dmp

Re: [BUILD] The Rude Tube IVORY ====== Official build & support thread
« Reply #140 on: May 05, 2017, 11:34:21 AM »
Quote
Thanks Bern, it's the 5402 the problem, i actually checked the wiring to be sure and it just doesn't sound right with the 5402. it actually distort quite a lot and the overall low end is definitely lower.

The circuit can't drive a output transformer well, much less a 1:1 ratio. At a minimum you would want a 15k:600 (5::1 ratio) but then you lose gain and would need makeup gain to have line level. In my testing, even with a 10:1 step down output transformer the tone suffers.
I am working on adding a makeup gain stage that can drive a transformer as a solution.
As designed, I think this works great for unbalanced in, unbalanced out at instrument level but it does not work for balanced in/out with line level.


bernbrue

Re: [BUILD] The Rude Tube IVORY ====== Official build & support thread
« Reply #141 on: May 05, 2017, 11:40:06 AM »
You're probably right. A cathode follower as final tube stage would have been fine for transformer balanced output. I've used mine completely unbalanced and that work great.
Bernd

gaetan

Re: [BUILD] The Rude Tube IVORY ====== Official build & support thread
« Reply #142 on: May 06, 2017, 05:01:03 AM »
The circuit can't drive a output transformer well, much less a 1:1 ratio. At a minimum you would want a 15k:600 (5::1 ratio) but then you lose gain and would need makeup gain to have line level. In my testing, even with a 10:1 step down output transformer the tone suffers.
I am working on adding a makeup gain stage that can drive a transformer as a solution.
As designed, I think this works great for unbalanced in, unbalanced out at instrument level but it does not work for balanced in/out with line level.

I have some spare Gyraf srpp pcbs, might do the trick.

gaetan

Re: [BUILD] The Rude Tube IVORY ====== Official build & support thread
« Reply #143 on: June 08, 2017, 07:12:21 PM »
With some serious head scratching, lots of fails, i managed to get it to work with a gyraf SRPP circuit so i get balanced outputs with 5402 and without affecting the tone. and it actually sounds really nice.

I couldn't run both boards from the same power transformer as it was making some noise and i am actually going recreate the SRPP tube stage without the pcb onboad power supply, 

My question is can one powersuply board handle 4 tubes or should i use 2 boards?

bernbrue

Re: [BUILD] The Rude Tube IVORY ====== Official build & support thread
« Reply #144 on: June 09, 2017, 01:09:01 AM »
The board is not the problem. Check if your power transformer delivers enough power. Heater should have around 2A.
Bernd

gaetan

Re: [BUILD] The Rude Tube IVORY ====== Official build & support thread
« Reply #145 on: June 09, 2017, 05:02:48 AM »
The board is not the problem. Check if your power transformer delivers enough power. Heater should have around 2A.
Bernd

it's rated 2.5, but to be honest i don't mind having 2 power trafo. I'll do more experiments.

What a fun project, thanks Bern!

gaetan

Re: [BUILD] The Rude Tube IVORY ====== Official build & support thread
« Reply #146 on: October 12, 2017, 02:53:30 PM »
Here is the machine, it took me a while to get it to sound the way i wanted and i finally found the right tweaks and it sounds insanely good.

labak

Re: [BUILD] The Rude Tube IVORY ====== Official build & support thread
« Reply #147 on: October 19, 2017, 04:39:07 AM »
Hello Gaetan,

Such a nice beast.

Could you tell us more of you did at the end with G-pultec stage? What about Transformers?

Thank you.
Best regards.

Chris.

gaetan

Re: [BUILD] The Rude Tube IVORY ====== Official build & support thread
« Reply #148 on: October 30, 2017, 09:29:17 PM »
Hello Gaetan,

Such a nice beast.

Could you tell us more of you did at the end with G-pultec stage? What about Transformers?

Thank you.

input transformers are Edcor 600/15 which turned out to be a great for testing as the output is easy to swap to center tap to get less signal. i used a dual G-pultec board from PCB grinder with lundahl 5402 . i modified the output knob and added some extra resistors to reduce 20dB or so. the Gpultec runs off a secondary transformer as i struggled with a ground loop. if i remember well the floor noise is around -80dB now.
If i had to redo it i would run the rude tube into the EQ section of the Gpultec without input trafo, so i have the 20 dB of reduction already and there is a slight reduction in the low end that requires a little boost on the output.

One last fix i need to do is the bias control, i think i have a 5k pot into R15 and i will change to a multi turn to get more precision.
the current through that pot goes up to 1.25 ma with the pot fully clockwise so i just added a 100ohm resistor to get the needle in the middle when it sounds right. i think it is great for recalls to have that meter if you decide to go with a bias pot.

I would have shown the inside but i have tried so many things that it now looks like a spaghetti dish. quite embarrassing.