ATBL and the Variplex

Jack71 · Post by **Jack71** » Fri Feb 29, 2008 11:02 pm

RACKSYSTEMS wrote:To answer a few things the heaters dropping with the variac is a huge tone thing. At one point I had a filament transformer hooked up to a variac to see what effect the heaters dropping had on tone. Well it was a lot, also if you want to use it right you should bias the amp while at 90 volts. The variac that comes with the amp is more for vol then anything. Dave

So is dropping the voltage to 90ma with the stock variac and then biasing to 50ma not safe? Or for that matter, is it pointless tone wise?

sinasl1 · Post by **sinasl1** » Fri Feb 29, 2008 11:04 pm

Jack71 wrote:
RACKSYSTEMS wrote:To answer a few things the heaters dropping with the variac is a huge tone thing. At one point I had a filament transformer hooked up to a variac to see what effect the heaters dropping had on tone. Well it was a lot, also if you want to use it right you should bias the amp while at 90 volts. The variac that comes with the amp is more for vol then anything. Dave
So is dropping the voltage to 90ma with the stock variac and then biasing to 50ma not safe? Or for that matter, is it pointless tone wise?

It's important tone-wise. And it's safe.

Good Guest · Post by **Good Guest** » Fri Feb 29, 2008 11:50 pm

Just don't go too low on the voltage: Tube life vs. Heater voltage

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tonepilgrim · Post by **tonepilgrim** » Sat Mar 01, 2008 12:49 pm

If you believe a chart like this, then running an amp at 90v, which is 75% of the nominal value (120) would result in tubes pooping out within a couple hrs if not immediately. Obviously that is not true.

Whenever the topic of running an amp on a variac comes up, on any forum, it is guaranteed every time someone chimes in about the horrors of cathode stripping, substantially reduced tube life, danger danger, proceed at your own peril, etc. I understand the academics of it, but in several years of running an old marshall with a variac turned down, I can honestly say I have never seen it. The tubes in my old marshall last just as long as my other amps, and I don't think I have ever had to change my preamp tubes. Based on my experience, I take these types of concerns with a grain of salt.

Star*Guitar · Post by **Star*Guitar** » Sat Mar 01, 2008 1:45 pm

Your not reading the chart right. At 90v the tube life is estimated to be about 2000 hrs.

But I agree, I take all that with a grain of salt. And...I don't give a crap if the tubes wear out once a week if the tone is there.

SDM · Post by **SDM** » Sat Mar 01, 2008 3:38 pm

Star*Guitar wrote:Your not reading the chart right. At 90v the tube life is estimated to be about 2000 hrs.

But I agree, I take all that with a grain of salt.

No he's reading it right, it's percent heater volts, not voltage on the bottom there. I do take that graph with a grain of salt though, here's a little article with another graph opposing the one above about lower heater voltages:
http://www.tubecad.com/july2000/page10.html

bmf5150 · Post by **bmf5150** » Sat Mar 01, 2008 4:20 pm

SDM wrote:
Star*Guitar wrote:Your not reading the chart right. At 90v the tube life is estimated to be about 2000 hrs.

But I agree, I take all that with a grain of salt.
No he's reading it right, it's percent heater volts, not voltage on the bottom there. I do take that graph with a grain of salt though, here's a little article with another graph opposing the one above about lower heater voltages:
http://www.tubecad.com/july2000/page10.html

steve,you are the man.did you find another les paul you wanted yet?

tonepilgrim · Post by **tonepilgrim** » Sat Mar 01, 2008 4:25 pm

Interesting insight in that article SDM. I guess that's another data point that lower heater voltages are not necessarily that bad, if at all, for tube life. I still don't really understand why, I just know my experience is consistent with that.

Good Guest · Post by **Good Guest** » Sat Mar 01, 2008 9:23 pm

Actually the chart is probably correct during the time it was made.The materials used in heaters and the various coatings at that time are different than the metal alloys and coatings used now. That has a great effect on tube life , quality and tone.

Could it be ...todays tubes are better quality in the heater department? This is good news if they are.

KG MD · Post by **KG MD** » Mon Mar 03, 2008 10:45 pm

Pete I'm asking out of pure ignorance but what is the idea behind using an attenuator when the Variplex has the variac that I thought acted as a "power scaling" feature? I'm referring to the variac wired into the amp itself, not the variac I think you are using to drop the whole amp's power to 90 v. Does the use of the internal variac alter the sound as the voltage is lowered?
I think the clip sounds awesome - I have had some interest in this amp since the first clips were posted several years back.

sinasl1 · Post by **sinasl1** » Tue Mar 04, 2008 3:47 am

well actually that's a good point... I just think that the attenuator would be the more transparent option, rather than variacing an already variaced amp if you know what I mean... might get a little too squishy. but I didn't compare the 2 options. The attenuator has to be used around here cause it's just too loud for my neighbors if I'm wailing away and they are home...

MARCO · Post by **MARCO** » Tue Mar 04, 2008 2:05 pm

Hey Pete
Get some sound boards that they use in studios to absorb the sound. Wont those help?? I have the same problem too since I live in a townhome and have people on either side of me.
"Good day!"
Pete if you had a choice of buying an old Marshall or a V-Plex which one would you go for....from a tone aspect, not a resale or investment standpoint??

sinasl1 · Post by **sinasl1** » Tue Mar 04, 2008 7:06 pm

MARCO wrote:Hey Pete
Get some sound boards that they use in studios to absorb the sound. Wont those help?? I have the same problem too since I live in a townhome and have people on either side of me.
"Good day!"
Pete if you had a choice of buying an old Marshall or a V-Plex which one would you go for....from a tone aspect, not a resale or investment standpoint??

Well, honestly, unless you find a killer sounding old Marshall for an incredibly good price- I'm of the mindset that buying a new amp is the way to go. I mean, listen to all the guys who post clips of their home builds on here, they sound great, and are cheaper and waaaay more reliable if built right) than an old amp will be.

In other words- if you can find a 50 watt marshall that sounds as good as a Variplex, for the same price as a Variplex, and it's been all gone through and is solid- I guess the smart move would be buy the old Marshall (for collectability/resale reasons). But that's probably not going to happen....

I own 3 Divided By 13's, 3 Komet Concordes, a Suhr Badger, a Top Hat Emplexador, a THD Flexi 50. an EVH 5150III- and one old Bassman head. So I'm clearly in the new/boutique camp....

MARCO · Post by **MARCO** » Tue Mar 04, 2008 7:26 pm

Good Day!!
Hey Pete, thanks for the tips. I guess thats why I had an old Marshall Super Lead and had Dave re-vamp it. I like your choices in amps....you can cover the entire tonal spectrum with those. Do you like the EVH for other things than EVH stuff?
I have had a Diezel Herbert, THD Plexi 50 head, Soldano SLO-100, VHT Pitbull, 5150 etc. I miss my SLO the most but I like the sound of the new 5150III.
Any thoughts?

tubez · Post by **tubez** » Wed Mar 05, 2008 10:23 am

Marco,

I recenly picked up a pitbull 45 1x12 combo and it sounds killer through my 2x12 cab. I will be replacing the speaker in it with a scumback shortly as the combo speaker just doesn't do the amp justice. Does the brown sound pretty good IMO.