The Amp Garage

And putting the first filter cap, on the front side of the choke, back in the circuit confirmed that! Back up to 500 volts at that stage.

Thanks xtian!

Joe

I'm just checking the high voltage power power supply on a tube tester that's been my project for awhile. I've found that I'm losing about 12 volts off a 500 volt supply across a choke with no load on the supply. For testing purposes, I've isolated the stage such that the rectifying diodes feed stra...

I'm trying to measure some low level AC currents and getting unexpected results. Don't know if this is the measurements themselves or incomplete understanding of ohm's law on my part, at least in terms of passive circuits. 2 examples: 1. I tried to measure heater current in a 12au7, which would be a...

A friend of mine just built this kit. I brought it up for him on the variac when it was first finished and was blown away by the overdrive channel at low volume. The amp really does just as advertised. I'm a blackface guy, but if I was after something to get me into creamy tube overdrive at a low vo...

Howdy, I was nearing completion on my homebrew tube tester when I was treated to 2 nice pops, each of which took out 2 panel meters, a transistor, and a zener diode. I've attached what I hope is the info necessary to diagnose what might have went wrong. I think I have some rough ideas. In a nutshell...

Here is a sketch. It's a negative bias supply. Measuring from ground to point 1 is about -25v and ground to point 2 is about -23. I think I understand what's going on, i.e. the meter pulling current through the resistor as with the meter connected to point 2 there is 2 volts across the resistor as m...

I'm finishing up a home brew tube tester I've been working on for awhile. The "gas"/grid current check will place resistance in series with the grid circuit and look at effect on plate current, which I understand is a standard way to do this. In testing this concept, I soldered a 1 meg resistor to t...

rp, (or anyone), can you recommend a DAC for about $100? I tried the Dragonfly, made sure it was the one designed for computers and not mobile devices, and it was literally like throwing a blanket over my speaker when compared with the stock sound card in my budget friendly office depot laptop. Afte...

I do. I'm going to wire it up again tonight or tomorrow night, let it sit for a while, and take the temp.

Thanks as always!

Joe

I just picked up a Hammond 100-watt, 500ma filament transformer for use as a wide varying negative bias supply in a tube tester I'm building. I was proto-boarding the bias circuit earlier, and I noticed when I was taking things down, the transformer was slightly but noticeably warm, despite the fact...

This is a timely thread for me. At 40, and a lifelong music lover, I've just scratched the surface of hi-fi with a Mullard 3-3 build I got a good deal of help with here a few months back. I'm just running it with a $60.00 Fostex full range driver in a bass reflex bookshelf cabinet setup and it's jus...

I've been delving deeper into all things tube and am noticing that that prices on some of the 7-pin "versions" of our favorite preamp tubes are often much cheaper than the 9-pins, including NOS Mullard, etc. Long story short, would 2 mullard 6AV6/EBC91's be equal or near to 1 Mullard ECC83/12AX7 reg...

I'm working up a tube tester design that will use real-world voltages. I'd like to have a pretty wide sweep on the negative bias supply and about .5 volts to 90 or so volts negative is what I've settled on. The following is what I've come up with. My main intent is to get the desired range without e...

I'm working up a design for a multi-function tube tester/power-supply/cap leakage tester. At the core would be a tube-amp-like power supply and 2 Hall amp style VVRs. The inputs to the VVRs would actually be shrouded banana plugs that could connect to the different nodes in the power supply and the ...

No, to make the h-k leakage measurement a voltage potential has to be included in a series loop including the h-k pins. If one wanted to do this outside the context of the u-tracer, could the heater windings come from the same PT secondary as the voltage potential in series with the h-k loop provid...