plotting out deluxe rvb with some dumble bits

[didit]

I love the vibrolux. In fact, I use mine often in a head form with an 8r 2x12 cab, and absolutely love it. The issue is that it will be too loud. On our last tour, one of the other guitar players used a Vibrolux and was playing it on 2, with it often being too loud!
It’s tricky, but I think staying in the deluxe realm volume wise, but cleaning up the low end a little bit, is the ticket for what I need to do.

Two speakers makes an amp louder, and seem more powerful. Put them in the right cabinet and even more so. I've a well ported closed back 2x12" with paired with a pair of high efficiency speakers --- just a Champ through it seems almost deafening. A 35W Vibrolux amp played through Deluxe cabinet single 12" is objectively less than 3dB more powerful electrically than the integral Deluxe.

However, I was a bit unclear. I was attempting to nearly nothing changed in your Deluxe except the output tubes, using 5881s, and with a beefer 6.6K output transformer. That is, with any desired changes to the earlier stages to shift toward the things you want from Dumble's recipes.

The suggestion of a Bassman chassis is intriguing. Going to give that thought.

Best .. Ian

[imo1]

I guess I'm worried that the change to the 5881's would be a big enough volume change to make a difference in stage volume that would be an issue.

One of the other guitar players was suggesting that we all go out with blues juniors, to give you an idea of the volume level we are gonna be playing at.

I am trying to work off of the deluxe reverb platform, and already will be pushing it with the additional capacitance, and efficiency, which will be boosting level. I'm hoping that this could work as is.

[imo1]

It’s tricky, but I think staying in the deluxe realm volume wise, but cleaning up the low end a little bit, is the ticket for what I need to do.

There are some standard tricks for this, i.e. decrease the size of the PI coupling caps, and/or increase the grid stoppers on the 6V6's. Have you tried any of that?

I have not tried these on a deluxe build. I did build one a year or so back for my older kid that was a single channel design, but for that, it was more about knocking off some AC voltage going into PI.

Have you done these before? I'm curious to hear thoughts and ideas on implementation. The issue I am going to run into is that I am touring all summer and I have to commit to a general design. I can tweak a bit, but once I'm done the amp will live in Austin, and I live in Seattle. Working on amps on the road, away from my shop, and often between soundcheck and shows, is a stressful undertaking. I'll do as much as I can ahead of time and then hopefully have it pretty dialed in by the time I ship it to Austin.

I'm going with the standard deluxe reverb design.. I'm gonna do SS rect, the higher smoothing. I'll try a couple of the early cathode caps down around 5u for starters, and I'm gonna build in the PAB and boost circuits. I'll add a mid knob(on back) as well as a dwell knob for reverb

[martin manning]

Have you done these before? I'm curious to hear thoughts and ideas on implementation.

I have not done these on a DR, but I have a Marshall Studio 15 that has 22n PI coupling caps and 100k grid stoppers on its 6V6 power tubes. The bass sounds great, and in that location the large grid stoppers do not affect the high end. https://www.drtube.com/schematics/marshall/4001m88.gif

[imo1]

I will look at the smaller coupling caps. I think I'm gonna build it "as is" to start, with some of the changes I am doing, and then see what it sounds like.

I have a couple of questions.
-To implement the PAB function with a Fender tone stack, isn't it simply lifting the mid to ground? I am going to use a mid knob; probably 10k or 25k, so my mid knob would go to a switch(slider and footswitch) that I can lift the ground.
-Since I'm not gonna have 2 channels, but rather channel 1 going through a relay into the OD section, I'm thinking i would insert the OD section after the 500p(where channel 1 enters the reverb driver tube, with it either bypassing through the relay to reverb, or going through OD circuit into reverb. Does this seem right?

[martin manning]

.
-To implement the PAB function with a Fender tone stack, isn't it simply lifting the mid to ground? I am going to use a mid knob; probably 10k or 25k, so my mid knob would go to a switch(slider and footswitch) that I can lift the ground.

Yes. See Bluesmaster schematic here: https://ampgarage.com/forum/files/bm_dc ... 01_595.pdf
You can also pad the ground lift to give a partial lift. That has been a popular trick.

.
-Since I'm not gonna have 2 channels, but rather channel 1 going through a relay into the OD section, I'm thinking i would insert the OD section after the 500p(where channel 1 enters the reverb driver tube, with it either bypassing through the relay to reverb, or going through OD circuit into reverb. Does this seem right?

I think I would leave it where it is but do the "reverb on both channels mod." Then the OD relay would cascade the channels for OD mode. I'll study this a bit more.

[imo1]

Thanks for the bluesmaster scheme Martin. That is basically how i see it.

Regarding the insertion bit for the OD channel, I am referencing the deluxe circuit. I am assuming you are referencing an OD circuit by saying "keep it as it is"?
Im thinking that the best spot would be after the 500p coupling cap and before the reverb driver, as shown here:

deluxe.jpg

Im also realizing that I could use the tone controls on the drive channel, in theory, to help sculpt a bit, especially if it is too fizzy. I just need to figure out a way to get a 4th knob on that channel 1 section of the deluxe chassis/faceplate

[imo1]

Just to clarify, I am planning on not using the amp as a 2 channel amp, but instead using what was "channel 1" as my OD circuit, and it would be out of circuit until I click on the relay, which would engage the OD, as in the dumble style ODS

[martin manning]

I wasn't very clear, but I think we are saying the same thing. What I meant was run the clean channel straight into the reverb (a la the 'verb on both channels mod), and then insert the other channel between the clean output and reverb input in OD mode. I imagined keeping the second channel tone controls, maybe moving the tone stack (but not the volume) after the second OD stage like an HRM. The second volume becomes the OD drive. You do have two unneeded 1/4" input jack holes available on the panel.

[imo1]

Oh! Thats true.. Awesome!
I could even fit the mid knob on it(there isn't one a standard deluxe reverb).. The HRM is pretty similar in design to the bluesmaster that you linked? It has the tone stack after the two gain stages.

The OD section you linked has a bunch of alternate values. Are these different mods that Dumble did, or debate on what was used? I found another schematic for a bluesmaster that is using the 220k/3.3k and 150k/2.2k on the drive sections

Do you have any thoughts on how to enter the OD section? I know there is the trimmer at the top. I'm assuming the 120k going into it is necessary to create the voltage divider there.

[martin manning]

The OD section you linked has a bunch of alternate values. Are these different mods that Dumble did, or debate on what was used? I found another schematic for a bluesmaster that is using the 220k/3.3k and 150k/2.2k on the drive sections

Bluesmaster is a legit D amp design, of the HRM (post OD tone stack) family. The schematic I linked has some mods (by MDRoberts), but it is basically standard D configuration. There is a BM layout in the files section by T Albany that is accurate as best we know.

Do you have any thoughts on how to enter the OD section? I know there is the trimmer at the top. I'm assuming the 120k going into it is necessary to create the voltage divider there.

I would keep that feature as you will need to reduce the signal down to about 7-8% of the clean output level.
Don't forget you only need one input jack, so you could repurpose one clean channel jack hole to have four knobs there (VTMB), and one vib channel hole for a mid and one for an OD volume.
This is starting to sound like a 2x 6V6 ODS HRM with Fender tone stacks and a built-in reverb in the FX loop.

[imo1]

You are right on where it is going! However, I am using the MojoTone chassis and boards, so the trick will be figuring out how to utilize what is there and augment it.
-I can get most of the filtering done in the doghouse.

-I'm gonna have to add some eyelets to the board, and that is gonna take a little bit of planning. The main thing is around the insert point of the OD circuit, so as long as I have a new eyelet for the 500p to sit in, I should be able to implement that. I can do most of the rest of it with a couple of tag boards. Makes sense to use the "normal" channel for my base clean tone and then do the "vibrato" to build out the OD section. Makes for a little less wire

The front panel is gonna be a little silly. Probably will keep V, T, and B to use the existing lettering, and then add any additional controls in spare input holes. These are the things that drive me batty!

I'm getting the fat stack DR OT from Mercury. I get a price break from them, so it's not too bad.

I'm using the 5V windings for my relays, so I'll use a couple of diodes and a capacitor to bring them into the 5V realm. I dislike cutting out slide switches (I don't have good tools), but I also dislike using toggles for the drive and PAB, as they get flipped too easily. I may just set up toggles temp to test the circuit, and then wire to the relays and footswitch one it all works. I want to make sure that the fundamental sound of the amp is where I want it.

[imo1]

OK! I realized i needed to get this down in a schematic form. This is just the pre amp, without power section, or power amp.
Mainly trying to make sure I'm inserting the OD section correctly. The schematic software didn't have relays so I use DPDT switches.

Since I don't have 2 proper channels, I'm using the one 220 mixing resistor going out to PI. Am I missing anything or are there any things that could be better implemented?

deluxe_HRM_preamp.png

[didit]

Hello Ian --

The blending of AB763 reverb and ODS doesn't sit right. Are you borrowing from a known source design that works?

That 3M resistor in the clean "mixer" input on Fender's schematic keeps the reverb output sufficiently attenuated so there's nil feedback into the reverb input via that path. The "dwell" variable dump to ground might work fine, but other familiar designs have the forward signal off the wiper on a constant 1M or 250K resistance to ground. There's no signal drawn into the grid on V4b. While one might guess at your intentions better to connect the dots for us.

Overall at high level this approach feels right for your stated goals. My earlier suggestions were to build up to a fulsome robust low bass response a la hifi (or a beefy '60s Ampeg). However, closely filtering that response below 100Hz with smaller coupling and bypass caps is a well known and sound recipe too. One quite likely staying a bit closer to the Deluxe Reverb character you're after.

Best .. Ian

[imo1]

Hello Ian --

The blending of AB763 reverb and ODS doesn't sit right. Are you borrowing from a known source design that works?

That 3M resistor in the clean "mixer" input on Fender's schematic keeps the reverb output sufficiently attenuated so there's nil feedback into the reverb input via that path. The "dwell" variable dump to ground might work fine, but other familiar designs have the forward signal off the wiper on a constant 1M or 250K resistance to ground. There's no signal drawn into the grid on V4b. While one might guess at your intentions better to connect the dots for us.

Overall at high level this approach feels right for your stated goals. My earlier suggestions were to build up to a fulsome robust low bass response a la hifi (or a beefy '60s Ampeg). However, closely filtering that response below 100Hz with smaller coupling and bypass caps is a well known and sound recipe too. One quite likely staying a bit closer to the Deluxe Reverb character you're after.

Best .. Ian

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.

As far as my intention, it is to basically make a deluxe reverb in terms of the normal channel circuit with the reverb and tremolo, but not use the tube rectifier, and use the Dumble style of DC smoothing. My plan was to use the "normal" channel as a switchable overdrive. Adding that dwell control at the input of the reverb is a common Fender mod that I really like and have used on a bunch of my amps.

My premise is that the OT I am using, along with the additional filtering, will get me close. I've done quite a bit of experimenting with bypass caps, and found a good mix for my ear and playing style in some other amps I've built. I do find that the small bypass caps, when used in a full circuit tend to make the bass feel kind of "pointy" to me in a way that I don't like. I do like them in general earlier in the preamp. I have done a little experimenting with coupling caps, but not a ton. Martin suggested possibly using smaller caps feeding the PI, and that was something I was gonna look into once I built the circuit as I was planning it, and see what it sounded like.

I would love to hear your thoughts on the when and where of coupling caps, especially in a Fender circuit.

I know this becomes kind of apples and oranges at a certain point. As I've explored the Dumble styles of building, I have found my own path through them. A lot of the style of rhythm/lead mixed playing I like doesn't sound as cool to me with some of his circuit design. In a perfect world(with no volume restrictions) I would mix his much tighter sounding amps with more of a classic Fender style looseness, but in order to get that you need to have a volume that is just not doable these days