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Reply With QuoteI think the cathode bias on the first stage of the PR section should make up for some of the loss due to the reverb mixing resistor. I see no reason not to do it.
Hi,
I would like to start a project that I've had in the back of my head for a long time ... a "tweedish" amp with bias trem and reverb so I can get rid of my two stomp boxes.
So first thing that came to mind was to merge two existing and known good designs. My all time favorite tweed sound is coming out of the 5F4/5E7 style amps. The blackface amp I like most, especially for it's reverb and trem is the princeton, which has a similar power section design as the tweed super/Bandmaster. So what about combining these two? I know, this would not be like slapping both circuits together and you have a perfect amp but I wonder if this would be something that should work as a starting point ... then i can take it from there and tweak it ...
ok, here goes:
this is the schematic of the princeton reverb:
http://www.mudcats.at/amps/princeton.jpg
I would replace the marked section with this:
http://www.mudcats.at/amps/5f4.jpg
As far as I understand it, the point where I cut them is in both cases the decoupled signal coming from the preamp, going to the PI (with the reverb in between on the princeton). I don't know if the gain would be in a useable range or at least if I can get it there. Any thoughts?
Many thanks in advance!!!!!
I think the cathode bias on the first stage of the PR section should make up for some of the loss due to the reverb mixing resistor. I see no reason not to do it.
I think there'll be enough gain from the preamp. If you compare your PR schematic to a Champ II (http://www.webphix.com/schematic%20h...s/champ_II.pdf) you can see the Champ II's preamp gain is good enough to use a master volume. The difference of the second stage in your build being a cathode follower is negligible IMHO. Actually the Champ II can sound from chimey fendery clean up to classic rock a la AC/DC when the mid boost switch is engaged. You could add a switch like that to bypass your 250pF treble coupling cap for more gain.Originally Posted by Bluefinger
Just my 2 cents
But if I bypass it, I would have the full plate voltage at the treble pot ... or I'm I getting something wrong here?
I did something similar (tweed bassman front end with reverb and bias vary trem - albeit with a LTP and 6L6s a couple of years ago - works really well). It took me a good 12 months of farting around with various reverb circuits, but this is what I ended up with. As far as keeping the tweed front end goes, I found this to be the most optimum reverb circuit. Uses a lot of real-estate and pre-amp tubes tho'. But it does sound really nice. I don't have this amp any more - I'll see if I've got some soundbytes tho.
Building a better world (one tube amp at a time)
Sounds very interesting, thanks! That Bassman preamp is a bit cleaner than the 5F4 I guess but I'd be very interested in some soundbites anyway. A tweed amp with reverb seems to me like the most obvious thing in the world ...
Yeah sounds interesting, but not easy to implement well. The amp I did in the schematic utilises the Allen Old Flame reverb circuit, and it works supremely well. Here is a clip - Me accompanying myself on strat, recorded dry-mic'd with an SM57 through my desk into garbageband on my Mac - trem sample at the end. Amp has 2 x G12M (25W) greenbacks
Building a better world (one tube amp at a time)
Sounds great ... I like the mellow tweedish response in combination with a real tube reverb.
No you don't get it wrong. Look at the Champ II schematic. The switch is after a 2n2 coupling cap. No plate voltage after the cap (usually).
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