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Old 31st May 2009, 09:38 AM   #21
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Default course it would!

Quote:
Originally posted by dsavitsk
Wouldn't it be easier to leave out C1, R4, and R5 (see my post above)?
BUt hey - I'm learning here too...

Concepts right though isn't it? And the numbers within the ballpark? And doesn't your scheme rely on all the voltage amp and cathodyne resistors AND the two triodes being on-specification? Good for simpicity of build, bad for tolerance of calculation and design error...

Or am I over-complicating here?
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Old 31st May 2009, 05:21 PM   #22
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"I'm amazed that the power supply is putting out 405V if the transformer is only rated for 88mA. Are these monoblocks then?"

These are indeed monoblocs. Sorry I forgot to mention that.

The B+ voltage went up when I installed the SS rectifier , of course, but also went up when I raised the value of the 6V6's cathode resistor to compensate the bias for the higher B+.

As I raised the resistance of the cathode resistor, the B+ went up too. So I raised the resistance of the cathode resistor again, and again the B+ went up. I went through this 3-4 times before I got to the value of 500 ohms on the cathode resistor. Seems as though it works pretty well like this. Sounds MUCH better than the stock bias and 5Y3 rectifier did.


Not that I know anything, but I thought that a 2 stage amp with the first stage being a PP/phase splitter should have less distortion than a 2 or 3 stage that used the first stage or two SE. Is this thinking on the right track, or not in reality ?


Thank you all for your help. I need to purchase some books and read up on this stuff , perhaps I wont have as many questions then.


...............................Blake
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Old 31st May 2009, 05:35 PM   #23
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Default Re: course it would!

Quote:
Originally posted by aardvarkash10
And doesn't your scheme rely on all the voltage amp and cathodyne resistors AND the two triodes being on-specification? Good for simpicity of build, bad for tolerance of calculation and design error...

There's a lot of wiggle room with tubes. Take a look at SY's RLD amp (http://syclotron.com/?page_id=3) The part you are interested in starts on page 3 of the article.
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Old 31st May 2009, 06:04 PM   #24
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http://www.aikenamps.com/LongTailPairDesign.htm

Are C1 and C2 absolutely necessary, or can this be run without them ?

Are they needed to block DC , or are they just used for bandwidth/circuit stability ?




........................Blake
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Old 31st May 2009, 06:07 PM   #25
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Here you go, as promised. Not exactly what I would do, but it's pretty simple.

Click the image to open in full size.

Quote:
Originally posted by Nihilist
Are C1 and C2 absolutely necessary, or can this be run without them ?
99% sure that you can ignore them. I included them on my schemo just because I had that page open, but I've only actually had input caps once on an amp.
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Old 31st May 2009, 06:17 PM   #26
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Thanks !

What is the numbering in the right upper corner, "3.8W .6% 3rd" a power/distortion figure for 3rd order harmonics ?


.......................Blake
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Old 31st May 2009, 06:40 PM   #27
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Yup. I ran the output stage through Push-Pull Calculator (a simulation program). Power at full output should be 3.8W, 3.0 of which are in class A, with .6% 3rd harmonic and .04% 5th harmonic. The bias point, for future reference, is -24V, 35mA per tube.

Of course real-world values might be a bit different..
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Old 2nd June 2009, 01:21 AM   #28
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After reading some of the stuff my helpful fellow DIYer's wrote and linked to , I have come to the realisation that the 6SL7 can't drive the Triode tied 6V6's properly . That being said , I wonder about what this gent mentioned :

"...or even...
ditch the phase splitting completely from the driver stage, and leave it to the outputs as per .Simple EL84 from Yeo... This would allow paralleling of the sl7 to provide better drive"

Would THIS allow the 6SL7 to work better than my previous incarnation ?

http://img188.imageshack.us/img188/3...gt6v6simpl.png

Is there a way to implement a Long Tailed Pair for the 6V6's , or is that reserved for driver circuits ? If it can be done with output circuits, can it be used with the phase inverting format like in the schematic ?


Thanks for all the help guys ! ......................Blake
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Old 2nd June 2009, 01:49 AM   #29
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Default gentleman? Moi?

thanks for the upgrade in my status Nihilist...

The basic idea is correct, but I cannot comment on the values you have in place. Be aware that you are limited to Class A operation only, so sorenj's values given above won't apply. The best solution is to put a CCS in the tail of the outputs a la Yeo's lazy man's CCS.

My thinking was that having shifted phase-splitting to the outputs, your 'SL7 can concentrate its meagre energy on overcoming the various capacitances it faces. Paralleled (as you have shown it) I would hope it had enough grunt to do this.

Purists will deride the phase splitting at the outputs thing, but it does address the majority of your issues including keeping the recycling to a maximum!
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Old 2nd June 2009, 04:23 PM   #30
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I am about to build my El86 version of this amp. i will use a 6AU6 as the driver and have it driving the output pentode with plate to plate feedback. The second tube will be a simple pentode with regulated screen and earthed grid.
For the output I will have a pair of CCS, one in each cathode (rather than Yoe's single CCS which needs DC balancing) which will allow me to precisely control the standing DC through the output. I will then tie a pair of back to back caps (1000uf each) between the cathodes, with the junction tied to earth via a 1meg resistor, and this will turn the outputs into a DC balanced AC LTP.
That is how I will be doing it.

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