Parallel output tubes

[drj759]

Nothing special then but 1626 plate resistance possibly lower than what you calculated as 6080 is actually 250.

I went back and checked my original Darling notes and I used a rp of 1700 ohms in my calculations. Seemed to work out with the voltages that I measured. I used the RCA data sheet for the 2400 ohms that I calculated yesterday. I found that the tung-sol data sheet at franks tube data site listed the 1626 rp as 2500 ohms (both 1625 and 1626 are listed on the same data sheet). I'm not sure how the data for Class C operation in the RCA data sheets changes for Class A.

http://www.mif.pg.gda.pl/homepages/frank/sheets/127/1/1625.pdf

My calculation on the 6080 did seem a bit high for that low of mu. I should have known better. My haste. I probably need to be more careful for what I put forward on the web.

There's a 7236 set on my short list which I expect to confirm that very low plate resistance coupled to an opt with much too high Zout (4k) is one recipe for impressive low-end.

I'm not familliar with the 7236. You might want to take a look at pages 557 and 558 of RDH4. Figure 13.14 illustrates the effect on power output and distortion versus plate load for a 45 triode. Principles should be the same for other triodes.

Dave

 

[drj759]

Simon,

I finally had a chance look up the 7236. I think I understand a bit more your direction with the 7236 but I am curious how that relates to the information in RDH4 I referenced in my previous post. Again, just me trying to understand the concepts. Thanks.

Dave

 

[Klimon]

I found that the tung-sol data sheet at franks tube data site listed the 1626 rp as 2500 ohms

Thanks, so roughly the same as my triode-strapped el84s

My calculation on the 6080 did seem a bit high for that low of mu. I should have known better. My haste. I probably need to be more careful for what I put forward on the web.

that's okay

but I am curious how that relates to the information in RDH4 I referenced in my previous post

I checked the link but I'm not sure the explanation can be found in the relationship between harmonic distortion and plate load. I think the good bass of the 6080 family (with high 4-5k load like I tried, maybe also with more conventional 1-2k load) has more to do with damping factor. I'm intellectually very lazy (and more pragmatic than engineer) but will search for the technical explanation... will check back later

Simon