Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: plexi50 on November 06, 2012, 06:34:45 pm
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This is a princeton reverb clone i build last month. The reverb itself is to harsh and the decay is to long. There is no 10pf cap on the 3.3M reverb r. I left it off for that reason. I didnt want an overly bright reverb. Smooth and full but not to surfish. I am using a 1959 12AT7. I had tried several different reverb tanks before ordering the original 4AB fender tank for the princeton reverb. Hell i have an old hammond organ tank that sounds better than the 4AB belton made in korea. Why? What happens if i reduce the 3.3M to 2.2M ?
I have a thick cardboard on the bottom of the tank and the tank is even turned upside down. No change
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What happens if i reduce the 3.3M to 2.2M?
You will get more dry signal.
You can put a small (pF) from the 12AT7 plate to the cathode. Might kill some of the high end harshness.
Brad :icon_biggrin:
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Is more dry signal to be interpeted as less surf and a smoother reverb tone?
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If you have more dry than the dry to verb mix is different than what you have now. Try it and see if you like it.
Brad :icon_biggrin:
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Changing 3.3M now to 2.2M. I am now also using a 12AT7 in both send and return. Sounds much better but want to try 2.2M
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Nay on the 2.2M. New question:
How can i get a tad deeper reverb tone. Higher bypass cap value on the send or return?
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I would try the bypass cap values for sure,but keep in mind the gain will increase a bit too.
Sometimes using a thicker reverb bag,or one lined with soft cotton or rayon,makes quite a difference.Also a small,thin piece of foam on the underside of the tank to keep the springs from hitting the metal of the tank and maybe a bit to keep the springs from hitting the cardboard.
And using a bit of silicone seal on the transducers themselves to keep them from moving around.The newer tanks are all over the place in my experience;some sound great and some are kind of metallic sounding.The Gibbs tanks are awesome for the most part.
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Try a 12AU7 for the reverb driver tube.
Brad :icon_biggrin:
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How can i get a tad deeper reverb tone. Higher bypass cap value on the send or return?
Make the 500pF cap a little bigger. 0.01uF should answer whether that does the trick for you.
Add a cap to ground from the grid of the recovery stage. Start with small-pF caps (50-250pF) and experiment. This will shave highs.
Keep the 10pF cap across the 3.3MΩ. This brings back a little treble to the dry signal only.
Try a different tank. I like the 9AB2C1B medium delay "6 spring" tank (it's really 6 spring connected to form 3 delay lines). I tried that tank in the Accutronics era, not the Belton/Accutronics era.
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I have been all over the place with tryng to find a good reverb tank. I bought a Belton 8AB2A1B and it sucks. I bought a Belton (Accutronics) 4AB3C1B and it is terrible. My fault for not checking the decay time (long)
I found my tank while trying the 12AU7 driver. It is a 60's Gibbs (Hammond). I have 4 of them and they all sound good but i hear slight differences between them. One of them is dead spot on smooth and decay rate is faster than all the tanks i have. I dont want any more gain from the reverb so i am leaving the reverb caps alone. I hear from a friend that some of these old Fender reverb tanks are fetching $150.00 and up online. Crazy man. Belton sucks. I have the number to the real accutronics in Carey Illinois (Scott Fletcher) I talked to him a few years ago. They are still in business but on a smaller scale. He will build you a tank the old fashioned way if you want. I may just be doing that in the near future just to compare. What the heck! Why not. This Korean and Taiwan tanks suck. I mean they really suck. They come apart,the springs snap off easily. Ive seen 3 of them in the VOX AC30 CC2 that were in pieces when removed. Crazy man. The Gibbs tank sounds fantastic. No delusion tonight. Happy dance! :worthy1: :worthy1: :worthy1:
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Have you tried the MOD tanks, a new one I bought recently sounds much better than the tank I have in my '72 Twin Reverb.
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Plexi, did you try the 12AU7 for the verb driver tube? If so how did it sound?
It's supposed to take the deep surf out but still leave a very nice verb.
Brad :icon_biggrin:
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Willabe i did try a 12AU7 reverb driver and it sounds the best in taming that overkill splashy tone. I like it 100% better
No i have not tried the MOD tanks. Maybe in the future. Good to know