Aikido All-In-One Octal B+ measurement. - diyAudio
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Old 13th March 2011, 12:45 AM   #1
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Default Aikido All-In-One Octal B+ measurement.

I'm using this board with 6SN7's in all four locations. I stuffed the board using the "Typical Part Values" for this configuration specified in the manual and tested it with a 240Vac transformer borrowed from another project.

The transformer I'm trying now is a Hammond 185E230 with series secondaries measuring 260Vac. The B+ measurement test pad measures 350V. This seemed kind of high given the documentation frequently mentions B+ and 300V in the same sentence.

I've finally realized that the B+ test point is before the R12 resistors after having just changed them to higher values to lower B+ but then seeing no result.

The voltage across C5 is now 289V. The Typical Part Value table that I built to references a B+ voltage = 300V and Vac to Rectifiers = 240Vac.

Anyone know where I'm trying to hit 300V, B+ test point or C5?

I've also just emailed this question to Broskie but I've emailed him on a couple other occasions without a response. Don't know if I'm making it through his spam filter or what.

Note: The attached image mentions "Typical Part Values" but this is not the table I was referring to. Will post that table next.
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Old 13th March 2011, 12:53 AM   #2
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Attached is the table showing the typical part values. I'm using the values in the left column.

Currently R12a/b is a 6.8k and 10k in parallel for a value of 4048.
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Old 13th March 2011, 01:01 AM   #3
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B+ would normally refer to the voltage, measured under load, from the power supply before it hits the circuit..... so in your first pic, where it says "left" or "right" and with the tubes in place.

Fran
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Old 13th March 2011, 03:55 AM   #4
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Thanks. I'll start inching back towards 2k for R12 until I hit 300V at C5.
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Old 13th March 2011, 06:30 PM   #5
DF96 is offline DF96  England
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A circuit designed for 300V will probably work fine at 350V, provided that any capacitors can stand the extra voltage. Don't panic!
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Old 13th March 2011, 06:46 PM   #6
SY is offline SY  United States
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IME with the octal Aikido, the higher the voltage, the better for linearity, assuming your parts can stand the extra volts.
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Old 14th March 2011, 08:07 AM   #7
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Quote:
Originally Posted by SY View Post
IME with the octal Aikido, the higher the voltage, the better for linearity, assuming your parts can stand the extra volts.
My PS caps are 450V and C4, C5, and my coupling caps are all 400V.
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Old 27th April 2011, 11:53 AM   #8
page28 is offline page28  United Kingdom
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sorry if this isn't quite on topic , but I've just received a rev A All In One Octal board hoping to make a White CF variant to use with my Sennheiser HD 650's, there's a packof resistors for R22 saying refer to manual but nowhere in the manual does it mention R22 or configuring it as anything but a line amp. I'm beggining to suspect the sheets inside the cover are for a non rev A guide, ultrachrome does your guide mention R22 at all?
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Old 27th April 2011, 02:20 PM   #9
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Originally Posted by page28 View Post
sorry if this isn't quite on topic , but I've just received a rev A All In One Octal board hoping to make a White CF variant to use with my Sennheiser HD 650's, there's a packof resistors for R22 saying refer to manual but nowhere in the manual does it mention R22 or configuring it as anything but a line amp. I'm beggining to suspect the sheets inside the cover are for a non rev A guide, ultrachrome does your guide mention R22 at all?
also, there are 2 capacitors - c23, marked "optional" which are not mentioned. Any idea what these are for? the amp seems to work fine without r22 and c23.
I've emailed Mr. Broskie, but no answer yet.
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Old 27th April 2011, 03:02 PM   #10
page28 is offline page28  United Kingdom
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C23 looks like the C3 in the Stereo Octal board rev C guide and should be at least 470uf when configuring a a HeadPhone amp
although in that guide JB writes
On the other hand, if only 300-ohm headphones are going to be driven,
then the best choice might be to use a 6SN7/12SN7 and both cathode resistors, R8 and
R11, leaving both resistors unbypassed. The output impedance will be higher, but the
distortion will be lower.
hmm maybe I'll just build it as a line amp and see how it drives the Senns
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