• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Photo Gallery

Nice compact 6C33C amp
 

Attachments

  • DSC03373_resize.jpg
    DSC03373_resize.jpg
    348.2 KB · Views: 803
  • DSC03375_resize.jpg
    DSC03375_resize.jpg
    193.1 KB · Views: 832
  • DSC03377_resize.jpg
    DSC03377_resize.jpg
    322.2 KB · Views: 797
Finished my new tube buffer. Aikido cathode follower PCB from GlassWare Audio Design formed the base for this build.
Tortuga Audio ePotV3 Mini with LDR module and apple remote is in charge of attenuation and is doing a great Job. Unlike the S....C.... LDR, the Tortuga has left/right balance as well and it is small enough to fit into the same enclosure. Build quality is of the highest standard. Input impedance can be selected upon ordering which is a bonus.
So far the buffer is doing a great job, is quiet and sounding very musical indeed.
 

Attachments

  • Tube buffer inside.jpg
    Tube buffer inside.jpg
    992.5 KB · Views: 661
  • 20210607_100606.jpg
    20210607_100606.jpg
    809.4 KB · Views: 643
  • 20210607_100441.jpg
    20210607_100441.jpg
    783 KB · Views: 400
Could you give the achieved technical characteristics of your amplifier and especially the harmonic spectrum? I also want to implement a similar project on the same lamps. Please provide the characteristics of the interstage transformer.
Thank you in advance and wish you continued success.

I have yet to do distortion analysis, will post this later.
As to the amp itself:
- B+ is 220V after CRCRC, custom made power transformers
- drivers are 6J52P biased by 3 SiC diodes in the cathode, at 23mA or so
- 6C33C is on fixed bias via Pete Millett's regulators
I am running only half of 6C33C's heaters, don't ask how I ordered wrong transformers. I might try to stress the trafos for full heater current later, and/or I plan to try 6C41C's for outputs
- Signal transformers are from Silk Audio, IT's are I-511S, OPT's are S-1-6C33
Case mostly ordered from Rapiddirect
All in all very simple. I only had to go though a few 6J52P's to get a non microphonic loosely matched pair
 
6SJ7 drivers with Zener regulated screens. 6BG6 single ended pentode. Power tube screen and driver tube voltages are regulated by VR tubes and MOSFET follower. 10% shunt feedback, a little GNFB. This is not Hi-Fi. It's Fun-Fi! I also had to stuff the biggest coupling capacitor I could in there.

attachment.php


attachment.php


attachment.php
 

Attachments

  • Amp.jpg
    Amp.jpg
    525.3 KB · Views: 1,556
  • Glow.jpg
    Glow.jpg
    521.4 KB · Views: 1,570
  • Guts.jpg
    Guts.jpg
    836.6 KB · Views: 1,064
Last edited:
Possibly OC3.

At closer look, the purple is on the outside glass, but the inside glow is closer to amber (?) than to purple.

So many different type gas regulator tubes; so few amplifiers and so little time.

OC3 also seems to be the perfect regulator for the 717A pentode.
I have a pair of those 717A pentodes.
 
Last edited: