Search found 3022 matches

by Firestorm
Tue Nov 16, 2021 6:47 pm
Forum: Fender Discussion
Topic: Fender Idea Needs Fresh Eyes...
Replies: 9
Views: 1190

Re: Fender Idea Needs Fresh Eyes...

It's worth noting that in later tweed amps that had it, the middle was a 25k linear. But in the blackface amps with a middle pot it was 10k log. It's why the Twin sounds more "scooped" than the Pro. If you set the mids on "5," resistance to ground at the bottom of the stack will be 1k or 1k5.
by Firestorm
Sun Nov 07, 2021 5:50 pm
Forum: Technical Discussion
Topic: Clean Preamp Configuration?
Replies: 25
Views: 1723

Re: Clean Preamp Configuration?

You have to design the loop to have enough wet gain for the effects you are using. Old-school rack-mount gear will output at 0dB or even +4, but most pedals will be -10 or -20. The dry signal can be at unity, but you can add or decrease dry gain by changing the relative values of the resistors that ...
by Firestorm
Fri Nov 05, 2021 11:18 pm
Forum: Trainwreck Discussion
Topic: Kitchen Sink Trainwreck
Replies: 3
Views: 1643

Kitchen Sink Trainwreck

I got a commission to build a pair of amps in the style of Ken Fischer, from a guy who likes some bells and whistles. (I previously made him a 6L6-powered combo based on Dumble #124, but with a full-blown loop, plus spring reverb, plus a tube rectifier, plus Power Scaling, extra cup-holders, etc., e...
by Firestorm
Thu Nov 04, 2021 6:28 pm
Forum: Technical Discussion
Topic: Unity Gain Stage
Replies: 17
Views: 1206

Re: Unity Gain Stage

Whereas a cathodyne will invert with near unity gain, it also has half as much headroom as a fully-bypassed gain stage with the same load. This may not be desirable for a channel striving for "clean as possible". Attenuating the signal and then running it into an inverting gain stage like a parapha...
by Firestorm
Thu Nov 04, 2021 4:44 pm
Forum: Technical Discussion
Topic: Unity Gain Stage
Replies: 17
Views: 1206

Re: Unity Gain Stage

The Vibrato channel in AB763 is three stages, not two. The reverb mix stage attenuates the dry signal by about 95% by running it through the voltage divider formed by the 3M3 with the 220k/470k shunt, but does invert it.
by Firestorm
Wed Nov 03, 2021 4:08 pm
Forum: Technical Discussion
Topic: Is Classictone transformers kaput?!
Replies: 9
Views: 1089

Re: Is Classictone transformers kaput?!

Pacific, too.
by Firestorm
Mon Nov 01, 2021 4:22 pm
Forum: Technical Discussion
Topic: Loss of volume and gain after modification
Replies: 26
Views: 1776

Re: Loss of volume and gain after modification

Mikante: My comment about building a board wasn't meant as a suggestion for you, as you've already come this far with the mod. It was a more general comment that I can't see putting that much effort into modifying that PCB. While the video is only about 18 minutes, my guess is that's been edited fr...
by Firestorm
Mon Nov 01, 2021 1:19 am
Forum: Technical Discussion
Topic: Loss of volume and gain after modification
Replies: 26
Views: 1776

Re: Loss of volume and gain after modification

Mikante wrote: Sun Oct 31, 2021 8:20 pm Replaced r3 r7 r14 r17 r25 r26 with jumper wires.
If you really jumpered r7, you're pumping a huge amount of negative feedback onto the cathode of V2B.
by Firestorm
Sun Oct 31, 2021 9:20 pm
Forum: Technical Discussion
Topic: Strange red plating tubes on new build
Replies: 33
Views: 2793

Re: Strange red plating tubes on new build

So that's 4.365 watts. Kind of the textbook definition of biased too cold, certainly not red plate territory. BTW, -30 VDC bias voltage doesn't seem right for that reading. I'd think the tubes would be pulling way more current.
by Firestorm
Sun Oct 31, 2021 8:39 pm
Forum: Technical Discussion
Topic: Strange red plating tubes on new build
Replies: 33
Views: 2793

Re: Strange red plating tubes on new build

You have you meter set to current instead of voltage. Measuring across a 1 ohm cathode resistor you want millivolts, not milliamps. Let's see what the tubes are really pulling.
by Firestorm
Sun Oct 31, 2021 6:51 pm
Forum: Technical Discussion
Topic: Strange red plating tubes on new build
Replies: 33
Views: 2793

Re: Strange red plating tubes on new build

On a stock 2204, the standby switch interrupts the high voltage supply to the diodes. If you wired it that way, it can't possibly redplate on standby. How are you measuring plate current? Unless it's oscillating, I can't see how it could idle at 10mA and redplate.
by Firestorm
Tue Oct 19, 2021 3:52 am
Forum: Technical Discussion
Topic: Parallel single ended 6v6 amp with a half power switch
Replies: 16
Views: 1885

Re: Parallel single ended 6v6 amp with a half power switch

I built something along these lines with parallel Hammond 125ESEs wired to three sets of taps for 2K5, 5K, and 10K primary impedance (secondary load is always 8R). There's a volume pot in front of each output tube so you can turn them up, down or off. I used the "E" OTs to get a high enough DC curr...
by Firestorm
Fri Oct 15, 2021 4:06 pm
Forum: Technical Discussion
Topic: Parallel single ended 6v6 amp with a half power switch
Replies: 16
Views: 1885

Re: Parallel single ended 6v6 amp with a half power switch

I built something along these lines with parallel Hammond 125ESEs wired to three sets of taps for 2K5, 5K, and 10K primary impedance (secondary load is always 8R). There's a volume pot in front of each output tube so you can turn them up, down or off. I used the "E" OTs to get a high enough DC curre...
by Firestorm
Wed May 29, 2019 5:35 pm
Forum: Fender Discussion
Topic: Finally finished, Blackface Vibroverb
Replies: 11
Views: 3738

Re: Finally finished, Blackface Vibroverb

Wow Charlie! The only thing missing is Lupe's name on a piece of tape.
by Firestorm
Mon Mar 18, 2019 2:40 pm
Forum: Fender Discussion
Topic: Vibrochamp insanity!
Replies: 17
Views: 2564

Re: Vibrochamp insanity!

Is it that faint buzzy sound that cuts off suddenly just before the note fully fades? You might try shielding the leads to the tone controls. If you have multiconductor shielded cable, you can put them all in one shield. It's worked for me on some Fenders.