If I eq a single coil guitar so that it's gain and frequency reponse resemble that of a humbucker guitar I get some of the basic characteristics of earlier breakup, more compression, darker tone, etc. I know an eq will never clone the tone of two guitars but if I take out the eq and gain factors, I'm left with the difference in impedance.

1. Is there any effect of the impedance on the final sound, response or feel? (or anything else im not aware of)
2. If there is, how do buffers play into this since they turn the signal into low impedance?

I have an old philips 17tx140a with all miniwat tubes (so no american stuff) but it recently broke when i turn it on it does everything it should except make static sound and display static on the screen when i turn it off the display displays static while warming down and it slowly disapears i have asked some profesionals but they didnt get it farther so if anybody knows how to fix this please comment

*Torched

I think I know the answer to my question but throwing it out there anyway.

I have a pair of output transformers for a Dynaco- ST35 (EL84, PP, UL 23%) clone project that I think I might have torched.

No voltage sag when applied across the secondary so I think that side is fine. However, there are big resistance discrepancies between the two OPTs when measuring resistance between the plate and the UL leads.

OPT 1

Plate 1 > UL 1 - 164.4 ohm

Plate 2 > UL 2 - 177.7 ohm

OPT 2

Plate 1 > UL 1 - 109.3 ohm

Plate 2 > UL 2 - 95.6 ohm

I'm thinking that's real bad and a fatal diagnosis.

I have a second set of OPTs from a different source that are fresh from the box. These have a 25% winding on the UL. The resistances are almost dead-on.

OPT 1

Plate 1 > UL 1 - 125 ohm

Plate 2 > UL 2 - 115 ohm

OPT 2

Plate 1 > UL 1 - 124.8 ohm

Plate 2 > UL 2 - 114.5 ohm

The first pair is toast, isn't it?

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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Check out the Harley Benton 15 Tube Head from Thomann in Germany, which is also known as Monoprice, etc. They've messed it up. The gain dual pot is swapped! If this is supposed to be a Laney Cub 12R (the build components are 100% identical), they've completely reversed the 100k and 1meg pots. For anyone wondering why the amp has such limited headroom and why there are these insane volume jumps when adjusting the gain—well... now you know.

If anyone wants to check on their device, I'd be interested to know—Is the head different from the combo? I also have a suspicion that the combo and head have different output transformers (OT).

9 months ago while pulling a 12DW7 out of a chassis, it loosened quickly, my hand shot up, and the tube made one distinct clink. I searched for hours and never found it. Fast forward a 8 months and things got moved around in the basement. Today, while finally putting the drums back in place, there this little Yugoslavian 12DW7 was lightly clinging to a cymbal stand.

Hi, I am fairly new to building tube audio amps, for my next project I decided to try to make a high quality tube amp that has outputs for speakers(and able to drive higher power ones), low impedance headphones and high impedance headphones(like the koss pro4aaa and similar headphones). I use the Cranberry TwoC as a base design and I want to modify it maybe add another output transformer which I can change out with a switch or design my own transformer for options to handle the high impedance headphone. Can you help me what the best course of action is to modify this design? Is it a good design to build upon for such a purpose? Thank you for your help.

This is the schematic I want to build upon and modify

Hello, I’m building a preamp using a UTC LS-50 Transformer in a parafeed configuration. The LS-50 cannot run DC current so I have a choke on the plate of a 10Y triode and a capacitor to the plate connection on the LS-50. What value do I need for this capacitor?

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.

After three monts from the last post where i presented to you this project i can finally share with you this project. This build is part of my Bachelor's degree thesis so i couldn't share it before.

In this post i will share:

• Italian Thesis Available at this link to see the process to reach this result
• Gerber files to build your own pcb
• Schematic to remix the project as you wish [Credit if you share please] (Please tag me if you significantly improve the design, to improve even my prototype)

The schematic and gerber are available for free in Easy Eda editor, OSHWlab: open in EasyEDA project

The amplifier is fully working, with common USB-C trigger board as powe source, drawing 28W, and giving an output of almost 0.12W, not so good, but pretty good to listen to.

The tubes involved in this project are: 12FM6, 12DV7 for the pre-amp stage and 12DL8, space-charge tube on the output.

Few tweaks can be, done and i'll improve the design further in the future, the first thing is for sure adding a global feedback to improve bandwith at least till 20 Hz, since now the frequency response is 150 Hz - 40 kHz

The Output transformer need an impedance of 800 ohms, i used a pa OT line transformer at rating 100V and 15W taping, so i have a 667 ohms impedance, the best i could find in italy.

The circuit is rated for maximum 6 Amps, by trace calculations and clearance drc on PCB.

Contact me or Comment if you need more info.

Photos and Videos are available on OSHWLab!

Thanks again to Sergey Engel and u/2748seiceps for trubleshooting and advices.

NOT FOR COMMERCIAL USE

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.

Sitting on a box of tubes. Open to suggestions on what to build.

Assuming that I want to use the miller capacitance of a 12AX7 to make a low pass filter with 20kHz cutoff frequency, that means I’ll have a 40k ohm resistor with a 200pF miller capacitance approximately.

Now, if I have a passive guitar that has a 20k ohm output impedance, does that mean that my actual filter shall consider that impedance too? If so, my grid stopper would be 60k, and my cutoff frequency would go down to about 13.2 kHz.

Is that how it works?

Sorry for the dumb question.

Just wanted to share this beauty I scored today, a Neuberger WE238 tube tester, made in Berlin, Germany ca 1930.

Cosmetic condition is almost like new. Electrically I have not tested it yet.

I had given up on getting myself a tube tester due to their prices. But I kept an eye open both here and there and I could finally purchase this one for an almost unbelievable $30. (The seller knows exactly what it is and had set the price as a part of a bigger clearance.)

Even if it would be completely fried in the inside it is well worth its price as a workshop decoration. But I fully expect it to be as well kept on the inside as on the exterior. I'm really looking forward to the restoration!

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.

Anybody have any thoughts on this PCB that includes Gillespie's EFB enhancement and eliminates the single 7247 per channel and swaps in a 12ax7 and 12au7 sharing duties?

Link to eBay listing - Dyna St-35 clone

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 all,

I run 100s of dual triode tubes through the Project Ember headphone amp I have to listen for microphonics, general quality, noise, etc. That is a lot of wear and tear on the socket. I had to fix a broken socket pin recently, but it got me wondering if there are any lever-based sockets that are similar to a pin based CPU socket. Anyone ever see something like that?

Here’s the latest iteration of my PP KT88 Stereo Power-Amplifier. See what you think.

i am an electronics grad,very new to the vacuum tube audio! (Enthusiast,) Currently reading books about designing vacuum tube amps.. I am serious about getting into designing tube amps! But so far accomplished fever amp diy kit. I know tubes are voltage driven,if the secondary windings of the OPTs is wound with very less power rating ,would that be safe to drive the low impedance loads??! Need guidance! Thank you 😊

I'm restoring this receiver. The mica caps in the tuner look like a ceramic coin and are filled in the bottom with a paste. The paste has unfortunately cracked revealing the metal wafer underneath. My first thought was to just toss them out and replace but 616pF isn't gonna be an easy match. I'm aware RF isn't you guyses speciality but I would just like a second opinion. Is there even any point in trying to fill it back in with silicon or epoxy, or even leaving it exposed as is. I'm thankful for any thoughts. 😊

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.