Put sovtek 12ax7lps in the XXX

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tweed

tweed

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in position one and two, tung sol in 3 and the standard eh in 4, along with el34's from Valve Queen. Sounds pretty dang good. I know there was a thread or two a while back about putting these pre's in certain spots of certain types of amps would cause some big problems if they went boom. Hoping that's not an issue with the Peavey XXX head.

Anyone else using LPS'?
 
Love LPS in my Engl Screamer. Nice and woody...

I don't know if the XXX (which I also own) has cathode followers or not...in those positions you shouldn't use LPS. I personally use Ruby pre's in my XXX with a lower gain JJ in V2.
 
Not sure if the XXX has cathode followers or not. Anyone know?

Also I gotta get a bias probe of some sort soon. Had to use Peavey's suggestions for the test points on the back so who knows how hot this thing is running right now lol. Put it at 42.5 like they suggest but have no real idea how hot that is as the test point measure volts. And you can't get to the power tube pins inside the amp, there is a daughter board situated right over the top of the sockets :aww:
 
Voltage = Current X Resistance

Your multimeter probably has a 1 ohm resistor in it to complete the circuit when set to amperage.

Voltage = Current (which is in mA).

So, when you use an external test point to measure, as opposed to pulling the chassis and measuring pin to ground, you are actually measuring volts, not amps. But, with the DMM, it is the same thing as you are measuring the potential across two points with a fixed resistance as supplied by the DMM. In your case, the bias reading is 42.5mA, which is a little on the high side, depending on plate voltage.

Class dismissed.....
 
I really dig the LPS in my EVH. Sounded great in my 5150 combo when I had it also.
 
steve_k":2nmvxpe3 said:
Voltage = Current X Resistance

Your multimeter probably has a 1 ohm resistor in it to complete the circuit when set to amperage.

Voltage = Current (which is in mA).

So, when you use an external test point to measure, as opposed to pulling the chassis and measuring pin to ground, you are actually measuring volts, not amps. But, with the DMM, it is the same thing as you are measuring the potential across two points with a fixed resistance as supplied by the DMM. In your case, the bias reading is 42.5mA, which is a little on the high side, depending on plate voltage.

Class dismissed.....
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Many thanks for that Steve! I think in that case I will back it down to around 38 or 39 just to be on the safe side. Thanks again for the education. :thumbsup:
 
Unfortunately the bias test points in the Peavey aren't what you think. It measures grid voltage with respect to ground, and backwards yet. It's normally a negative voltage but they purposely wired the test points to read positive. This is just a measurement of the voltage on the grid pins of the output tubes, which is responsible for setting up the current draw, not a measurement (direct or indirect) of that current draw. It's related but not the way you expect. The fact it's an a measurement of whole volts and not millivolts is a hint about what the measurement is.

I recommend you use a bias meter to determine the current draw. Peavey's grid voltage measurement is ok for most tubes (if they're operating in the ranges they're supposed to) but it provides no indication of what the tubes are doing.

Also, the lower you go with this voltage, the less safe it is. -42V is setting the tubes at a colder idle than -38V (which is actually a higher number). What they do with the test points makes this confusing, unless you already know what the test points do.
 
JamesPeters":2o588mot said:
Unfortunately the bias test points in the Peavey aren't what you think. It measures grid voltage with respect to ground, and backwards yet. It's normally a negative voltage but they purposely wired the test points to read positive. This is just a measurement of the voltage on the grid pins of the output tubes, which is responsible for setting up the current draw, not a measurement (direct or indirect) of that current draw. It's related but not the way you expect. The fact it's an a measurement of whole volts and not millivolts is a hint about what the measurement is.

I recommend you use a bias meter to determine the current draw. Peavey's grid voltage measurement is ok for most tubes (if they're operating in the ranges they're supposed to) but it provides no indication of what the tubes are doing.

Also, the lower you go with this voltage, the less safe it is. -42V is setting the tubes at a colder idle than -38V (which is actually a higher number). What they do with the test points makes this confusing, unless you already know what the test points do.
Click to expand...

SonofBeachSheet.....

thanks James, I'll start looking for a bias probe very soon. That or i'll sell off this amp and by something else. Why the hell would they design and amp like this if the test points are different from the norm? Maybe I am just spoiled after dealing with the DSL for the last two years...

Gonna give a whirl tonight with the band and see how it sounds overall. I'll try and nab a meter from work so I can get the tubes back up around 42. I see either an old school MV marshall or JCA22h in my near future... :doh:
 
You should be playing the vplexi :). I played Traces Amps this weekend and I was digging them.
 
I checked the bias on mybrand new 6505+ yesterday and it measured 9ma using my Webber bias rite. Maxing out the bias pot got me to about 21ma. Still sounds pretty good even though it's still a fairly cold bias level.
 
You should fins a JAN Philips 12AX7A and put it in V1 of that XXX. With an EL34 power section, that is a killer combination. I have done it a few times for people and they love it. Sounds unreal.
 
dstroud":16h45f4j said:
You should be playing the vplexi :). I played Traces Amps this weekend and I was digging them.
Click to expand...

Gotta clean it up a bit and put it back in the headshell. ;)

But it's has no loop and no room to install one that may cause me an issue or two lol.
 
tweed":o7228ft8 said:
thanks James, I'll start looking for a bias probe very soon. That or i'll sell off this amp and by something else. Why the hell would they design and amp like this if the test points are different from the norm? Maybe I am just spoiled after dealing with the DSL for the last two years...
Click to expand...

This way they can keep it "simpler", avoid talking "too technical" with the average person and still ballpark a decent bias range for most tubes that would be used in the amp. That's all I can really think of though.
 
Played it with the band last night and holy crap what a difference 34's make in that amp! Great rock tones, great warm clean tones, it just may knock the DSL to the back of the line for a while.

@D-Rock - I gotta figure the cathode follower thing out soon. I read somewhere on a forum that v1-v3 are all cathode followers which is making me somewhat nervous. :no:
 
Well, I can tell you that these amps along with the JSX used to ship with all EH's in the pre. The concern with the cathode follower stage is with russian tubes. So I think you'd be alright with either a Tungsol, Sovtek or EH. I run JJ's in V1-3. I never liked EH's or Tungsols in the XXX/JSX
FWIW.
 
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