The Amp Garage

I'm in search for a Blackface bassman chassis. Drilled & punched already.

Does anyone know a source for one of have one lying around? All the standard places seem to be sold out at the moment (ie: Mojotone, etc..).

Phil, Thanks for the comment. It’s not the guitar or cable. Those were the first things I ruled out. It buzzes just the same with humbuckers and single coils. I also tried a couple different cables. Also, it’s not dirty power either. I tested on different circuits in my house as well as at a friends...

Alright - done. The 1M and 33k resistances check out.

So.... this amp is a hybrid Fender-esque circuit that I designed and have built several of now. It’s essentially a single channel 35w blackface vibrolux in a Princeton sized package with cathode biased 5881s. Has reverb but no trem. This particular one though is buzzing right at the input and I can’...

The vibrolux choke was just one I had on hand. I have the Hammond choke you mentioned on order. The OT ‘s were recommended by Mercury Mag for a bold and big sounding SE EL84 amp. I personally asked what they recommended besides the typical AC4 OT. The amp sounds really good. I wish it were slightly ...

The choke I was using was a Vox AC15 replacement. I swapped it for a Fender vibrolux choke and now I have 270vdc pre-choke and 260vdc post-choke. With the plates and screens fed from same node (post-choke) separated by 100R 5W resistor. I’m using two SE Mercury Magnetic OT’s that are 9k on the prima...

I’m using a Mercury Mag Princeton Reverb PT with lower B+. (250-0-250)

The choke is a MM Vox AC15 choke. Maybe it has too much DC impedance? It’s dropping from 274vdc to 246vdc through the choke from B+ node 1 to B+ node 2

So Colossal’s suggestion worked. Moving the B+1 node post choke killed the hum! My issue now is that my plate voltage on the EL84s is down around 250VDC and my output power and volume is lower than I want it to be. I need to put my scope on it now and see where it is and monkey around with ways to i...

That makes total sense! I’ll give it a try and report back. Thanks

Thanks for the replies! So the power supply i’m using is essentially taken from the Trainwreck rocket schematic with slightly less filtering. CLC (60uF/Choke/30uF) with the B+1 on the 30uF cap. Also, I have tried elevating the heater center tap to the cathode of one of the EL84s. That didn’t help an...

I have been working through a new amp design that incorporates two single-ended EL84 amps in one amp chassis (stereo). The amp is complete and sounds really great, but it has a slight 60HZ hum when the standby switch in switched into play mode. The hum comes from both SE amps, but only if the power ...

This is great info! Thanks for sharing.

I like the idea of the mixer but I’d like to be able to have the option to have zero reverb on one channel.

I'm working through a 2-channel design where I'm implementing a tweed preamp and a BF style preamp within the same amp. I want both channels routed to the spring reverb but each with its own send control so the amount of 'verb can be set per channel. Would two 500k pots (one from each channel) to gr...

Both 0.022uf 716P caps i pulled from the tone stack measure good. Spot on actually. Weird... The EQ definitely wasn't working properly with them in. The amp was shrill and lacked bottom end. The Mallory 150s have made the difference! Amp is sounding great now. Just need to work out a better bright c...

Colossal - That is a possibility. I need to measure capacitance of the 716P caps I pulled out to see if they are in spec...

I'll report back.