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Simple PCL805 push-pull amplifier

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AbaddonD

Member
Joined 2015
#1
Hey guys
I'm looking for a simple-ish PCL805 push-pull amplifier which has been proven to work.
I have 2 PCL805s, a 170V power supply, and a transformer.
I have made a class A amplifier using one of those tubes and it sounds great with about 20W of power at a 3Ohms speaker ( 2 x 6Ohms ).
I would like it to have only 2 PCL805s and no solid state devices except diodes.

Thanks, guys!
 
#2
Here are:
 

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#7
Well I was able to shove about 150mA at 170V into one PCL805 and get 20-25W with a 220V to 12V mains transformer without any red-plating. It sounded great BTW, someone which I had not expected.

The problem I have right now with a push-pull design is that they need a transformer with a center tap, which I don't have.
 
#8
AbaddonD said:
Well I was able to shove about 150mA at 170V into one PCL805 and get 20-25W with a 220V to 12V mains transformer without any red-plating. It sounded great BTW, someone which I had not expected.
Click to expand...

Are you sure? Because, the xCL805 is a very small tube (unable to handle that amount of power), and in SE Class A it MIGHT be 30% efficient (unable to convert that amount of input power to audio power).

From what you have said, you have either developed a new branch of physics or you are misinterpreting your data.
 
#9
AbaddonD said:
Well I was able to shove about 150mA at 170V into one PCL805 and get 20-25W with a 220V to 12V mains transformer without any red-plating. It sounded great BTW, someone which I had not expected.

The problem I have right now with a push-pull design is that they need a transformer with a center tap, which I don't have.
Click to expand...


u have to note that pcl805 tube can't provide 20 watts at all,never sth like this happens!!
by the way
again u remember that pcl805 if u used it's pentode in triode mode,can sounds nice,but in push-pull although your output power increases but u cancel Even harmonics,
and this cause that the final result wont be pleasent:wave:
 
#11
An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

This was done at 8.2Ohms at 91Hz. I think the RMS value calculated on my El Cheapo scope is wrong cause don't we multiply the P-P by 0.7071?
Anyway, this is why I think it's giving out about 20W or so.
With two 3Ohms speakers connected in parallel, it shakes the doors, windows, and the floor.

One of those speakers:
An externally hosted image should be here but it was not working when we last tested it.
 
#14
An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

This was done at 8.2Ohms at 91Hz. I think the RMS value calculated on my El Cheapo scope is wrong cause don't we multiply the P-P by 0.7071?
Anyway, this is why I think it's giving out about 20W or so.
With two 3Ohms speakers connected in parallel, it shakes the doors, windows, and the floor.

Two of these speakers:
An externally hosted image should be here but it was not working when we last tested it.
 
Last edited:
#15
AbaddonD said:
Hi!
So class AB doesn't sound better? It thought they did LOL!
I think I am. I will post a few pictures of the input current and output RMS voltage and stuff later.

Thank you all for your replies!
Click to expand...

what do yo mean by 'sound better' ?
in AB mode your output power increases,so this way is the main issue that many people prefer to do,cause that with more power you can drive wide range of speakers,but in single ended A mode your output power decreses

note that AB may not be as musical as A
 
#17
Direct link from this forum to google drive does not work (for a good reason). To see your images, the link should be copied from the post and pasted on the browser address bar - and only works for people that are logged on Google services. Use the attach function on the editor of this forum instead. I downloaded the most relevant picture on this post: from the scope screen, I believe that this amplifier output is 2,65 W RMS, and it seems to be clipping hard. The Artosalo 2W clean power prediction is therefore confirmed. Your high efficiency speaker is well matched to this low power amplifier. Old boombox speakers like that one were built to be loud with only a few watts of power, with a strong emphasis on some bass frequencies for the shaking effect. They are usually a bit lacking on the high frequencies but your vintage output transformer is likely uncapable to manage them anyway.
 

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#18
pcan said:
I believe that this amplifier output is 2,65 W RMS, and it seems to be clipping hard. The Artosalo 2W clean power prediction is therefore confirmed. Your high efficiency speaker is well matched to this low power amplifier. Old boombox speakers like that one were built to be loud with only a few watts of power, with a strong emphasis on some bass frequencies for the shaking effect. They are usually a bit lacking on the high frequencies but your vintage output transformer is likely uncapable to manage them anyway.
Click to expand...
Hello!

I will try to hook it up to the speakers and give a picture of the scope again. Again, I think the calculated RMS is wrong on the scope. If we take the 13V or so peak-to-peak and multiply it by 0.707, it should give us the right RMS.
These speakers are for a Sony CD-cassette stereo. It says on the main unit that each of the speakers are 125W RMS. They have a tweeter and their highs are decent.
I have had a Tripath amplifier, the stereo 15W version. It got fried so I can't compare them, but I in my opinion, this sounds much louder with the same speakers.
 
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