plotting out deluxe rvb with some dumble bits

[sluckey]

Thanks for alerting me! I have the Deluxe reverb schematic, but I had been looking at Mojotone's schematic for the amp, and wrongly assuming it was 100% accurate. I'm going to talk to them and see if that is an error on their part or if they meant to put the 68k there.

68K is an error on mojo's schematic. Their layout correctly shows a 3.3M.

[imo1]

I noticed the error when Ian pointed it out in the schematic.

My default is to jump into a build without documenting it. This isn't good practice, but I'm often in a hurry, and I try to be methodical with the build itself; the prep tends to be the sacrificial component.

I am trying to do a better job of prepping and documenting my materials. My whole foray into electronics comes from a conversation many years ago with my neuroscientist cousin in which I explained to him my frustrations with my nonlinear creative brain. He suggested I take up a hobby that forced me to think in a more linear fashion. That was building audio gear.

I leave for a month long tour on Wednesday. My goal is to have the documentation pretty much done, and have an idea of how to populate and build out this design. I will be using the Fender boards, so if I do build an actual layout, I need to use the deluxe as the base. If anyone knows of good ways to alter an exisiting layout with added bits, I would love to hear it. I need to get any new eyelets on the board before I start populating it. As of now, I am rough drafting a small change on the board to add my insert point to the OD circuit at the 500P. I think I can get most of the rest of the additions done with a few tag boards.

[imo1]

Here is a first take on poweramp/power section. The dropping resistors are just placeholders. I need to go through circuit and rough out what I want per section.
I'm using the 5V windings to power the relays. I figured i could use a FW rectifier, and then just drop approximately 2V with the diodes. Is there any reason this wouldn't work?

I know the voltage to the tubes will be a bit high. The PT I am using is 350V, so I am assuming I may need to come up with some solution for dropping overall voltage. I will probably use a 20uF 500V cap after the choke.

[imo1]

I roughed in my voltages to try to get a decent starting point for my power section.
Thinking 470 coming in.

deluxe_BM_power-with B+.png

[martin manning]

I'm using the 5V windings to power the relays. I figured i could use a FW rectifier, and then just drop approximately 2V with the diodes. Is there any reason this wouldn't work?

The full wave bridge will have two diode drops, so you may only need two more diodes to get down to 5VDC, but of course that winding will be delivering over 5V with such a light load.

See below for a couple of corrections. Also, you should arrange the Clean/OD switching to ground the OD input when clean is selected.

470 is awfully high for 6V6's, and I believe it will sound better if the plate voltage is closer to 400.

[imo1]

I'm using the 5V windings to power the relays. I figured i could use a FW rectifier, and then just drop approximately 2V with the diodes. Is there any reason this wouldn't work?

The full wave bridge will have two diode drops, so you may only need two more diodes to get down to 5VDC, but of course that winding will be delivering over 5V with such a light load.

See below for a couple of corrections. Also, you should arrange the Clean/OD switching to ground the OD input when clean is selected.

470 is awfully high for 6V6's, and I believe it will sound better if the plate voltage is closer to 400.

Thanks for your response, Martin.

Yes, I'm thinking the same thing. I was looking at the HV center-tap dropping options. It looks like the MOSFET dropper is not that difficult, and I could experiment with a couple of different voltages. I know a lot of Deluxes run around 420-430, and I could also try to lower voltage to @400 and see how that feels.

-33k was just a clerical error. I will fix that. Thanks for pointing it out.
-Same on the 3.3M/10P I put the tube in the wrong way and it didn't show the grid connection. Fixed it.
-grounded OD circuit when not in use

deluxe_BM_preamp_v2.png

[martin manning]

My point with moving the reverb parallel bypass network (3M3 and 10P) was that as drawn you are always taking the reverb bypass from the clean output stage, rather than switching the OD stage in between the clean output and the reverb input.

The Dumble HRM's have separate masters, one for clean and one for OD. As it stands you don't have a clean master. Adding that, I'm counting one input jack and 14 controls (15 total) where a DR faceplate only has 13 holes.

I have not done one yet, but dropping B+ voltage with a MOSFET seems potentially unreliable. Maybe others can comment, but the last thing you want is your amp going silent during a live performance.

[didit]

I know the voltage to the tubes will be a bit high. The PT I am using is 350V, so I am assuming I may need to come up with some solution for dropping overall voltage.

Why this choice vs the "replacement" 325-330V options available?

Best ..

[imo1]

Mojotone offers the transformer as part of their "Blackface Deluxe Reverb" kit. I get a deal with them, and it made sense to get the whole thing in one fell swoop.
I ordered the kit and as I was looking at the specs of the PT realized it was a bit higher- https://www.mojotone.com/Deluxe-Reverb- ... er-125P23B

[imo1]

My point with moving the reverb parallel bypass network (3M3 and 10P) was that as drawn you are always taking the reverb bypass from the clean output stage, rather than switching the OD stage in between the clean output and the reverb input.

The Dumble HRM's have separate masters, one for clean and one for OD. As it stands you don't have a clean master. Adding that, I'm counting one input jack and 14 controls (15 total) where a DR faceplate only has 13 holes.

I have not done one yet, but dropping B+ voltage with a MOSFET seems potentially unreliable. Maybe others can comment, but the last thing you want is your amp going silent during a live performance.

-OK. So the 3.3M needs to be downstream of the OD section to mix it with the dry signal properly. I didn't clearly see that. Thanks for pointing it out. I will amend this.

-I wasn't envisioning needing a clean Master. I was imagining being able to set the clean amp for a base sound that worked for me and then using the internal trim to set the input accordingly to the OD section. It seems that this would accomplish a similar thing since the circuits are in series. Is there another reason for having a master before the trim?

-The higher voltage is a bit of a question mark for me. I don't know why Mojotone is selling a 350V PT when line voltage has gotten higher over the years. I like the idea of eliminating the rectifier tube, and I like the idea of the larger filtering. I don't want to push the power tubes too hard. I have an early silver face Deluxe Reverb that sounds good around 440-450 with a GZ34. I wouldn't be unhappy with that voltage and sound, but 470 is pushing it. I am looking to make a road-worthy amp, so if the MOSFET adds a degree of unreliability, I don't want to chance it. I was trying to come up with a solid way to get in the low 400's. I can buy another PT, and maybe that is the solution. I was hoping to get there mostly with the components in the kit.

[imo1]

I am looking around at some other PT's and in general they are around 330V AC. The 350 is high, but they seem to all sit around this voltage. I know that using a solid state rectification for a Deluxe Reverb is not that out of the blue, and know there are a number of amp companies making similar designs. Maybe they are using lower voltage PT's to do this. I don't know.

I amended the pre amp schematic to address the post OD reverb combine.

Deluxe_BM_preamp_v3.png

[didit]

Mojotone offers the transformer as part of their "Blackface Deluxe Reverb" kit. I get a deal with them, and it made sense to get the whole thing in one fell swoop.
I ordered the kit and as I was looking at the specs of the PT realized it was a bit higher- https://www.mojotone.com/Deluxe-Reverb- ... er-125P23B

I'm unfamiliar with Mojotone's spec writing details -- if their 354V is "unloaded" AC all is good. That'd yield a lower filtered DC.

Given the time and effort you're putting into this, adding a FBFDR-PM to your Mercury order would seem a sound solution.

..

[imo1]

,

Ive been trying to read up on the use of the MOSFETs for bringing down power supply voltages. The MOSFET reducer mentioned here https://ampgarage.com/forum/viewtopic.php?t=27035 appears to have been used by several individuals. It seems to be pretty reliable, although I have limited experience with it based on my research. Have you encountered any issues with this design?

This is a crossroads of sorts. I can either go with the tube rectifier, which would eliminate my plan to use the added PS filtering, or I could use the SS rectifier with some power dump to lower B+.

My touring amp for the last few years is a 6L6 amp with SS rectifier and stiffer filtering. I would like to build a similar style amp, but with a smaller, more manageable volume. The Deluxe is a good platform for this. It seems that building this essential circuit would be a good route to go

[imo1]

Mojotone offers the transformer as part of their "Blackface Deluxe Reverb" kit. I get a deal with them, and it made sense to get the whole thing in one fell swoop.
I ordered the kit and as I was looking at the specs of the PT realized it was a bit higher- https://www.mojotone.com/Deluxe-Reverb- ... er-125P23B

I'm unfamiliar with Mojotone's spec writing details -- if their 354V is "unloaded" AC all is good. That'd yield a lower filtered DC.

Given the time and effort you're putting into this, adding a FBFDR-PM to your Mercury order would seem a sound solution.

..

As much as I'd like to stop spending money, this is probably a good idea

[martin manning]

-I wasn't envisioning needing a clean Master. I was imagining being able to set the clean amp for a base sound that worked for me and then using the internal trim to set the input accordingly to the OD section. It seems that this would accomplish a similar thing since the circuits are in series. Is there another reason for having a master before the trim?

The so-called second generation Dumbles work that way, with a fixed OD input attenuation set internally, and one master volume for clean and OD at the PI input. The clean output either goes straight into the OD entrance or direct to the MV. Some people have added a clean master, and found that to be useful. That's following the evolution of the ODS by adding the ability to use the clean volume to set the level going into the OD, and have a separate control for the clean volume in clean mode. The first iteration added an OD volume (at the OD output) that allowed the relative Clean/OD levels to be controlled, and the overall level still set by the MV. Finally, separate masters were used, one at the output of the clean and one at the output of the OD, with each going direct to the PI input as determined by the OD relay.

-The higher voltage is a bit of a question mark for me. I don't know why Mojotone is selling a 350V PT when line voltage has gotten higher over the years. I like the idea of eliminating the rectifier tube, and I like the idea of the larger filtering. I don't want to push the power tubes too hard. I have an early silver face Deluxe Reverb that sounds good around 440-450 with a GZ34. I wouldn't be unhappy with that voltage and sound, but 470 is pushing it. I am looking to make a road-worthy amp, so if the MOSFET adds a degree of unreliability, I don't want to chance it. I was trying to come up with a solid way to get in the low 400's. I can buy another PT, and maybe that is the solution. I was hoping to get there mostly with the components in the kit.

For the DR I built, I used a Hammond 290BX PT (330V Spec), and a 5U4GB to drop the B+ ~50V to ~400V. Unloaded, it produced something like 490 VDC. Ian's MM proposal is even better at 315. Mojo used to sell kits without transformers, IDK if they still do that.