Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: cboysen on April 26, 2019, 07:07:51 am
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Alright, I just wanna share my enthusiasm.
Since building my first amp, The Tweed Deluxe Reverb, a year ago, and after a few successful builds for friends, I decided to strip it completely, and rebuilt it. Using only what I had at hand. I first tried the 5e3 thing, which was cool, but eventually reinstalled the blackface tone-stack, and went with a "Beefed up Princeton" with cathode biasing.
Pretty much stock Princeton, without tremolo and a with few tonal tweaks to the NFB, Mid and Cathode bypass resistors. The biggest mod is upping the cathodyne voltage (from 200 to 260), which keeps the PI from breaking up before the power section. Power Tube Plate Voltage is 410V using a GZ34.
From sparkly clean with great snap and punch to sweet breakup into heavy overdrive when lifting the tone stack. It's surprisingly loud for an amp like that. Tried it with an external 1x12 V30 cab at a rock gig - with the volume at 3, it kept up with the heaving hitting drummer without breakup. Its own low sensitivity small magnet Jupiter speaker breaks a little sooner, but still clean at gigging levels. It's also completely hum free, except from a slight hiss when the reverb pot is fully turned.
So all in all, I'm pretty happy with it.
So thanks for all the help this forum has provided me, in getting better at building amps.
I've added a before and after picture. The blue board is before, and the red board is after.
Kind regards
Christian
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Very nice. I've thought about rebuilding my TDR also. I rarely drag it out these days. Not because I don't like it, mostly I just have several other amps that are always ready to go and easier to plug in and stir the neighbors. Only takes a few minutes to satisfy (or frustrate) me these days. Fingers don't bend like they used to and ears don't hear so good.
So, why did you decide to rebuild the TDR?
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Thanks for mentioning it! Never heard of the project before, now it sounds like a killer idea. This will probably be my next build.. and thanks Sluckey too for the design :worthy1: :worthy1: :worthy1: cool page!
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Very nice. I've thought about rebuilding my TDR also. I rarely drag it out these days. Not because I don't like it, mostly I just have several other amps that are always ready to go and easier to plug in and stir the neighbors. Only takes a few minutes to satisfy (or frustrate) me these days. Fingers don't bend like they used to and ears don't hear so good.
So, why did you decide to rebuild the TDR?
Thanks Sluckey! I had considered rebuilding it for a while, mainly as a learning experience, and to see 'how far' i'd come. The previous build was a bit noisy, and could use some tidying up on the lead dressing. Also I wanted to try a cathodyne PI and Cathode Bias to hear/feel the difference.. It's not a big difference - but I do like it more, in this application at least. The first rebuild, had a switch to disable the whole reverb section, but without a relay, the long wiring took a toll on the treble. So I removed it, and eventually got back to the blackface thing. The amp sounded good before, but sounds great now - and I've gotten a little smarter rebuilding it.
The only "problem" I have left, is that when a bypass cap is included at the reverb driver, the driver gets raspy/blocking. I believe it's an osciliation problem, maybe due to the poor placement of reverb transformer/plugs, but without an osciliscope, I've learned to live with it. For now the reverb driver is unbypassed, and still plenty wet and springy for my playing.
I've also included a master volume, which is a 1M variable resistor to ground right before the input of the cathodyne. I didnt want to use a voltage divider, due to long wire runs to the PI grid input. Now the PI is cathode biased, with a 1M running to the cathode resistor as per stock settings, so I can't really figure out if using the master is scewing with the PI bias. I have it on an on/off switch, which pops a little when the master is turned down. Other than that, it's probably the most natural sounding master I've tried. It retains all clarity throughout, and takes the amp into quite a great sounding preamp overdrive, at reasonable levels. Maybe someone can shed a light on the math/science behind it.
Kind regards
Christian