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Old 3rd October 2005, 03:15 PM   #1
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Default Aikido + EL34 Intergrated

I'd like to build a SE dual mono integraded EL34 based power amp using the Akido as the input stage driving a single EL34 per side.

The peak input voltage on the grid of the EL34 is 22 volts before clipping for the operating points I've chosen.

SE Amp Cad calculates an output of 3.5 watts RMS with an output voltage of 5.32 RMS. This should be plenty loud driving the pair of Klipsch LaScala's this amp is destined for.

Will an Aikido line stage using 6N1P's into 5687's develop the 22 volts necessary to drive this design to full output?

Thanks for your responses.

dr._sleep
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Old 5th October 2005, 11:42 AM   #2
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Very good question - I am also curious about this and my post is mainly intended to get this thread in the top again.

I can't say, actually.. With the little I know I would say: The gain of the aikido is half the mu of the first tube. Using the 6N1P with a gain of 35 would held a gain of 17,5 for this stage. Multiplied with the 2VRMS output of a CD player this would be 35VRMS... (I suppose the 22V you talk are also RMS) But this calculation seems to simple - it doesn't account for feedback (maybe feedback isn't necessary with the EL34 in triode) and I don't know ot the Aikido can swing 35VRMS (probably it can, John Broskie mentioned you could use it as a driving stage, or even as an output stage - and if you use an ECC83 in the first stage, the output would have an even greater swing)

Well, anyone feel free to correct me and give the good answer!
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Old 5th October 2005, 07:27 PM   #3
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I will test for the cathode output voltage with my oscilloscope using several input frequencies and amplitudes into an apprioate load. And post the results.

Do you remember where John mentioned using the Aikido as a driver stage?

dr._sleep
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Old 6th October 2005, 04:04 PM   #4
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Hi dr._sleep

I beg your pardon. Actualy John didn't mention the use of the aikido as a driver stage - I made this assumption when he was talking about using the aikido topology for the output stage - and I tought - well if you use it for the output stage it can be used for the driver stage too... the gain of the aikido can be enough - the problem is I don't have a clue about the the maximal swing at the output

I am curious how your measurements will turn out.

Erik
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Old 6th October 2005, 11:24 PM   #5
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I made some I and O measurements this afternoon.

What I am getting, for an input of .25 Volts RMS at 1000Hz, the non-transformer output is 2.0 Volts RMS without the feedback circuit and .3 Volts RMS with the feedback circuit switched in.

I do not have a signal generator and cannot input a higher voltage with my computer.

I will download and burn some wave files to CD and run them through my CD player's tubed output that generates @ 2.5 Volts RMS. It will either clip the input or we may get 20 volts RMS output from the Aikido.

But is that enough to drive a SE EL34 or EL84 to full output?

dr._sleep
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Old 7th October 2005, 06:36 AM   #6
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Just as a data point, I use the pentode Aikido as a driver in my amp and a friend uses one also in his amp. The Aikido stage is swinging +/- 50volts in my amp and +/- 100V on my friends amp. No problems what-so-ever. We are both using higher B+ that JRB uses. I'm using 300V and my friend is using 400V (ish its a bit higher I think)

James
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Old 7th October 2005, 11:09 AM   #7
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To James D.

What do you exactly mean with penthode aikido - you use 4 penthodes connected as triodes (per channel) or is it a completely different idea?

Quote:
But is that enough to drive a SE EL34 or EL84 to full output?
I know that the EL84 needs 8 VRMS for full output (without feedback applied)

Erik
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Old 7th October 2005, 03:46 PM   #8
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http://tubecad.com/2004/blog0013.htm


dave dove

james

time to tell?
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Old 8th October 2005, 01:49 PM   #9
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Erik,

Just a quick note as I'm in transit.

The pentode Aikido uses a pentode as the first stage, as shown on the link that Dave provided. As you probably guessed it is Dave and I who have the two amps configured this way.

So the pentode provides the voltage gain and the Aikido output stage cancels a lot of the psu noise and provides plenty of drive into the output stage.

Dave

If you want to kick it off I'll follow up once I'm home.

James
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Old 8th October 2005, 06:10 PM   #10
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Hi James D.

Thanks for the reply! Now I know for sure (I already guessed so) that the (output from) the Aikido can swing enough voltage to drive a power tube. Someday I will build mine

Erik
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