ETI Hybrid EL34 amplifier

[soundbrigade]

I am a bit disappointed that you left your original idea. When the jornal came out I was almost prepared to try that design and I am even today ready to try it.

There may be an EL34 project in the pipeline w2ith some leftovers (trannies), but I have to be a bit ON- and, now OFF-topic by sharing another hybrid amp.

 

[KatieandDad]

I'm looking at some component value tweaks that help stabilise the simulation. Dropping the value of C12/C13 from 220uF to 25uF appears to have a fairly substantial effect on it's own. Increasing C9 to 220nF appears to also help. Removing C4 & C5 on the cathode of EF86 in combination with the above appears to virtually remove the LF peak. (down to just under a 1dB rise)

Unfortunately it's not an easy job to get at the solder side of the PCB.

C12/13 are only 47uF not 220uF

 

[KatieandDad]

One thing I am going to try is to reduce the B+ down to 450V.

I'm just going to add 200R 50W resistor in series with B+ between the reservoir caps to make CRC.

Each amplifier should draw approximately 125mA.

 

[KatieandDad]

I'm still waiting for the schematics for my alternative PCB.

I'm guessing that the EL34 version of the Williamson 5-20 will also use B+ @ 450V.

What would the B+ be with KT88s ?

It might be easier to use the hotter tubes.

 

[KatieandDad]

The PCB and its schematics allow for variations in tubes.

EL34 should give about 40W

KT88 about 60W

There is also provision for KT99 and KT100 but they are rare.

 

[KatieandDad]

I'm going to start a new thread for the new build.

 

[KatieandDad]

The new thread is here - https://www.diyaudio.com/forums/tubes-valves/368756-williamson-5-20-40w-build.html#post6556625