The Amp Garage

Or, you might use a switch with resistors, that way you have different levels of regulation for KT88s or EL34s. A potential failure point as I see it is the power rating of Piher trimmers. A cermet type would be better but a higher rated switch is just easier to source and install. Oh yeah. I guess...

Just for knowledge At the begin I didn't understand well why you want to use a pair of Mosfet in parallel for VVR for the same reason .... I can't imagine a tube amp needing parallel MOSFETs for VVR. however reading your post I remembered a circuit a friend sent to me some years ago Double Mosfet V...

Even though I have much more modding to do to the schematic, especially regarding the relay situation, my OCD won't let me not post the current schematic I am working on that reflects the Screen Supply VVR:

Whoops! I see a mistake in the VVR drawing! I forgot to add in the 1Meg pot! I though you were going for fixed bias. Is there any reason you need this to be adjustable? Probably not. I think I could just measure my current values and put resisters in instead. I think it was more for experimental pu...

Right now I'm looking for that FET level knob mod with relay switching that Martin had drawn somewhere... and trying to figure out what transformer works well for the relay power... There's info on these in the ODS boards .pdf here https://ampgarage.com/forum/viewtopic.php?f=5&t=29630 Whoa! Thanks ...

For an 18W amp in an aluminum (not steel!) chassis I'd just bolt to the chassis. Don't forget heatsink grease/paste or one of those fancy silicone pads. For a 50W amp I'd use a real adequate heatsink. For a larger amp I'd just get an 18W amp. :mrgreen: Amen Brother! I'm just trying to keep options ...

What was your thinking with the power MOSFET for the B+ branch feeding your reverb and FX loop? To get the magic 30V on the cathode your "B+5" voltage should be in the order of 260V on the plate of the driver and 360V on "B+4". With these values, the 30V is all but certain. That MOSFET is a VVR for...

... You aren't likely to need the 68pf cap on the Master though. Good to know. Thanks. I'm out of the loop on any discussion on that one. I see most with the 68pF, one with 15pF, and some with none. I guess with bright switch in the loop, and a presence control later, it becomes pretty irrelevant?

If power handling is a worry and I'm worried about that MosFET, can I just add a second MosFET in parallel? I can't imagine a tube amp needing parallel MOSFETs for VVR. Thes devices are rated for high power/high current with proper heatsink. For example, the NTE2973 that is commonly seen in many VV...

After doing a bunch more suggested reading on the Loop, Stephen, I lifted your circuit from your 183 build. In the interest of not drilling too many more holes or installing parts that I think won't get used, I removed the the line/instrument switch as well as the jacks for the passive loop. I'm thi...

That is one hellified heatsink! With a fan across it, it should create frost on your FET. Haha! Ya, I think it definitely needs the fan. The fins are so thin, they don't have any mass on their own. I think it really depends on that heat transfer to the air that is being blown off. I've had this sit...

Yeah, man! Who are you building this amp for? You really don't need to do what anyone else did, myself included - do what makes YOU happy. Big thumbs up. Mind you I would definitely sort out the relay situation first. In a standard D-style chassis, there isn't a ton of space and installing them aft...

Yup, I keep changing my mind. I'm thinking I'd like to build it leaving space for a classic Fender 2-tube reverb before the loop. Sort of a future expansion idea after I've played the regular 102 circuit and can judge properly if the reverb circuit compromises anything by being added. May 11.jpg I'm...

They also need to be mounted right next to each other so that all wire length used is the shortest. So, this is the part that also makes me wonder if 2 parallel mosfets even buys any more wattage rating since they would have to be close enough to each other that they would end up sharing the same l...

I'm leaning toward drawing out the full vision and going for the whole build at once, instead of the trial steps. (so I will do a more full conversion of the filtering, including add the choke). So I'm still refining that vision. I'm currently experimenting what it would look like to add reverb to t...