Tim Williams SE OTL amplifier questions

[Tyimo]

Hi!

Is it possible to modificate the original Parallel Cathode Follower 6DK6 OTL amp to use 6C33C tube?

Greets:
Tyimo

 

[ErikdeBest]

Yes!

 

[jhstewart9]

I recall that cct. And Tim, a teenager. He was very active on RAT, studying at home. Don't recall he ever built it. Tim often posted his brain storms, many of them not practical.


Don't know what he is doing now.

 

[ErikdeBest]

There is not much one can do wrong in such a CF design.
- provide enough clean gain. The 6C33C will have a gain of about 1/2 in CF, so for 1W in 8ohms (2,83VRMS), the driver will have to provide at least 2x2.83VRMS, say 6VRMS.
- provide enough current in the output stage. Pure class A, so the 200mA (based on the choke figure) of standing current can only swing between 0 and 400mA. Output power with 200mA is about 8ohm * 0.2 * 0.2 = 320mW. So, more 6C33Cs and a bigger choke!

 

[dhaen]

Didn't Tim post here as Sch3mat1c? or is my memory failing me?

 

[jhstewart9]

Checked Tim's handle on the search button. He was here but the last post was a few years ago. Perhaps he has a real job!

 

[TonyTecson]

the 6080. can also be used.....otoh, the 6DK6 is still a dollar a pop at Stan's ...Summer Dollar Days - Vacuum Tube Sale - $1.00 Vacuum Tubes

 

[Tyimo]

There is not much one can do wrong in such a CF design.
- provide enough clean gain. The 6C33C will have a gain of about 1/2 in CF, so for 1W in 8ohms (2,83VRMS), the driver will have to provide at least 2x2.83VRMS, say 6VRMS.
- provide enough current in the output stage. Pure class A, so the 200mA (based on the choke figure) of standing current can only swing between 0 and 400mA. Output power with 200mA is about 8ohm * 0.2 * 0.2 = 320mW. So, more 6C33Cs and a bigger choke!

So it is only usable for headphones and high Ohmic speakers.

 

[jhstewart9]

Any loadline steeper than 2 rp creates much distortion.