Author Topic: Uber tuber issue  (Read 943 times)

SirEgno

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Uber tuber issue
« on: June 17, 2019, 10:10:35 AM »
Hi,
I just made a uber tuber.
The tube is a 6021 from smallbear. Every value as from the BOM, but C4 is 10n on socket.
I set the trimmers to have about 11,5V on each plate (drive knob at 0%).
The sound is very dark, SAT and CUT doesn't do anything.
I probed it. On pin 1 of CUT knob (all the way up) the sound is brighter.
I don't have tool to measure except my multimeter and my ears.
What can I do?
Here two photos of my building:



Thanks!

shiftybuilder

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Re: Uber tuber issue
« Reply #1 on: June 17, 2019, 10:11:55 AM »
I am having the same issue with the sat and cut knobs not doing anything.

EBK

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Re: Uber tuber issue
« Reply #2 on: June 17, 2019, 10:35:50 AM »
Yep. Me too. The design is very sensitive with regard to the tubes, it seems.  Some simply won't work.  I originally built mine with a tube from smallbear.  While my Cut control worked, Sat did nothing.  Seemed the gain for my tube was too low or something.  Did my best to tweak the resistors to no avail.  I eventually changed the tube, but haven't got it quite working yet (think I messed something up when I was removing the tube board).  Mine is sitting on my debug heap waiting for me to pick it up and try it again.
Technical difficulties in abundance.  Please stand by.  ;-)

SirEgno

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Re: Uber tuber issue
« Reply #3 on: June 17, 2019, 10:44:39 AM »
I'm thinking to change the two cathode resistors, maybe trying 1k.

zgrav

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Re: Uber tuber issue
« Reply #4 on: June 18, 2019, 09:22:09 AM »
I built the Uber Tuber and my Sat control works but it is subtle.  Running a hotter signal to the input helps.

SirEgno

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Re: Uber tuber issue
« Reply #5 on: June 19, 2019, 04:49:13 PM »
I tried to socket the cathode resistors. It didn't work.
With both 1k the sound is too distorted, but still with low output.
The tube is to blame.
I have another 6021, but is the same batch. I'll try next days.

SirEgno

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Re: Uber tuber issue
« Reply #6 on: July 03, 2019, 01:43:09 AM »
Ok, today I got 20 6111. At least one should work!  ;D

EBK

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Re: Uber tuber issue
« Reply #7 on: July 03, 2019, 03:33:05 AM »
Good luck.  Looks like you have two different batches there, so there is a chance.
Technical difficulties in abundance.  Please stand by.  ;-)

SirEgno

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Re: Uber tuber issue
« Reply #8 on: November 16, 2019, 08:47:02 AM »
Update (not so updating): I tried 3 different 6111 (different batches) and the result is quite the same.
If I take the signal at TP1 (using a 10uF capacitor) and set the plate at 15v the sound is a lot better, but at TP2 it become dark and low again, even with higher plate voltage.