc.) is IMHO a much preferable method of getting where the OP wants to go, easier and cheaper (even at $250 a pedal <G>).

My 2¢...

[epluribus]

Originally Posted by WaltC

If you've not looked inside a new AD140C Orange lately, it's not a place you'd want to send an unsuspecting amateur. PC-board mounted tube sockets, surface mounted pc-board 1/4w resistors, coupling caps and jumper wires connecting differing parts of the pc-board. Very little correspondence between the schematic and the physical layout of the circuit board. No published layout diagrams, and (finally <G>) the above listed schematics are the Trace Elliot developed ones, not necessarily the same (is several instances I know they're not the same, the AD30HC and combo models) as the shipped Orange Amp schematics. I don't have my Orange schematics here at home (I'm an auth. Orange service "center" <G>), but adding a quality clean boost or relatively transparent OD pedal (Any of the Xotics, AC, RC or BB, G2D Cream Tone, etc.) is IMHO a much preferable method of getting where the OP wants to go, easier and cheaper (even at $250 a pedal <G>).

My 2¢...

Ruh-Roh, bummer...the Amp Chassis Page seems to no longer be with us. They had a terrific collection of chassis photos, would have been interesting to see this one. 'Preciate the heads up, Walt.

--Ray

[somedude]

Originally Posted by epluribus

Ruh-Roh, bummer...the Amp Chassis Page seems to no longer be with us. They had a terrific collection of chassis photos, would have been interesting to see this one. 'Preciate the heads up, Walt.

--Ray

Sorry about the quality, it's what I could find on the internet. I'll try to borrow a camara tomorrow.

[somedude]

Originally Posted by WaltC

but adding a quality clean boost or relatively transparent OD pedal (Any of the Xotics, AC, RC or BB, G2D Cream Tone, etc.) is IMHO a much preferable method of getting where the OP wants to go, easier and cheaper (even at $250 a pedal <G>).

My 2¢...

Cheaper if I find the right pedal on the first or second time around the block. I've been through well over $1000 worth of OD pedals already trying to find what I'm after, and I just spent another $160 last night trying yet again (OCD+shipping).

Fortunately I don't take a full loss when I resell them, but it does add up over time.