The Amp Garage

You were almost there. That's the 100k in red. As mentioned above, if you use an On-Off-On switch, you have Preamp Boost in the middle position. Martin, ive finally gotten around to doing this as live got pretty busy for a bit there. I have to say the difference here is astonishing! The amp is so c...

The sizzle im talking about seems to be inherent in these amps. I hear it in my amps as well as most demos you hear. You dont hear it with two rock, dumble clones etc, but i hear it in all fenders. I love almost everything about these amps, but would really like to find a way to correct this. Have ...

I have 3 AB763 fender amps and they all exhibit the same qualities. There is a sizzly top end that I cannot stand… Exactly which amp models? There are various differences between various models. Which channel/s are you using? Depending on the particular model, there’s various differences between th...

Hey Martin, thanks for this. Attached is what I’ve drawn up so far. It is not complete as I cannot quite wrap my head around how to wire the 100k resistor in the fashion you’ve explained.

I love the amp with the treble turned up, as it makes the amp much more percussive and punchy. Unfortunately, along with that, the sizzle I’m attempting to dial out gets worse. It almost seems to be a sort of clipping? It's very possible that the sizzle is a parasitic oscillation that kicks in when...

If you want to do the whole #124 Skyliner clean channel in Rock mode it would look like this. Amazing! Thanks so much for this. What values change if I want to try it in ‘jazz’ mode? I’ve tried the 220k resistor you mentioned, and didn’t notice much effect. I love the amp with the treble turned up,...

Another very easy thing to try is on the first gain stage. Install a resistor before the 100K plate load resistor to drop the plate voltage at the tube down by 20 to 25 volts . You may then need to bring the cathode resistor down to 1200k , but I find that needing such is in responce to how strong ...

That’s a classic stack . Significant differences. Sky liner uses .01uf mid cap , 250k mid pot , 500k bass pot , 10k tail resistor off bass pot , .001 cap across bass pot, with 220k/500p grid stopper v2B. You have two threads going on the same topic. Here is the bare bones Skyliner stack. You are sh...

I thought I was talking on a functional level. Most of the Marshall amps use a 47pF cap across the PI plates. Some actually place the cap after the coupling caps but the effect is the same. Apologies, I was not using the proper verbiage. I should have stated on a 'electrical/mechanical' level. I un...

You have two threads going on the same topic. Here is the bare bones Skyliner stack. You are short a mid pot, too. But, there are other ways to reduce some high end. An easy experiment would be to place a large resistor in front of the second triode's grid at pin 7. Try a 220k right at the tube soc...

sluckey wrote: ↑Tue May 30, 2023 3:20 pm

Jake1524 wrote: ↑Tue May 30, 2023 3:18 pm What exactly am I accomplishing by adding a cap across the plate load resistor or PI plates?

You are cancelling out some of the high end sizzle.

Sluckey, thanks for the info. I understand what it would be doing, im more tying to wrap my head around whats happening on a functional level

Basically you would be replacing what is in the red rectangle. The full implementation needs three switches (including Bright) plus the PAB relay, but if you use an 0n-0n-0n for the Rock/Jazz you can have PAB in the middle position. There are a couple of additional parts, and I don't know how easy ...

The easiest thing to do is back off the treble pot a bit and turn the bright switch off. Or load the cab with some Celestion speakers. If you want to go inside the amp, put a 100pF cap across each 100K plate load resistor for V1 (normal channel) and/or V2 (Vib channel). Put another 100pF between th...

martin manning wrote: ↑Tue May 30, 2023 2:39 pm Do you want Rock/Jazz and PAB?

No need for PAB and on the fence about Rock/Jazz. If adds a lot of flexibility, might as well include it.

I have 3 AB763 fender amps and they all exhibit the same qualities. There is a sizzly top end that I cannot stand. The harder I strum my guitar, the more apparent this is. Is there a way to dial this out? I would much prefer a much rounder, less fizzy high end, while still staying clean. I have buil...