Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: fingersoccer on May 17, 2016, 03:09:57 pm

Title: Removing the tremolo circuit from a Deluxe Reverb
Post by: fingersoccer on May 17, 2016, 03:09:57 pm

I'm going to build a Deluxe Reverb from scratch, but I'd like to leave out the tremolo. The tremolo circuit is easy enough to identify and pull out of the schematic, but I want to make sure I'm not accidentally removing some crucial bit of the bias circuit in the process. I looked at the Blackface Bassman schematic (since it doesn't have tremolo) and came up with what you see here. It looks right to me, but I could use some wise eyes on this to double check.

I found a useful thread on the (DIY Audio Forum (http://goo.gl/74yclg)), but the images links are broken, rendering it a bit less than helpful.


(http://i.imgur.com/2Vr387O.png)

Title: Re: Removing the tremolo circuit from a Deluxe Reverb
Post by: sluckey on May 17, 2016, 04:06:33 pm

Looks good. Your R20 should be 47Ω for a Deluxe Reverb using an 8Ω speaker. R40 and R41 should be 10K.

Title: Re: Removing the tremolo circuit from a Deluxe Reverb
Post by: Shack on May 17, 2016, 04:52:53 pm

How do you see that lol.....what would be the difference if the 100 ohm was left there?

Title: Re: Removing the tremolo circuit from a Deluxe Reverb
Post by: sluckey on May 17, 2016, 05:15:01 pm

Quote from: Shack on May 17, 2016, 04:52:53 pm

How do you see that lol.....what would be the difference if the 100 ohm was left there?

I see it by looking at a DR AB763 schematic. NFB would be stronger using a 100Ω. Probably not hear much difference. That's just how Leo did it. All his AB763 amps that connected to an 8Ω speaker load used a 47Ω resistor in that position. The amps that had a 4Ω or 2Ω speaker load used a 100Ω resistor.

Title: Re: Removing the tremolo circuit from a Deluxe Reverb
Post by: fingersoccer on May 17, 2016, 06:15:49 pm

sluckey: The values for R20, R40, and R41 were all pulled from the Hoffman 1ch Deluxe Reverb build (http://el34world.com/Hoffman/files/Hoffman_AB763_1.pdf). Do you think those values should be replaced with the original Fender values?

Title: Re: Removing the tremolo circuit from a Deluxe Reverb
Post by: fingersoccer on May 17, 2016, 06:17:41 pm

Oh look, I found another thread with a very similar objective: http://el34world.com/Forum/index.php?topic=18882.0 (http://el34world.com/Forum/index.php?topic=18882.0)

Title: Re: Removing the tremolo circuit from a Deluxe Reverb
Post by: sluckey on May 17, 2016, 06:36:25 pm

Quote from: fingersoccer on May 17, 2016, 06:15:49 pm

sluckey: The values for R20, R40, and R41 were all pulled from the Hoffman 1ch Deluxe Reverb build (http://el34world.com/Hoffman/files/Hoffman_AB763_1.pdf). Do you think those values should be replaced with the original Fender values?

That is Hoffman's AB763 amp. It's not specifically a Deluxe Reverb. Hoffman shows Deluxe Reverb specific values in this file...

     http://el34world.com/Hoffman/files/Hoffman_AB763_2.pdf (http://el34world.com/Hoffman/files/Hoffman_AB763_2.pdf)