Van Halen brown sound

[dscottguitars]

I have a question about the 'brown sound' that Eddie Van Halen had.

Does turning down the wall voltage-which makes the secondary voltage less-have any difference than cutting the secondary voltage?

EX:

120v steps up to 350v for about 450v on the plates
So then, EVH uses 90v and should step up to 263v for about 350v on the plates.
I can just reduce the plate voltage w/o buying a Variac but I'm not sure if this is the same.

Thanks,

Daniel

 

[GloBug]

Yes, you can lower your B+ but keep your heater voltages the same for long tube life.

 

[dscottguitars]

I did not think of the heater voltage. So that means EVH's setup w/a Variac gives less heater voltage too. Does that effect the tone in anyway?

 

[firechief]

GloBug is right. What kind of amp was he using? Perhaps we can find a schematic and make suggestion about just how the B+ could be changed. Of course this can involve working with dangerous voltages, soooo. Are you actually going to atempt it yourself?

 

[GloBug]

In the original version, he had a variac before the amp, so it would have lowered the heaters a bit aswell. The cost of tubes was not a priority for EVH at the time.

I don't think it effected the tone as much as the plate voltage.
A variac at 90v would have gave him a lower heater @4.73v. It is lower, but I don't think it changes the sound nearly as much as the B+.

The main effect is the lower B+ which causes the particular distortion known as the "brown sound"

The name came from the rolling electrical "brown outs" which were used at the time to save electricity during the summer.

 

[dscottguitars]

Thanks,

Yes I can and will do the mods myself. I've built a couple and wondered about putting a switch to select different B+ voltages to achieve that 'brown sound'; and to really see if it's something I notice or like. But my main concern was any effects the transformer has with less voltage going through it vs dropping the secondary.

I will try different voltages and see what it does.

How would putting a voltage divider on the plate/screen lead work? That way the voltage to the rest is high. (just thought of that)

And is there a low limit I don't want get below?

Thanks for all your suggestions...

Daniel

 

[GloBug]

I will let others advise the best way to lower the voltage.

I don't think you will bother the transformer at all by running at a lower voltage, if you go that route.

 

[dscottguitars]

Clarify: 'main concern' I meant to say 'I wonder if it adds to the effect of the sound having the voltage lower on the primary'. Since it is what is 'sought after'.

 

[GloBug]

I don't think it matters which way you arrive at the lower voltage.
The amp can only see the secondary voltage.

You could intentionally design a new amp to run a lower plate voltage-having an earlier break-up. (distortion)

As you may know a power supply can have an effect on how the guitar feels or responds, due to how much 'sag' or voltage drop it has under load.
Some of this is determined by the rectifier used. Tube rectifier=sag, solid state=stiffer, faster response.

 

[firechief]

Thanks a lot. I'v neen walking around work all afternoon with "running with the devil" playing in my head, Oh well, could be worse.

 

[dscottguitars]

Ha Ha Chief, that's good. I can't think of a better earworm.

I've got the voltage down to 330v on the plates using about 1k ohms.

I used 4 resistors in series, 220/5w,220/5w,250/5w,250/10w. Because I don't have any that are high wattage. But they still get hot, around 225°F. I tried two 1.8K/10w in parallel and they were hot too. Is this normal? I'm not worried about heat 'bleeding' over to the caps, the resistors are far away enough.

I placed them from the Standby switch to the B+ that goes to the OT.

Any thoughts?

BTW: The sound is really nice, I get breakup at much lower volume now. Happy

 

[GloBug]

I expect they would get hot.
Ohm's law will tell you how much heat your making, then get the right wattage resistor, if needed.
Sounds like fun!

 

[shanx]

Ha Ha Chief, that's good. I can't think of a better earworm.

I've got the voltage down to 330v on the plates using about 1k ohms.

I used 4 resistors in series, 220/5w,220/5w,250/5w,250/10w. Because I don't have any that are high wattage. But they still get hot, around 225°F. I tried two 1.8K/10w in parallel and they were hot too. Is this normal? I'm not worried about heat 'bleeding' over to the caps, the resistors are far away enough.

I placed them from the Standby switch to the B+ that goes to the OT.

Any thoughts?

Is that on a Marshall 100 W head?
There has been a lot of guessing going forever on about EVH's brown sound, variac use etc. There is a mod that I would not recommend as it will eat up tubes and possibly the OT, but allegedly the way he setup the amp was putting power resistors across (parallel )the coil primaries of the OT (google Cerram mod), that was so he could run the output tubes full out with reduced volume.
I am unsure whether that is an actual fact, maybe the mod was really what you have done, in effect dropping the B+ only.
Maybe the variac at 90 volts helped preserve the tubes and OT, as they were for sure running those tubes saturated and with high bias. Also another mod rumour is that on the second preamp stage there was 330 uF added across the 820 Ohm cathode resistor. that would increase that preamp gain on 2nd stage. Good luck with it and hope you have fun

 

[dscottguitars]

No, it's a Bassman clone, but I use 2 full 12AX7's wired in parallel in the preamp.

That 330uF is a Marshall standard, I don't think it was added, and it's used for both triodes in parallel, so the tube 'see's only 165uF. I've tried large values and don't notice any difference larger than a 68uF on parallel tubes, so that's what I've been using. Nice bass response from them that grinds the OT. I also use about 820 ohm on the resistor.

 

[dscottguitars]

Hi, I'm concerned about the heat I'm getting with this dropping resistor. None of my other dropping resistors get hot and they didn't before I tried this. I chose 2-2K ohm/10W in parallel for 1K and 20W(?) total. The temperature is pushing 165°C! They are cement filled Asian cheapos and looking online they seem to be rated for -55°C to 275°C. This falls within the range, so that's not my concern.

My concern is why this resistor(s) get hot when none did before?

I'm dropping 430v down to 330v using 1K ohms from the standby switch (on/off/on)-choosing between normal and brown sound. This goes to the junction of the OT center tap/plates and a 400 ohm dropping resistor going to the filter for the screens. Is this correct:

W=VV/R; 100*100/1K = 10 watts


Thanks,

Daniel

 

[GloBug]

10watt is pretty hot, you can solder with a 15w or 25w.

I'm not sure what you mean about it not getting hot before, you mentioned the 4 dropping resistors were around 225F.

Double check your numbers and you should be fine, keep them away from other items as you have been doing.

I wonder if you could find a light bulb with around 1K resistance when hot. Might do the trick!

 

[dscottguitars]

Those 4 dropping resistors were the ones to lower the B+, the one's that didn't get hot were all the ones in the power supply before I tried lowering the B+.

The power transformer is quite warm now too, much more than without the drop.

 

[GloBug]

Oh OK. They were not hot before as they were not dropping 100v.

Generally if you can hold your hand on the PT for several seconds without major discomfort then it should be OK. Hot is OK, scalding hot is not.

 

[GloBug]

I picked up a Variac of eBay for $35.
I might stick it in a DIY amp one day, if I come across a separate heater transformer, or a second suitable transformer using the heater from one and the B+ from the other.

Might be a good way to lower the voltage without having to make so much heat.

 

[shanx]

No, it's a Bassman clone, but I use 2 full 12AX7's wired in parallel in the preamp.

Nice amp that Bassman. A bit of a different breed than the 67 Marshall 100 W but a beast nonetheless.
The '67-'68 Marshall EVH apparently used had a couple of interesting things going on, based on ''hearsay'' from at least 2 techs who got to get a look at it. It is almost to the point of folklore now..I don't think it was extensively modded. That head, if it is in fact the standard 67 schematic I was referring to: V1A/V1B share a common 820 Ohm/250 uF pair off their cathodes. After the preamp channel volume pots, the V2A as standard only has the 820 Ohm. Apparently on the EVH a 330 uF was added across it on V2A increasing the stage gain, and the 250 uF was replaced with a 330uF. The 250 pF on the tone stack may have been removed too, according to one tech.
Just a suggestion, but I would check your output tubes biasing when running at reduced plate voltage. If tubes are over biased the amp will be pulling a lot more DC idle current the normal, through the OT (and dropping resistors).