300B driving 845

[deafbykhorns]

The LL1671 can be configured for 1:1 and is rated for 30ma, its 35H which is fine.
See the plot at 35H on the 300b

 

[wredny]

Do you think 30mA is enough for 300B? I can order ll1671 gapped for 40, 50, 60 and 65mA. I think it 30mA is more than enough for occasional A2, but I've read somewhere on this forum that 300b sound better biased with higher current.

 

[deafbykhorns]

I'm guessing at 60ma, you might have around 10HHere's a plot, not ideal but acceptable. I had the Hammond at 25ma and was fine. I would split the difference and use either 40 or 50ma. I'm running mine at 44ma.

 

[wredny]

I was aiming at 50mA version, seems like that's the one Mr. Ciuffoli used in his first 845 project: the 845 Single Ended Amplifier

I asked manufacturer about parameters list for 50mA version, but they're shut down for another two weeks due to summer break, so I guess I just have to wait...

 

[hpeter]

300b+845 looks good, but having two great toobz at once .. like making cake with too much sugar in it. 😀

(ll1671 in 1:2 --- that would give good gain though..if you aiming for class a1)

i use similar ll1660 with primaries in serial/parallel, no problems .

 

[wredny]

It's not like I have a choice. As I stated in one of the posts above, I already bought an amp containing those tubes capacitor coupled and now I'm just trying to make it work as it supposed to 😉.

My speakers are 90db so occasional a2 would be handy, and that's why I'm looking at 1:1 interstages.

I got 410V on plate, minus about 70-75V for cathode bias, minus 10-15V drop on IS gives me operating point around 325V and about 500Vp-p with 1:1 interstage. Do you think that's not enough to drive 845 properly or my math is wrong?

 

[hpeter]

oh, ok then go for it.

you can see if your theory is ok : Triode / Pentode Loadline Simulator v.1.0 (20161216 www.trioda.com) but 500vpp should be plenty

 

[wredny]

Thank for reply. I know that triode/pentode simulator but still have to figure out how to use it for inductive load.