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Building a Aikido preamplifier
Building a Aikido preamplifier
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Old 25th December 2019, 12:04 PM   #611
soldersober is offline soldersober  Hong Kong
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Quote:
Originally Posted by john65b View Post
I wonder if I should just plop in another transformer, or just pull the regulation transistor for the heater circuit...

I cant be the ONLY ONE that has seen this issue....right?


Thanks!!!
I am not sure what heater voltage sounds best, but if you want regulated 6.3VDC off 6.3VAC winding I see two options
- valve rectification into voltage doubler and then regulate down to 6.3V - this is the approach implemented in at least some of Broski's boards
- shottky (low Vf) rectification into low drop out regulator

First approach obviously needs double the current from the secondaries. Second one is kind of more expensive in parts cost
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Old 25th December 2019, 02:08 PM   #612
Steve Morley is offline Steve Morley  Canada
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Default Doubler might be the answer...

You'll get more than double, ~2.8x actually, because of the peak of the sine wave not the RMS.

From Broskie: V dc = (Vac x 2.8) -2V diode
No free lunch though: I out = I ac / 3.6

A voltage-doubled 6.3 will have a lot more than 12 volts so there's lots of headroom for the regulator.

Here's the thing, connect both 6H30 filaments in series (12 volts @ 0.9A) and both 6N1Ps, (12 volts @ 0.6A) so only 1.5 amps of filament current needed. So if the fil trans is rated at 5.4 amps or better, you're good to go. (1.5 x 3.6)

If it's a Hammond with a 5 volt winding that's not being used and the HT winding is under-taxed (likely) the 6.3 volt winding is probably good for a bit more current.

The other way, even with fancy diodes, a LDO reg. needs a bit more than 1 volt headroom, which you might not have.

Cheers, Steve
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Old 25th December 2019, 04:20 PM   #613
soldersober is offline soldersober  Hong Kong
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Quote:
Originally Posted by Steve Morley View Post

No free lunch though: I out = I ac / 3.6

The other way, even with fancy diodes, a LDO reg. needs a bit more than 1 volt headroom, which you might not have.

Cheers, Steve
Yes, sure, 1/1.8 for a simple bridge, 1/3.6 for a voltage double, the law (Ohm's) is the law

I have done the LDO trick, it works, I used MIC29502
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Old 7th January 2020, 06:37 PM   #614
migkiller1971 is offline migkiller1971  United States
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The new Octal all in one is sold out
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Old 7th January 2020, 10:33 PM   #615
TonyTecson is offline TonyTecson  Philippines
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dc voltages depends on the actual power traffo you have in your aikido lineamp...
different traffos will have different dc winding resistances and so the dc rails would behave differently....

while formulas give you approximate values, in actual circuits, they may not follow...

i would rather have more dc rails since it is easier to lose voltage....than when you feel you never had enough...
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Old 16th January 2020, 04:54 PM   #616
bloozestringer is offline bloozestringer  United States
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Quote:
Originally Posted by Steve Morley View Post
Blooze,

The Anteks are a good price (in the US, shipping is a bit of a killer to Canada). The advantage of the Hammonds and Triads are the dual 115 volt secondaries. In series you get a little over 300 volts raw DC after the rectifier, in parallel about 170. So if you switch over tubes like I did (see above) a different B+ trannie isn't needed.

Steve


Steve, would you mind sharing the Hammond or Triad part numbers you found useful?
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Old 16th January 2020, 05:15 PM   #617
kodabmx is offline kodabmx  Canada
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Building a Aikido preamplifier
Triad VPT230-110 (25VA) VPT230-110 — Octopart
or VPT230-220 (50VA) VPT230-220 — Octopart

Hammond 1182E117 (30VA) 1182e117 — Octopart
or 1182G117 (50VA) 1182g117 — Octopart

Koda
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Old 17th January 2020, 03:08 AM   #618
bloozestringer is offline bloozestringer  United States
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Thank you!
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Old 17th January 2020, 05:25 PM   #619
Steve Morley is offline Steve Morley  Canada
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Default Choices

Blooze:

If you are building an Aikido using 6DJ8s a 25VA filament transformer is adequate. Hammond 185C12 or Triad VPT12-2080 will work fine, I've used both.

If you are building a 6SN7 Aikido a 25VA trannie for the filaments is kind of marginal. In this case I'd go with a Hammond 43VA p/n 185D12 or Triad 50VA p/n VPT12-4170.

All of the above will give you the option of wiring the secondaries in parallel for 6 volts or series for 12 volts. 12 volts, wiring pairs of tube filaments in series is the way to go IMO.

For the B+ supply a 25VA transformer is fine for any Aikido build. Hammond 185C230 or Triad VPT230-110.

Good luck!

Steve
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Old 31st March 2020, 05:56 PM   #620
Svenson84 is offline Svenson84  Germany
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Hi all,
i am new to this forum and also my Aikido is the first contact with tubes in the world of electronics.
I bought the Aikido Noval Rev. E from Glassware some time ago and finally i now have time to start this project... But some things are confusing me!
In the manual (page 5) i found the hint that the heater voltage shall be biased to 1/4 of B+. My B+ runs at 300V so, Heater shall be referenced to 75V by a voltage divider 300k/100k. I also found the information in my tubes datasheet that heater to cathode voltage is max. 100V. That makes sense so far!

Now the first part i am struggling with: i only have one heater per tube, but two triodes. In the Aikido there are connected in series, so as i understand lower triode sees 0-150V B+ and the upper triode 150-300V. Isn't there a violation of heater to cathode voltage for the upper triode?

Second part: In the Aikido manual are also some recommended values for the components (page 14). Against the recommendation described before (page 5), here the recommended values for the heater-to-cathode voltage divider is 300k/300k, means 50%(150V) B+ instead of 25%(75V). That will violate the tube specification of max. 100V heater-to-cathode!?

Could anyone may help me to understand, how the heater is biased in the correct way?

Thanks and stay healthy!

Sven
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