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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Aug Wed 31, 2016 3:07 pm 
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Hello john
Well I will


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Sun 11, 2016 4:07 am 
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OK I am building this headphone amp using the op275. I still don't understand the power supply. Why in the world Should I add two 9 volt batts to get 18 volts, then separate into dual 9 volt supply and making a new virtual ground, when I already have the circuit? Is there a reason for this?
https://tangentsoft.net/audio/cmoy/misc ... nt-sch.pdf

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Sun 11, 2016 4:12 am 
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john8750 wrote:
OK I am building this headphone amp using the op275. I still don't understand the power supply. Why in the world Should I add two 9 volt batts to get 18 volts, then separate into dual 9 volt supply and making a new virtual ground, when I already have the circuit? Is there a reason for this?
https://tangentsoft.net/audio/cmoy/misc ... nt-sch.pdf
What do you mean by "already have the circuit?"

The opamps need a dual supply and two batteries make one.


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Sun 11, 2016 6:33 am 
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Flipperhome wrote:
john8750 wrote:
OK I am building this headphone amp using the op275. I still don't understand the power supply. Why in the world Should I add two 9 volt batts to get 18 volts, then separate into dual 9 volt supply and making a new virtual ground, when I already have the circuit? Is there a reason for this?
https://tangentsoft.net/audio/cmoy/misc ... nt-sch.pdf
What do you mean by "already have the circuit?"

The opamps need a dual supply and two batteries make one.



Hi Flip.
If I just use the two batts, the common of those batts would make the ground. That will be the power supply, not needing any other components.
Isn't that ok? Or am I missing something?

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Sun 11, 2016 7:06 am 
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john8750 wrote:
Flipperhome wrote:
john8750 wrote:
OK I am building this headphone amp using the op275. I still don't understand the power supply. Why in the world Should I add two 9 volt batts to get 18 volts, then separate into dual 9 volt supply and making a new virtual ground, when I already have the circuit? Is there a reason for this?
https://tangentsoft.net/audio/cmoy/misc ... nt-sch.pdf
What do you mean by "already have the circuit?"

The opamps need a dual supply and two batteries make one.



Hi Flip.
If I just use the two batts, the common of those batts would make the ground. That will be the power supply, not needing any other components.
Isn't that ok? Or am I missing something?

Yes John.. that's right.. but ONLY as long as both 9v batteries are the same exact voltage.
Since one may not match the other perfectly.. this circuit does the trick.
It takes, whatever the combined voltages add up to and divides that in half.
So the two halves will always match.

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Last edited by Pbpix on Sep Sun 11, 2016 8:25 am, edited 1 time in total.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Sun 11, 2016 7:44 am 
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john8750 wrote:
Flipperhome wrote:
john8750 wrote:
OK I am building this headphone amp using the op275. I still don't understand the power supply. Why in the world Should I add two 9 volt batts to get 18 volts, then separate into dual 9 volt supply and making a new virtual ground, when I already have the circuit? Is there a reason for this?
https://tangentsoft.net/audio/cmoy/misc ... nt-sch.pdf
What do you mean by "already have the circuit?"

The opamps need a dual supply and two batteries make one.
Hi Flip.
If I just use the two batts, the common of those batts would make the ground. That will be the power supply, not needing any other components.
Isn't that ok? Or am I missing something?
Oh, I see what you mean now. Peter is correct that it's to keep both halves the same. Why that matters varies with opamp design but suffice to say that dual supplies isn't just 'tradition', there's a reason for them. For one, power supply rejection ratio. You essentially don't have any with a 'single supply' (like the 6502 preamp) and it's greatly diminished with simply 2 batteries. Moreover imbalanced supplies lead to an imbalanced output (offset), the rail with the least voltage is the limiting factor for output swing, distortion increases, and some opamps become unstable (heavy loads feeding back through the poor PS rejection ratio).

Whether any of that 'matters' depends on the design requirements and what you're trying to accomplish but it's usually 'safer' to just design with equal supplies and then you don't have to worry about the potential effects and 'tradeoffs'.


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Sun 11, 2016 8:20 pm 
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I understand men. I wanted to know why. That makes perfect sense. So, I will use that PS circuit.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Sun 11, 2016 8:23 pm 
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I found an all tube amp using the 6V6 power tubes. What do you guys think about this?
viewtopic.php?f=12&t=306595
Its on the second page.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Sun 11, 2016 9:30 pm 
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john8750 wrote:
I found an all tube amp using the 6V6 power tubes. What do you guys think about this?
viewtopic.php?f=12&t=306595
Its on the second page.

Hi John:

What's your goal?
Why are you wanting/needing an "all tube" amp at this point?

What is it about it that you need?

The one you refer to seems somewhat typical... but with no voltages shown (and no text info about the choice of tubes or the whys and wherefores of the particular design) ... and so I can't easily determine what class it is running. What are the "special" or particular features of this amp that makes it desirable to you or which makes it "better" than others? .. or "better" for your particular application?

You should first describe to us what you are trying to achieve.
...Because there are tons of amps and many are average some better some not so much.

Here's a few:
http://lilienthalengineering.com/wp-con ... -PP-ed.png
http://www.grommesprecision.com/grommes ... review.PDF
http://www.diyaudio.com/forums/attachme ... gty-pp.jpg
http://www.knizefamily.net/russ/blog/wp ... ic-amp.jpg
Here's a bunch more:
https://www.google.com/search?hl=en&sit ... +schematic

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Mon 12, 2016 12:34 am 
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My goal is to build a stereo all tube amp. I like the 6V6 so would prefer those for the outputs. I think a PP would be the best.
It must have tone controls and be hi-fi, THD as low as possible. And an amp that I already have some parts for.
I already have the amp I will use in my listening room at home. The 6V6 we built. The 5902 is going in the Zenith in my shop.
Thanks for that list Peter. I really like the second one. But don't know how to add tone controls.
You might have looked at the wrong amp schematic on the other page. It is the one from tube radio. And has no tone control.
But shows all parts, tubes, and transformers.
What do you think of the very simple PS?

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Mon 12, 2016 12:39 am 
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john8750 wrote:
My goal is to build a stereo all tube amp. I like the 6V6 so would prefer those for the outputs. I think a PP would be the best.
It must have tone controls and be hi-fi, THD as low as possible. And an amp that I already have some parts for.
I already have the amp I will use in my listening room at home. The 6V6 we built. The 5902 is going in the Zenith in my shop.
Thanks for that list Peter. I really like the second one. But don't know how to add tone controls.
You might have looked at the wrong amp schematic on the other page. It is the one from tube radio. And has no tone control.
But shows all parts, tubes, and transformers.
What do you think of the very simple PS?

I see that it's his schematic... but no voltages shown and no info about which class it operates at and the THD etc.. nothing about why he chose those particular tubes. No info about performance or even if he's ever actually built it or is it just an idea that he drew on paper.. y'know?
etc etc.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Mon 12, 2016 1:41 am 
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Pbpix wrote:
john8750 wrote:
My goal is to build a stereo all tube amp. I like the 6V6 so would prefer those for the outputs. I think a PP would be the best.
It must have tone controls and be hi-fi, THD as low as possible. And an amp that I already have some parts for.
I already have the amp I will use in my listening room at home. The 6V6 we built. The 5902 is going in the Zenith in my shop.
Thanks for that list Peter. I really like the second one. But don't know how to add tone controls.
You might have looked at the wrong amp schematic on the other page. It is the one from tube radio. And has no tone control.
But shows all parts, tubes, and transformers.
What do you think of the very simple PS?

I see that it's his schematic... but no voltages shown and no info about which class it operates at and the THD etc.. nothing about why he chose those particular tubes. No info about performance or even if he's ever actually built it or is it just an idea that he drew on paper.. y'know?
etc etc.
He said he it's what's in his 1950 Silvertone and used with his Hammarlund SP-600 JX-17. The driver and phase splitter were 'what's already there'.

It's pretty much a standard Class AB 6V6 with a 10k OPT, which means B+ is around 250V (probably a little higher) but there's no feedback so it isn't 'Hi-Fi'. To get better frequency response it uses the Edcor CXPP.

It's okay but over a 100 bucks, not counting shipping, just for the iron (more if you want stereo).


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Mon 12, 2016 5:53 am 
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Its just a fun thought men.
I have a few things to finish up first.
My 6V6 will be hard to beat anyway. It will pass 20hz through my Genesis
speakers that can be heard and felt. The THD, I can guess is > 1%
I just want to build an all tube amp, to show off with.
I do much appreciate your help and understanding.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Mon 12, 2016 6:54 am 
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john8750 wrote:
Its just a fun thought men.
I have a few things to finish up first.
My 6V6 will be hard to beat anyway. It will pass 20hz through my Genesis
speakers that can be heard and felt. The THD, I can guess is > 1%
I just want to build an all tube amp, to show off with.
I do much appreciate your help and understanding.
It's a matter of personal taste but if it were me I would try different tubes. After all, you already know what the 6V6 sounds like. Newer tubes in the 9 pin miniature also have advantages, like more gain.

Also, if you're dead set on tone controls (still don't know why) they'd serve best in a separate preamp so you can mix and match to your power amps. Besides simplifying things it would be a shame to have a boffo power amp that needs to be reworked for less than satisfactory tone controls, and vice versa. If they're separate you can optimize each without affecting the other.

In addition, what do you want to 'explore'. I like, for example, to see how 'inexpensively' a power amp can be made (and I can make more that way) but others might want to shoot for 'power', like 50 Watt. (I'd like to make a 'high power' amp too but the cost is prohibitive.)

Here is an amp I designed but haven't built yet using 'dollar days' tubes (which was the inspiration). It's the 'full power' version of the Princely Pauper.

Attachment:
6HB6 - 6BR8 Princely Pauper - Edcor OPT&PS v2.jpg
6HB6 - 6BR8 Princely Pauper - Edcor OPT&PS v2.jpg [ 97.87 KiB | Viewed 4864 times ]


The 6BR8 is a different base version of the 6U8, which was used in audio amps. The 6HB6 is a vertical deflection tube that look like a 6BQ5 (6GK6) on steroids (20,000 umhos). As a backup, it's pin compatible with the 6GK6, the tube I use in StealthAX and Topcat. It looks like it has lower plate dissipation but that's because of the vertical defection service (the 6V6 is derated too). I've substituted them in my StealthAX breadboard and they perform perfectly but are 1 buck each. I don't have spice models for it so R3 and R4 may need some tweaking to get the correct current and voltages.

Since it uses negative feedback I figured on using the cheaper XPP series Edcor but, of course, the GXPP and CXPP could be used in the exact same circuit.

The 'full power' version takes an Edcor power transformer, which isn't too bad a cost hit now that radio Shack has discontinued their el-cheapo 12.6V 3A filament transformer, plus it looks better. (I used that RS transformer and the Triad N-68X combo for the cost in some of my projects, like the Paraphaser, but it's limited to 50VA).

Attachment:
6HB6 Pauper PS - Edcor.jpg
6HB6 Pauper PS - Edcor.jpg [ 68.89 KiB | Viewed 4864 times ]


Anyway, it's just an example of one approach.


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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Mon 12, 2016 7:00 am 
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john8750 wrote:
Its just a fun thought men.
I have a few things to finish up first.
My 6V6 will be hard to beat anyway. It will pass 20hz through my Genesis
speakers that can be heard and felt. The THD, I can guess is > 1%
I just want to build an all tube amp, to show off with.
I do much appreciate your help and understanding.

Ok..John,
Then you should search the hifi forums and read the reviews.
.... and find and read about a few 6v6 designs that others chose to build and what the results were and if others also built it and got good results.
Try to find an amp that has something that appeals to you... like maybe low cost & hi quality, or one that uses only a few tubes. Or a redesign of a commercial amp made by a respected company.
Try to think about what features are best for you.
The 1st good idea is that it uses the 6v6 which you like and already have some.

Then think of why you might like some of the various designs you see that others also felt were respectable and for which you can also hopefully find good output transformers at a decent price.
I think if you read about some designs here and there around the hifi forums you'll start to find one that stands out to you most.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Mon 12, 2016 7:07 am 
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John:
Check this:
1.) http://www.instructables.com/id/Buildin ... /?ALLSTEPS
https://cdn.instructables.com/FSA/A2B6/ ... MEDIUM.jpg

2.) http://audiokarma.org/forums/index.php? ... pg.437513/

3.) http://www.diyaudio.com/forums/tubes-va ... -help.html

http://www.diyaudio.com/forums/attachme ... og6gk5.gif

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Tue 13, 2016 6:24 am 
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Thanks again Men. Busy with the BOD tonight, will be back with you all tomorrow........

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Wed 14, 2016 7:51 pm 
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Flipperhome wrote:
john8750 wrote:
Its just a fun thought men.
I have a few things to finish up first.
My 6V6 will be hard to beat anyway. It will pass 20hz through my Genesis
speakers that can be heard and felt. The THD, I can guess is > 1%
I just want to build an all tube amp, to show off with.
I do much appreciate your help and understanding.
It's a matter of personal taste but if it were me I would try different tubes. After all, you already know what the 6V6 sounds like. Newer tubes in the 9 pin miniature also have advantages, like more gain.

Also, if you're dead set on tone controls (still don't know why) they'd serve best in a separate preamp so you can mix and match to your power amps. Besides simplifying things it would be a shame to have a boffo power amp that needs to be reworked for less than satisfactory tone controls, and vice versa. If they're separate you can optimize each without affecting the other.

In addition, what do you want to 'explore'. I like, for example, to see how 'inexpensively' a power amp can be made (and I can make more that way) but others might want to shoot for 'power', like 50 Watt. (I'd like to make a 'high power' amp too but the cost is prohibitive.)

Here is an amp I designed but haven't built yet using 'dollar days' tubes (which was the inspiration). It's the 'full power' version of the Princely Pauper.

Attachment:
6HB6 - 6BR8 Princely Pauper - Edcor OPT&PS v2.jpg


The 6BR8 is a different base version of the 6U8, which was used in audio amps. The 6HB6 is a vertical deflection tube that look like a 6BQ5 (6GK6) on steroids (20,000 umhos). As a backup, it's pin compatible with the 6GK6, the tube I use in StealthAX and Topcat. It looks like it has lower plate dissipation but that's because of the vertical defection service (the 6V6 is derated too). I've substituted them in my StealthAX breadboard and they perform perfectly but are 1 buck each. I don't have spice models for it so R3 and R4 may need some tweaking to get the correct current and voltages.

Since it uses negative feedback I figured on using the cheaper XPP series Edcor but, of course, the GXPP and CXPP could be used in the exact same circuit.

The 'full power' version takes an Edcor power transformer, which isn't too bad a cost hit now that radio Shack has discontinued their el-cheapo 12.6V 3A filament transformer, plus it looks better. (I used that RS transformer and the Triad N-68X combo for the cost in some of my projects, like the Paraphaser, but it's limited to 50VA).

Attachment:
6HB6 Pauper PS - Edcor.jpg


Anyway, it's just an example of one approach.



I like it Flip. Especially the very simple PS. Yes I realize the silicone aspect.
What about the hi-fi and THD value? Any ideas about what power transformer to use.
I would like the best OT's possible, Edcor?

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Wed 14, 2016 8:06 pm 
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Pbpix wrote:



I really like number one. What about ultra linear, and NFB, CCS's.
Looks very simple.
I would like to use one power transformer.

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 Post subject: Re: 6V6 / 6AQ5 PP Stereo Amp
PostPosted: Sep Wed 14, 2016 8:22 pm 
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Here is a simple tone preamp. Only need one 250 volt PS, and heater circuit.
Check out the Brimar tone control circuit.
http://www.angelfire.com/electronic/fun ... one-A.html

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