TubeStore Winged C's in HRG C+

[mreeve25]

I ordered a quad of SED Winged C's from the TubeStore.

I specifically told them the tubes were for a Mesa Boogie Mark IIC+ 60/100 w/ 105pt.

They said ok, and then they were shipped out. They will be delivered today.

How many MA would be appropriate for these tubes, for this amp for optimal tone and longevity?

Thanks.

 

[adonixx]

I tested bunch of tubes on my HRG C+ with 100PT:

Here are results (values are for each tube):

SED =C= 6L6 x2 rated "21" 16.9mA \ 18.6mA
SYLVANIA 6L6GC STR415 x2 (pair #1) 22.1mA \ 23.6mA
SYLVANIA 6L6GC STR415 x2 (pair #2) 25.6mA \ 35.6mA
Phillips 7581A x2 (pair #1) 28.0mA \ 28.4mA
Phillips 7581A x2 (pair #2) 26.7mA \ 26.3mA
Mesa 6L6 STR440 Green x2 23.4mA \ 24.1mA

 

[swbo101]

Nice....would you have any values for SED =C= EL34's?

 

[zodiac272]

Mike B. said they should be in the mid/high 20's mA to low/mid 30's mA. Think that's at about 400 Vplate, not sure the resistance. The lower end of the range will last longer cause they aren't pushing as hard. Just check them from time to time, make sure they aren't going nuclear.

scott

 

[mreeve25]

Well...I got the tubes today.

They are all matched at 22MA.

That is too low for my HRG C+ w/ 105pt correct?

 

[adonixx]

Well...I got the tubes today.

They are all matched at 22MA.

That is too low for my HRG C+ w/ 105pt correct?

You mean they are "22" rating from Tubedepot?

Anyways, if they read 22mA on 105pt, that means that each pair draws 44mA

My understanding of formula is: (30W/485v)*70%=0.043*1000=43mA

So you should be at ~70% MPD with those tubes.

 

[mreeve25]

Yeah, that is what I meant, :lol:

So these should be good then right?

 

[swbo101]

You mean they are "22" rating from Tubedepot?

Anyways, if they read 22mA on 105pt, that means that each pair draws 44mA

My understanding of formula is: (30W/485v)*70%=0.043*1000=43mA

So you should be at ~70% MPD with those tubes.

I just want to make sure I understand the formular..not to hijack your thread...

30W = is this the wattage of the tube? and if so I should be able to get that info where? spec sheet?
485v = is this the plate voltage of the amp?

thanks...most helpful information!

 

[zodiac272]

That formula looks good, to determine the plate current, and you are getting 43mA or so and splitting that across two tubes to get 22 mA each... My question is why don't you use 60 watts for the equation since you are calculating two tubes plate current.

Scott

 

[mreeve25]

Scott,

This is how I am setting up the preamp tubes:

V1: RFT
V2: Sovtek
V3: RFT
V4: Sovtek
V5: Sovtek

I will likely buy something better for V5 when I get a chance. A tungsram came w/ the amp that I could use, looks in good condition, but I do not have a way to test it.

 

[zodiac272]

That looks like a good preamp lineup... It will sound great... Maybe A/B with that tunsgram in there somewhere, maybe V1, and put the RFT's in 2 and 3. When you send it in to Mesa, they can test any tubes for you, and Mike can tell you if you are getting the most dB gain out of it.

Scott

 

[adonixx]

That formula looks good, to determine the plate current, and you are getting 43mA or so and splitting that across two tubes to get 22 mA each... My question is why don't you use 60 watts for the equation since you are calculating two tubes plate current.

Scott

Actually that is something i was trying to research myself. People constantly use this or a similar formula but never really clarify if the result is for pair of tubes or each tube.

From my understanding, each tube has full voltage applied to, in this case 485v or so. Thats why i divide 30w/485v. So when 485v is applied to each 30w tube, there is current flow flow of 43mA.

I am still not expert in Boogie amps, but i think that tube in pairs are connected in parallel so:
In a parallel connection: Current gets distributed over components connected in parallel. Voltages are the same across all components connected in parallel.

In this case, the current flow is 43mA, or when distributed each tube draws 21.5mA

 

[zodiac272]

Ok cool, thanks...

Yes it seems that how they were wired together answers that, so it would depend if they are wired in serial or parallel...

Scott

 

[JOEY B.]

This webpage http://www.webervst.com/tubes1/calcbias.htm will do automatic bias calculations, as well as a bias table for various power tubes. There is no mention of the tubes being wired in pairs, just the current draw per tube. Furthermore, if the said Tube Depot =C= tubes were measured at anything other than the stock plate and bias voltage of the 105 PT C+(485 plate and -52 bias), then the 22 number is meaningless. Any variance of either the plate or bias voltage will cause the current draw to move, sometimes to the extent of the tubes not being matched. The best bet might be to send the tubes to MESA with the RA #, and have Mike check them in the amp on his bench. 8)