Weird fuzz from Aikido Pre, HELP! - diyAudio
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Old 27th February 2009, 11:16 PM   #1
Renron is offline Renron  United States
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Question Weird fuzz from Aikido Pre, HELP!

This is my first tube project and may be my last too.....
After 2 years of reading and trying to understand how valves work, I finally built my Aikido Preamp. I used John Broskie's octal board with 6sn7 input and output. Mr. Bas' Tube HV power supply board and Mikkel's attenuator with display and remote functions. All were kits.
The build went well and it looks GREAT!

There is a weird fuzziness to the sound, but not a crackle, almost like a poorly tuned AM radio station. It's not a hum or a buzz that would be associated with a transformer noise or AC related electrical field. More like being too close to a microphone kinda fuzzy. Think drunk DJ with a cheap microphone at a wedding kind of fuzzy. I can hear the clarity of the music in the background but it's
hidden by the fuzz.

I think it's a grounding issue somewhere, but I've tried every possibility I can think of and I need help. I just don't know enough to get this working right. I'm very frustrated.
Signal input and output grounds are isolated from the chassis, thanks Gregg; (AKA Geek)
I have run a wire from the -Ve to the chassis...no difference.

I've checked the solder joints on the attenuation board.....nope.
Solder joints on the Aikido board......nope.
I've bypassed the attenuation board altogether..........nope.
I've checked the voltage of B+ , the B+ bias, Heaters and jumpers on the board.....all are fine.
I've replaced the rectifier tube ..........nope.
I've removed the output caps and used .33 PIOs instead......nope.

I'm out of ideas and could use some help. Please.
Any inputs or ideas you may have will be appreciated. I'm happy to give anything a try. But, I am a newb, so speak/type slowly.

Failing my own attempts at finding the cause:
I live in the Sacramento area and would be happy to provide your favorite beverage for a hands on look if you could spare some time. I'll drive, just give me directions and what beverage you would like.
I know there is someone in Davis that is a valve lover, I just cannot remember whom it is to directly beg their help.

I've attached a link to a sound file hosted elsewhere on the net.

Fuzzy sound file
Make sure to click the "Skip this Ad" at the top of the PoP UP window.

It's taped up so I don't scratch the Carbon Fiber while working on it.
The top I powder coated at home, mods for the PC gun I posted on this website.
Thanks for the helping hand,
Ron

edited several times .....'cause I care!
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Old 27th February 2009, 11:22 PM   #2
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Looks great.

From someone who has had their fair share of problems as they build.... take a step back, find your innner calm (! I'm not a hippy honest!) and then remove your emotions from it (hence your frustrations). Then start logically to work through it step by step. I honestly don't mean to sound glib, its just I know exactly how you feel!!


Or you could ignore all that and post a few upskirt pics! (a good idea anyway)


Beautiful chassis and build though.

Fran
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Old 27th February 2009, 11:31 PM   #3
Renron is offline Renron  United States
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Thanks Fran.
I took a week off from Fuzzy detective work, today I took everything out and started again......same results. That's why I'm frustrated.
Thanks for the encouragement though!

Ron
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Old 27th February 2009, 11:38 PM   #4
Renron is offline Renron  United States
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If the heater TX and the HT Choke are next to each other could that cause the fuzzy sound?

Ron
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Old 27th February 2009, 11:50 PM   #5
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Up Skirts as requested. Good idea, thanks

Ron
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Old 27th February 2009, 11:51 PM   #6
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Upskirt 2
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Old 27th February 2009, 11:58 PM   #7
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Up Skirt 3

Signal wiring is Silver with Teflon spaghetti tubing.
Heaters are DC right at 12.6V with jumpers J1 and J4 on the Aikido board setting tubes in series for 6.3V each.

HT is 292V steady.

I'm lost.....

Ron
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Old 28th February 2009, 12:21 AM   #8
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Consider a minimalist approach. Can you disconnect your attenuator PCB (I'm assuming it's the board with the sand all over it), input selector, etc. and just run one set of RCA inputs into a simple vol pot and then to the Aikido PCB and out?

This "stripped down" config will let you figure out if it is related to the Aikido boards or something else.
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Old 28th February 2009, 01:16 AM   #9
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What is the other PCB besides the Aikido, Bas' power PCB, and your attenuator PCB?
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Old 28th February 2009, 01:24 AM   #10
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BW,

I do not have an input selector, so that makes it somewhat easier...LOL
Yes, the attenuator is the sandy unit with the foam underneath to quiet the clackity - clack of the relays. I have tried as you suggested, bypassing the attenuator completely using a very quiet song straight from the CD player to the RCA jacks, then Aikido board's inputs, from the outputs; straight to the RCA jack out to the good 'Ol Haffler amp. same effect........Fuzzy. Heell, I didn't even use a pot and it's still fuzzy
Sorta pointing to the Aikido board, huh....

If a choke makes a PS ring...what does that sound like??? And could that be heard as fuzzy on the signal side.
I have a 8.5 H choke on the Mr. Bas' PS board.

I'll strip her down again tomorrow and try it again, maybe I missed something. (DUHH)!

Thanks for the help,
Keep'em coming.

Ron
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