The Amp Garage

Passive fx loops are trouble. The best Passive FX loop I have ever been able to pull off is a 470k + 15k voltage divider after the tone stack = 14.56k output impedance. 20ft cable = 1nF = 10.931kHz. Just with a cable you will hear that... it may even be nice. Maybe. Most people will not like this. B...

You need to shield the input jack and tie that shield to ground. All the metal on the hot side of the jack acts like one big ass antenna. I make a thin cardboard form and then contact cement.005” thick brass around it. I get this brass sheet from hobby shops or on line. I mainly use this mod on the...

Here is another with resonant frequency at 100Hz, but without quite as extended of a top end:
https://www.parts-express.com/GRS-5PF-8 ... er-292-405

We have closed back cabs and then the have closed AND closed front cabs. I've never been able to wrap my head around how to think about the isolation cab where one side of the speaker doesn't face a large room. Possibly this is a good solution. Essentially a speaker mounted on a board in a closed bo...

Can't do LTSpice on Mac without the shortcut sheet!

https://www.analog.com/media/en/news-ma ... ice-models

26 awg should be good. Pickup wiring typically is 28 awg and we know that stuff gets bent all around by the average person with a soldering iron.

Thats interesting. I always assume the smaller the resistor, the lower the noise. I would be interested to know what the final verdict on if large grid stoppers cause noise or not. That 470k gives the mesa dual rectifier a lot of its characteristic tone- mostly that it darkens it. Additionally, it c...

The 20p is noticeable when you remove it, but not all that much. And certainly there are no oscillations when you remove it. You can also jump the 470k with a 10k, which is much more effective due to Miller capacitance-still no oscillations. It will basically sound like a DR, but much less dark, 90'...

Reeltarded wrote: ↑Mon Apr 04, 2022 6:11 am You should add the simple master after the tone stack on a separate control... monsterous at around 7+7.. its like free steaks.

Totally agree here! I think you have perceptive ears

I mean turn bias as far negative as possible to lower current draw. That may not totally work though as something oscillationg can reach absolute maximums. I'd probably remove the phase inverter tube before testing while powered on. Good luck. Might be a good idea to consult a tech. This amp is prob...

Before you do anything, jack that -Vbias up all the way! It's hard to work on something that is melting down.

I've never seen a 12ax7 red plating. The plate resistors should limit current to well below what is needed to red plate. Very peculiar.

There are a lot of Russian tubes out there being horded. I know higher ups in several online distributors that just pulled their listings because certain people/companies were making multiple order/day for 500tubes/order. So, they could either totally sell out, or take the listing offline and wait t...

Yeah, that's about how I understand it. 1)Take a Plexi 2)add a 12ax7, but only use 1/2 3)make a bright channel to cascade into the plexi and put the "jumpered channels" on the push pull switch to jumper them. 4)install DPDT push pull 1M master volume. configure the DPDT to swap the master volume bef...

1/8" panels? Wow. That is thin! You could cut that easily with a CO2 laser. You can even cut 1/4" with most CO2 lasers over 50 watts.

I see! The 300V B+ is a bit low for 50W with the usual output transformers. Ho would you tackle that? Re-label the secondaries to reflect a lower primary impedance? Really interested to hear of your results. Has anyone discovered the schematic? Maybe it could be modified to deliver ~477v B+? (first ...