Got me an express

[blaren]

clone.
Hey fellas..I'm new. I just scored an express clone so I've been lurking around here for a while doing some research (before my "aquisition" and since). Been seeing some familiar faces like just tonight reading a thread and Richie replied...hey Richie, how YOU doin? Do you guys realize who this guy is? he's RP as-in "36RP"!!...anyway..sorry for the smoke blowin'..lol..there are some SERIOUS amp builders/gurus here..wow.
Anyway, my new amp is a Ceritone chassis and faceplate with, Paul Ruby Heyboer Trainwreck transformers, Clarostat Pots, Sprauge Atom and Mallory 150 capacitors, External bias pot and jacks, Rear mounted PEC master volume, marshall cliff jacks, Micalex tube sockets.
I used it at a gig last weekend and I'm trying to like it as much or more than my 36w (which is my fave and I have a LOT of amps) but I'm having a hard time. I havent given it a fair shot yet and I still need to "learn" it more. I'm gonna gig with it again this weekend.
My first 'issue" or question is...why do most people bias their expresses at around -30mA...I mean mV..? I get a bit less than 390V on the plates (forget exactly) and where I come from, that means that, without using a calculator, I should be biasing my el34s at somewhere around -44mV.? From what I've read, the 390V is in the same neighbourhood as everyone else so why 30??
My second question is....about how many real expresses were built?
Finally, anyone got a good source for some, any kind of headcase available in Canada? I've heard about the drawers and ceriatone does have a cab but it'd be nice to find something reasonable that's available in Canada. Nik's shipping on one is pretty high.
Thanks in advance

[dartanion]

I always say bias to what sounds right. No redplating and you're all good.

I had Reason make me some nice cabs that'll fit that chassis. Price is good too, and I know he ships to Canada.

Wrecks are a bit different than other amps. Set the tone controls, presence and volume, then use your guitar's controls for everything. Roll back for clean. Roll up for distortion. Flavor with pup selection and tone. Wrecks are not for the roll everything to 10 and leave it on the bridge pup constantly crowd. There is so much gain on tap that you can dial lots of different tones with just the guitar volume.

Good to see you here blaren.

[BBQLS1]

Anthony Reason makes great Tolexed Cabs. Jeff Swanson makes any kind of cab.

[Lonely Raven]

I always say bias to what sounds right. No redplating and you're all good.

I hate to admit...I couldn't find my bias rite, and I've been too busy/lazy to put the 1ohm resistors in (I'm waiting on test ports and external bias pot to show up in the mail), so I biased completly by ear. I'm probably running hot, but I'm running inexpensive current production tubes so I'm not worried about tube life.

And personally, I think I found the sweet spot just dialing in by ear. There is a point where the amp seems to wake up and become more dynamic and the notes bloom a bit more. And by bloom I don't mean the feedback that many here call bloom, I mean the richness in harmonic content type bloom you get from a well tweaked boutique amp.

Mine is still not there yet, but getting there.

Say blaren, you didn't get that amp super cheap, like under $400 without tubes or cab, did you? If you did, you snagged that one just before I did apparently! LOL Though I'm glad I built my own...I appreciate the amp much more since I built it myself.

[drhulsey]

... anyone got a good source for some, any kind of headcase available in Canada?

If you want a furniture grade cab that your wife will let you put in the living room (like the one below), check out Distortion's (Larry Mann) cabs.
http://ampgarage.com/forum/viewtopic.php?t=3770
Doesn't that cab just make your spine tingle

[Buschman]

I think that most of the amps bias at -30 volts, not mA or mV. That's where Ken said to put it & leave it. A 6v6 will bias there as well. It's a middle ground. I think I am running at -32v. Seems like that put my bias at around 41mA of current.

[blaren]

I think that most of the amps bias at -30 volts, not mA or mV. That's where Ken said to put it & leave it. A 6v6 will bias there as well. It's a middle ground. I think I am running at -32v. Seems like that put my bias at around 41mA of current.

Dammit...I was in the middle of a nice long winded reply and this pos computer shut down. FRICK.
Like I was saying before I was so rudely interrupted...
I thought that by adding the 1ohm1watt resistor between pins 1,8and ground we were converting mA to mV..straight across. I dont get it. am I missing a calculation for biasing a trainwreck? How does -32V equal 41mA?

As for gear in the livingroom...already had that battle...I WON!...kinda...now I'm a single Dad with a TON of gear in the livingroom (and basement and kitchen and bedrooms and....ha ha beeatch!!) lol.

I do realize the concept behind a tw. While messing with it trying different tubes (including 6V6s..damn...thing has WAY more balls with 'em than any of my other old 6v6 amps). I stayed with some cheap new EL34s for now. I was a bit worried about volume at the gig so I had the master backed-off a bit. When I'd back off on the guit's vol, the clean tone lacked punch and snap. With the volume cranked it overdrove(?) nicely but wouldnt "sing" for me. I also found that a couple of single higher notes didnt "pop" with the authority that they do with other amps. I'm thinking that all this could have something to do with the fact that I'm biasing "correctly"? Seems odd that they'd be biased to a point so that the amp will "function" with ELs OR 6v6s rather than biased optimally for each. On Friday I'm gonna use it again but with the master cranked. I figure that'll help with the cleans but not sure if it'll help the amp give-up the "goods" in the dirt department...maybe?.
Hopefully someone explains this 30V biasing stuff to me and that'll fix it. 30mA or mV or V ??? seems a long way off from 44mA. When I tried the 6V6s I think I had it biased (according to my calculations) somewhere around 29 mA or mV or whatever. They are some SWEET philips labeled blackplate 6V6s that match PERFECTLY. didnt even remember having them. NOS NIB too.
Right now I have a mule in V1 (I61), RFT in V2, and an ultra sexy old Tesla ECC803S in V3. I have a nice 5751 to try in V1 if I cant get that clean sparkly punchy tone I'm after but I dont know if that'll do anything good to help me SQUEEZEout some nice harmonic feedback which is what I'm having to do now...SQUEEZE and beg. Say uncle you dirty pig!! lol. My poor guitar is taking a beating and it isnt even it's fault lmao.

Even though it may be obvious that I have marshall blood, I dont dime my stuff and I do use my volume pot on the guitars a lot. I also use an old TS9 for some extra poop.

Without "divuldging" too much information (in case I want to sell it) about how much I paid and where I got it....all I can say is next time, dont hesitate for even a second when you see a smoking deal on a tw with no case and no tubes for under $400. Not saying it was me or anything but if it WAS, I would have given him more than he was asking cause he had to ship it to Canada....I mean IF it was me who bought it for more than $325 but less than $400...which, I'm not prepared to admit to at this juncture. lol.
Next time someone says "if it seems too good to be true..." tell them to f^$% 0##.
Thanks again

[mlp-mx6]

I thought that by adding the 1ohm1watt resistor between pins 1,8and ground we were converting mA to mV..straight across. I dont get it. am I missing a calculation for biasing a trainwreck? How does -32V equal 41mA?

I do not believe you two are talking about the same thing. One is discussing the actual bias voltage (-32V applied to power tube grids) and the other is discussing the mV to mA conversion allowed by using 1ohm resistors in the cathode path.

Setting the bias by measuring the cathode current is NOT measuring the bias - it is measuring the EFFECT of the bias on quiescent tube current. Converting from mV voltage drop to mA of current by use of Ohm's law.

[dartanion]

A MV on a Wreck pretty much ruins the interaction of the stages and thus in lies your issue. You wont get that singing tone with the MV dialed back, but I bet it comes back once you crank it up. A good attenuator would be a good call.

[Lonely Raven]

Without "divuldging" too much information (in case I want to sell it) about how much I paid and where I got it....all I can say is next time, dont hesitate for even a second when you see a smoking deal on a tw with no case and no tubes for under $400. Not saying it was me or anything but if it WAS, I would have given him more than he was asking cause he had to ship it to Canada....I mean IF it was me who bought it for more than $325 but less than $400...which, I'm not prepared to admit to at this juncture. lol.
Next time someone says "if it seems too good to be true..." tell them to f^$% 0##.
Thanks again

All I have to say....You BASTARD!

But thanks for making me build my own.

[gearhead]

Look at

http://www.diyguitarist.com/GuitarAmps/ ... beBias.htm

Plate voltage with corresponding currents.
(please correct me if I oofed this up:)

1) The (power tube) Plate Voltage is a -Design- thing. In the case of the Express, 395-400V is the goal.

2) How much current the power tube draws, at idle, is a set in line with that Plate Voltage.

3) The bias voltage cited (-30V or -33V) is directly related to a set bias voltage between the Cathode and the Control Grid (Input).

2) and 3) are a direct result of the exact Bias Pot value you've set.

So, you can measure the current indirectly by measuring the voltage across your installed resistor. V=I*R (1mv is the same as 1mA times 1 ohm). Turn the bias pot until you're in the zone according to the plate voltage.

Or, you can measure the bias voltage directly, and turn bias pot till you get that -30 or -32 value that Ken F. was apparently using as his measure. If you do this, you should probably find that the current is in the zone too.

Disclaimer - I've never done either of these -directly- myself. Have always used an Alessandro bias meter.

[blaren]

God! you guys GOTTA try to keep to single syllable words and speak REAL slow for me.
this still doesnt make sense to me. While I am pretty illiterate looking at circuits or schems, it sure looked to me like (I'm not in front of it right now) the bias ports on the back were tied to the same place that I put probes to bias my other EL34 amps (off the 1ohm1watt resistors). So that's NOT what's going-on here and I actually want to plug my meter into the ports and dial it in till it reads about -30V?
well suck me dry and call me Dusty!

I know right

[mlp-mx6]

...it sure looked to me like (I'm not in front of it right now) the bias ports on the back were tied to the same place that I put probes to bias my other EL34 amps (off the 1ohm1watt resistors). So that's NOT what's going-on here and I actually want to plug my meter into the ports and dial it in till it reads about -30V?

Uh, did you read what I wrote? What gearhead wrote?

NO - you cannot get the test points you mention to -30V. They measure in positive millivolts. It is exactly like what you referenced - the 1 ohm resistors. (because that is what it is)

On what are you not clear? Or, what are you still asking?

[blaren]

I wasnt "berating" anyone, I'm really THAT dumb. So what I'm reading at the bias ports IS mV and I should bias as normal? 70% dissipation/plate volts (17.5/390=44.9mV). So I dont get where everyone is getting this -30V. They are measuring the "bias voltage directly"? Didnt know you could do that. How do you do that? What's the point of using the resistors then?
I hope I'm not sounding like a dick. I'm genuinely confused.

[jjman]

Expressed another way:

Bias Voltage: The negative voltage applied to the grid which is not what you generally measure or care about.

Idle current: milliamps of current going thru the tube with no signal. This is what you generally measure and always care about. One way to measure is to read the voltage drop across a resistor on the cathode. (aka "bias taps.")