The Amp Garage

Magnatron wrote: ↑Wed Feb 21, 2024 4:43 pmturn the unit on, the fuse blows. It's happened now 5 times.

When does the fuse blow, immediately when you throw the power switch, or 10-20 seconds later, after tubes heat up? Do you have a standby switch, and does it relate to the problem? What fuses are you using, amerpage, quick or slow?

WhopperPlate wrote: ↑Wed Feb 21, 2024 6:27 pmbut it doesn’t pay to disbelief the person with perfect pitch because you can’t find a tuner.

Difference being, perfect pitch can be easily and repeatably tested and demonstrated.

I removed the main PCB, disconnected the microcontroller daughterboard, resoldered many points, painted all connections with DeOxIt, reassembled. No change in noise!

maxkracht wrote: ↑Wed Feb 21, 2024 3:16 pm Is r36 supposed to be green?

Yes. I replaced it last night anyway (one of the PI's plate resistors).

Is the Presence pot wired backwards or has reverse taper?... No, the Presence control effects the guitar tone exactly as you'd expect...but it affects the noise in the opposite! My voltage scaler control on my Carr Telstar is scratchy every time I turn it. Could there be an issue with the power sca...

The bug showed up. Bacon frying with occasional pops. Noise is post MV, and strangely, turning the Presence all the way UP causes the noise to become DARKER, like rolling the treble off. Weird. Not an FX loop issue. Same bad noises with different set of tubes. Noise is not sensitive to knocks or cho...

Well. That was a long walk off a short pier...

I bought another "project" amp on a whim. This is some modern, whiz bang engineering. 40 watts, only 17.5 pounds. Seller's warning was, "This amp makes intermittent popping and cracking noises." I played it for an hour with no problems exhibited. This is a little concerning, because I won't feel con...

Have you tried it vertical? I've tried vertical 2x12s in the past. Maybe fine on stage, but in my room, I sit near the cab when I play, and I always hear comb filtering when I sit near a vertical 2x12. This cabinet is already sitting on a 2" base of walnut hardwood, and the top surface makes a grea...

Here is a quick shopping list from Amazon: DROK AC multimeter https://www.amazon.com/gp/product/B09998YBHW Square plenum box https://www.amazon.com/gp/product/B003A2GWX4 Square work cover https://www.amazon.com/gp/product/B005JC6PLW 2 pack toggle switch/output https://www.amazon.com/gp/product/B07WS...

Ten Over wrote: ↑Mon Feb 19, 2024 8:21 pm

bepone wrote: ↑Mon Feb 19, 2024 8:16 pm 1k is there for bias........

No. It is biased way off center. It is there to set the gain.

How would we center bias this input stage?

This is awesome, Martin!

Can you show photos of the wiring inside, and show what you've used for the input and output AC plug/socket?

martin manning wrote: ↑Mon Feb 19, 2024 6:38 pm The Zeners protect against Vg-s getting anything larger than ~8V. Bypassing Rs with a cap has pretty much the same effect as in a triode stage.

And is the only possible source of this voltage whatever the user puts into the input?

I'm preparing to build a half-wattage (two EL84s instead of four) Liverpool, using Blues Junior iron. My OCD hates the idea of the unused triode, and I'd like to delete one preamp tube, so I'm experimenting with replacing the first gain stage with a LND150. Because it's nearly impossible to overdriv...

Screen resistors serve as current limiters, and help prevent burning up your tubes. These have little effect on perceived performance, and are a good, modern update to classic designs.