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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Fri 09, 2018 7:02 am 
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john8750 wrote:
I just noticed that one of my Edcors is missing the sticker. Strange.
Also have two questions.
On the very first 5902 schematic there are 2.2uf ecaps, and some .1 caps in the opamp circuit. We don't need them anymore?
And, in the 20volt supply, I used a 470uf instead of a 220. I am guessing that will be ok.
I should have the amp section working by Sunday. Its going together quick.

The 2.2uf caps on the old schematic were decoupling to eliminate any noise on the VCC line.
Flip didn't show any decoupling caps when he designed the +/- 20 for Vcc ... and so, I forgot about them. But it's always a good idea to add decoupling caps like that as close to the Vcc input on the chip as possible to avoid any chance of noise on the Vcc line.
But you are using 470uf filter caps and .. I am actually using 1000uf @35v or 50v filter caps since they were so cheap and I have plenty of them. So large 470 or 1000uf caps make the 20v lines extremely quiet... certainly no ripple.

BTW Are those ceramic caps on the CCS .1uf?

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Fri 09, 2018 7:07 am 
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Are you going to paint the laminations of the pwr transformer to make it look nicer or is that white goop not so noticeable?

Maybe spray paint the whole trans?

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Fri 09, 2018 7:49 am 
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Pbpix wrote:
john8750 wrote:
I just noticed that one of my Edcors is missing the sticker. Strange.
Also have two questions.
On the very first 5902 schematic there are 2.2uf ecaps, and some .1 caps in the opamp circuit. We don't need them anymore?
And, in the 20volt supply, I used a 470uf instead of a 220. I am guessing that will be ok.
I should have the amp section working by Sunday. Its going together quick.

The 2.2uf caps on the old schematic were decoupling to eliminate any noise on the VCC line.
Flip didn't show any decoupling caps when he designed the +/- 20 for Vcc ... and so, I forgot about them. But it's always a good idea to add decoupling caps like that as close to the Vcc input on the chip as possible to avoid any chance of noise on the Vcc line.
But you are using 470uf filter caps and .. I am actually using 1000uf @35v or 50v filter caps since they were so cheap and I have plenty of them. So large 470 or 1000uf caps make the 20v lines extremely quiet... certainly no ripple.

BTW Are those ceramic caps on the CCS .1uf?



I will add those caps because I have some and wont hurt anyway.
I am gonna scrape of the glue on the transformer and paint it black.
The .1 caps are little ceramic disc type, 50volt.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Fri 09, 2018 10:07 pm 
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Here she is. Mounted and ready for wiring. Purple wires for CCS. Green and white for grid inputs.
Gonna wire the NFB through a cut-out switch on the rear panel.
Attachment:
20180209_124435.jpg
20180209_124435.jpg [ 181.67 KiB | Viewed 115 times ]

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 10, 2018 12:41 am 
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You can use 2.2uf or as AD suggests 10uf and .1uf

Analog Devices (on their application sheet) shows a typical decoupling arrangement as a 10uf and .1uf cap on each of the two supply pins. + and - lines.

I took a look at my op-amp board today and I see that I DID add the 10uf decouplers... but forgot the .1 uf

Ref: http://www.analog.com/media/en/technica ... /OP275.pdf

Attachment:
opamp decoupling.jpg
opamp decoupling.jpg [ 46.16 KiB | Viewed 114 times ]

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Last edited by Pbpix on Feb Sat 10, 2018 3:17 am, edited 1 time in total.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 10, 2018 1:58 am 
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I put 4.7 ecaps on the 20volt supplies. And will add the .1's. Want to do the best I can.
Thanks Peter. You make it very clear.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 10, 2018 6:59 am 
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I see that, in fact, I did also have the .1uf caps installed.
I used these tiny .1uf 50v monolithic ceramic types.
Image

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 10, 2018 8:01 am 
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john8750 wrote:
I have decided to build the original amp. I could go crazy with improvements. :(
I thank you guys for all the work you do on this.
Here is the original schematic. I re-routed the UL circuit. Is this correct?
Will get this amp working, then add the other stuff, thanks Flip for that suggestion.
I hope that 100va PT can handle this, plus. :wink:
Attachment:
build.png

When you tie off the UL leads... I don't know how that affects the impedance.

For 6V6 PP:
Typically when UL is not used.... the reflected impdance should be 10k.

When UL is used then the reflected is supposed to be 8k....

so since this is an 8k UL OT.... I have no clue how it looks to the tube impedance-wise when the UL taps aren't used.

Good question to call Edcor to ask.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 10, 2018 8:41 am 
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Pbpix wrote:
john8750 wrote:
I have decided to build the original amp. I could go crazy with improvements. :(
I thank you guys for all the work you do on this.
Here is the original schematic. I re-routed the UL circuit. Is this correct?
Will get this amp working, then add the other stuff, thanks Flip for that suggestion.
I hope that 100va PT can handle this, plus. :wink:
Attachment:
build.png

When you tie off the UL leads... I don't know how that affects the impedance.

For 6V6 PP:
Typically when UL is not used.... the reflected impdance should be 10k.

When UL is used then the reflected is supposed to be 8k....

so since this is an 8k UL OT.... I have no clue how it looks to the tube impedance-wise when the UL taps aren't used.

Good question to call Edcor to ask.



That's a good point Peter. I was going to get the amp working as the schematic shows first. I think it will be fine.
What advantage will there be by not using the UL transformer taps? There could only be a tradeoff.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 10, 2018 9:01 am 
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john8750 wrote:
Pbpix wrote:
john8750 wrote:
I have decided to build the original amp. I could go crazy with improvements. :(
I thank you guys for all the work you do on this.
Here is the original schematic. I re-routed the UL circuit. Is this correct?
Will get this amp working, then add the other stuff, thanks Flip for that suggestion.
I hope that 100va PT can handle this, plus. :wink:
Attachment:
build.png

When you tie off the UL leads... I don't know how that affects the impedance.

For 6V6 PP:
Typically when UL is not used.... the reflected impdance should be 10k.

When UL is used then the reflected is supposed to be 8k....

so since this is an 8k UL OT.... I have no clue how it looks to the tube impedance-wise when the UL taps aren't used.

Good question to call Edcor to ask.



That's a good point Peter. I was going to get the amp working as the schematic shows first. I think it will be fine.
What advantage will there be by not using the UL transformer taps? There could only be a tradeoff.

Power is supposed be increased to a degree.... how much I don't know.

But it would be good if you call Edcor to ask what the 8k UL will look like to the 6V6 w/o the UL tap.
I do not know.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 10, 2018 9:37 am 
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john8750 wrote:
Pbpix wrote:
When you tie off the UL leads... I don't know how that affects the impedance.

For 6V6 PP:
Typically when UL is not used.... the reflected impdance should be 10k.

When UL is used then the reflected is supposed to be 8k....

so since this is an 8k UL OT.... I have no clue how it looks to the tube impedance-wise when the UL taps aren't used.

Good question to call Edcor to ask.
That's a good point Peter. I was going to get the amp working as the schematic shows first. I think it will be fine.
What advantage will there be by not using the UL transformer taps? There could only be a tradeoff.
Using, or not using, UL taps has no effect on impedance. An 8K OPT is an 8K OPT.

The 6V6 Datasheet OPT for 285 V plate (plus 19 V for cathode bias = 304 V B+) is 8k, without UL taps. The 1955 Acrosound UL OPT for the 6V6 is 8k.

Datasheet power for a standard OPT is 14 Watt. You'll be lucky to get 10 Watt UL. Of course, those numbers are for the 6V6 fully driven and neither OPAMP will do that (although the OP604 gets closer).

Note: the recommended UL taps for the 6V6 are at 20%. All Edcors are at 40%.


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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 10, 2018 6:37 pm 
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Those durned details again. I don't think my Cousin, or I, will know the difference. Except for loudness.
And I drought Edcore will know anything, other than selling.
So, I will stick with the plan. I am thinking about building the original 6V6 with all tubes sometime, including the rectifier, Why, I don't know. Just something to do :roll:

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 10, 2018 6:39 pm 
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I bought this Heathkit FM4. Hope to get it working better than the FM3.
https://www.ebay.com/itm/Tube-Receiver- ... 1438.l2649

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 10, 2018 8:32 pm 
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Flipperhome wrote:
john8750 wrote:
Pbpix wrote:
When you tie off the UL leads... I don't know how that affects the impedance.

For 6V6 PP:
Typically when UL is not used.... the reflected impdance should be 10k.

When UL is used then the reflected is supposed to be 8k....

so since this is an 8k UL OT.... I have no clue how it looks to the tube impedance-wise when the UL taps aren't used.

Good question to call Edcor to ask.
That's a good point Peter. I was going to get the amp working as the schematic shows first. I think it will be fine.
What advantage will there be by not using the UL transformer taps? There could only be a tradeoff.
Using, or not using, UL taps has no effect on impedance. An 8K OPT is an 8K OPT.

The 6V6 Datasheet OPT for 285 V plate (plus 19 V for cathode bias = 304 V B+) is 8k, without UL taps. The 1955 Acrosound UL OPT for the 6V6 is 8k.

Datasheet power for a standard OPT is 14 Watt. You'll be lucky to get 10 Watt UL. Of course, those numbers are for the 6V6 fully driven and neither OPAMP will do that (although the OP604 gets closer).

Note: the recommended UL taps for the 6V6 are at 20%. All Edcors are at 40%.



Flip- an amp fully driven, means to the point of a noticeable distortion? Or, does that mean more wattage to the speakers?
More volume?
Thank you Sir..

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sat 10, 2018 10:34 pm 
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Flipperhome wrote:
john8750 wrote:
Pbpix wrote:
When you tie off the UL leads... I don't know how that affects the impedance.

For 6V6 PP:
Typically when UL is not used.... the reflected impdance should be 10k.

When UL is used then the reflected is supposed to be 8k....

so since this is an 8k UL OT.... I have no clue how it looks to the tube impedance-wise when the UL taps aren't used.

Good question to call Edcor to ask.
That's a good point Peter. I was going to get the amp working as the schematic shows first. I think it will be fine.
What advantage will there be by not using the UL transformer taps? There could only be a tradeoff.
Using, or not using, UL taps has no effect on impedance. An 8K OPT is an 8K OPT.

The 6V6 Datasheet OPT for 285 V plate (plus 19 V for cathode bias = 304 V B+) is 8k, without UL taps. The 1955 Acrosound UL OPT for the 6V6 is 8k.

Datasheet power for a standard OPT is 14 Watt. You'll be lucky to get 10 Watt UL. Of course, those numbers are for the 6V6 fully driven and neither OPAMP will do that (although the OP604 gets closer).

Note: the recommended UL taps for the 6V6 are at 20%. All Edcors are at 40%.

Flip:
Rather confusing.
Wasn't it you who advised us to use 8k instead of 10k if UL was desired. Right?

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sun 11, 2018 12:34 am 
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john8750 wrote:
Flipperhome wrote:
Using, or not using, UL taps has no effect on impedance. An 8K OPT is an 8K OPT.

The 6V6 Datasheet OPT for 285 V plate (plus 19 V for cathode bias = 304 V B+) is 8k, without UL taps. The 1955 Acrosound UL OPT for the 6V6 is 8k.

Datasheet power for a standard OPT is 14 Watt. You'll be lucky to get 10 Watt UL. Of course, those numbers are for the 6V6 fully driven and neither OPAMP will do that (although the OP604 gets closer).

Note: the recommended UL taps for the 6V6 are at 20%. All Edcors are at 40%.

Flip- an amp fully driven, means to the point of a noticeable distortion? Or, does that mean more wattage to the speakers?
More volume?
Thank you Sir..
Both. As you increase power the power tube's distortion increases but at 'clipping' the distortion shoots up dramatically. That's the 'measurement' point for 'max power'. But, in your case, the opamps will clip before the output tubes do so they'll not reach their maximum (undistorted) power output.

What the combined effect of that is is murky because small (<50 Watt) amps are often operated with 'clipping' on transient peaks. I.e. to get the 'loudness' the amp is usually overdriven but the opamps will have a different clipping characteristic and, hence, different distortion products than an 'all tube' amp.


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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sun 11, 2018 6:15 am 
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Flipperhome wrote:
john8750 wrote:
Flipperhome wrote:
Using, or not using, UL taps has no effect on impedance. An 8K OPT is an 8K OPT.

The 6V6 Datasheet OPT for 285 V plate (plus 19 V for cathode bias = 304 V B+) is 8k, without UL taps. The 1955 Acrosound UL OPT for the 6V6 is 8k.

Datasheet power for a standard OPT is 14 Watt. You'll be lucky to get 10 Watt UL. Of course, those numbers are for the 6V6 fully driven and neither OPAMP will do that (although the OP604 gets closer).

Note: the recommended UL taps for the 6V6 are at 20%. All Edcors are at 40%.

Flip- an amp fully driven, means to the point of a noticeable distortion? Or, does that mean more wattage to the speakers?
More volume?
Thank you Sir..
Both. As you increase power the power tube's distortion increases but at 'clipping' the distortion shoots up dramatically. That's the 'measurement' point for 'max power'. But, in your case, the opamps will clip before the output tubes do so they'll not reach their maximum (undistorted) power output.

What the combined effect of that is is murky because small (<50 Watt) amps are often operated with 'clipping' on transient peaks. I.e. to get the 'loudness' the amp is usually overdriven but the opamps will have a different clipping characteristic and, hence, different distortion products than an 'all tube' amp.




Then, could the opamp preamp have something to account for the very nice sound of the 6V6 amps peter and I have built?
They have lower power, but because of that, wont drive into the point of clipping and distortion?
Does any of your amps use an IC preamp?
Have you any experience with a possible opamp amplified with a transistor to feed the grids? Sounds complicated, if possible.
Just a fun thought.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sun 11, 2018 7:35 am 
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john8750 wrote:
Then, could the opamp preamp have something to account for the very nice sound of the 6V6 amps peter and I have built?
They have lower power, but because of that, wont drive into the point of clipping and distortion?
Does any of your amps use an IC preamp?
Have you any experience with a possible opamp amplified with a transistor to feed the grids? Sounds complicated, if possible.
Just a fun thought.
There's no such thing as 'no clipping'. The hybrid amp just clips earlier than an all tube amp, but it's still clipping.

No, I haven't used an opamp in any of my amps.


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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sun 11, 2018 8:25 pm 
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Test results.
No problems, but some situations.
The acv leaving the PT is 145. That makes the B+ 343. And the filaments above 36.
I figured on changing the 10uf dropper in the filament circuit to 8uf. Should give about 26v.
Is the B+ too high?

L1-----25.38v----25ma-----grid .132
L2-----25.83v-----25ma-----grid -.131
R1-----26.21v-----24ma-----grid .158
R2-----24.06v-----24ma-----grid -.158


These will be noted as actuals.
Here she is under test. Now I will tidy up the wiring before proceeding on.
Attachment:
20180211_111201.jpg
20180211_111201.jpg [ 185.47 KiB | Viewed 44 times ]

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Feb Sun 11, 2018 8:36 pm 
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How is this for the 8uf dropper cap.
https://www.ebay.com/itm/US-CBB61-AC450 ... Sw4A5YpAqW

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