UltraPhonix with a few twists

[talbany]

Tony, I believe the schematic attached the first post was taken from the photo of the Bandmaster. I’m just not sure of some of the resistor values including those mixing resistors.
CW

Cool! Thanks Charlie. Just wondering if that schematic was taken from that exact amp since HAD took some liberties with respect with RP/Rk values and there respected bypass caps.After seeing several schemo's and shots and others who have been in them are telling me they are all a bit different or custom voiced!

Tony

[fred.violleau]

Hey guys, thanks for sharing your words of wisdom! Busy job, two kids and wife are slowing me down a bit on the schematic, but the layout is almost done. I Will gladly share and hope there aren't to many mistakes.

In the meantime, cheers!

Fred.

[fred.violleau]

I think that plan is reasonable since you don’t need a high signal level to send out to the FX. The send buffer has high input impedance, and approx unity voltage gain. Even with nothing in the loop you’ll have the recovery gain you need.

So It would look like something like this (taken from MHartman's schematic here
https://ampgarage.com/forum/viewtopic.php?f=4&t=29722

Capture d’écran 2018-11-13 à 21.24.55.png

Questions :
-Do I need the local feedback ? (22M / .047uf)
-Can i put it on switch to see how it affects the sound?
-I suppose I need the coupling 0,47 cap and then I could send to the on/off switch of the D-Lator instead of the 1M Level pot

What is the difference sonically speaking with this recovery stage ?

Capture d’écran 2018-11-13 à 21.34.29.png

Which one would you recommend?

I thought I could put the filters on a bypass switch. Although both filter at noon seems to bring unity (not affect the signal) I am sure adding a recovery stage in the equation will somehow. What are your thoughts on this ?

Many thanks.

Fred.

[dorrisant]

Fred, you could tap the junction of the 22M and the .047uF. Break the circuit or ground this point with a switch to render it out of circuit.

I too am interested in the sonic difference between the two recovery stages. I'm leaning toward the last schematic you posted... looks like #002. Kinda pausing at this point for an SSS layout I want to build. This is a great discussion, much to learn.

[fred.violleau]

I too am interested in the sonic difference between the two recovery stages. I'm leaning toward the last schematic you posted... looks like #002. Kinda pausing at this point for an SSS layout I want to build. This is a great discussion, much to learn.

I am leaning toward the second one also. From what I read on the forum and the schematics I studied, the LNB trick Dumble over-used on Hmartin SSS seems to play a big part in the silky sound. Or maybe I am wrong, I am not keen on electronic to understand all that is happening on the circuit

My goal is to lean towards the Dumbleland more than the SSS. I want the amp to break up hence the Ultraphonix values. There seems to be variations on the cathode values, probably based on player's need to get more or less clean headroom. Again I will lean towards the dark Side

Which is why I am trying to figure out which would be best to implement !

Thanks for sharing your thought!


Fred.

[fred.violleau]

So I took a little time to organize a preamp schematic to make the conversation easier.
It's a first for me, and the schematic is untested so there might be errors all over the place.

Preamp offers
-mid boost, PAB on relays
-the usual bright, rock/jazz and deep switch
-2 way LNFB (Smooth switch)
-Martin Manning Filters
-a recovery stage for the filters (2 options)

Capture d’écran 2018-11-18 à 09.03.18.png

UltraPhonix Fred.pdf

From what I understand (or think I do) option 2 seems to allow to isolate the filters better than the option 1 where the CF from V1b will still bleed some signals back into the chain after V2b even if the switch is closed and drive the signal straight into the master pot, right?

Also, both designs use a different cap value at the output of the filters (in orange on the schematic).
Are these both a Low Pass filter ? Then .047uf would let more bass through than .01uf right?

Which design seems to you the best option?
Any recommendations?

[fred.violleau]

So here is the complete schematic.
Hopefully I did not make too many mistakes.
I called it the bluesmaster EXTRA, as it borrows a lot from the bluesmater, but a few thing I took from the Ultraphonix as well. I added the deep switch to the design, although many say the Bluesmaster is bass heavy, so I don't know if it really is a good idea.

Bluesmaster ULTRA.pdf

If you catch some errors, please let me know so I can adjust.
I am not sure yet about the dropping strings after the choke for the B+ rail.
I have different options for the power transformer. I will get into these discussions once the preamp, filters and D-lator stuff is figured out.

Let me know what you experts think, and if it makes sense, tonally, electrically, and philosophically as we refer to Dumble designs.

I must say I borrowed from the works of M. Manning, Aaron, Steve Ahola, MHartman and many of the passionate builders here.
None of this would be possible without the fantastic work of Mr Dumble of course.
Thank you all for the inspiration.

Fred.

[Charlie Wilson]

Hello, minor detail but the schematic that goes along with Tony's layout for the Dumbleator is good. I am talking about the recovery side of your loop schematic. The 1.5k cathode resistor should be 1.3k and the cathode cap should be 47uf.
CW

[fred.violleau]

@CharlieWilson, thanks for the review! I thought the 47uf was a mistake, I will update accordingly.

And I realize I forgot to thanks you and Tony for all your contributions including this one! Cheers!

BTW, some reading on Merlin Blencowe on designing Tube preamp and specifically the CF chapter, convinced me to go after option 1.

Also after thinking about the implementation of this design, I will also replace the filters switch with a DPDT. That way I can I can ground the signal coming back from the CF when not used.

I will first try to let it bleed through the signal chain and hear what it does.

Fred.

Fred.

[martin manning]

Fred, I think you have some problems here. I see you have no coupling cap ahead of the channel switches, so you are switching high voltage, and you are putting a high DC voltage on the master pots. Also, I don’t understand what you are doing in option 1, where there seems to be some kind of feedback loop, but in any case it’s source and the output from the CF are from ground, at the bottom of the 100k resistor. My suggestion (same as I made to D Beasley) is to run the filters into the send buffer stage, the output of which will be sufficient for the FX, the recovery stage will boost the signal back up before it hits the PI.

[fred.violleau]

Martin, thanks for jumping in! I think I forgot one of the basics here, with the coupling cap. There used to be a .047uf that I removed ... I will correct it.

As for the second part, I tried to reuse what was done on the SSS #2 schematic isolated here:



It looks like a DC coupling design, isnt it? Is There something wrong with it?

Thanks.

Fred.

[fred.violleau]

Ah I see, I made a mistake and connected the DC coupling after the 100k resistor, should have been before the resistor. I will adjust too.

Thanks!

Fred.

[martin manning]

Are you going for SSS or ODS wih step filters available on both channels? If it’s the latter, I would simplify and eliminate the gain stage following the filters, and just use the loop buffer with no LNFB.

[fred.violleau]

Martin, it seems to gravitate towards the ODS more than the SSS, but without the OD channel. I am willing to get a great clean Platform with a bit of breakup if pushed above 6 or 7, something between the Ultraphonix and the bluesmaster hence the mix with Ultraphonix rk and ck values on the clean V1 section.

I understood that I could drive the filters from V1b, but needed recovery stage after. After reading on the benefits of DC coupling CF on Merlin's book (Soft clipping capabilities etc..) I thought that option 1 was the best to follow sound wise, and following a design by Mr Dumble, I was on par with philosophy as well

So should I drop the recovery stage for the filters? Would the signal be strong enough for the FX Loop stage?

Thanks again.

Fred.

[Synchu]

Why not look at Small Special?
Niki