KT120 "triode" and Hammond 1650N

[MelB]

No special reason to parallel I just wanted to try a single gain stage and a concertina to see how it would work driving KT120's. I started with an EF86 triode connected but there was not quite enough gain (60) so I went to the 12ax7 (100). Just thought I might as well hook them together as leave one empty. The only advantage I can see from that is 3 dB lower noise from the pair. Weather that is noticeable in this late stage I don't know. This amp can be driven by most standard "audio outs" now (1v).

wow, that's neat stereo amp 🙂

any special reason to parallel input tube ?

I think a dc cathode-follower could be 'reconfigured' to work as cathodyne phase splitter

only asking because I'm looking into that right now 😉

 

[tinitus]

... but there was not quite enough gain (60) so I went to the 12ax7 (100).

This amp can be driven by most standard "audio outs" now (1v).

I'm surpriced so much will be needed ... more things to think about ... thanks

so I may need both a concertina dc cathode follower, and a triode connected 'whatever' ... 😀

 

[MelB]

To drive it to where it just starts to clip it I'm at 0.85v input and that is giving 11.6v into a 4 ohm resistor at 1000Hz (33.6 watts)

 

[multi]

MelB.
Very good sq wave at 10K; I am just finishing an amp with the 1650T {1900 P-P} and DA42's.
Hope I get as good a sq wave at 10K.
How many Db feedback did you use?
Phil

 

[MelB]

MelB.
Very good sq wave at 10K; I am just finishing an amp with the 1650T {1900 P-P} and DA42's.
Hope I get as good a sq wave at 10K.
How many Db feedback did you use?
Phil

Zero dB of feedback. That was the whole idea of the all triode with the concertina to see how it would perform without feedback. I don't like global negative feedback.


I also ordered a couple Russian 6N6P to try.

 

[multi]

MelB
The 10K sq wave is very good with no feedback!!!!
I have over-damped speakers Altec 515B so I use very little feedback. The 515b appears to have very little bass with transistor amps or Tube amps with Lots of feedback.
Phil

 

[MelB]

Here is what I am using: JBL E140 in a 200 pound box tuned at 30 Hz. The E140 should be a very similar speaker to your Altec 515B. I'm very happy with my Bass from these things (old school).

 

[TheTubeAmper]

Here is what I am using: JBL E140 in a 200 pound box tuned at 30 Hz. The E140 should be a very similar speaker to your Altec 515B. I'm very happy with my Bass from these things (old school).

Excuse my stupidity but how in the WORLD is that box 200LBS?

And more importantly, I also wanted to say that your amp is beautiful. I especially like the colors you chose for your trafo end bells as well as those caps.

Good Work! 🙂

 

[MelB]

OK so I just love this amp so I decided to "upgrade" it. I went with a huge hammond power transformer 378CX (400-0-400 465mA) and some Tango FW-50-5 output transformers and just for fun grid chokes on all four power tubes.😱

 

[MelB]

And the new schematic. I am now getting 42.5 watts out in to 6.8 ohms.