Tube Amp Archive

Old thread but those faceplates are gorgeous! The rest of the build is top-notch too.
Update from the original poster please. Maybe final schematic, voltages, pics, satisfaction...

I like that your design has an extra node of power supply filtering compared to the original fender design. That really reduces hum and reduces the (my opinion) excess B+ in the ab764 version of the Vibrochamp. If you want power tube distortion :D you need even lower B+. To reduce the excess voltage...

I use a 5R4GYB in my DR clone with a Weber power transformer. It puts out 408 volts. A Sovtek 5AR4 puts out 458 volts.

I am very pleased with the performance using the 5R4GYB.

I am totally ignorant of oscilloscopes so take my idea with a pound of salt.
Does the output of the phase inverter stage show the same signal change? How about the stage before that??
Good luck with your brain teaser!

I used the same PT with my modified deluxe reverb. Needed to use the 125 volt primary wiring to get the heaters to 6.5 volts. I have 1 fewer premp tubes to draw current. Get 348 B+ volts with a Sovtek 5AR4. I prefer the slightly softer sound of 404 volts with a 5R4GYB and adjusted string dropping re...

Yup, I find that a CLC filter is necessary for all single ended amps when using a speaker with any bass response at all. Using only a capacitor for B+ filtering makes too much ripple (hum). Some deluxe reverb chokes are only rated for 40ma. If I was going to drive this amp HARD I would opt for the l...

That's a real dilemma. Your 100k feedback resister made for good tone but allowed too much hum. Your 1k feedback resister cancelled the hum but caused sterile tone. Neither one sounds acceptable. It seems that you have to put the 100k back in there and find the cause of the hum. I vote for removing ...

My ears hear that you have far too much negative feedback and that makes your amp too sterile. 1k feedback resistor into 5k presence pot. Try setting your adjustable feedback resistor to it's other extreme (100k) and see how it sounds. 101k into that 5k pot would be about perfect.

"White to live and black to neutral ideally" NOT IN THE USA!

Mojo's way of describing the specs is confusing to me. I "think" they mean it is a 330-0-330 at 150 ma. If I were building with 6V6GT power tubes, I would not want any higher voltage or amperage than that. I will be curious to see what others think.

I love these builds cause I had so much fun with my first one-a Newcomb record player conversion. The beginning of an addiction. The heat issue and more gain issues are complicated to answer. The amp running too hot could result from modern line voltage being higher than when the power transformer w...

That 22k negative feedback resistor is too big to allow much negative feedback. You could get a cleaner sound (if you wish) bu using the 2.7k value from the vibrochamp or princeton reverb circuit.

My very unscientific opinion is that 22uf is sufficient. I used the CLC that you have adopted and found it gave me great hum rejection and 22uf gave me sufficient reservoir for a 5881 power tube. I have removed standby switches from my builds after reading assessments by real experts here. You may f...

https://el34world.com/Forum/index.php?topic=15254.0 The Kaligstro post in the above link shows the EC VibroChamp schematic which uses a 2.2k resistor with a 47 ohm tail resistor for the feedback circuit. The 27k value in the original circuit gives the proper amount of feedback when connecting direct...