UltraPhonix with a few twists

[fred.violleau]

Even the Super Reverb schematic does not talk about an orange tap.

Screenshot_20190528-073835.png

Although I found a replacemen PT that seems to match the description, but I am missing the heaters CT...

Screenshot_20190527-174839.png

Fred.

[erwin_ve]

Hi Fred, recently got the same with my PT. https://ampgarage.com/forum/viewtopic.p ... 30#p397917. It is the tap connected to the transformer iron, creating a faraday shield when grounded.

[fred.violleau]

Thanks Erwin_we!

So if I want to test for continuity in order to validate the orange wire is connected to the core, it should have continuity with both sides?
Fred.

[erwin_ve]

Thanks Erwin_we!

So if I want to test for continuity in order to validate the orange wire is connected to the core, it should have continuity with both sides? Primary and secondary?

Fred.

It isnt connected to the primary or secondary. Think about it like a shielded wire.

[norburybrook]

just test it against the Transformer body for continuity in that case.

M

[fred.violleau]

Thanks Marcus and Erwin_ve
Yeah giving a second thought and looking at your drawing Erwin, I was like it cannot connect.. you confirmed it!

Thanks guys! Tonight I should install the OT.

Fred.

[pompeiisneaks]

Took a pic of the actual wires:
IMG_20190527_201600.jpg

2 black primary wires
2 green heaters wires 6.6v
2 yellow rect heaters 5.2v
2 red HT 713v
1 red & blue 50v bias tap
1 red and yellow HT CT
1 orange Primary ground?

@Martin, I will check continuity tonight!

Fred.

Often orange is the faraday cage. Grounds some more hum from the transformer.

~Phil

[fred.violleau]

Thanks guys !

As I am using an old fender Super Reverb Output Transformer, I only have a 2 Ohms tap.
How should I adjust the negative feedback resistor value? For now it is 4.7k 2w. Rule of thumb from what I have seen on a schematics and layouts is value of the resistor is decreasing with the Ohms output value. So 4.7k for a 4 ohms NFB would you imply 2.xk for a 2 Ohms output ? 2.4k, 2.7k?

Fred.

[fred.violleau]

And BTW, can't get to connect through the Tapatalk app. Anyone else having this issue?

[norburybrook]

And BTW, can't get to connect through the Tapatalk app. Anyone else having this issue?

yes, I've been having the same problems whilst on the road this last few weeks.


M

[erwin_ve]

Thanks guys !

As I am using an old fender Super Reverb Output Transformer, I only have a 2 Ohms tap.
How should I adjust the negative feedback resistor value? For now it is 4.7k 2w. Rule of thumb from what I have seen on a schematics and layouts is value of the resistor is decreasing with the Ohms output value. So 4.7k for a 4 ohms NFB would you imply 2.xk for a 2 Ohms output ? 2.4k, 2.7k?

Fred.

You could try 4k7/1,4=±3k3

[pompeiisneaks]

And BTW, can't get to connect through the Tapatalk app. Anyone else having this issue?

yes, I've been having the same problems whilst on the road this last few weeks.


M

I mentioned this in the 'site problems' thread. they were notifying me I had an out of date addon, so I updated it and broke it, and I can't get it working again, I'll try again later, but their instructions basically don't work to do an update.

~Phil

[fred.violleau]

@erwin_we thanks! If I leave the value to 4.7k it means I am "blocking" or "adding" more feedback?
Would I really hear the difference between the two? I might try to leave it on and then clip a resistor in parallel and let me ears decide

I checked on my voltages and the output is like 480 VDC on B+2. Quite high... I am assuming that since I don't have anything hooked up but the power tube filtering it is normal. My goal is to debug as I go so I have less to do in the end. I have almost finished hooking up the PI. Next is the onboard D-lator and then I should be able to plug in the return Jack and see if I get a sound right?

@Phil thks for the update, hopefully it will get sorted and posting will be as easy as it used to be

Fred.

[erwin_ve]

@erwin_we thanks! If I leave the value to 4.7k it means I am "blocking" or "adding" more feedback?
Would I really hear the difference between the two? I might try to leave it on and then clip a resistor in parallel and let me ears decide

I checked on my voltages and the output is like 480 VDC on B+2. Quite high... I am assuming that since I don't have anything hooked up but the power tube filtering it is normal. My goal is to debug as I go so I have less to do in the end. I have almost finished hooking up the PI. Next is the onboard D-lator and then I should be able to plug in the return Jack and see if I get a sound right?

@Phil thks for the update, hopefully it will get sorted and posting will be as easy as it used to be

Fred.

Leaving the gnfb resistor at 4k7 @ 2 Ohm is less negative feedback and you have more high end. The difference between 4k7 and 3k3 is noticeable. It's a matter of taste choosing between the two.

Yes a unloaded B+ means higher voltages. It will come together once all tubes are in.
When finishing the PI don't forget to hook up the bias circuit.

[fred.violleau]

Thanks for the info erwin_ve !

I have made progress and have plugged in the tweed channel. Works fine.

Here is an updated layout with the latest developments:

TweedMasterLayout.pdf

I still have a few questions : I added a switching input with a relay so I can toggle between channel A (Tweedle Dee Bright channel) and channel B (bluesmaster).
1 - I hope the input switching wiring is good, can someone confirm?
2- Will it induce a major "pop" when channel is being switched?

I also added a red circle at the output of both channels before they feed the onboard D-lator. My initial layout was without mixing resistors. I added some based on some UP pictures although, values may differ a lot.
3- Do I need the mixing resistors?
4- If I do need these, what value would you recommend ?
5- Am I right to assume the higher the value of the mixing resistor, the more loss on the signal strength down the line?

Thanks for your input, and I hope you all enjoy a great summer!

Cheers!

Fred.