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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Sun 14, 2018 2:04 am 
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Flipperhome wrote:
You didn't do the calculation correctly and that it's "almost right on" is a serendipitous confluence of those errors, and the fact it's already a working design. For example, how do you know it'll regulate? There's nothing to take into account ripple. E.g. put a 1 uF cap for C2/3 and it falls apart but your calculations are perfectly happy with that.

But you've also overestimated the load. I don't know where the 40 mA comes from but, in any case (I'll use your numbers), that's not right and has the effect of overestimating the load by twice. I.e. Two 20 mA (max) supplies at 18.5 V is .0.37 W x 2 = 0.74 W, not your 37 V x 40 mA = 1.48 W.

All I'm saying is that the ACTUAL voltage after the 1uf dropper came out to be 37.3v AC .. RIGHT?
And the AC current at that spot feeding the two sides of the supply is 34.5ma AC
That's 17.25ma AC per side.
That comes out for each side to be .. roughly 10ma for two chips + 7ma for the Zener ... right?

So if I want to use the spread sheet to come up with a value of the dropper cap.

All i need to do is tell it what the anticipated load's combined voltage and current is... right?
It doesn't care what it is for. It's a max load for calculations... that's it.

That's roughly 40v... right? and not more that 40ma.

So I start off knowing:
Each chip needs approx 5.5ma for both +/- 20 voltages ...so that's roughly = 11ma per chip (per +/- side)
Two chips = 22ma
allowing at least 2 ma (Iz) minimum for each Zener = 4ma
plus roughly an extra 6 ma per Zener for future possible loads = another 12ma

22ma + 4ma + 12ma= 38ma total = or (roughly 40ma)

To calculate by using the spreadsheet...
1.) I know each Chip supply requires only 20v but the avail voltage must be well above the 20v Zener level to allow the Zener to act as a regulator, so add 15v for Zener excess voltage.
20v + 15v = 35v+ but not more than say 40v

So with these parameters in mind, if I enter into the speadsheet a load of roughly 40v @ 40ma I come up with .95uf
roughly 1uf.

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Last edited by Pbpix on Jan Sun 14, 2018 2:21 am, edited 3 times in total.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Sun 14, 2018 2:15 am 
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john8750 wrote:
Not enough room to mount the power transformer under the chassis. The power supply components are already there.
Attachment:
20180113_162134.jpg

Plenty of room on top. Will need to make a cover over the terminals. Maybe a wood box over the transformer. It could match the chassis. Vent holes in the floor and in rear.
Attachment:
20180113_162305.jpg

Will it fit under chassis on the side wall?

If not does that mounting fame come off to mount it on its side on top?

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Sun 14, 2018 4:15 am 
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Pbpix wrote:
john8750 wrote:
Not enough room to mount the power transformer under the chassis. The power supply components are already there.
Attachment:
20180113_162134.jpg

Plenty of room on top. Will need to make a cover over the terminals. Maybe a wood box over the transformer. It could match the chassis. Vent holes in the floor and in rear.
Attachment:
20180113_162305.jpg

Will it fit under chassis on the side wall?

If not does that mounting fame come off to mount it on its side on top?



Forgot to try that Peter. I would need to relocate the power supply components. But could work it out. Remember, I need another small 12volt transformer under the chassis, and regulating network for +12v.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Sun 14, 2018 10:05 pm 
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Looks like the outer ring is part of the housing. I don't want to mess with that. So, the only other idea I have is to mount on top and cover the terminals.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Sun 14, 2018 10:14 pm 
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Guys. I think you all told me that The filament circuit must be connected to B-. If possible, I could power the filaments off the incoming line. That would leave plenty of power from the isolation transformer.
Please let me know. I am thinking that we discussed this before, and a reason why it wont work.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Sun 14, 2018 10:22 pm 
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john8750 wrote:
Guys. I think you all told me that The filament circuit must be connected to B-. If possible, I could power the filaments off the incoming line. That would leave plenty of power from the isolation transformer.
Please let me know. I am thinking that we discussed this before, and a reason why it wont work.

How did you miss all this info earlier in the thread?

Yes... didn't you see my post about that to Flip a few posts back?

Flipperhome wrote:
Pbpix wrote:
BTW:
If you run the filaments on a small 25 or 12 or 6v transformer then the Main transformer is free to power up all op-amp chips everywhere you want... no?
Of course, if he has the room and it would cost. It would take a 2 amp 6.3 VAC transformer.



Then I suggested other types of supplies:
Pbpix wrote:

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Sun 14, 2018 11:03 pm 
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john8750 wrote:
Guys. I think you all told me that The filament circuit must be connected to B-. If possible, I could power the filaments off the incoming line. That would leave plenty of power from the isolation transformer.
Please let me know. I am thinking that we discussed this before, and a reason why it wont work.
It won't work (right) because there's no reference from one side of the transformer to the other so what would heater voltage be relative to ground? It has to be less than 200 V but, being isolated, it could be anything.


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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Sun 14, 2018 11:07 pm 
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BTW John,. I'm sitting here this cozy Sunday afternoon listening to all my favorite jazz & cocktail music (which you have now too) on my great little 5902 PP amp.
Holy cow! ... Every time I decide to switch from the 6V6 amp to this 5902... I'm always reminded and amazed at the power and depth of bass ... wow.
What a lovely little amp with such room-filling power..

Schematic for those unfamiliar with it:
http://www.pbpix.com/amp/5902%20PP%2020 ... change.png

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Sun 14, 2018 11:15 pm 
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And Flip... if you feel like building this 5902 amp w/either op275 or opa604
Ill be glad to send you a gift of 4 nos 5902 tubes.
All you'd need is a cpl OTs.

Both John and I would certainly love to hear your feed back after you get a chance to listen to it.

It's so fast and easy to toss together ... you should give it a try.

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Last edited by Pbpix on Jan Sun 14, 2018 11:22 pm, edited 1 time in total.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Sun 14, 2018 11:19 pm 
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Pbpix wrote:
john8750 wrote:
Guys. I think you all told me that The filament circuit must be connected to B-. If possible, I could power the filaments off the incoming line. That would leave plenty of power from the isolation transformer.
Please let me know. I am thinking that we discussed this before, and a reason why it wont work.

How did you miss all this info earlier in the thread?

Yes... didn't you see my post about that to Flip a few posts back?

Flipperhome wrote:
Pbpix wrote:
BTW:
If you run the filaments on a small 25 or 12 or 6v transformer then the Main transformer is free to power up all op-amp chips everywhere you want... no?
Of course, if he has the room and it would cost. It would take a 2 amp 6.3 VAC transformer.



Then I suggested other types of supplies:
Pbpix wrote:



I did not overlook that Peter. I don't want to add another large transformer. BUT- come to think of it, I do have a rather small 24v .5 amp tranny.
Let me think about that. I have a 50watt iso transformer that would fit on top, wired. So I could use that and the 24volt one for the filaments.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Sun 14, 2018 11:22 pm 
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Flipperhome wrote:
john8750 wrote:
Guys. I think you all told me that The filament circuit must be connected to B-. If possible, I could power the filaments off the incoming line. That would leave plenty of power from the isolation transformer.
Please let me know. I am thinking that we discussed this before, and a reason why it wont work.
It won't work (right) because there's no reference from one side of the transformer to the other so what would heater voltage be relative to ground? It has to be less than 200 V but, being isolated, it could be anything.



There we have those derned details again.....

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If I did something right, I made a mistake.


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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Sun 14, 2018 11:23 pm 
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Pbpix wrote:
And Flip... if you feel like building this 5902 amp w/either op275 or opa604
Ill be glad to send you a gift of 4 nos 5902 tubes.
All you'd need is a cpl OTs.

Both John and I would certainly love to hear your feed back after you get a chance to listen to it.

It's so fast and easy to toss together ... you should give it a try.




Gotta agree, it is amazin 8)

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If I did something right, I made a mistake.


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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Sun 14, 2018 11:28 pm 
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Pbpix wrote:
Flipperhome wrote:
You didn't do the calculation correctly and that it's "almost right on" is a serendipitous confluence of those errors, and the fact it's already a working design. For example, how do you know it'll regulate? There's nothing to take into account ripple. E.g. put a 1 uF cap for C2/3 and it falls apart but your calculations are perfectly happy with that.

But you've also overestimated the load. I don't know where the 40 mA comes from but, in any case (I'll use your numbers), that's not right and has the effect of overestimating the load by twice. I.e. Two 20 mA (max) supplies at 18.5 V is .0.37 W x 2 = 0.74 W, not your 37 V x 40 mA = 1.48 W.

All I'm saying is that the ACTUAL voltage after the 1uf dropper came out to be 37.3v AC .. RIGHT?
And the AC current at that spot feeding the two sides of the supply is 34.5ma AC
That's 17.25ma AC per side....
No, it's not "per side," as you mean, it's just 17.25 mA and the power calculation proves it. Looking at it another way, it takes "both sides" to complete an AC sine wave. I.e. 17.25 mA on the positive cycle and 17.25 mA on the negative cycle gives you 17.25 mA for the whole AC cycle.

You're conflating AC current and DC current as if they're the same thing, and they're not. Then you're doubling the current over what it really is and declaring victory when the answer comes out sort of in the ball park.


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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Sun 14, 2018 11:37 pm 
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Flipperhome wrote:
john8750 wrote:
Guys. I think you all told me that The filament circuit must be connected to B-. If possible, I could power the filaments off the incoming line. That would leave plenty of power from the isolation transformer.
Please let me know. I am thinking that we discussed this before, and a reason why it wont work.
It won't work (right) because there's no reference from one side of the transformer to the other so what would heater voltage be relative to ground? It has to be less than 200 V but, being isolated, it could be anything.

I'm sure there are some simple easy and/or creative safe ways to do it.
This guy did it by making a resistor divider to reference other side of the reversed 120v to 12v transformer so it wouldn't just "float"

This guy has a version for the filaments on his PP 5902 amp:

Ref: https://jjs.at/electronic/class_ab_subminiature.html

" The heaters (and therefore also the power connector!) are elevated to about 80 V to rise the heater voltage above the cathode voltage. This prevents them of acting like a forward biased diode and effectively removes mains (50 Hz) hum being fed into the cathode. "
Image

R1 100 ohm
R2 100k
R3 270k
R4 270k

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Mon 15, 2018 12:15 am 
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Pbpix wrote:
Flipperhome wrote:
It won't work (right) because there's no reference from one side of the transformer to the other so what would heater voltage be relative to ground? It has to be less than 200 V but, being isolated, it could be anything.

I'm sure there are some simple easy and/or creative safe ways to do it.
This guy did it by making a resistor divider to reference other side of the reversed 120v to 12v transformer so it wouldn't just "float"

This guy has a version for the filaments on his PP 5902 amp:

Ref: https://jjs.at/electronic/class_ab_subminiature.html

" The heaters (and therefore also the power connector!) are elevated to about 80 V to rise the heater voltage above the cathode voltage. This prevents them of acting like a forward biased diode and effectively removes mains (50 Hz) hum being fed into the cathode. "
Image
You could do that too, if you were using a 12 VAC power input. Of course, you'd still need a power transformer (wallwart) that could handle the whole thing to power it, which puts us right back to the same problem.


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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Mon 15, 2018 1:28 am 
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Looking through my transformer stash, I found an interesting item. Don't remember where it come from. Is there any hope of using this here?
Attachment:
20180114_160336.jpg
20180114_160336.jpg [ 106.32 KiB | Viewed 276 times ]

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If I did something right, I made a mistake.


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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Mon 15, 2018 1:39 am 
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john8750 wrote:
Looking through my transformer stash, I found an interesting item. Don't remember where it come from. Is there any hope of using this here?
Attachment:
20180114_160336.jpg

I guess you could change the supply and nor use the doubler.
Instead use a FW bridge for B+ feeding the filtercaps
The run the filaments on 6.3vac

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Mon 15, 2018 1:47 am 
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john8750 wrote:
Looking through my transformer stash, I found an interesting item. Don't remember where it come from. Is there any hope of using this here?
Attachment:
20180114_160336.jpg
Sorry, but it doesn't have enough power. There's only 32.4 Watt of B+ and, using a full wave bridge, you'd need at least 45 Watt for B+ alone (not counting the opamps).


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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Mon 15, 2018 1:55 am 
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Thanks Men, just a fun thought. I did find a 12.6volt at 1amp that will fit underneath. That should do the heaters. And have enough left for the 12+ zener regulated supply for the tone board?? Maybe??

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Jan Mon 15, 2018 2:10 am 
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Flipperhome wrote:
No, it's not "per side," as you mean, it's just 17.25 mA and the power calculation proves it. Looking at it another way, it takes "both sides" to complete an AC sine wave. I.e. 17.25 mA on the positive cycle and 17.25 mA on the negative cycle gives you 17.25 mA for the whole AC cycle.

You're conflating AC current and DC current as if they're the same thing, and they're not. Then you're doubling the current over what it really is and declaring victory when the answer comes out sort of in the ball park.

If you have a radio that uses a 1/2wave power supply and it looks like a 18ma load to the AC meter in your house... then you are consuming 18ma AC right?
And if you plug in two radios each drawing 18ma AC from the AC meter in your house, ... the total of the two radios will be drawing 36 ma AC... right?

back to our circuit.
But if, as YOU say, it's NOT 38ma but it's only 17.25ma ... what happened to the 38ma AC going in to the whole circuit?
I understand two 1/2 cycles... but still the total AC load measures 38ma and that just doesn't disappear and dwindle to 17.25ma.
That 38ma STILL has to feed the total load ... and there are two AC halves in that load each 1/2 feeds a diode... But still the total 38ma AC current is splitting to feed each half.

But all I'm saying is that the total AC load still looks the same to the dropper cap.
A load is a load.

Think of it as a black box with DC loads and stuff inside.
But it still looks like a fixed AC load of some sort to the AC side. Right?
Then if that load has two equal halves.... the AC current has to split equally to feed the two halves... No?

the AC current DOES split to feed both 1/2s

Example:

Attachment:
AC split current.jpg
AC split current.jpg [ 54.22 KiB | Viewed 273 times ]



To prove that the AC current splits in 1/2 to feed each half of the load.. I built this test ckt. I measured the total AC current gong into the two loads combined as 39maAC.
Then I measured the two separate AC current paths feeding each diode as 18.5ma AC
So the 39ma AC current SPLIT into two 18.5ma AC currents.:

Attachment:
AC split current 2.jpg
AC split current 2.jpg [ 53.62 KiB | Viewed 273 times ]

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Last edited by Pbpix on Jan Mon 15, 2018 2:42 am, edited 8 times in total.

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