Tube Amp Archive

Idly thinking about the classic Fender *whatever* Reverb models and that 3.3Meg series resistor where the 'Normal' and 'Vibrato' channels are summed. I get the impression that guitarists favor the 'Vibrato' input even if they never use the reverb or vibe functions. Is that because that resistor adds...

I'm not quite seeing the path from Input to Send, and it looks like Return comes back to the Send node (red rectangle).
Then again, I'm far more comfortable reading schematics than layouts.
Hope this helps!

solderhead wrote: ↑Wed Apr 16, 2025 6:20 am On a related note, what are you using for the 1U chassis?

Something I bought off eBay:
https://www.ebay.com/itm/285760941690

It's acceptable, so far.

I almost think I'm happy with this version. The Creepage and Clearance should comply with IPC 2221B now. I did punt and will be using off-board wires for the heaters and high voltages.

honeybeeamps wrote: ↑Wed Apr 09, 2025 4:30 pm Wooow, nice build!
May I ask you where can I buy those Dralolic resistors?
Many thanks for your answer, keep it up your good work!
Mark

I promise this only looks like a wise-assed answer as a typo is likely, but try spelling it Draloric.

So I see in the schematic you are using a DC to DC high Voltage converter outputing around 300VDC. I am really curious to understand if there is any effects on the B+ vs a beafier toroid transformer that would get the secondaries up to 300VDC. Have you messed around with these DC to DC HV units bef...

Neat! An actual explanation.

It's NOT a proven design, yet, and have not ordered boards with personal funds yet. I based the circuit on the MonkeyMatic HotRodDeluxe to ODS conversion PCB - a design that's at least 12 years old. The topology is pretty constant, so changing the BOMs can shift you among BluesMaster, HRM, Skyline e...

One scheme I thought of was to measure the heater current to all the tubes. This starts out high when the power switch turns on, and reduces to a steady state when they're hot. There are chips that use Hall effect to measure current that could do this. you would read the peak then look for it to hi...

Yes, but automate that using some measurement other than just time.

Hi. I was looking at your board in PCB-Way Gerber viewer. I wanted to ask if these ( yellow arrow) are screw in terminals for the wires connections to the pre amp tubes for example. Also what are the dimensions of your preamp board? ** Hey, Guy - those are connectors with a 3.5mm pitch from the Mol...

So, since I have the luxury of space and time, if I wanted to *measure* something to tell me when to hit the HT supplies, what would I watch for? Assume I have a Raspberry Pi or Arduino set up to watch the heater current and bias supply voltage, what am I looking for? I think it would be the heater ...

Traces widened and separation improved.
BOM priced as of 28MAR25 with Mouser and other partnumbers.

You are invited to use or kibbitz if you wish.

You *can* order these from Samtec with only every other pin installed. If that helps at all.

Second pass with beefed up +12V rail (1mm/40mils).

Default traces 0.5mm (20mils).

Cheers!