One last VVR question

[bluesbear]

I'm buying it today so it's time to resolve this question! I want the VVR to affect the actual tone as little as possible. It's for a cathode biased 6V6 amp. I'm not sure if I should just do the power tubes or if I should include the PI (standard BF Deluxe style). Has anyone tried both for comparison? I'm working in very tight quarters and want to mess with it as little as possible. Luckily, I've been around long enough to know I can trust your opinions.
Any thoughts on the pros and cons of either method would be appreciated.
Thanks,
Dave

[LooseChange]

If you don't have a master volume, do the plates and screens only.

[bluesbear]

I do have a pre PI master volume. While the amp's apart, I'm switching it to a post PI. So, the MV isn't an issue. Does that change your advice?
Thanks,
Dave

[LooseChange]

With a post PI, plates and screens is good to go.

[Tone Junkie]

Im curious as to why you would have a post PI MV and a VVR dont they pretty much do the same thing.
Sorry if I missed something.
Thanks Bill

[JB]

If you reduce the plates and screens then as they drop the output stage headroom reduces.  So the distortion goes up.  At the point it's the right volume level it may be way too distorted.  If you then turn down the channel volume, or your pre-PI master, then that will reduce the distortion to everything else, not just the PA. So your tone will change which is not what you want.

So what you need to do reduce the drive signal immediately before the stage controlled by the VVR.  If you go for PA plates and screens then a post PI master is ideal.  If you also apply the VVR to the PI then a pre-PI master will be good.

Think of it as drive reduction, rather than master volume.

[Tone Junkie]

Thanks JB see you guys teach me something every day almost.
Bill

[bluesbear]

This is great and answers most of my question (far better than I get elsewhere in my life). Now, I just need to know the difference between *just plates and screens* and *plates, screens, and PI*. I understand about the MV differences, I'm just interested in how much more it would affect the tone.
Thanks!!
Dave

[jojokeo]

JB's info was nicely stated but I'd like to hear Geezer and tubenit weigh in too (or others w/ a number of these builds too).
I've only built one amp w/ VVR at this time and it's SE so I don't know if my experience or opinion has a whole lot of merit or value? I didn't want to build something bigger until I had done it at least once to get a feel for it. Mine has only a typical single vol after the tone stack and the VVR only is on the plate & screen and theVVR is my master volume literally and figuratively. The headroom response describes it well but I don't notice any real change in tone when it's turned down from 10 - only headroom. VVR is great for overdrive and distortion at various vol levels but doesn't seem suited to be in any amp meant for clean tones.

[LooseChange]

I find it's very important to be able change the amount of signal that goes into a scaled part of the amp.  As the amp is scaled down the unscaled preamp will easily overload the scaled portion. Adding master volume controls in front of the PI and in front of thee power amp (Post PI) you will get the most our of the amp.

I've Power Scaled and VVR'ed many amps and I find that plates and screens is best. All the amps have some sort of master too.

[Tone Junkie]

Ok LooseChange you lost me there you say plates and screens is that on the power amp section the power amp and phase inverter which . I havnt used a VVR but I have been thinking of using one on several differant builds I just dont have any experiance with them.
Thanks Bill

[bluesbear]

Well, from what's been stated, I'd say I'll be happiest with screens and plates only. I love how my amp sounds; I don't want to change that! I 'll pass on my opinion in a few days.
Thanks to all!!!
Dave

[TIMBO]

Hi bluesbear, I hope it works out for you,i guess that the thing with these scratch builds is you don't know how it will turn out until its built.I'm at a snails pace trying to get the Silver Jubilee finished. I've added a VVR as well mainly to reduce the volume for bedroom use and was hoping to keep the cranked sound at a low level.I too are not tech enough to for see what the final sound created when adding these mods to known amps.I followed Tubenits VVR mods and they have the PI in the circuit so thats how i've done it but i keen to hear if there is any difference if only the plates and screens are in the circuit.I think my layout will allow me to do either. Keen to know your final outcome, Thanks

[tubenit]

I am not as experienced as LooseChange is with the VVR's. I done 3 amps with VVR and used them on the power amp and the LTPI. I like the results. Never have tried it with just poweramp and using a PPIMV.

I think the PPIMV at around 1/2 (or "5") without a VVR does a good job retaining tone. Lowering it below 1/2, I think it loses some tone quality.

I think the VVR does a good job retaining tone til about 1/4 (or "2-3") but below 2-3, it loses some tone quality and is a little fuzzy sounding.

As far as trying to record something at home using Mixcraft, I have trouble making a PPIMV (alone) work for me but a VVR gets the job done reasonably well.

With respect, Tubenit

[punkykatt]

Bluesbear, how did you make out with the VVR?

[bluesbear]

The VVR is sitting on the bench! My son's been using that amp till we get his retubed. He ordered the tubes Monday so I should be working on it by the weekend. I'll update then.
Dave

[bluesbear]

Well, my son's amp is done. He dropped off the tubes yesterday. Now, I just have to get him over to switch mine for his. It may not be easy. He's discovered the secret: 45 watts aren't better than 15! I'm not sure I can talk him into letting me change his over from EL34"s and a 5AR4 to cathode biased 6V6's and a 5Y3... but I'll try. Anyway, I'll be installing the VVR soon. And mainly, this brings this thread to the top where it's easier to find when I get it done!
Dave