Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Lectroid on July 14, 2022, 01:05:30 pm
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I am building a single channel AB763 DR in a Princeton AA964 chassis. Reverb, no tremolo. With no trem, I have two extra holes on the chassis front plate. Hoffman's circuit adds a Mid pot, which I've never done before, but have been meaning to try. For the second hole, I decided to add a Dwell to get more control over the reverb. Perfect solution--all holes filled.
Then I came across sluckey's Tweed DR design and liked it a lot, especially the Master Volume control, which I've also been wanting to try out. But my faceplate's already full unless I drill another hole.
I'm not a tone-purist at all, more of a "close enough for rock 'n' roll" type. I have Mid on my little Marshall JTM30 and hardly ever move it off midpoint. If I had to pick two, I'd take Dwell and MV.
I'd really love to hear from any of you who have built amps with these controls.
Would a Mid control add enough to justify the extra trouble?
Also, does anyone know a source for decent custom faceplates?
Thanks,
Rich
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I have a single channel deluxe reverb as well. I have mid, dwell, and MV. Of the three, MV used to get the most work by far. Mid and dwell control the least. I played with the Mid control for a while and I've ended up setting it approximately near the fixed value anyways. It's a classic sound and I like it. I like Dwell at half and thats where it stays now and the standard reverb control does the rest. I find the reverb range more useful for me and my playing. YMMV. Now that I've built a good attenuator, I set the MV to near breakup and use the attenuator for volume control.
If I had to rank the usefulness of these three it would be;
1. MV - most useful
2. Dwell
3. Mid - but its a close race between Dwell and Mid.
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Dwell and Master. The mid control can be moved to the rear, or swap controls, dwell at the rear, mid up front.
--pete
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A mini 3-way on/on/on will get you 3 mid positions and not take up much space
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Mid control isnt so great.. id go MV and then dwell.
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I built a similar reverb with a dwell pot just to try it. I found that, as a player, the dwell pot became a sort of nuisance because there are so many options when you have two pots controlling the reverb that I eventually just set the dwell to max (1Meg pot) and left it there to keep things simple, relying on the reverb return to control the mix. So instead of the dwell pot, I could have simply used the standard 1M resistor to ground. Mind you, I used a dual concentric pot for the reverb dwell and return, which was annoying because they both want to sort of stick and turn at the same time.
But anyway, I think the dwell is my least favorite.
The master volume would be my #1 option because it gives you tonal control of the output, and you get a feel for the amp's behavior and parameters - ie. preamp break-up versus power tube break-up. This control gives you a fairly deep insight into how well the amp design is performing as a whole. Valuable info.
The mid is not a silly idea, but my guess is that you can come close to what you want using a standard resistor for mids, a la Fender's TB stack. But a mid pot might be handy for someone who plays different types of guitar through the amp (like a strat AND a 335), which sound very different and might benefit from the added tone control.
Good luck on your build.
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I do not have much love for a dwell pot with the blackface circuit either. On the other hand, I find a mid/raw pot to be indispensable for having useful alternate voices for my amps. In the Blackface circuit I use a 50k pot with a 6.8k resistor to ground. At a setting of "1" it gives the traditional mid-scooped Fender sound. The mids become much more prominent at higher settings which gives a hard-edged tone, especially at high volume distorted settings. Adding a master volume to a blackface amp works much better when the mids are cranked. With the standard scooped mids circuit the master just increases mud and fizz.
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Everyone,
Thanks for all your comments and suggestions, especially the longer discussions by Joel, shaun, and ac427v. That's exactly the kind of advice I was hoping to hear.
Master Volume is a popular favorite, so it goes in, along with the Mid control. I'll implement ac427v's suggestion to wire in the standard 6.8K mid resistor in series with a 50K pot. His idea to put some extra Mids on tap when needed is a nice innovation I haven't seen before.
DummyLoad's idea to place Dwell on the back panel was genius because I like a lighter touch of reverb. I may not adjust it very often, but it will never get in the way back there.
Thanks again for all the help and encouragement, :worthy1:
Rich
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Another worthwhile change to the reverb circuit... Replace the typical 100K-L reverb pot with a 100K-A pot. You'll have much better control of the reverb level and may even find the dwell pot to be unnecessary.
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Thanks, I'll definitely try that.
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Mid control isnt so great.. id go MV and then dwell.
would love to try those in a deluxe. On a princeton reverb, I found my mid implementation to be very enjoyable, and as a surf reverb junkie, I surprisingly didn’t like the dwell control as much. Instead I found the maximum dwell point i think sounds best and replaced the pot with a resistor. stock reverb gets way too dark with pronounced reflections. not very useful to me.
replacing the linear reverb pot with a log pot is very good, however.
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I've been working on the amp, tweaking component values and such. The combination of Vol/MV gives me good control of the clean/dirt mix as well as being able to boost the overall loudness.
I've also added cboysen's Bright Cap on the MV and it really eliminated all harshness and buzzing from the overall tone.
See: https://el34world.com/Forum/index.php?topic=23821.msg256182#msg256182 (https://el34world.com/Forum/index.php?topic=23821.msg256182#msg256182)
I found that I agreed with Owen and ac427v that the Dwell wasn't as useful as a master volume. I tried a dwell pot but anything over 5 or so was just too ringy. I swapped the stock 1M dwell resistor for 470K and it's a great improvement. Now the Intensity pot gives me all the range I need without that clangy ringing over-reverbed sound and without adding a Dwell pot on the rear panel.
Also sluckey's suggestion to use a 100K-A pot instead of a linear pot also gave good control over reverb intensity. A good change.
Thanks again to everyone.