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Old 6th August 2007, 01:29 PM   #51
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Quote:
Originally posted by revintage


Nope,
In my calculations the winding-ratio is 31,6:1 which corresponds to 8k:8ohm impedance-ratio.
ooppps, my bad, my finger slipped, yes you are correct.....


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Old 6th August 2007, 03:04 PM   #52
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Quote:
Originally posted by Shoog
Choke in the anode would be better. Finding the right choke to set the bias would difficult, or you would need supplementary fixed bias to set it right. Also you would need to bypass the choke for AC.

I have got my 807 parafeed setup with Microwave Oven Transformers as the anode choke load. Works well - but not as good as a CCS.

Shoog

If I pass the parafeed choke by a cap, I will short signal to the ground, right or at the worst build a generator?

--Yag
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Old 6th August 2007, 03:21 PM   #53
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Quote:
If I pass the parafeed choke by a cap, I will short signal to the ground, right or at the worst build a generator?

--Yag
The original question was about placing a choke in the cathode for bias purposes. I think this would be difficult to set the correct bias point and so I wouldn't recommend it at all. I think you would need a CCS as well to fix the current through the choke, and if you do that you don't need the choke. If you could get that to work you could create a cathode follower by placing the output transformer in parallel with the choke, but with its own parafeed cap. Overall I think this is just a bad wasteful idea.

If using a choke in the anode then bias is set by whatever you place in the cathode.

Shoog
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Old 6th August 2007, 08:29 PM   #54
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Quote:
Originally posted by Shoog


The original question was about placing a choke in the cathode for bias purposes. I think this would be difficult to set the correct bias point and so I wouldn't recommend it at all. I think you would need a CCS as well to fix the current through the choke, and if you do that you don't need the choke. If you could get that to work you could create a cathode follower by placing the output transformer in parallel with the choke, but with its own parafeed cap. Overall I think this is just a bad wasteful idea.

If using a choke in the anode then bias is set by whatever you place in the cathode.

Shoog
Nope. The original question was about impedance matching. Nothing about biasing. The main reason behind using a choke in the cathode in parafeed xformerless was low voltage at the output. Just in case something goes wrong with a cap.

I actually made it in headphone amp based on 6C45PI as an output tube.

--Yag
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Old 7th August 2007, 08:43 AM   #55
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Quote:
I actually made it in headphone amp based on 6C45PI as an output tube.
How did you set your bias point ?

Shoog
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Old 7th August 2007, 09:50 AM   #56
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Quote:
Originally posted by Shoog


How did you set your bias point ?

Shoog
That is what I have done. See attach.

--Yag
Attached Images
File Type: jpg choke_output.jpg (48.2 KB, 307 views)
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Old 7th August 2007, 01:23 PM   #57
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Seems like a good solution for a headphone amp.
How does it sound, and does it sound better than a simple cathode resistor.

Shoog
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Old 7th August 2007, 01:53 PM   #58
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Quote:
Originally posted by Shoog
Seems like a good solution for a headphone amp.
How does it sound, and does it sound better than a simple cathode resistor.

Shoog

Weeell. The performance was good for Sennheiser SL450 but Philips HP1000 (Zo=32ohm) was not satisfactory. However I think I made a wiring fault or there is a problem with the phones. Have not checked yet. As I remember details are better. Need to do some more work on that.
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