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Old 4th April 2007, 11:24 PM   #1
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Default All quiet on the SN front - about darned time!

It had to happen, especially if I played about long enough.

I finally got the DC regulator built for the Aikido heaters. I purchased the high current regulator kit from Welborne Labs. It did finally arrive, minus the PCB, which (after an email) arrived promptly. Last night, I put it together. However, the heatsink supplied with the kit is obviously a substitute and doesn't quite fit the PCB, so I have temporarily mounted it to the underside of the PCB, until the correct one arrives. Anyway, from a 6.3VAC transformer, I get around 5.9VDC.

That totally cured the 60Hz hum. GREAT. Of course, that also allowed the 120Hz hum and hiss to become noticeable. So, a quick partial rewiring of the signal circuitry (Pot to PCB replaced with twisted pair) has reduced all that noise to levels that are only noticeable when the ear is next to the speaker and the volume turned up to MAX. Swapping all signals to twisted paris can now wait.

Wow.....is all I can say.

The moral of the story is that hum and other hash probably result from a number of sources and woring implementations that act synergistically to inject crud into the signal. In other words, don't skimp on the wiring, etc., etc.

What a learning experience! And how many pesky posts I have made to the forum! I hope that I'll now be able to contribute back to the forum.

Hmmmm.....now which dram to accompany tonight's listening? A smoky Ardbeg, sherried Springbank, or a good ol' highland single malt?

Thanks Guys!
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Old 5th April 2007, 01:20 AM   #2
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Quote:
What a learning experience! And how many pesky posts I have made to the forum! I hope that I'll now be able to contribute back to the forum.
Way to go Charlie!

Charlie think of it as a positive experience. Everyone gets to sharpen there skills when problems arise. Now you are probably the formost expert on Aikido noise problems.
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Old 5th April 2007, 04:28 AM   #3
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Congrats! I knew it was only a matter of time. Want to get together and compare this weekend or sometime soon?
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Old 5th April 2007, 07:07 AM   #4
Salas is offline Salas  Greece
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Noisebusting isn't only a matter of eliminating nuisance.
Hum is always indicating hidden problems. Its the tell tale smoke of a fire somewhere. All hum busted circuits sound higher in fidelity. Congratulations.
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Old 5th April 2007, 05:32 PM   #5
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Yup, things are great. But, the remainder of the hum, which is inaudible during music (even quiet music) is troubling. I'd really like to hear absolute zero as far as noise is concerned - the eternal tweaker and want-to-be perfectionist in me is straining for attention.

Funny thing is that last night, I flipped over the Aikido and touched a few signal wires, and whenever I touch the twisted pair between POT and PCB, I get loads of hum. It is not a case of moving the wires, but just touching them. Could the presence of a finger and thumb change capacitive coupling between the wires.

Anyway, SY posted details of his signal wiring. I'll try and do something similar, using a twisted pair with a separate shield and the shield connected to the PCB GND.

All these things can wait a while.

Bruce, this next weekend will be first that Kara and I have not had family in town, so how about the weekend after? I can bring my stuff over to your place, if you want. Did you find a replacement CD-player?

Charlie
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Old 5th April 2007, 06:09 PM   #6
Tweeker is offline Tweeker  United States
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A certain amount of noise is unavoidable, it stems from the resistors and tubes themselves. Some tubes are noiser than others. Thermal noise is unavoidable without recourse to liquid helium, though it can be mitigated.

Use higher power resistors (ei 2watt rather than 1/2watt). WW resistors are the lowest noise type, but are more inductive. Whether this matters depends on location and value. For 10k-100k in audio "ni" ww resistors are not significantly inductive. Carbon comps are the noisest type, then carbon film, then metal film, these types produce some noise of a type which wws do not. In some locations lower inductance is more important than noise, such as grid stoppers. There isnt much power across the grid stopper and its not a high value, so its not a large contributer.
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Old 23rd April 2007, 12:53 AM   #7
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Hello,
What model # high current regulator from Welborne Labs ?
Cambe
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Old 23rd April 2007, 05:25 AM   #8
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I purchased the PS-HREG from Welborne. However, while the webpage says that it can output up to 12VDC, it seems that the supplied caps - either 10V or 16V may not be rated high enough. Certainly the 10V aren't. Luckily, I got 16V with mine, but to give a solid 12VDC from the regulator, the caps may see more than their specified value.

While Ron does email back with answers to any questions, I have had a couple of annoyances. He changed the heatsink, such that as specified in the original instructions, one of the smaller value caps needs to be mounted horizontal to the board. I only realized this problem after I had mounted it in the normal (vertical) manner. Consequently, I had to mount the regulator on the reverse side of the PCB, where it receives a much lower air-flow in my amp. Of course when I emailed Ron about this, he said that I must of have been sent older instructions. He did send a PDF that was updated, but the creation date on the PDF file was a few hours after I had emailed the original problem to him - go figure.

So, in order to get 12V, I'll need to upgrade the caps (not too expensive around $2 ea.). However, Ron thinks that I may need to use a larger heatsink. Anyway I have paid $65 for a kit, which may not really be able to operate as specified on his webpage.

Mind you, I must say that at 6VDC. Ron's product works extremely well (as far as I can tell). It really reduced the hum to a point where my amp is extremely quiet.

If you want a regulator that works for less than 10V, the Welborne kit will not disappoint you. It was also worth paying the extra money to get a kit that has a nice PCB and works (as along as it is not 12V). Furthermore, the kit includes the schematic, so next time I want such a regulator, I'll simply source my own parts and build my own.

Charlie
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Old 23rd April 2007, 12:02 PM   #9
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Hello Charlie,
Thank you for the info. I have the Aikido dual mono PCB's and plan to use 6SN7's throughout. If you think of anything else I should know, e-mail me. This is my first tube project.
Cambe.
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Old 23rd April 2007, 04:22 PM   #10
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Cambe,

Great. My Aikido - the stereo Octal was my first tube project. It almost drove me crazy. There doesn't seem to be one power supply that is the BEST - there are many excellent designs that all work exceptionally well. If you ask for a PSU recommendation, you'll get many different answers. Choose a PSU design for which you can easily get parts. If you're going to use 6SN7's then you want to aim for a B+ of 300V or a little higher. However, I made the mistake of going for larger valued chokes, which meant that my 6SN7's were likely not pulling enough amperage to force the chokes to work properly, so I ended-up with a bleeder resistor to draw more current through the PSU.

In the newsgroup, Sy offered lots of advice on how to wire my signals, using a shielded cable. I modified his version and found that I reduced hum significantly. In fact, I found that a number of "tweaks" all seemed to work synergistically to lower the noise floor as far as hum is concerned. Using a ground-lift network (http://sound.westhost.com/earthing.htm) with 20 ohm of lift; shielded signal cable; regulated heaters all gave dramatic and significant improvements in hum reduction.

I also found a neat circuit for adding a delay system using a $20 NOS Amperite delay tube and a regular relay. I switch on the amp, and the Amperite is energized. Ater 30 seconds, the Amperite triggers an $8 relay which simultaneously switches on the B+ and powers down the Amperite. I can send you details of that if you'd like. It looks good, as the Amperite tube looks pretty unusual.

Regards,
Charlie
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