VVR Placement Advice (Traynor YBA-1) Update

[Blindog]

You are going to get "fizzy" tone as you draw the power down but the signal that has not been reduced will now appear bigger to the reduced stages. If it is all of them, the guitar input needs to be reduced. Dana has mentioned that he reduces the signal with the guitar.

Stanz, I'm scaling the whole amp, so I thought that scenario applied to output reduction only, correct? After tweaking and playing a bit I was wrong about the fizz factor anyhow

Once you reduce the voltage to say 1/4 your tubes won't be drawing as much current and the heat will go down from 1/2 voltage to it's lowest setting. I have a bigger heat sink that I can send you if you want to try it

Dana, that's great info. I didn't realize the heat will drop when when you go lower. I was a liitle afraid to try it past 1/2, thinking the heat will keep increasing. I have to mount my heatsink inside the chassis, so if you think your heatsink will work, I'd be thankful to try it out! PM me for payment info. Thanks!

Mark

[UR12]

Dana, that's great info. I didn't realize the heat will drop when when you go lower. I was a liitle afraid to try it past 1/2, thinking the heat will keep increasing. I have to mount my heatsink inside the chassis, so if you think your heatsink will work, I'd be thankful to try it out! PM me for payment info. Thanks!

Mark

Why do you have to mount the heatsink on the inside? The one I have will have to be mounted to the outside side of the chassis. Mounting any heatsink on the inside of the chassis won't work as there will be no air circulation to aid the heatsink in getting rid of the heat. Is your chassis and your cab pretty much the same size (width)? There is no payment required for the Heatsink. These are pulled out of used equipment and cost me nothing and I am happy to pass on the nothing price

[Richie]

you probaly need to install the .1uf cap and 1 M resistor at pin 2 and pin 7

You can use a terminal strip, and remove the V1 tube base screws,and put in some small bolts for the terminal strips, one that has a ground,and one terminal floating on each...

[Blindog]

Why do you have to mount the heatsink on the inside? The one I have will have to be mounted to the outside side of the chassis. Mounting any heatsink on the inside of the chassis won't work as there will be no air circulation to aid the heatsink in getting rid of the heat.

Man I feel dense as a black hole Sinus meds have got me feeling loopy. Yeah, my issue is clearance on the side of the chassis. It's a tubes down mount. I guess my only option is move the mosfet to the top of the chassis. Then I'm afraid of getting the noise back. I appreciate the "pay it forward" mindset for the heatsink!!

you probaly need to install the .1uf cap and 1 M resistor at pin 2 and pin 7

Richie, I was wondering about that. Since this is a four input like a Tweed Bassman or Marshall, Ineed to do that for both sections of V1, and the same to V2a right after the mixer resistors, correct? Will this affect the tone or is it more to keep the DC off the volume pots?

I gotta tell ya, after Dana's info I went back down and played the amp with the VVR set to about 1/4 from 0, and I was coaxing some pretty cool tones with the channels jumpered. Although, I will probably use it most about the 1/2 position to lower the stage volume when gigging with it.

Thanks for the info guys, this is very cool!!

Mark

[Stanz]

You are going to get "fizzy" tone as you draw the power down but the signal that has not been reduced will now appear bigger to the reduced stages. If it is all of them, the guitar input needs to be reduced. Dana has mentioned that he reduces the signal with the guitar.

Stanz, I'm scaling the whole amp, so I thought that scenario applied to output reduction only, correct? After tweaking and playing a bit I was wrong about the fizz factor anyhow

What do you mean by wrong about the fizz factor? Not as bad as you thought? In the end it is about how hard the first reduced stage sees the incoming signal. All stages after that will be reduced in a similar matter, so won't be overloaded.

The same principle applies. If you are drawing down the first preamp stage (plus all other stages) but your guitar input signal remains the same, it will appear larger to that stage. Now this may actually be used on purpose. I built this into a Twin I have (power tubes only), and it allows me to drive the power tubes harder without knocking out a wall or two when I hit my first chord. Normally I would have to crank the volume up to about 7 to get that out of that amp. But can I assume that you would only reduce power in "intimate" situations. If you are on stage and need to reduce power, I would imagine it wouldn't be that much. So for other situations where you might want to reduce it more (more likely to be fizzy), not as crucial having only half of your volume range on the guitar.

Just wondering out loud, would some kind of pedal help with lowering the signal? Hopefully without killing the high end.

I will say, I really do like this approach of reducing power. I no longer am a fan of really loud. It works really well. Keeping MOSFETs cooled with a 100W amp is an issue, but other than that, pretty easy to do.

[Blindog]

What do you mean by wrong about the fizz factor? Not as bad as you thought?

Yeah not as bad as I thought. I found I needed to spend some time getting to know the amp at different settings to appreciate what was happening. I'm like you, I dig the VVR!!

Mark

[Blindog]

Dana was kind enough to hook me up with a heatsink. The only place I can mount one would be either on the back or the top of the chassis. Got to looking where the convenience outlet was mounted, took it out, and the mosfet fits right in that area. The large heatsink makes a world of difference.

I had to be careful to keep the AC wires away from the mosfet as well as the twisted wires to the VVR pot. The pic shows the happy medium that works without picking up noise. I installed the caps and resistors to keep the DC off the volume pots as well.

While I was in there I added a bias pot and replaced the bias supply electrolytics. I also took off the the common screen resistor and now each tube has its own. I also modified the dropping string to match the 50W Plexi circuit, and split the cathodes of V1 and added 2k7/.68uF bypass cap/resistor. Also added a .68uF cap to V2.

The result? Awesome! Cranked up Plexi tones without your ears bleeding Thanks again to Dana, Richie, and everyone else who gave advice. Love the VVR.

Mark