Tube Amp Archive

I see the "Too Many Requests" error frequently. Also, the site logs me off and then says I entered the wrong password when I try to log on.

Economics also dictates that very seldom is an odd core material or bigger core size used. Sure, they could theoretically be used, but there's almost no difference in ordinary transformer iron, and hasn't been for decades. Don't 50Hz transformers have a slightly bigger core ? In the USA, the vast m...

There are several factors that affect overall tone. When a transformer is swapped out, you need to confirm that the output tubes are biased the same and the Voltages are the same throughout the amp. One often overlooked Voltage is the Heater Voltage. Don't believe me ? Try this experiment. Connect t...

Looking at the link the OP posted in reply #3, I see only opamps and diodes. Not a single transistor or FET. Is there no schematic available ?

Edit: AH, there is a schematic: https://docs.pedalpcb.com/project/LeadS ... dalPCB.pdf

Can you provide a schematic or link to the SLO pedal ?

I've been using Snap-in caps in eyelet boards for years. I don't rely on the snap-in feature to hold the caps to the board. I just use the Keystone 40 series 1/8th inch hole eyelets. You can fit four or five #20 or #22 USWG bare wires in the eyelet to make a nice tight star ground on the negative te...

Does the amp have a bad Mains frequency hum ? Or there could be a bad ground connection between amp and generator ? Try setting the Trigger Source to Line and slow the sweep speed down to 20ms or so to see if your sine wave is riding on a Mains frequency wave.

The high peak to peak Voltage signal coming off the Treble control is too much for some effects if they don't have their own level control at the input.

Working on SMD, I've almost never used flux. I always remove the part, remove solder from the pads on the PCB with solder wick, clean the board with IPA, add solder to one or two pads to hold the part exactly where it needs to be. Then position the part with tweezers and tack it in with the pre-sold...

Aren't some of the motor run caps rated for AC Voltage ? This creates confusion when trying to select caps for DC operation in a guitar amp.

The rectifier tube should have it's own 5VAC winding (usually yellow wires) on the power transformer.

Missed the data sheet you posted,

12A?7s are linear when they're not being driven into distortion. You can't easily drive the first gain stage into distortion with an electric guitar. The LND150 sounds exactly the same to me as using a valve as a first gain stage. That's true, but the point of my question is how the LND150 behaves ...

Question: How does the LND150 front end sound with Overdrive pedals ? I've always been under the impression that a 12AX7's grid current played a significant role.

Not mentioned so far... If an engineer wants to use a part that isn't in Fender's part catalog, there is a mountain of paperwork to fill out.

What most builders get wrong is that the feedback to the "100K" side of the PI is actually in phase with the input signal that is going to the "82K"side. But that's not NEGATIVE feedback you say. It is because a positive input to the "100K" side SUBTRACTS from the positive signal on the "82K" side. ...