The Amp Garage

Yeah, just for further clarification. The YBA-3 schematics have 3 pages. There are 47 ohm screen grid resistors, so I have not misread anything, and as already been mentioned, increasing screen grid resistors for modern tubes, EL34's especially, is standard practice. The only 'issue' you might run i...

First thing I'd do is swap the 47ohm (according to the schematic) screen grid resistors to at least 1k, maybe 1.5k.

I'd probably Zener down the screen voltages below 450VDC and just use regular new production tubes rather than trying to cherry pick rugged enough tubes to handle the duty.

i don't know how anyone can write by dumble if it's not a dumble. nothing positive here I guess the same way, how you see 'Shelby Cobra' kit car replicas listed as "Shelby Cobra kit car replica" when they are sold, even though they weren't built by Carol Shelby. People in the automotive realm don't...

If someone is going to spend 60k-200k+ on an amp, it's kind of their responsibility to properly authenticate the product they're trying to purchase just like how someone buying expensive artwork should be doing the same, to ensure they're not purchasing a counterfeit. Not saying I support building c...

Jumpering the NFB resistor will give you a TON of NFB. Lifting/disconnecting the NFB resistor is what will give you more grit as you're breaking the connection between the OT and the cathode of the preamp stage, completely, eliminating the NFB network. Jumpering the NFB resistor will eliminate all r...

Sounds like you may have way too much NFB and it neutering the stage it's wired to. Check your wiring and all the component values, might have a decimal in the wrong place somewhere like a 2.2k in place of the 22k NFB resistor.

Oh wow, didnt expect to see him do an amp with a fake faceplate like that. I've seen people give a lot of flak for doing that even if they're honest about it not being a genuine Dumble.

I'm really looking forward to seeing this one. Any more progress on the schematic? I'm making one and for now, I've decided to keep it to myself. James is still in business and is selling them, albeit slowly, so it doesn't seem right to publish the schematic. At the time I started the layout of the...

. I am interested ine the "sag resistor" option but even after some reading, not sure what value to use. can you help determine that value ? You can calculate the value if you know how much current you're drawing. Then you just have to decide how much voltage drop you'd want. Most people would prob...

Leave the filtering stock. Add a 'sag' resistor to increase voltage drop in the power supply. You could also replace the choke with a resistor of higher resistance for a similar effect. More sag and lower B+ will 'soften' the amp up.

Until I can get it worked on I’d like to brighten it up considerably. What should I do? I’m thinking about a different cap on the master. I'm a little surprised it's not bright enough if it already has a cap on the master. (Personally, I always felt the master bypass cap added too much icepick even...

The BJ runs those EL84's way too hard. My friend won one in a contest and lost a power tube in under 6 hours of use. Suggested mods are cool the bias down, increase screen grid resistor value (and wattage) and elevate them off the PCB. This will help significantly with tube life. While you're at it,...

I think he is going for a 183 which has 311K on the layout. On my 102 I went with a stock 500K but I'm in the process of redoing all the pots and have an Alpha at 396K :D Ah, ok. Just thought I would mention it. The 102s I've built with that modded pot have all had plenty of bass but it is tight an...

8K and 8.5K is not ouptut - it's resistance. cheers, Thank you. I know but, is that not how pickups are generally refered to ? For a given magnet type and arrangement, yes, the pickup’s resistance is a general indication of its likely output level. But those details are, as yet, unknowns here. Also...

I'm not a fan of PRS, but are they really that different from Robben's old Fender Esprit with the exception of .5'' difference in scale length?