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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
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LFLab
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
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Posted: Tue Oct 18, 2016 2:25 pm Post subject:
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Haven't tried it myself (all my cans are low impedance), but it'll probably work. You can always do away with the series resistor on the end, or add a resistor from the node between the output transistors to "-" input of the opamp, rather than having a direct wire, to add some gain if it is not loud enough. |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
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Posted: Thu Oct 20, 2016 7:26 am Post subject:
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hi LFLab, how are you?
thanks for replying.
i was asking about this cause when reading about the gyraf one you gave me it says it will not handle 600ohm headphones. _________________ http://www.myspace.com/mgmtrance |
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LFLab
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
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Posted: Thu Oct 20, 2016 7:32 am Post subject:
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Well, the main limitation are the rails, and so yes, there might be better amplifiers around. But it will probably work.
The headphone amp I did is aimed at very good quality audio (hence the use of a 15 euro potmeter ), in low impedance transducers, and so there are amplifiers better suited to 600ohm cans.
Maybe try it first? It will not kill anything.
Curious to know what kind of headphones you'd like to use it with? Most recent headphones are 250ohms and less.
More info:
http://sound.whsites.net/project113.htm
(similar amp) either 120mW or 82mW into 600ohm, depending on sensitivity, it might be enough. |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
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LFLab
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
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Posted: Thu Oct 20, 2016 12:16 pm Post subject:
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No other ideas than "give it a try", I think it will be hard to find something that excels at all impedances.
But IF you want something that drives everything, I'd go for the Gyraf one, use an opamp which can handle higher rails (although those usually are specialty opamps not aimed at sound reproduction) and follower transistors which can do some serious pushing if needed (the BD139-BD140 pair).
There are still a couple of headphones I'd like to try, and Beyerdynamic (in my case DT770) is certainly one of them, I'd go for the 80 ohm version I think, one of the three impedances apparently sounds the most neutral, 80ohms IIRC. |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
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Posted: Thu Oct 20, 2016 5:28 pm Post subject:
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this is great, thanks
BTW, do by any chance know the current draw of the gyraf HP amp for both rails? _________________ http://www.myspace.com/mgmtrance |
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LFLab
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
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Posted: Fri Oct 21, 2016 1:05 am Post subject:
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No I don't, it'll depend on the bias of the follower transistors primarily.
In some builds it's a 1N4148, in some I used two Schottky's in series for more bias current, also built a few with LED's for a lot more bias current.
Measure voltage drop over R9 and R10 and do the math (ohms law) |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
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LFLab
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
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Posted: Fri Oct 21, 2016 2:16 am Post subject:
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Nope, R9 and R10 |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
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LFLab
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
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Posted: Fri Oct 21, 2016 2:58 am Post subject:
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Oh, sorry, I was talking about my own schematic:
In the power supply section, lower left. |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
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LFLab
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
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Posted: Fri Oct 21, 2016 10:30 am Post subject:
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LFLab wrote: |
In the power supply section, lower left. |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
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Posted: Fri Oct 21, 2016 11:36 pm Post subject:
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Sorry, ive missed that
Do you think i can some how do the same with the MFOS wall wart power supply?
I just dont want to built a new one.
Thanks man, this is a great idea! _________________ http://www.myspace.com/mgmtrance |
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LFLab
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
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Posted: Sat Oct 22, 2016 6:44 am Post subject:
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Sure!
By the way, there is a potentially enthousiastic mistake in the schematic I posted, some of the electrolytics need to be reversed!
I'll correct the schematic to prevent someone from building it this exact way. |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
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Posted: Sat Oct 22, 2016 12:06 pm Post subject:
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BTW, in the MFOS wall wart power supply i have only 2 load resistors, this is where i need to check the V after connecting the HP amp? _________________ http://www.myspace.com/mgmtrance |
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LFLab
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
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Posted: Sat Oct 22, 2016 12:53 pm Post subject:
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Are they in series with the headphone amp, or from each rail to ground? In the first case "yes" else "no".
If they are in series, the current drawn by the load will cause a voltage drop over the resistor, which you can easily measure and calculate current with the value of the series resistor. |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
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Posted: Sat Oct 22, 2016 1:23 pm Post subject:
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do you mean like Yusynth does to his modules, protection resistors from each power rail 10ohm value? _________________ http://www.myspace.com/mgmtrance |
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LFLab
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
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Posted: Sat Oct 22, 2016 2:09 pm Post subject:
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Yes, those are the ones!
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
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