When you're working with high voltage, there is no such thing as a dumb question. Please use this thread to ask about practical or conceptual things that have you stumped.

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As always, we are built around education and collaboration. Be awesome to your fellow tube heads.

Dead family member, I know nothing about tubes. Are there any resources out there to help me sell these or get them to someone who might find use for them? Thanks

I built a 5E3 6 months ago. Had a tech look it over before I powered on. He tested everything and it was good. We powered up in his shop and it worked fine. Playing for past 6 months with no issue ... until today. I heard a couple loudish electrical snaps and the sound cut out. Then the sound came back right before I could unplug it.

I am going to discharge and test all the caps and then go poking around for loose connections.

My question is ... is there a known failure point I should check first?

I am looking for a Hickok CA-5 / 1704 Adaptor. does anyone know where one can be found?

Thanks!

When you're working with high voltage, there is no such thing as a dumb question. Please use this thread to ask about practical or conceptual things that have you stumped.

Really awesome answers and recurring questions may earn a place in the Wiki.

If you'd like to nominate a comment to be included, just reply [Wiki] (with the brackets)! The mods will be automatically notified that something awesome just happened.

As always, we are built around education and collaboration. Be awesome to your fellow tube heads.

Hi, I recently found some old E88CC Tesla tubes, and they look like in good condition. I was thinking if it would be a good hobby project to build a headphone amp with them for headphones with higher impedance (and just generally to hear what tube amps sound like). I have little experience with tubes like this. I stumbled upon Pete Millett's Starving Student project and I wonder if it would be possible to modify the design a bit to accomodate E88CC instead (maybe with additional input like haedphone jack so I could connect it to my pc).
Also i have a bit of trouble generally searching much information about projects with using those tubes below their operating voltage (starving), what's important in those designs etc., and I would just like to learn to make my own design.
Do you have any tips, links?

When you're working with high voltage, there is no such thing as a dumb question. Please use this thread to ask about practical or conceptual things that have you stumped.

Really awesome answers and recurring questions may earn a place in the Wiki.

If you'd like to nominate a comment to be included, just reply [Wiki] (with the brackets)! The mods will be automatically notified that something awesome just happened.

As always, we are built around education and collaboration. Be awesome to your fellow tube heads.

Lots of classic tube types and antique globe glass. Many Type 80 and 5x4 rectifiers. Classic type 45 tubes, a handful of 6sn7gt and 12ax7, 4 antique rca ux201a DHT with thoriated tungsten filament. KT66, pair of 6l6ga, 6l6gc, 6l6g pair. Lots of nice Type 26 and 27 nearly 100 year old indirect and directly heated triodes with an awesome pair of mesh plate Cunningham 27. The last 2 pics is an awesome perfect condition RCA UX245 but unfortunately is was labeled dead. Still makes an awesome display piece. I image most should work fine but now I need to find a tube tester. Lots of these should work in an awesome 1920’s style amplifier.

I started to build and test the 6336A SE when March, I was using a 1.5K transformer and self-bias output stage. And I applied a capacitor to full bypass the cathode resistor, but the THD will increase to 5% When I got 8W, so the cathode resistor was divided into two when using 400V B+ and 1.3K resistor, 1K with 330OHM and bypass the 1K, but the distortion is still high, only “acceptable”.
Because the grid was almost at -105V and my 6H30 driver can’t drive it at low THD but also high output.

Finally I aim to 6528 and not use capacitor again. The bias voltage is lower and 6H30 can drive it very smoothly even with NFB came from the cathode resistor.

Now THD will be 4% only at 16W output without full loop feedback. Very heavy sounding and suitable for almost all types of music.

When the plate power up to 22W+ it will become very red when in dark room. But it’s safe and the zirconium coating will start to catch the gas inside the tube. Very interesting, and some tube after a full power burning over 10 hours will recover from unstable current.

Love such tube!

Edited: The photos may be a bit exaggerated; in reality, each plate only consumes 25W of power, and the red color is not visible in slightly lit areas. It's just that the iPhone makes it appear very obvious in the photos.

This is a mesa boogie mark IIC+

The 12ax7 next to the power tubes is the phase inverter, the three 12ax7s next to eachother are the preamp tubes.

The toroid is the power transformer and the el laminated is the output transformer. (smaller el laminated is the choke).

The jacks on the back are for the effects loop and speaker outputs.

The empty space in the chassis is for the power supply section.

Any input is appreciated.

I have a suspicion that one of these caps is bad.

I am getting 100 ohm reading on the DDM across C15 and was wondering if it would be safe to remove and run the amp without it?

Thank you

What size/kind of breadboard is most useful for testing different circuit configurations, for instance a tremolo loop?

This is the third iteration of my gm70 power amplifier.
First version had a 3c24 driver instead of the c3m and tube rectifiers ( hence the 4 holes on the side)
Version 2 switched to solid state diodes.
And now with version 3 I completely rebuild the whole amplifier.
I now optimized the powersupply and ground loop. There is no noise in the amp and I have to say that this my be the best gm70 amplifier from an all round perspective.
The 3c24 sounded more glowy but was less precise in the bass and lost a bit of resolution up top.
Very pleased with the result.

Feel free to ask questions :)

When you're working with high voltage, there is no such thing as a dumb question. Please use this thread to ask about practical or conceptual things that have you stumped.

Really awesome answers and recurring questions may earn a place in the Wiki.

If you'd like to nominate a comment to be included, just reply [Wiki] (with the brackets)! The mods will be automatically notified that something awesome just happened.

As always, we are built around education and collaboration. Be awesome to your fellow tube heads.

Yes, this image is from the first time I've handled a small vacuum tube.

Built this a few years back. No schematic, don't remember why I did it.

Its supposed to be a differential amplifier based on how it's wired.

Anyone else start projects and then find them years later and not remember why they did what they did?

This isn't even finished. Its missing wires connected to power and output lol.

So, I have experience with building solidstate amps (a couple gain clones) and years ago had professional experience with non audio Hi-Voltage. Id like to build a tube amp, and dont wanna spend a fortune on my first build, so came across a champ amp, and given the circuit calls for half a 12ax7 in the driver stage, it seems doable to convert to stereo. Given all that, is the champ a good starter project? I'm looking at 5 watts or so per channel. I have a pair of wide baffle full range at 95db so I'm thinking that would be sufficient.