UltraPhonix with a few twists

[fred.violleau]

OK, completed all the wiring.

Tested the amp, and nothing burned, yay!

Got a few readings to make sure everything works, and it looks like I have a preamp tube that reads a bit low on one side.
So far,
- Power amp looks OK
- Switch between solid state and tube rectification works (450V vs 432V)
- D-lator seems good too, although voltages may be a bit high

It looks like the two preamp channels interact with each others, so I gotta have something wrong on the switch for the input and/or at the place where I am supposed to put the mixer resistors, I plugged everything straight into the D-lator input. Gotta say the Tweedle Dee has a lot more output than the Bluesmaster channel.

I will put all the voltages later tonight as I have to run some errands

Cheers,

Fred.

[fred.violleau]

Here are the voltages I get :

RECTIFICATION : Solid State
OT CT 454.5
B+2 446.5
B+3 364.0 Feeds V4
B+4A 385.6 Feeds V3
B+4B 313.0 Feeds V3
B+5 322.4 feeds V1
B+6 299.0 feeds V2

Tube Type Pin1 Pin2 Pin3 Pin4 Pin5 Pin6 Pin7 Pin8 Pin9
Bluesmaster preamp
V1 12AX7 152.3 1.17 195.7 1.83
Tweedle Dee pramp
V2 12AX7 196.1 1.51 175 1.23
D-lator
V3 12AX7 314 37.04 237.8 1.75
Phase Inversion
V4 12AX7 214.9 39.72 229 39.72
PT1
V5 6L6GC 55.1mV 450 444.9 -42.4 447 55.1mV
PT2
V6 6L6GC 54.9mV 451.5 445.4 -42.4 446.5 54.9mV


RECTIFICATION : GZ34
OT CT 436.0
B+2 429.2
B+3 349.6 Feeds V4
B+4A 371.4 Feeds V3
B+4B 301.2 Feeds V3
B+5 309.1 feeds V1
B+6 287.2 feeds V2

Tube Type Pin1 Pin2 Pin3 Pin4 Pin5 Pin6 Pin7 Pin8 Pin9
bluesmaster preamp
V1 12AX7 145.5 1.13 188.2 1.76
Tweedle Dee preamp
V2 12AX7 188.3 1.46 168 1.18
D-lator
V3 12AX7 301.3 35.75 229 1.69
Phase Inversion
V4 12AX7 207.1 38.34 220.8 38.25
PT1
V5 6L6GC 43.3mV 435.2 428.5 -42.7 429.7 43.3mV
PT2
V6 6L6GC 43.2mV 433.7 445.4 -42.7 429.4 43.2mV

I think I made a mistake hooking up B+5 and B+6 and got them feeding the wrong tube.
I will switch these tomorrow morning.

Any comment is welcomed!

Fred.

[fred.violleau]

UPDATE :

I switched the B+5 and B+6 so I feed the correct voltages to each preamp :
V2 (Tweedle Dee preamp) receives around 298V and V1 (the Bluesmaster preamp) receives 320V.

I also added 220k mixer resistors, and the 2 channels don't interact with other, I don't get any oscillation.
I may try the 470k value that is on Aaron's UP schematic and report how is sounds.

I get a "pop" when I switch channels but it's bearable. If someone knows a trick that could make it totally silent, I am down to try it !

So far everything is fully functional, all switches on the Bluesmaster channel work as well.

SONICALLY
The Tweedle Dee channel is really outstanding, I get a great crunch out of it on a strat, and pushed to the extreme, a good fat singing distortion.
The Bluesmaster channel sounds a bit weaker compared to the Tweedle Dee unless I engage the Rock Switch and The Mid Boost, then It compares volume wise to the output of the Tweedle Dee.

BM clean channel feels a little spongier than the HRM skyliner clean channel, a bit fuller as well, I will have to AB test the amp to be more precise on how they feel.
BM EQ works fine, and offers a lot of Bass!! The bass volume pot has a lot more impact on the sound than on the skyline EQ.
Smooth switch has a subtle effect, need to really push the volume to get it, but it seems to liquify the distortion and ease into it, less harsh.

I am playing on a 8 ohms speakers when my output is 2 ohms. I know I won't burn anything, but sonically it may impact what I hear not sure in which way though...

UPDATE :
Switching from tube rectification to solid state has many impact :
Sound feels spongier on tube rectification, but bass is a bit flabby if you push hard on the strings.
Bass is way stiffer with the solid state rectification.

On the D-lator, I replaced the .2uf cap with a .02uf cap, that makes the response a bit more focused on mids when I engage the active loop, which I quite like so far. I will to play a bit more with to see if I keep it that way, or if I revert to the original.

So far I am quite happy with the amp.

I will give a try to the 470k mixing resistor before I put the components into a more permanent position.
I have a few solders left to finalize here and there.
I will also correct the layout that I posted as there are a few missing connections.
I will also updates the voltages reading that I get, but so far things seems on par and stable.
Next will be Martin Mannings filters button in a small box so I can test these through the D-lator.

And here are a few pictures of the amp

IMG_20190717_113728.jpg

IMG_20190717_113802.jpg

IMG_20190717_113813.jpg

IMG_20190717_113742.jpg

IMG_20190717_113808.jpg

Cheers!

Fred.

[fred.violleau]

Actually the Tweedle Dee channel has almost no headroom, it starts to break up around 1.5, and keeps on distorting afterwards..
Anybody with a Tweedle Dee experiencing the same early break up?

Fred.

[norburybrook]

Actually the Tweedle Dee channel has almost no headroom, it starts to break up around 1.5, and keeps on distorting afterwards..
Anybody with a Tweedle Dee experiencing the same early break up?

Fred.

Fred,

No, my Tweedle dee has a fair amount of clean headroom, like the tweed deluxe, I play single coils mostly though. Have you got your NFB sorted? I have a three way switchable NFB and it makes a huge difference in clean headroom/gain.



M

[fred.violleau]

Hey Marcus,

Thanks for the reply!
Actually playing through the TD channel, it feels like when I push hard on the strings, the preamp distorts, and sort of "fart" distortion..
I checked all the connections to ground and did reflow one that was weak, but still the same issue..
Any other idea?

As for the NFB, I have the 4.7k in place, and so far I like it.
I might try to put another resistor in parralel to take it down a notch and hear the results, but I am focused on finding where this bizarre distortion comes from on the TD channel
I might get a sound clip to make it clearer.

Fred.

[norburybrook]

Hey Marcus,

Thanks for the reply!
Actually playing through the TD channel, it feels like when I push hard on the strings, the preamp distorts, and sort of "fart" distortion..
I checked all the connections to ground and did reflow one that was weak, but still the same issue..
Any other idea?

As for the NFB, I have the 4.7k in place, and so far I like it.
I might try to put another resistor in parralel to take it down a notch and hear the results, but I am focused on finding where this bizarre distortion comes from on the TD channel
I might get a sound clip to make it clearer.

Fred.

Fred, my Tweedle Dee overdrives very sweetly. It has a lovely clean and a great crunch tone too. There's obviously something different on your build about the gain stages perhaps.

when your amp is in Tweed mode is the chain the same as a tweed all the way to the power tubes or does it vary at some point to a different topology? I suppose that's where you could start.

This is not an area I'm very good at Fred so I'm just thinking aloud

build looks great though


M

[fred.violleau]

Hey Marcus,

Thanks for the kind words! I tried to do my best in keeping things tidy and organized.

Signal chain is quite simple :
guitar > relay to switch between the two preamps > preamp (Tweedle Dee verbatim or Bluesmaster lowish plates) > D-lator (which I can bypass) > Phase Inversion > Power amp

On the TD channel, depending on how hard I hit the strings (strat single coils), I get the clean sound, or a clean sound with some kind of solid state distortion on top of the clean sound.
And this is not happening on the Bluesmaster Channel, which BTW starts to break up gently around 7.5
So I may put aside Power Amp, PI, and D-lator .

That leaves me with the relay and the preamp board.

I checked all the resistor values and all check out with my layout. I did check with the original layout, and I dont see any mistakes.

Here is a link to a small video so you can the two channels:
https://www.youtube.com/watch?v=9xNnOz3VVNc

I use the D-lator to tame the overall output volume

Fred.

[norburybrook]

Fred,


Nice to hear your voice you're a real person

Amp is sounding great apart from too much gain on the tweed. nice playing too

thinking about it; the BM is a master volume amp with a switchable extra gain stage for the OD. The amp has a lot of clean headroom.

the tweed is a non master volume amp that breaks up early.

I wonder if these too topologies are always as going to be a little unbalanced.

Joe Bonamassa runs a pair of ODS and a pair of tweed twins BUT he runs the ODS amps permanently in OD so they blend and respond well with the tweed twins. If I run my ODS with my Trainwreck I do the same thing otherwise the wreck is starting to OD and the ODS is completely clean. If the ODS is in OD mode then using the guitar volume will clean it up in the same way as the wreck.

I hope someone above my pay grade can chime in here with help regarding excessive gain on your tweed channel and help you Fred.


M

[fred.violleau]

Hey Marcus,

You are the most dedicated and reliable expert on this forum these days ! Surelly everyone is enjoying summer!
Again, thanks for the kind words, and yeah we forget sometimes there are actual human beings behind these words

You have a great point in comparing the master volume setup vs non master volume. In the same idea I thought this morning of measuring the output in mV of each channel and see how they compare. Maybe the TD channel is feeding too much signal into the D-lator.

Fred.

[norburybrook]

You have a great point in comparing the master volume setup vs non master volume. In the same idea I thought this morning of measuring the output in mV of each channel and see how they compare. Maybe the TD channel is feeding too much signal into the D-lator.

Fred.

that's a good point Fred, i'd forgotten about the dumbleator, you might be right on that as it's the only unknown variable in the Tweed side of things. Can you jumper/Bypass the Dumbleator to try this on the tweed side?


M

p.s. I might be reliable but I'm no expert

[erwin_ve]

The Tweede Dee has a cathodyne phase inverter with Lnfb. A fair amount of drive is generated in the PI.
I Imagine that would be a tad different in comparison to the LTPI.

[fred.violleau]

Hey Erwin_we, thanks for jumping in!

That was my initial thought when designing the amp.
I thought that the LTPI would provide a little less distortion (unless pushed into the extreme of course).

Marcus, I have a bypass on the D-lator, and it is still distorting when I bypass the D-lator. So it may come from the PI being overloaded..
I mean the signal difference is really huge.

Here is my setup for tests :
a sine wave of 125Hz feeding the input switcher
-TD channel has 0.584V right after the 33K resistor
-BM channel has 0.612V right after the 33K resistor.

Then I took a measurement on V1B and V2B (all controls at noon for each channel excluding volume pots)
-TD channel delivers at full volume 28.05V
-BM delivers around 5.08V

Massive difference..
That tells me there is one to tame, I will go back on the BM layout see if Tony did document voltages on this side, see if I can get a sense of what it should be.

Fred.

[fred.violleau]

Actually, I can't find that type of info on the layouts.
I will use my HRM and see with the same setup, what is the maximum output of the clean side, in order to get a sense of where the truth is.

Fred.

[erwin_ve]

Fred, that is indeed a huge difference. On one of my Ods amps with a 12at7 in the PI position I measured the signal on the input of the PI and the Speaker output. Right before clipping a 8,5v PP sine wave signal generated a clean sine wave at the output.

A bluesmaster PI has even less headroom.