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Any rationale for a Vox-style CUT control on an 18-watt build? I just picked up a Dr. Z Stang Ray (EF86 into 4xEL84 with Celestion Cream) and it's CUT control adds some really nice, biting high end.

I've never heard of an 18watt lacking high end bite. If anything, there's often too much that needs to be tamed.

I see the Modern Classic uses a .01 uF cap off of the PI plates into the PT grids, whereas a Top Boost circuit I just looked at uses .047 uF and a cut control with a 250KL pot and a .0047 uF between the PI coupling caps and PT grid stop resistors. I wonder how much tonal difference that makes after the preamp?

I originally included a Vox cut control in my 18 Watt head amp. Found I never used it (ie. it always was turned all the way down / no cut) and I removed it when I needed the knob space for VVR.

If it's straight out of the Vox, turning up the cut control reduces top end. You'd have it turned all the way down for max top end, and my EF86 channel (Vox values) into the 18 Watt PI/PA, well biting is a good word for it. Great compliment to the other channel which is modified Normal channel as per the Lite IIb.

katopan wrote: ↑

Thu 11/18/21 5:16 pm

I originally included a Vox cut control in my 18 Watt head amp. Found I never used it (ie. it always was turned all the way down / no cut) and I removed it when I needed the knob space for VVR.

I've found the exact same thing. I included a cut and PPIMV on a build for a gentleman and while he does use the cut for just fine tuning his overall sound (he's a Tele player), I don't feel that I need it. I play Les Pauls and prefer the woody, chimey tone with the Lite IIb. I don't find the high end to be excessive. I wouldn't want any more of that sparkle and top end clarity to be rolled off.

That's right. I have never heard an amp that's so present in the room as an 18W. Even with a single 12" speaker it's all over the place on the sound spectrum.
It seems to blend in with the other instruments without being experienced as annoying. When you kick its ass it will really jump out... they're hard to beat IMHO

Bieworm wrote: ↑

Fri 11/19/21 4:55 am

That's right. I have never heard an amp that's so present in the room as an 18W. Even with a single 12" speaker it's all over the place on the sound spectrum.
It seems to blend in with the other instruments without being experienced as annoying. When you kick its ass it will really jump out... they're hard to beat IMHO

That's the thing!

Very interesting. The only two amps I have with "CUT" controls are both Dr. Z amps, and when I turn the control up, the high end goes up. These may therefore be wired backwards? I haven't pulled the chassis on a recently received Dr. Z Stangray--EF86 into 4xEL84--that amp is a full-on BEAST. It's cut control, when turned up, definitely increases high end. It also has what feels like a Baxandall tone control that boosts preamp highs and especially lows when turned up. I plan to draw a schematic for it when I do open it, but it's at my office right now. Perfect for end-of-day grinding, OMG.

ViperDoc wrote: ↑

Fri 11/19/21 9:21 pm

Very interesting. The only two amps I have with "CUT" controls are both Dr. Z amps, and when I turn the control up, the high end goes up. These may therefore be wired backwards? I haven't pulled the chassis on a recently received Dr. Z Stangray--EF86 into 4xEL84--that amp is a full-on BEAST. It's cut control, when turned up, definitely increases high end. It also has what feels like a Baxandall tone control that boosts preamp highs and especially lows when turned up. I plan to draw a schematic for it when I do open it, but it's at my office right now. Perfect for end-of-day grinding, OMG.

With the 18W amps, I've found it's 'either or', meaning, you can control/balance the high end content in the preamp or in the poweramp, but both wasn't useful or even desireable, for me anyway. The [Lite IIb] Tone control behaves pretty much the same as a Cut control with respect to rolling off higher frequencies, with the added interaction with the Volume control to slightly affect gain.

Vox amps were wired such that their Cut controls "backwards". To me, and the way Z wires the control is more intuitive, higher is brighter, counter-clockwise "cuts" highs; just like a Treble control. There is more high end content in the Vox topology. If you compare the 18W and Vox PIs, you'll see the Marshall is biased warmer and the Vox colder. There is more of the breaking glass ssshhh sound with the Vox PI when overdriven, so with a higher gain, colder bias PI, a Cut control makes good sense to just take that edge off, while preserving the delicate, extra glassy, chimey, bell-like and all the flowery adjective qualities that is the Vox sound. I really like a (modified) Normal Channel AC30 for the same reason as the 18W. It's just pure muscle and no fat, no controls stinking up the signal path.

GREAT score on that Stangray. That is a ferocious and very loud amp.

That's great info, and I appreciate the "either/or-but-not-both" recommendation. I'm working on a Triwatt right now, after which I think I see either a EF86 Modern Classic or a slightly simplified AC30 on the horizon.

The Stangray has something that my other amps don't, it's a wonderful amp. And yes, it's VERY LOUD.

On the Vox, turning up the cut control for 'more cut' makes sense. But it always seems backwards to our trained notion of more treble as you wind up. I didn't realise the action was reversed on the Dr Z amps.

colossal wrote: ↑

Sat 11/20/21 9:03 am

ViperDoc wrote: ↑

Fri 11/19/21 9:21 pm

Very interesting. The only two amps I have with "CUT" controls are both Dr. Z amps, and when I turn the control up, the high end goes up. These may therefore be wired backwards? I haven't pulled the chassis on a recently received Dr. Z Stangray--EF86 into 4xEL84--that amp is a full-on BEAST. It's cut control, when turned up, definitely increases high end. It also has what feels like a Baxandall tone control that boosts preamp highs and especially lows when turned up. I plan to draw a schematic for it when I do open it, but it's at my office right now. Perfect for end-of-day grinding, OMG.

With the 18W amps, I've found it's 'either or', meaning, you can control/balance the high end content in the preamp or in the poweramp, but both wasn't useful or even desireable, for me anyway. The [Lite IIb] Tone control behaves pretty much the same as a Cut control with respect to rolling off higher frequencies, with the added interaction with the Volume control to slightly affect gain.

Vox amps were wired such that their Cut controls "backwards". To me, and the way Z wires the control is more intuitive, higher is brighter, counter-clockwise "cuts" highs; just like a Treble control. There is more high end content in the Vox topology. If you compare the 18W and Vox PIs, you'll see the Marshall is biased warmer and the Vox colder. There is more of the breaking glass ssshhh sound with the Vox PI when overdriven, so with a higher gain, colder bias PI, a Cut control makes good sense to just take that edge off, while preserving the delicate, extra glassy, chimey, bell-like and all the flowery adjective qualities that is the Vox sound. I really like a (modified) Normal Channel AC30 for the same reason as the 18W. It's just pure muscle and no fat, no controls stinking up the signal path.

To me the typical Vox breakup, from the cold-biased PI, sounds fizzy. So I greatly prefer the Marshall 18W's power tube breakup, with the more evenly-biased PI.

Close inspection of the Lite IIb's tone control reveals it's basically just the James (passive Baxandall) stack's Treble control.

My rendition of the 18 Watt Lite IIB circuit uses a cut control. I also have a bass-cut control. One is pre PI and the cut is of course a standard Vox style cut with the orientation being 10 = no cut and 0 = full cut. I tried the standard 18-watt tone circuit and I found it took too much gain away and was too interactive between bass and hi-cut. With the two separated functions, they are not interactive and you can achieve a little bit of a mid-cut, to mid-boost kind of thing.