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Old 1st February 2013, 01:48 AM   #111
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Quote:
Originally Posted by tinitus View Post
I mean using autoformer instead of normal OPT
and connect to cathode for low impedance
and maybe this way use ordinary toroid with good result

I know it could work as a circlotron design, but could it also be done as single ended ?
Sure it can.

See my previous pictures.
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Old 1st February 2013, 02:58 AM   #112
12B4A is offline 12B4A  United States
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I don't know where the circuit design is going but I have a good idea for the chassis:

Click the image to open in full size.
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Old 1st February 2013, 03:53 AM   #113
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Quote:
Originally Posted by 12B4A View Post
I don't know where the circuit design is going but I have a good idea for the chassis:
Camel is a horse prototype designed by big team.
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Old 1st February 2013, 08:48 AM   #114
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I think things will become clear when a few of us actually build working models of an all-DHT headphone amp. Yes - they will be different, but all should work! That's what we found with the 26 preamp thread. It started off as theory and by now I wouldn't be surprised if there as many as a hundred working examples. They fall into distinct categories - active load, plate choke, transformer coupled - and people build what they can afford and are comfortable with.

I'm sure Sowter can provide a transformer solution, but I'm expecting that some of us will be looking for cheaper alternatives as well. We haven't talked about the ratio of headphone to speaker listening either. In my case I never use headphones, though I do have them.
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Old 1st February 2013, 11:45 AM   #115
regal is offline regal  United States
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Quote:
Originally Posted by tinitus View Post
how about 'the ordinary' 2A3 ....parafeed ?
I am leaning in this direction. Dsvavitz has some real good point on his website in support of Parafeed for headphones. The ability to use a permalloy core really is a benefit for headphones, first its better with low level signal integrity/loss, and second most importnt you don't end up with a secondary 32 ohm winding with 12 ohms DCR and too much induction.

I asked Magnequest to quote their 2A3 nickel parafeed with a 32 ohm secondary months ago, with nothing, they just aren't interested.

I think this little transformer parafeed could be the way to go: Sowter Type 8650 Headphone Output transformer

It only handles 0.5W at 20 hz, but is good for 2W at 50 Hz, if it was the next core size up it would be perfect for a 2A3 or parallel 4P1L's.

Quote:
Originally Posted by andyjevans View Post
I think things will become clear when a few of us actually build working models of an all-DHT headphone amp. Yes - they will be different, but all should work! That's what we found with the 26 preamp thread. It started off as theory and by now I wouldn't be surprised if there as many as a hundred working examples. They fall into distinct categories - active load, plate choke, transformer coupled - and people build what they can afford and are comfortable with.

I'm sure Sowter can provide a transformer solution, but I'm expecting that some of us will be looking for cheaper alternatives as well. We haven't talked about the ratio of headphone to speaker listening either. In my case I never use headphones, though I do have them.
Very well said. I respect all input on this as we are treading new ground.

What is your opinion on parafeed?
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Old 1st February 2013, 12:17 PM   #116
12B4A is offline 12B4A  United States
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Well, with just single stage 26 alone I am able to drive my own headphones beyond my comfortable listening level but they are 100dB+/mW efficient (Sony 7506s). I was using a parafeed MQ EXO-45 (1uF motor run cap) in the test circuit and now I'm waiting for Edcor to ship EDCOR - PCW10K-7K/300-32 which would allow for better impedance matching. It certainly wouldn't drive Orthos well but it is dead quiet and would work very well for nearly every other headphone from high 90's sensitivity and above. I think one aspect of the goal of this discussion that has been missing is that can a DIY'er buy the parts for this design with off the shelf components that are not 'the most exotic' in the world? So far, Rod's and Iko's circuits seem to fit that particular concern.
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Old 1st February 2013, 02:24 PM   #117
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Quote:
Originally Posted by 12B4A View Post
Well, with just single stage 26 alone I am able to drive my own headphones beyond my comfortable listening level but they are 100dB+/mW efficient (Sony 7506s). I was using a parafeed MQ EXO-45 (1uF motor run cap) in the test circuit and now I'm waiting for Edcor to ship EDCOR - PCW10K-7K/300-32 which would allow for better impedance matching. It certainly wouldn't drive Orthos well but it is dead quiet and would work very well for nearly every other headphone from high 90's sensitivity and above. I think one aspect of the goal of this discussion that has been missing is that can a DIY'er buy the parts for this design with off the shelf components that are not 'the most exotic' in the world? So far, Rod's and Iko's circuits seem to fit that particular concern.
The Edcor can drive 97dB/mW of Sennhs HD600 with only 0,5W?
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Old 1st February 2013, 02:34 PM   #118
12B4A is offline 12B4A  United States
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I haven't tried but why wouldn't it? If 1 milliwatt produces 97dB then what is 500 milliwatts going to produce? Permanent hearing loss is my guess.
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Old 1st February 2013, 03:17 PM   #119
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And broken headphones.
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Old 1st February 2013, 03:25 PM   #120
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I checked Edcor site and doesn't have in stock "Product is built to order.", do you know how many time takes to build & deliver?
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