Mind blown!

[Wally]

Okay…Editted. I should wake up and read everything carefully before posting!! LOL….
the tube is cleaner than the transistor. so, do you have a ‘scope of the tube to compare the numbers?

 

[dougsta]

Okay…Editted. I should wake up and read everything carefully before posting!! LOL….
the tube is cleaner than the transistor. so, do you have a ‘scope of the tube to compare the numbers?

The solid state in the PI socket does seem a bit louder.

For the scope view and voltages, I'd say the test conditions were on the conservative side for a guitar amp.
I've just tried a EH 12AX7 vs the solid state 12ax-fake-7 in socket 1 of the JCA22H on the crunch and OD channels. V1 always feeds both channels.
The solid state has a lot more gain, hard to keep it on the edge of breakup, maybe more like running into a tube screamer (I never use em) 1st.
Will process the video recordings an upload them later

 

[dougsta]

Okay…Editted. I should wake up and read everything carefully before posting!! LOL….
the tube is cleaner than the transistor. so, do you have a ‘scope of the tube to compare the numbers?

I'll run the real 12AX7 and 12AU7 in the same test circuit...

 

[Wally]

Okay, I missed the Jet City info back on page 1. Duh…on me again. I was thinking…not much, evidently…that we were dealing with a 12AT7 PI tube. The 12AU7 might be too little gain. One wonders what a 12AT7 is like?

 

[dougsta]

Here's the voltages for the EH 12ax7, Brimar 12AU7 (1950's seems ok) and the 12AX-fake-7

HT = 200v - 100KΩ load resistor - 2.2KΩ Cathode resistor - 0.022µF coupling cap - 47KΩ Grid stopper - 12Vdc heater

EH 12AX7
Anode v drop = 56.9
cathode v drop = 1.22

Brimar 12AU7
Anode v drop = 108
cathode v drop = 2.38

12ax-fake-7
Anode v drop = 38
cathode v drop = 0.823

The JCA22H (Soldano designed) was my 1st 20W amp, cheap but no clean channel. I normally run an old RCA 12AU7 in V1, 12AX7's in V2,3,4 and a 12AU7 in V5, also modded it with a switch to tame V1 by paralleling in another 200KΩ load resistor. I've also put some PL83 output tubes in (a bit like a 9W EL84 with 15v heaters tho runs on 12v cathode starved for a nice sound too) and wound an OT for it too.

 

[dougsta]

And the scope photos.

 

[dougsta]

Next I'd like to test them at guitar amp 'gain' and observe the sine wave distortion.

 

[Wally]

Your little transistor ‘tube’ is hot, eh?

 

[dougsta]

Your little transistor ‘tube’ is hot, eh?

Am reckonin' at least a 5 alarm!

 

[gusfinley]

I bought a few of these LND150 when I found out Vox was using them for Trem circuits in their Custom Classic series of amps.

I pulled the preamp tube out of a champ-type amp and just shoved the LND150s into the tube socket. I've got a picture of that somewhere....

It worked! It didn't sound great, but it worked. I put the 12AX7 back in...

It looks like I tried it in an 18W build, too.

These are some great experiments!

 

[wangdaning]

You guys are heathens running from the power of the tube. Jk, carry on. I mean we always knew it would "work" right?

 

[dougsta]

Here's another one I made for a small 15W push-pull amp, this time 'stuffed' into an old can capacitor.

The donor cap was a nice size to fit in the base and even the retaining clip, Grundig brand from the 50's and dry inside.
I added heat-shrink around the leads in case of shorting to the can.