Lightning low power switch

[orrong65]

Hi there,

I am looking for suggestions on how to add a low power switch to my Lightning 15 clone, as I am starting to upset the neighbours.

I thought something like a 5W level would be suitable, as it get played on high master volume for the power amp distortion.

I have had a look at the DC-30, and although I understand the theory, it doesn't seem to be applicable to the lightning.

Any suggestions for a suitable circuit?

[UR12]

Usually you only add a 1/2 power switch to an amp with 4 bottles and the switch disconnects two. I doubt you would see a lot off difference in vol between 15 watts and 7.5 watts. Without trying to sound like spam (You can build your own without buying anything from me), I would suggest a VVR (Power Scaling). It's fairly cheap and easy to implement and works a lot better than a 1/2 power switch

[Phil_S]

Maybe you can think about a pentode/triode mode switch.

[Gee]

I can't say enough good things about installing a VVR. I have a Lightning/TH Royale and also a Spitfire clone both with VVR and it works very well. In my experience if 15W upsets your neighbours (as it does my neighbours) then 7.5W or 5W will also be too loud. I would buy a kit from Dana without hesitation if I needed another VVR.

[mcrracer]

I can't say enough good things about installing a VVR. I have a Lightning/TH Royale and also a Spitfire clone both with VVR and it works very well. In my experience if 15W upsets your neighbours (as it does my neighbours) then 7.5W or 5W will also be too loud. I would buy a kit from Dana without hesitation if I needed another VVR.

+1
I installed one in an 18 Watt, customer loved it!!!

[orrong65]

Thanks to all that replied!

What I am trying to achieve is a switched option where I can get the full range of amp tones at a variety of volume levels, without using a power brake as I dont like that tone effect. So I am after the full tonal range at 10%, 50% and 100% volume levels.

I have read through a lot of the posts on pentode/triode switches, and most say it achieves a reasonable reduction in output watts, but only a slight volume reduction. I might install this anyway as an experiment to see what tonal effects I can get, as we use a lot of vintage tubes which hav some interesting differences.

It seems the vvr power attenuator is the way to go. Reading through these posts I see that most people are very happy with the results, although I did see a comment that the vvr is not best used down to bedroom volumes.

Any further comments welcome.

[Structo]

Doesn't that amp have a master volume?

Since that amp has the post phase inverter master, it would seem that you can drive the PI hard by turning up the pre-gain and lower the MV.

[Rick]

Doesn't that amp have a master volume?

Since that amp has the post phase inverter master, it would seem that you can drive the PI hard by turning up the pre-gain and lower the MV.

Yes the lightning has the phase cancelling MV with a 180 pF cap on the pot, at least that's how I do them. Part of the problem is with cheap pots, the taper is wrong or the pots are just bad, I don't know which, but the MV is almost uncontrollable at low levels, it goes from off to on in just a smidgeon of a turn. Precision pots work much better and smoother. Just installing one of those may be a step in the right direction.

Some like the tone with the MV full up and adjust to taste with the Vol, then power scaling seems the only solution outside of an isolation cab or attenuation. Isolation cabinets are another thing that gets forgotten about, if you can handle headphones or set up some kind of lower volume monitor, you will want some kind of mixer likely with XLR inputs, a good isocab can get you incredible tones and no one will hear a thing! I have one in a closet under the steps in the basement all covered up with old blankets, pillows, etc., and you can barely hear it (downstairs!) with it cranked up 15 or 30 watts.

[Structo]

Yeah I think it's called a crossline master on those.

I tried that and it was as you describe, off then on.

I ended up using a boot strapped MV.

There is also a single bootstrap MV.

[orrong65]

Thanks rick, structo and Dana for your comments,

yes its a Master volume amp, but I end up playing it in the house either with the pre-amp on 9 and MV on a fraction above off (and I mean like 1/16" above off), or the MV on 9 and the pre-amp 1/16" above off. That way I get it into distortion both ways.

The difficulty is that the lower scale of both pots is difficult to get "just on" above 0.

But you have given me an idea about changing the taper of the pots (both vol and MV are 1meg log) so that the lower scale (from 0-5) is more useable. At the zero position (=off) both pots are seeing the full 1Meg of the pot, and the MV is wired as a rheostat. A linear pot should expand the lower pot range (and compress the upper range). Failing that, I will try a fixed resistor across the active input-wiper output.

[M Fowler]

Or you could go with the limiter control into PI tail from Carlsboro amps to control overall volume.

Mark

[Structo]

I installed a 1/4, 1/2 and full power switch on a little 6V6 amp I built.

It works but doesn't drastically drop the volume, but does change the character of the amp so it feels like a smaller amp.
I think it was a worth while mod.

[paulster]

If you really want to keep the same tone at low volumes (which will be much less than half power) then you've really got two options: power scaling or a transparent attenuator.

I like the attenuator option personally, but good ones don't come cheap, whereas Dana's VVR circuit will drop very easily and cheaply into this amp to give you a good deal of control over your volume.

I've never tried a pentode/triode mode switch that I actually liked, and always found that the volume reduction wasn't significant enough to warrant the degradation in tone, although it is a very quick and easy way to knock a few watts off if that's all you need.

Your situation sounds like you're going to need a fair degree of attenuation though since -10dB (1/10 power) is only audibly a halving of volume. That would put you down in the 1.5W territory and 1/4 volume (-20dB, 1/100 power) would be 150mW!