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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Mon 13, 2015 7:42 pm 
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Flipperhome wrote:
Pbpix wrote:
Show us how it should be designed please. Why not help here a bit...
First I want to say I do NOT endorse a line powered supply, because I don't consider it safe, so purely as a thought experiment...
Attachment:
Line Power Supply3.jpg

There's no reason for two series resistors other than to stay within power ratings and the lower 10 Ohm dissipates 5 Watt, hence the 10 Watt rating. 10 Ohm is more than enough limiting to keep max surge current under 10 A (a 1N4004 is rated 30 A). Average current is 175 mA (rounded up).

C1 has to sustain roughly 713 mA ripple. The Nichicon is rated 800 mA at 85 C and 120 Hz (The factor is .8 at 100 Hz and isn't good enough). At 132 VAC (+10 %) it has to sustain 785 mA of ripple and the Nichicon, again, makes it. Of course, a higher ripple rated cap increases reliability (the Nichicon was just the first I ran across) so the more the merrier (and costly). As a side note, when looking for 'high ripple' caps watch out for "at high frequency" types. The rating goes up with frequency and they often don't list what it is at 120 Hz (and it isn't the 'high frequency' number).

B+ current is for Class AB, 10K, which is 75 mA per PP pair (150 mA total), at a grid bias of 15 V. With plate (- cathode) voltage of 250 V that places B+ at 265 V. Simulations place B+ at 271 V but doesn't take into account AC source impedance and cap ESR losses so I figure it should come out about right, but it's close enough if not.


C1 is backwards.........if you apply power to it the way it's drawn, better run and duck, because the cap will probably explode pretty quickly if the fuse doesn't blow.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Tue 14, 2015 12:05 am 
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Flip:
I corrected the polarity on C1 in your schematic.
Here's what I've got with voltages just as they sit right now.
I kept the ccs at 25ma ... to see where the bias would end up. approx (17-17.5) with these two particular tubes in at the moment.
Attachment:
doubler.jpg
doubler.jpg [ 53.84 KiB | Viewed 6384 times ]

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Tue 14, 2015 4:44 am 
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I plugged some of these values into Chuck's PPamp software curve program.

With 268v B+
.... and -17v on G1 from cathode bias...
That puts the plate +250v above the +17v cathode.
W/25ma idle bias current and 8k plate load.

It indicates 9.1watts @ 1.36% THD

Using Chuck's Ultra-Linear version of that program with the same numbers shows THD <1%
but Power = only about 4watts pwr
So I don't know how accurate that is.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Tue 14, 2015 4:57 am 
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Mr. Detrola wrote:
C1 is backwards.........if you apply power to it the way it's drawn, better run and duck, because the cap will probably explode pretty quickly if the fuse doesn't blow.
Oops :mrgreen:

That's what I get for doing a rush job. Thanks. I'll correct the post.


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Tue 14, 2015 9:06 pm 
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Flipperhome wrote:
Pbpix wrote:
Show us how it should be designed please. Why not help here a bit...
First I want to say I do NOT endorse a line powered supply, because I don't consider it safe, so purely as a thought experiment.
Image
There's no reason for two series resistors other than to stay within power ratings and the lower 10 Ohm dissipates 5 Watt, hence the 10 Watt rating. 10 Ohm is more than enough limiting to keep max surge current under 10 A (a 1N4004 is rated 30 A). Average current is 175 mA (rounded up).

C1 has to sustain roughly 713 mA ripple. The Nichicon is rated 800 mA at 85 C and 120 Hz (The factor is .8 at 100 Hz and isn't good enough). At 132 VAC (+10 %) it has to sustain 785 mA of ripple and the Nichicon, again, makes it. Of course, a higher ripple rated cap increases reliability (the Nichicon was just the first I ran across) so the more the merrier (and costly). As a side note, when looking for 'high ripple' caps watch out for "at high frequency" types. The rating goes up with frequency and they often don't list what it is at 120 Hz (and it isn't the 'high frequency' number).

B+ current is for Class AB, 10K, which is 75 mA per PP pair (150 mA total), at a grid bias of 15 V. With plate (- cathode) voltage of 250 V that places B+ at 265 V. Simulations place B+ at 271 V but doesn't take into account AC source impedance and cap ESR losses so I figure it should come out about right, but it's close enough if not.

Edit: Corrected C1 wrong polarity.

Flip:
Thanks... It's working with these (actual) loads and voltages as I posted yesterday.
I also just noticed your note of "CAUTION" ... and wondered if you were really worried about the power supply police coming along to arrest us all.... lol

Image

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Wed 15, 2015 12:00 am 
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Pbpix wrote:
Flip:
Thanks... It's working with these (actual) loads and voltages as I posted yesterday.
I also just noticed your note of "CAUTION" ... and wondered if you were really worried about the power supply police coming along to arrest us all.... lol

Image
I don't want you coming back with "But you designed it, no?"

Btw, when I labeled B+ 150 mA that was the B+ load alone, not the total, and that corresponds to 108 mA on yours.


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Wed 15, 2015 12:35 am 
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Flipperhome wrote:
Pbpix wrote:
Flip:
Thanks... It's working with these (actual) loads and voltages as I posted yesterday.
I also just noticed your note of "CAUTION" ... and wondered if you were really worried about the power supply police coming along to arrest us all.... lol

Image
I don't want you coming back with "But you designed it, no?"

Btw, when I labeled B+ 150 mA that was the B+ load alone, not the total, and that corresponds to 108 mA on yours.

Yes.. total B+ sb about 108ma ( I still have a dummy load for the 2nd channel .. so not sure)
But.. ok.. so how did you come up with 150ma? ... lower bias voltage running at around 33-35ma/tube?

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Wed 15, 2015 5:20 am 
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Pbpix wrote:
Flipperhome wrote:
Yes.. total B+ sb about 108ma ( I still have a dummy load for the 2nd channel .. so not sure)
But.. ok.. so how did you come up with 150ma? ... lower bias voltage running at around 33-35ma/tube?
I thought it was rather clear. B+ current is for Class AB, 10K, which is 75 mA per PP pair (150 mA total), at a grid bias of 15 V. No 'tricks' or analysis on my part, it's simply straight from the 6AQ5 & 6V6 datasheets.


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Wed 15, 2015 5:28 am 
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Flipperhome wrote:
Pbpix wrote:
Flipperhome wrote:
Yes.. total B+ sb about 108ma ( I still have a dummy load for the 2nd channel .. so not sure)
But.. ok.. so how did you come up with 150ma? ... lower bias voltage running at around 33-35ma/tube?
I thought it was rather clear. B+ current is for Class AB, 10K, which is 75 mA per PP pair (150 mA total), at a grid bias of 15 V. No 'tricks' or analysis on my part, it's simply straight from the 6AQ5 & 6V6 datasheets.

Yeah I know that.... that's exactly what I just said to you: : "lower bias voltage (-15v) running around 33-35ma/tube" Right?

Who said anything about "tricks"? What do you mean "tricks"?

I, too, saw that the datasheet indicated AB 250v plate, running -15v G1 = 35ma idle.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Wed 15, 2015 5:47 am 
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Pbpix wrote:
Flipperhome wrote:
Pbpix wrote:
Yes.. total B+ sb about 108ma ( I still have a dummy load for the 2nd channel .. so not sure)
But.. ok.. so how did you come up with 150ma? ... lower bias voltage running at around 33-35ma/tube?
I thought it was rather clear. B+ current is for Class AB, 10K, which is 75 mA per PP pair (150 mA total), at a grid bias of 15 V. No 'tricks' or analysis on my part, it's simply straight from the 6AQ5 & 6V6 datasheets.
Yeah I know that.... that's exactly what I just said to you: : "lower bias voltage (-15v) running around 33-35ma/tube" Right?

Who said anything about "tricks"? What do you mean "tricks"?

I, too, saw that the datasheet indicated AB 250v plate, running -15v G1 = 35ma idle.[/quote]Plus screen current.


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Wed 15, 2015 5:52 am 
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Flipperhome wrote:
Plus screen current.

I measured screen current as it is right now at only 1ma
I don't know how that might change with ultra linear.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Wed 15, 2015 6:11 am 
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Pbpix wrote:
Flipperhome wrote:
Plus screen current.

I measured screen current as it is right now at only 1ma
I don't know how that might change with ultra linear.
You asked how I came up with 150 mA. It's 70 mA plate current plus 5 mA screen current for, as I indicated, 75 mA per pair and since it's a stereo amp that's 150 mA total.


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Wed 15, 2015 6:19 am 
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Flipperhome wrote:
Pbpix wrote:
Flipperhome wrote:
Plus screen current.

I measured screen current as it is right now at only 1ma
I don't know how that might change with ultra linear.
You asked how I came up with 150 mA. It's 70 mA plate current plus 5 mA screen current for, as I indicated, 75 mA per pair and since it's a stereo amp that's 150 mA total.

Yes, thanks I get that.

So... the way I'm doing it though now (less A more B) is running -17v @ 25ma. (9 watts in pentode mode I think - but what do you suppose that will come out when using UL?)
So B+ is only going to draw a little over 100ma + SG current. At min signal. Max signal will be what? .. another 10-15ma?

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Wed 15, 2015 6:34 am 
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Pbpix wrote:
Yes, thanks I get that.

So... the way I'm doing it though now (less A more B) is running -17v @ 25ma. (9 watts in pentode mode I think - but what do you suppose that will come out when using UL?)
So B+ is only going to draw a little over 100ma + SG current. At min signal. Max signal will be what? .. another 10-15ma?
I don't know with an 8K OPT but imagine it should be close to the datasheet of 79 mA plate and 13 mA screens, times two for 184 mA.

I don't know what it would be UL.


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Wed 15, 2015 6:47 am 
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BTW... had a difficult time locating those Nichicon Caps at a reasonable price in most dealers.
Then I found them at 56 cents at Newark.com but could not seem to get an est on shipping ....
So I called them and found they had a min qty of 150 pcs..

But they suggested Panasonic as a substitute. ... and for only 43.7 cents each. ( has ever higher ripple current 830ma)
Newark's number: 53W8293
Panasonic number: ECA-2CM221

So for 43.7 cents I bought 10pcs... shipping however was another $5.33

Newark seems to have very competitive prices.... only about 1/3 or Mouser and DigiKey

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Wed 15, 2015 6:53 am 
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Pbpix wrote:
BTW... had a difficult time locating those Nichicon Caps at a reasonable price in most dealers.
Then I found them at 56 cents at Newark.com but could not seem to get an est on shipping ....
So I called them and found they had a min qty of 150 pcs..

But they suggested Panasonic as a substitute. ... and for only 43.7 cents each. ( has ever higher ripple current 830ma)
Newark's number: 53W8293
Panasonic number: ECA-2CM221

So for 43.7 cents I bought 10pcs... shipping however was another $5.33

Newark seems to have very competitive prices.... only about 1/3 or Mouser and DigiKey
Mouser has them but that is a better deal.


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Wed 15, 2015 7:00 am 
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Flipperhome wrote:
Pbpix wrote:
BTW... had a difficult time locating those Nichicon Caps at a reasonable price in most dealers.
Then I found them at 56 cents at Newark.com but could not seem to get an est on shipping ....
So I called them and found they had a min qty of 150 pcs..

But they suggested Panasonic as a substitute. ... and for only 43.7 cents each. ( has ever higher ripple current 830ma)
Newark's number: 53W8293
Panasonic number: ECA-2CM221

So for 43.7 cents I bought 10pcs... shipping however was another $5.33

Newark seems to have very competitive prices.... only about 1/3 or Mouser and DigiKey
Mouser has them but that is a better deal.

What I have in there right now on the bread-board is just two 100uf 160v no-name caps in parallel with a 22uf 160v no name.
All running cool as heck. ...lol

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Wed 15, 2015 7:15 am 
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Pbpix wrote:
What I have in there right now on the bread-board is just two 100uf 160v no-name caps in parallel with a 22uf 160v no name.
All running cool as heck. ...lol
Your also running less than 3/4 the B+ current through them and ripple current doesn't decrease linearly with capacitance so two 100 uF (plus a 22 uF) is more than the ripple current of a 220 uF. For example, that ECA-2CM221 is rated 830 mA ripple but a 100 uF of the same voltage is 515 mA. The 22 uF is rated 175 mA so, all totaled, that's 1,205 mA whereas the 220 uF alone would only be 830 mA.


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Wed 15, 2015 7:20 am 
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Flipperhome wrote:
Pbpix wrote:
What I have in there right now on the bread-board is just two 100uf 160v no-name caps in parallel with a 22uf 160v no name.
All running cool as heck. ...lol
Your also running less than 3/4 the B+ current through them and ripple current doesn't decrease linearly with capacitance so two 100 uF (plus a 22 uF) is more than the ripple current of a 220 uF. For example, that ECA-2CM221 is rated 830 mA ripple but a 100 uF of the same voltage is 515 mA. The 22 uF is rated 175 mA so, all totaled, that's 1,205 mA whereas the 220 uF alone would only be 830 mA.

Oh.
I didn't know you could add up the ripple ratings for caps in parallel. Huh.

I have a question:
Why am I only running 3/4 of the current?
I have lamps that are connected now to B+ simulating the 50ma B+ load of the other channel.

I am playing Mp3 through the operating channel now and that's the total 123ma I measured through the 300 ohm resistor between C2 & C3

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Last edited by Pbpix on Apr Wed 15, 2015 7:23 am, edited 1 time in total.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Apr Wed 15, 2015 7:22 am 
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Pbpix wrote:
Flipperhome wrote:
Pbpix wrote:
What I have in there right now on the bread-board is just two 100uf 160v no-name caps in parallel with a 22uf 160v no name.
All running cool as heck. ...lol
Your also running less than 3/4 the B+ current through them and ripple current doesn't decrease linearly with capacitance so two 100 uF (plus a 22 uF) is more than the ripple current of a 220 uF. For example, that ECA-2CM221 is rated 830 mA ripple but a 100 uF of the same voltage is 515 mA. The 22 uF is rated 175 mA so, all totaled, that's 1,205 mA whereas the 220 uF alone would only be 830 mA.

Oh.
I didn't know you could add up the ripple ratings for caps in parallel. Huh.

I have a question:
Why am I only running 3/4 of the current?
I have lamps that are connected now to B+ simulating the 50ma B+ load of the other channel.
How could I know that?


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