trying to educate myself on the terms and function

[yasha]

hi guys. i am trying to fully understand tube amps particularly my roadster. i have done my research and the more i read the more i am unable to understand. this is my 2nd tube amp, the first one was blackheart little giant which i never bothered about the tubes. apologize if this has been discussed before. here goes.

1. on selecting the diode and recto-tracking, i understand that the diode is basically making the amp as a ss while the recto-tracking engages the 5u4. does this means that when i switch to ss, it bypasses the 6 12ax7? i always thought that 12ax7 tubes are the ones that gives out the crunch. if this is the case, then what is the function of 12ax7 in this amp? or am i confused between a solid state rectifier and the ones on roadster?
2. i have found forumers in this forum using the term v1, v2 etc. i understand that you are referring to the position of the 12ax7s. and i saw the guys are using different combinations (eg: different brands). why would you do that? any function in each position?
3. when switching to recto-tracking on channel 3 and 4, i am experiencing volume drops. is that normal?
4. what will affect if i change the preamp tubes and the power tubes?

bear in mind that i am sub consciously comparing the roadster with my little giant because that is all that i ever owned. i am still searching for a good website to continue my reading. appreciate if you guys can recommend a very very good website for me. thanks in advance.

 

[dylan7620]

1. It doesn't turn into a solid state amp. Only the rectification is diode. All you're 12ax7s and 6L6s are getting used.
2. Yes, V1 and V2 are different positions, different positions affect different parts of the amp. Anything from your gain channel to your reverb. Different brands have different sounds.
4. Changing the preamp tubes will change some of the core sound of the amp, this is where most of your tone shaping comes from. the poweramp is where the heavy lifting goes on, changing these won't affect quite as much unless you put in drastically different rated tubes. It makes more of a difference at higher volumes.

 

[screamingdaisy]

1. on selecting the diode and recto-tracking, i understand that the diode is basically making the amp as a ss while the recto-tracking engages the 5u4. does this means that when i switch to ss, it bypasses the 6 12ax7? i always thought that 12ax7 tubes are the ones that gives out the crunch. if this is the case, then what is the function of 12ax7 in this amp? or am i confused between a solid state rectifier and the ones on roadster?

The 'rectifier' is part of the power supply. It converts AC (alternating current) into DC (direct current). The solid state rectifier is efficient, thus your amp has more power fed to it. This makes the amp sound tighter and bolder. The tube rectifier is inefficient. This means that when you play notes the amp momentarily draws more power than the tube rectifier can provide. This creates 'sag', or a slightly squishy feel to the note.

The rectifier is only a power supply. Switching modes (tube/diode) has nothing to do with any other part of the amp.

2. i have found forumers in this forum using the term v1, v2 etc. i understand that you are referring to the position of the 12ax7s. and i saw the guys are using different combinations (eg: different brands). why would you do that? any function in each position?

Different brands have different tonal characteristics. Some are brighter, some darker. Some have more gain, some have less. It's basically fine tuning the preamp.

3. when switching to recto-tracking on channel 3 and 4, i am experiencing volume drops. is that normal?

Yes. Using the tube rectifier drops the power output from 100w down to around 70w or 80w.

4. what will affect if i change the preamp tubes and the power tubes?

A slight change in the final tone. To some it's a big deal, to others it's not. At the end of the day it'll still sound like a Rectifier.

 

[yasha]

thanks guys! i might have over complicated things...

on question no 2, is there any way i can know what is the function of each position? say i would like to have better reverb, what should i do?

 

[screamingdaisy]

thanks guys! i might have over complicated things...

on question no 2, is there any way i can know what is the function of each position? say i would like to have better reverb, what should i do?

It's in your amp's manual.

 

[MrMarkIII]

thanks guys! i might have over complicated things...

on question no 2, is there any way i can know what is the function of each position? say i would like to have better reverb, what should i do?

It's in your amp's manual.

Downloadable at Mesa's website. But get the Road King manual, the Roadster won't have the Tube Tasking Chart. It's Page 43. Reverb is V4.
Here:
http://www.mesaboogie.com/manuals/RoadKing2_v2.pdf

 

[Rocker]

Hi,

A couple of things. The recto tracking function is supposed to work like this: If you are using the 50 watt setting, and put the recto switch to the recto tracking position, you'll get the tubes. If you want the diodes, you need to move the retco switch to diodes. If you switch to 100 watts, you will always get diodes, no matter what position the recto switch is in. That's the 'tracking' part -- the amp automatically engages the diodes when you switch to 100 watts if it is set to the tracking position.

When I was learning about the pre-amp tubes, it wasn't clear to me which was which. V1 is the first gain stage for all channels, and is the most important. It's neatly tucked way behind the preamp power supply in my 2X12, right behind the guitar chord jack. It is an absolute PITA to get at , and once you get into trying different tubes, you'll be switching this one a lot. I don't know WTF Mesa was thinking about when they designed this thing. The others are in order (V2, V3, V4, etc) as you move to the left when looking at the rear of the unit. I think that the head unit is the same, but the whole thing is flipped upside down as you look at the back of the amp (?).

Good luck learning about your Roadster -- it is a living and breathing beast that can generate magical sounds with the right preamp tubes. I strongly prefer late 40's / early to mid 50's vintage RCA long black plate 12AX7's with the D-shaped getter in V1 with an RFT in V2. Seems to be a very strong combination, and I've tried them all. (lol) Telefunken smooth plates are also very nice in the V1 slot. Mullards are great for the clean channels, but if you like distortion with good character, the RCAs are better, and they are also very good in the clean modes -- I can't tell the difference compared to Mullards.

Later!

 

[domct203]

A couple of things. The recto tracking function is supposed to work like this: If you are using the 50 watt setting, and put the recto switch to the recto tracking position, you'll get the tubes. If you want the diodes, you need to move the retco switch to diodes. If you switch to 100 watts, you will always get diodes, no matter what position the recto switch is in. That's the 'tracking' part -- the amp automatically engages the diodes when you switch to 100 watts if it is set to the tracking position.

That is not how it works for the Roadster. You can select Diode or Tube rectifier regardless of output power setting. When in 50W, Recto Tracking selects one 5U4GB. When in 100W, Recto Tracking selects two 5U4GB's. When in Diode, it does not matter what the output power setting is.

Dom

 

[yasha]

thanks guys! i might have over complicated things...

on question no 2, is there any way i can know what is the function of each position? say i would like to have better reverb, what should i do?

It's in your amp's manual.

Downloadable at Mesa's website. But get the Road King manual, the Roadster won't have the Tube Tasking Chart. It's Page 43. Reverb is V4.
Here:
http://www.mesaboogie.com/manuals/RoadKing2_v2.pdf

thank you for that...i have been flipping the manual the whole night figuring out where the hell is the function of each position...

Hi,

Good luck learning about your Roadster -- it is a living and breathing beast that can generate magical sounds with the right preamp tubes. I strongly prefer late 40's / early to mid 50's vintage RCA long black plate 12AX7's with the D-shaped getter in V1 with an RFT in V2. Seems to be a very strong combination, and I've tried them all. (lol) Telefunken smooth plates are also very nice in the V1 slot. Mullards are great for the clean channels, but if you like distortion with good character, the RCAs are better, and they are also very good in the clean modes -- I can't tell the difference compared to Mullards.

just to make it clearer to me, when you changed the preamp tubes, did you biased them? in the manuals i am only seeing the term "matched set of MESA tubes" which to me refers to the power tubes. can i just swap the tubes as it is?

A couple of things. The recto tracking function is supposed to work like this: If you are using the 50 watt setting, and put the recto switch to the recto tracking position, you'll get the tubes. If you want the diodes, you need to move the retco switch to diodes. If you switch to 100 watts, you will always get diodes, no matter what position the recto switch is in. That's the 'tracking' part -- the amp automatically engages the diodes when you switch to 100 watts if it is set to the tracking position.

That is not how it works for the Roadster. You can select Diode or Tube rectifier regardless of output power setting. When in 50W, Recto Tracking selects one 5U4GB. When in 100W, Recto Tracking selects two 5U4GB's. When in Diode, it does not matter what the output power setting is.

Dom

thanks dom. i think i read it somewhere where it supposed to be like that. in 50w, one 5u4 and in 100w, two 5u4. but in the manual it says "engages the 5u4 rectifier tube automatically whenever 50w selection is made via the channel power select switch. when switching channels-if the channel power select is set to 100 watts, the diodes are automatically engaged to insure proper matching to the added load supply". maybe this is what rocker was referring to. but how do we relate this sentence from the manual to what you have said previously?

just to share, i am currently using 50w on all channels. channel 1 & 2 using the recto-tracking for my clean channels and channel 3 & 4 using the diodes for more crunch. i must say channel 4 is really hard to get use to.

thanks a lot guys! hope the above are not considered as stupid questions. :lol:

 

[screamingdaisy]

just to make it clearer to me, when you changed the preamp tubes, did you biased them? in the manuals i am only seeing the term "matched set of MESA tubes" which to me refers to the power tubes. can i just swap the tubes as it is?

Preamp tubes don't need to be biased.

 

[domct203]

thanks dom. i think i read it somewhere where it supposed to be like that. in 50w, one 5u4 and in 100w, two 5u4. but in the manual it says "engages the 5u4 rectifier tube automatically whenever 50w selection is made via the channel power select switch. when switching channels-if the channel power select is set to 100 watts, the diodes are automatically engaged to insure proper matching to the added load supply". maybe this is what rocker was referring to. but how do we relate this sentence from the manual to what you have said previously?

I see where the manual can be somewhat misleading:

I have taken bias measurements at 100W in both diode and tube rectifier and can see the plate voltage and cathode current drop when switched from diode to tube. The only thing Recto-Tracking automaticly selects is the number of 5U4GB's relative to power output. If the Roadster is set on diode, it's using diodes.

Dom

 

[yasha]

screamingdaisy: thank you sir.
Dom: after checking the hardcopy and the softcopy, found out that its 2 different sentence. thanks!

 

[Rocker]

Hi again,

"I have taken bias measurements at 100W in both diode and tube rectifier and can see the plate voltage and cathode current drop when switched from diode to tube. The only thing Recto-Tracking automaticly selects is the number of 5U4GB's relative to power output. If the Roadster is set on diode, it's using diodes."

I stand absolutely corrected! I mis-read the manual, and thanks guys for straightening me out!