ValveKing Texture Control

[rbcarleton]

I was trying to familiarize myself with the ValveKing texture control and try to pick out what's happening at a more technical level. I've mostly been going off the description in the ValveKing owners manual, trying to read between the lines. Here's an excerpt:

"As the TEXTURE control is rotated counterclockwise, the effect of one half of the 6L6GC power tubes is progressively subtracted from the circuit, while the gain of the driver tube is slowly increased. The driver's low-frequency response is also altered along with the gain, resulting in more even-ordered harmonic distortion from your power amp, even at lower-than-stage-volume settings. Finally, with the TEXTURE knob in the fully counterclockwise position, the result is a real single-ended power amp section that operates and responds exactly like a true Class A power amp, driven by a real single-ended high-gain tube stage."

It sounds like the primary effect of the texture control is to take work away from the push-pull power tubes and to transfer it to the last pre-amp tube, aka the driver tube. From what I understand, most preamp tubes are in a class A single ended configuration. It sounds like, the texture control is not really so much of a class A simulation. I'm guessing the power amp tubes might still be running class A/B, but are less of the overall gain, so the driver tubes single-ended class A sound is more obvious.

Do I have that about right, or is the push-pull circuit actually being transformed into some kind of single-ended circuit? Am I totally missing something?

Best,

--Bruce

[65 SG]

Do a search of the forum (or dig down a few pages), this topic was recently addressed. Short story is, the words "real" and "exactly" in the marketing speak are, well, "meh".

The PI ("driver") does not see any additional load or work harder BTW

Anyways, welcome to the forum!

[rbcarleton]

I took a look at the schematic. It looks like the texture control is taking the signal destined for the grids of V4 and V6 and shunting it off to ground when you turn the texture control counter-clockwise. C144 seems to protect the tube biasing from the texture control, so only the signal disappears to ground.

That must put a lot of pressure on V5 and V7 when the texture control is counter clockwise. Does that shorten their life?

[Enzo]

Oh, no more than only making left turns in your car is harder on the wheels of one side. It basically is just increasing the duty cycle of one side a little, but it isn;t like it is stressing anything. The remaining tube is not doing much more than it ever did.

[VanR]

I ripped that crap out of my Valveking and greatly improved the tone of the amp.

[rbcarleton]

I ripped that crap out of my Valveking and greatly improved the tone of the amp.

Do you mind saying how you removed the texture control? I guess your goal was to make the ValveKing power amp into a straight A/B configuration?

[65 SG]

Search is your Friend

here's one recent thread http://forums.peavey.com/viewtopic.php? ... re#p228226

[VanR]

http://ultimate-guitar-valveking.wikisp ... lectronics

[rbcarleton]

Thanks for the links!

[rbcarleton]

I took a look at the schematic. It looks like the texture control is taking the signal destined for the grids of V4 and V6 and shunting it off to ground when you turn the texture control counter-clockwise.

I think I managed to get this wrong. My schematic reading skills have declined a lot since my training in 86. I'm looking at Sheet 3 of 4 from the VALVE KING 100 (212 & HEAD) schematic, dated 6-23-2005_8:31.

Pin 2 of the texture breakaway is connected to the V4/V6 grids via C144. Pin 4 of the texture breakaway is tied to AGND2B. The V4/V6 grids and AGND2B have a fixed relationship in respect to changes at the texture control VR11.

What seems to be going on instead is that the grid signal for V4 and V6 is being redirected back to the pin 8 anode of V3 as some kind of reverse feedback. If I remember my tube theory right, this should reduce the output power of the plate on pin 6 of the V3 tube.

To say it another way, the texture control seems to be taking input from the grids of V4 and V6 and using it to reduce the output of the V3 driver plate.

As for what's going on with the push-pull pair, I'm not so sure. It seems like V4 and V6 are receiving less input while that same input is being used to reduce the output power of the V3 driver plate, the one on pin 6.

[MikeScott]

yes, it does something with the PI. Think that's about it. There is lots of info on this type of unbalance and the harmonic effects thereof. I googled and found another good explanation on top of what the guys on this forum (sometimes they're on other forums too, very helpful chaps )

The excuse of balancing the push-pull operation is complete hogwash: If the PI circuit uses both halves of dual the tube for phase splitting, the PI circuit is meticulously balanced, the power tubes and their bias are meticulously balanced/matched and the output transformer is meticulously balanced, then - and only then - a balanced tube might make a difference. Trust me, you won't be finding a guitar amp filling those clauses. Furthermore, you more likely will be finding guitar amps that deliberately unbalance the push-pull circuit more or less because it adds more distortion. Some amps even feature a control to do this, eg. Peavey's "Texture".

[rbcarleton]

What seems to be going on instead is that the grid signal for V4 and V6 is being redirected back to the pin 8 anode of V3 as some kind of reverse feedback.

I get in trouble like this when I think out loud. I reviewed how push-pull amps work. The anode on pin 8 of V3 is being used to drive V4 and V6. It seems by grounding out this V3 anode, its signal becomes un-available to the grids of V4 and V6, lowering their output I would guess. This seems to be how the texture control takes V4 and V6 out of the equation.

[rbcarleton]

I ripped that crap out of my Valveking and greatly improved the tone of the amp.

I wonder if Peavey has ever taken this as a feature request? They could try adding a switch that defeats the texture control circuit, though it's fair to say, leave the texture control fully clockwise.

[VanR]

I ripped that crap out of my Valveking and greatly improved the tone of the amp.

I wonder if Peavey has ever taken this as a feature request? They could try adding a switch that defeats the texture control circuit, though it's fair to say, leave the texture control fully clockwise.

Trust me. Leaving the texture control on full A/B (clockwise) isn't the same as removing the texture control completely.

[lordcrion]

http://ultimate-guitar-valveking.wikisp ... lectronics

This link is dead. I want to remove the texture control on my vk 100. Are there any other instructions on the forum on how to do this? I am a not an amp tech but I do consider myself handy with soldering iron. Does anyone here have step by step instructions on how to do this? Thank you so very much in advance!