jhstewart9,
(and other readers),
I am trying very hard to catch up to all the things that are going on in my life.
I do want to start posting my latest amplifiers, and the schematics for them.
So little time, and so little energy.
I will try . . .
(and other readers),
I am trying very hard to catch up to all the things that are going on in my life.
I do want to start posting my latest amplifiers, and the schematics for them.
So little time, and so little energy.
I will try . . .
Like famous 805 or 211 or 10Y , EL152 is RF power pentode. In my memory, Telefunken EL152 sounds like Telefunken EL156. Telefunken power tube has its sound signature. Actually I can upgrade my EL152 amp to EL156 amp by changing power transformer and minor modifications.
Like very rare sockets for the telefunken el156...I have them...they have twice the ra el152 has...different tube in my opinion.el152 is said to be the predecessor of gu50.
Yes I would say by now the harmonic is not so bad. A cello player and a pianist are listening to my EL152 amp with Dynaudio BM15. We have more AB listening test and tuneups to do.
You can buy EL156 sockets from China. Beware non-NOS ceramic EL152 socket, it may break the tube glass because the pin holder is too tight. MUST grinding the metal parts of sockets.
I would plan to make EL156 , F2A11 amp in the next year. Now I am assembling push pull 45 amp. As GU-50 , I may buy GU-50 amp for benchmark because it is available and not expensive.
Best Regards!
805 211 10Y are RF power triodes , EL152 is power pentode. 300B 845 are audio power triodes.
Please have a look at the datasheet's page 1. The parameter »Schirmgitterdurchgriff« is the inverse (= 1/µg2g1).
Note that LS50/EL152 etc. nothing have in common with the much more recent, post WWII EL156, besides the manufacturer, of course 😉 .
Best regards!
IMHO the "main" problem -not only the THD- is tube's enormous impedance (pentode mode), so to find appropriate OPT (150-200mA saturating current, enough large inductance) not an easy job.
Most OPT's inductance (in this range mainly not larger than 30..40H) isn't "enough" for good LF bandwidth, so optimal loading is problematic.
Sample:
The other "problem" is the relatively low B+.
This tube's anode voltage swing sooner ruins out (below 50V) if the operating point's anode voltage is 300V, so the THD relatively high even below estimated output power.
See Ale's measured curves.
https://www.bartola.co.uk/valves/2020/10/23/el152-pentode-spice-model/
If you see the curves, the suggested loadline rather 4k than 2k.
BTW the coupling capacitor with this first stage large output impedance and EL152 required grid leak resistor is LF limiting factor too, so increasing it to 0.68-1uF helps.
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Yes, SE operation always is a compromise, especially with this tube which really excels with higher plate supply voltages up to 1 kV and in class AB2. More recent tubes as e.g. the EL156 are more suitable with this respect.
Best regards!
Best regards!
Your simulation is so nice and elegant.
The output transformer primary winding is around 3000 turns and current capacity is 250mA. I tradeoff between primary inductance, primary winding and primary DCR. For the next EL152 amp I will raise OPT impedance. Low anode voltage and high current profile of EL152 are challenging in component selection. Large current causes large voltage drop in choke and OPT.
Best Regards,
Correct it. EI size 96 (96mmx86mm) , stack 45mm
Yes your simulation is right. The harmonic distortion is pretty high now. We will find pit the solution.