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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Thu 26, 2015 9:09 am 
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Was just wondering if a separate power supply for each channel of a stereo amp would make any difference.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Thu 26, 2015 9:13 am 
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There is a near perfect amp.
Have you ever seen "back To The Future?"

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Thu 26, 2015 9:18 am 
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john8750 wrote:
Was just wondering if a separate power supply for each channel of a stereo amp would make any difference.

I don't think so John.
.. That's the next part to figure out and build... maybe 2morrow?

BTW .. I'm listening to now... and it's really "sweet".

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Thu 26, 2015 9:19 am 
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Flipperhome wrote:
john8750 wrote:
Double blind testing?
What does that mean?
On a serious note, it has been found that when people know about the conditions or object of the test it influences the result, and that applies even to the giver of the test. It's not that it's necessarily 'intentional' either but subtle clues can be given off.

Double blind means neither the subjects nor giver of the test knows what's what so, in theory at least, they can't influence the results.



So, if I join in, we can be like the 3 stooges? I want to be Curley.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Thu 26, 2015 9:21 am 
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Pbpix wrote:
john8750 wrote:
Was just wondering if a separate power supply for each channel of a stereo amp would make any difference.

I don't think so John.
.. That's the next part to figure out and build... maybe 2morrow?

BTW .. I'm listening to now... and it's really "sweet".



Your sweet music through your sweet amp, and some sweet Sherry, how sweet....

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Thu 26, 2015 9:24 am 
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The 6AQ5 datasheet gives you the voltages and current. B+ should be 250 V and with cathode bias using up (datasheet numbers) 15 V that's 265 V. Plate current should be 35 mA. Two tubes combined, along with 5 mA of screen current, at 15 V, makes for a 200 Ohm shared cathode resistor, twice that with individual cathode resistors. Lower cathode current runs the risk of bias shifting.

Your power is low (but better than it was) because B+ is low (and the OPT is wrong).

With a 10k PP OPT that would produce 10 Watt (minus OPT losses) but since you're going to use UL, which reduces power along with improving linearity, an 8k OPT get's some of the power back. By no means not all, but some. In addition, you can run high screen voltage because it isn't constant and, hence, less power is dissipated in it. That means the 6V6, which normally has a 285 V screen limit, can be run at max plate voltage (screen is essentially the same) of 315 V, plus the cathode bias of 15 V, for 330 V (usually shown as a 'standard' 325 V. That doesn't quite add up because bias voltage will increase when B+ does but it's roughly correct).

All of that is in the Acrosound 6V6 UL schematic. (Note, people usually run the 6V6 screens at 310 V to 315 V regardless of the spec).


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Thu 26, 2015 9:36 am 
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So Flip:
Are you saying the 10k OT is better... but not if we go with UL? ... then 8k is best?
Is that right?

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Thu 26, 2015 10:21 am 
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Pbpix wrote:
So Flip:
Are you saying the 10k OT is better... but not if we go with UL? ... then 8k is best?
Is that right?
Yes.

See, with UL the power tube's voltage swing is less so a lower impedance 'fits' it better.

You could still use 10k PP on UL but the reduced voltage swing would produce less power (power is V squared over R).

On the other half of the coin, 8k 'normal' (not UL) produces less power because the tube can only do so much current (power is I squared R)

It's a balancing act between how much voltage swing there is and how much current the tube can produce. The 'optimum' is with both maximum current and voltage swing (power is V x I and R = E / I, bounded by the tube's ratings).


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Thu 26, 2015 10:24 am 
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Flipperhome wrote:
Pbpix wrote:
So Flip:
Are you saying the 10k OT is better... but not if we go with UL? ... then 8k is best?
Is that right?
Yes.

See, with UL the power tube's voltage swing is less so a lower impedance 'fits' it better.

You could still use 10k PP on UL but the reduced voltage swing would produce less power (power is V squared over R).

On the other half of the coin, 8k 'normal' (not UL) produces less power because the tube can only do so much current (power is I squared R)

It's a balancing act between how much voltage swing there is and how much current the tube can produce. The 'optimum' is with both maximum current and voltage swing (power is V x I and R = E / I, bounded by the tube's ratings).

Thanks:
That helps.

I saw this 60's version where they are only using 220v B+ but with 15v bias that's 34ma per tube.
REF: http://www.theradiofox.com/misc/radiohandbook.html
"BABY HIFI"
(4 watts plus)
Image

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Last edited by Pbpix on Mar Thu 26, 2015 10:31 am, edited 1 time in total.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Thu 26, 2015 10:31 am 
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It's hard to guess the logic of a "Baby Hi-Fi" unit but, off hand, I'd say it was to save money on the power supply, or maybe that was an existing power supply.


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Thu 26, 2015 10:37 am 
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Flipperhome wrote:
It's hard to guess the logic of a "Baby Hi-Fi" unit but, off hand, I'd say it was to save money on the power supply, or maybe that was an existing power supply.

It's right out of "The Radio Handbook, 16th Edition". 1962
here's the article:
http://www.theradiofox.com/misc/radiohandbook.html

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Last edited by Pbpix on Mar Thu 26, 2015 9:29 pm, edited 1 time in total.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Thu 26, 2015 10:46 am 
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Funny:
.... granted.. I've had abpout 3 oz of Tawny Port... lol
but ... I'm in my living room now listening to the 5902 amp on my "good" speakers... and it JUST never fails to "blow me away"... with a 3-D like beautiful -- room filling-- realistic sound. Amazing!
So even though I'll build this 6V6 / 6AQ5 just for the fun and beauty of it... I can't imagine how anything 6v6 or what ever could sound any better than the 5902 amp which I'm basking in the glow of ... as we speak.

I have a 30 watt ASL AQ1003DT EL34 amp right next to the 5902... and it doesn't seem to be "all that" better if even at all.... than the 5902.
It's "a charm".... really.

So... I'll be building this 6V6 for kicks. ...lol

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Thu 26, 2015 10:57 am 
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Pbpix wrote:
Flipperhome wrote:
It's hard to guess the logic of a "Baby Hi-Fi" unit but, off hand, I'd say it was to save money on the power supply, or maybe that was an existing power supply.
It's right our of "The Radio Handbook, 16th Edition". 1962
here's the article:
http://www.theradiofox.com/misc/radiohandbook.html
And your point is?


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Thu 26, 2015 5:00 pm 
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Pbpix wrote:
Funny:
.... granted.. I've had abpout 3 oz of Tawny Port... lol
but ... I'm in my living room now listening to the 5902 amp on my "good" speakers... and it JUST never fails to "blow me away"... with a 3-D like beautiful -- room filling-- realistic sound. Amazing!
So even though I'll build this 6V6 / 6AQ5 just for the fun and beauty of it... I can't imagine how anything 6v6 or what ever could sound any better than the 5902 amp which I'm basking in the glow of ... as we speak.

I have a 30 watt ASL AQ1003DT EL34 amp right next to the 5902... and it doesn't seem to be "all that" better if even at all.... than the 5902.
It's "a charm".... really.

So... I'll be building this 6V6 for kicks. ...lol


I agree with that. The speakers I use are not perfect. But in the caboose I live in, that little amp sounds very real.
I like to display the amps I build on a display rack in my listening room. because of that, they must be presentable, have some Bling.
I will build one for my cousin. He plays his music form vinyl only, and in his living room. So a tube amp is a must.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Thu 26, 2015 9:04 pm 
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Flipperhome wrote:
Pbpix wrote:
Flipperhome wrote:
It's hard to guess the logic of a "Baby Hi-Fi" unit but, off hand, I'd say it was to save money on the power supply, or maybe that was an existing power supply.
It's right our of "The Radio Handbook, 16th Edition". 1962
here's the article:
http://www.theradiofox.com/misc/radiohandbook.html
And your point is?

my point ..........was that ... since you said you found it "hard to guess the logic" .
...and so .. if you are straining to speculate on why they used THAT power supply... you might be able to glean an answer from the text of the article.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Thu 26, 2015 10:52 pm 
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Pbpix wrote:
my point ..........was that ... since you said you found it "hard to guess the logic" .
...and so .. if you are straining to speculate on why they used THAT power supply... you might be able to glean an answer from the text of the article.
Nope.


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Fri 27, 2015 11:16 am 
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I tossed this supply together from a doubler ckt I saw online.
I had to adjust everything ( lots of calculation plus trial and error because I had only one working channel and so I had to simulate the 50ma B+ load for channel two using two 7watt 120v night-light bulbs in series)

In any case... it actually works as it's shown.

John... I hope you like it...
If you want to ...You can increase cap values for C2 & C3 if you can get them easily to drop the ripple down lower than 100mv as now.

I tried a 250v cap for C3... but I felt much better increasing it

Attachment:
6aq5 supply.jpg
6aq5 supply.jpg [ 48.16 KiB | Viewed 3169 times ]
.

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Last edited by Pbpix on Mar Mon 30, 2015 1:33 am, edited 2 times in total.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Fri 27, 2015 9:47 pm 
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I updated the supply because I had forgotten to add the filament string power.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Sat 28, 2015 4:20 am 
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That's just beautiful Peter.
You forgot to add the softstart resistor in the filament circuit.
I like the 350 volters. Will start collecting parts.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Mar Sat 28, 2015 4:33 am 
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Forgot to ask if I need the 10 or 8K OPT's.
I want to get them on order.
Is there a standard ID just for transformers with the UL taps?
Changed my mind about the 1019 with a built in amp. I think I will have only the RIAA preamp on board.
That should make things easier to work with.

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