I have a spare 2xEL84 chassis that has punches for 3x preamp tubes and an octal socket. I had two of these and built a Matchless Lightning inspired amp with the first one.
The amp below it is my Rocket from the first RJ Rocket build thread.
I was considering building a tube rectified (GZ34 or ?) Liverpool with just 2x EL84s. What would be a good target for primary Z for this OT?
FWIW, that Lightning inspired amp uses alleged Matchless 15W transformers that are built by Heyboer (bought them at amppartsdirect). The 15W OT has a primary Z of 3800ohms. That’s right, 3800ohms. Often 2xEL84 amps are closer to 8k. It sounds amazing but it’s similar to an old Tweed amp in that there is a ton of low end and the bass control has to be set low. But it sounds so good I’m hesitant to try and ‘fix’ that. This may not apply to the Liverpool but thought I’d mention it.
Early brewers were primarily women, mostly because it was deemed a woman's job. Mesopotamian men, of some 3,800 years ago, were obviously complete assclowns and had yet to realize the pleasure of brewing beer.
Stevem wrote: ↑Wed Sep 20, 2023 3:39 pm
Well the first thing that comes to my mind is that 3.8k as compared to around 8k your going to be eating thru output tubes 50% faster.
The OT impedance also hinges on the plate voltage put to the outputs, so what will you be using?
The Matchless 15W PT in my Lightning is putting right at 350vdc on the plates at idle. I thought I’d just use another one of those.
But the Lighting has an unusual screen arrangement that (I think) saves the tubes. Instead of using the node on the other side of the choke for the screens like most guitar amps, that node is the common branch for four other nodes (all parallel, no series nodes), it’s actually not used as a node for anything other than this branch-off point. The screen node has a 22k resistor and then a 22uF/450v filter cap. This put the screens at a good 100v less than the plates. The 120R shared cathode resistor had only 8.5v on it. I then decided to adjust that 22k and see what it did and I can basically dial in any idle-current I want by adjusting the screen voltage. I settled on 10k and the cathodes are at 10v (2k2 yielded 11.6v on the cathodes).
A gut shot probably illustrates it better, the choke is connected to each side of the dual 33uF/450v filter with under board wires then branching to the four nodes. Screen node and PI node adjacent, 100R/3W screen resistors on the board:
Early brewers were primarily women, mostly because it was deemed a woman's job. Mesopotamian men, of some 3,800 years ago, were obviously complete assclowns and had yet to realize the pleasure of brewing beer.
Is this an amp that would be good for early Beatles Vox tones at a lower volume?
Reason I ask is that I am in a Beatles tribute band in the New England area. We do nearly 35 concerts every summer and now get a big following. I think we could do a little better on the early Beatles guitar amp Vox tones and have to wonder if this is something to consider.
Thanks, hope I didn't interrupt too much, just very curious about this project.
Yes, those tones are really crispy and raw and a tone that a typical Fender and even Marshall can't quite capture. It would be really nice to have a couple of low watt amps that do that tone. The other guitarist insists on using his Country Gentleman and although it is a very nice guitar in its own right, its not that great through his Fender Deluxe reverb, kind off flat and "glucky" sounding. it can sure use a little time simmering in the bacon grease pan. I built us both a "vox sounding pedal" off of Runoffgroove.com and that can help get you more into that territory but, we know it ain't going to be anything like a proper Voxish amp through a Blue type speaker.
Would love to do it. Enough to plan on it!
If you are aware of any clips that do well to showcase this circuit please feel free to lead me on.
thank you,
Phil D .
The Lightning amp above can cop some good, jangly Vox tones. I’ve never played a Liverpool but from clips it seems like more of a dirty amp. Clean to mean with the guitar volume, super touch responsive, lots of harmonics in the overdrive…that sort of thing. Oh…and loud without being ‘Marshall loud’.
Mercury Magnetics did some digging for me and found a custom Fender Deluxe Reverb OT with 6k6 primary and 2/4/8 secondary. Running it at 4/8/16 should get the primary where I think it should be for a 2xEL84 Liverpool. I’m just basing that on doubling the OT primary when going from 4 power tubes to 2 and the old Liverpool transformers were allegedly 6k6 primary. He said if I don’t cut the wires and just tack it in I could return it.
Early brewers were primarily women, mostly because it was deemed a woman's job. Mesopotamian men, of some 3,800 years ago, were obviously complete assclowns and had yet to realize the pleasure of brewing beer.
I'll need to find some audio clips of the amp. Yeah, those early Beatles tones seem to lie somewhere between notably clean, and notably broken up, not Fendery clean and not Marshally overdriven, just a nice chippy chimy tone with a healthy abundance of grit and slice where theres a good sting and crang but, you can still hear the separate strings fairly well, which helps to hold big chords together. The early Beatles after all used a whole bunch of bar chords with 2-3 octaves of 3rd's, flat 7th's and 9ths all in one chord. And it worked.
So, on my mission to see if I can "hear" this amp.
Thanks again and well, this is worth looking at for sure.
Well I've decided to not use the tube rectifier and instead put a dual can cap there. And I've got a couple of transformers being wound at Mercury Magnetics since they weren't in stock. The OT is that custom Fender Deluxe Reverb OT with 6k6 primary and 2/4/8 secondary that I mentioned. The PT is a VXP-15-LBP which has no 5v winding and is 253-0-253. That one drops right in laydown. The OT will be standup with L-brackets.
And I used the template for the Lighting above for the layout for the Liverpool using that diy app. The power supply is a little different but mainly just for the screens. I made it so one jumper makes it 'stock'. Black dots are mounting holes and grey dots are thru-holes for wires to pop up thru. That ghost over one of the screen grid resistors is just from the .png conversion.
OR maybe this:
Moved the SGRs closer to the sockets and a few other changes. I know where all the wires go and won't draw them in but I'm trying to account for every ground in this layout.
Early brewers were primarily women, mostly because it was deemed a woman's job. Mesopotamian men, of some 3,800 years ago, were obviously complete assclowns and had yet to realize the pleasure of brewing beer.
