Headphone switcher
- floppybootstomp
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#1 Headphone switcher
I put one of these together >> Link to use with my two EL84 push/pull monoblocks @ 10W each.
It works ok but when I turn the volume up I get distortion and the top end hurts my ears, it's kinda shrill.
I used the resistor values (all 3W +/- 5%) for the 20W output and wondered if using resistor values suited to 10W would help matters. I wondered what values for R1 & R3 might be suitable for 10W?
Have tried two sets of headphones, Pjilps Pro-Luxe PX-921's and some new-ish Sennheisser wireless HDR-160's, both of which display same characteristics as mentioned.
It works ok but when I turn the volume up I get distortion and the top end hurts my ears, it's kinda shrill.
I used the resistor values (all 3W +/- 5%) for the 20W output and wondered if using resistor values suited to 10W would help matters. I wondered what values for R1 & R3 might be suitable for 10W?
Have tried two sets of headphones, Pjilps Pro-Luxe PX-921's and some new-ish Sennheisser wireless HDR-160's, both of which display same characteristics as mentioned.
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- floppybootstomp
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#2
Nobody? Could anybody offer a view whether changing resistor values might make a difference to the sound?
I thought of maybe making R1 & R3 150R & 68R respectively might make it better suited to a 10 watt output.
Here's a few pix of the thing, the piece of vero is held in place with a couple of velcro squares and the box came from Maplins:
![Image](http://www.zen17796.zen.co.uk/public/switcher/hp001.jpg)
![Image](http://www.zen17796.zen.co.uk/public/switcher/hp002.jpg)
![Image](http://www.zen17796.zen.co.uk/public/switcher/hp003.jpg)
I thought of maybe making R1 & R3 150R & 68R respectively might make it better suited to a 10 watt output.
Here's a few pix of the thing, the piece of vero is held in place with a couple of velcro squares and the box came from Maplins:
![Image](http://www.zen17796.zen.co.uk/public/switcher/hp001.jpg)
![Image](http://www.zen17796.zen.co.uk/public/switcher/hp002.jpg)
![Image](http://www.zen17796.zen.co.uk/public/switcher/hp003.jpg)
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- Mike H
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#3
Only just got here!floppybootstomp wrote:Nobody?
![Very Happy :D](./images/smilies/icon_biggrin.gif)
Ah I think what's going on here is that that design assumes a transistor amp will be used ~ your valve amp's need 8 Ohms dummy loads to work properly.
So you need 8 Ohms between 'AMP L' (or whichever) and 'GND'.
I've found 10R and 47R in parallel are close enough. The 10R needs to be quite a few Watts rating, mine were 25W aluminium clad. Just in case. The 47R can be 6W or somesuch.
Unless you can find 8.2R 25W, but I haven't seen any for years.
HTH
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
- floppybootstomp
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#4
Thanks Mike. Now you mention it, I do recall having read that elsewhere here in the past but it clean slipped my mind... Time to order up some WW's
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- pre65
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#6
I have a few 15R Berco resistors. If Tony wants 4 (2 in parallel = 7.5ohms) just PM me with your address.
![Image](http://i111.photobucket.com/albums/n146/pre65/15Rresistor.jpg)
![Image](http://i111.photobucket.com/albums/n146/pre65/15Rresistor.jpg)
The only thing necessary for the triumph of evil is for good men to do nothing.
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G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- Mike H
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#8
Mmm, only needs a couple of sentences adding to say what to do in that case.
![Question :?:](./images/smilies/icon_question.gif)
Yep that'll work.pre65 wrote:I have a few 15R Berco resistors. If Tony wants 4 (2 in parallel = 7.5ohms) just PM me with your address.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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#9
Easy done I totally sympathisefloppybootstomp wrote:Now you mention it, I do recall having read that elsewhere here in the past but it clean slipped my mind...
![Very Happy :D](./images/smilies/icon_biggrin.gif)
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
- floppybootstomp
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#11
You sir, are a scholar and a gentleman, I am in your debt.
Thanks![Very Happy :D](./images/smilies/icon_biggrin.gif)
Thanks
![Very Happy :D](./images/smilies/icon_biggrin.gif)
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- pre65
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#12
Tony has not met me yet.floppybootstomp wrote:You sir, are a scholar and a gentleman.
Thanks
![Laughing :lol:](./images/smilies/icon_lol.gif)
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- floppybootstomp
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#14
That sorted it, pair of 7.2 ohm dummy loads, thanks Phil.
I am still occasionally surprised and warmed by human generosity.
This is probably a good thing![Wink ;)](./images/smilies/icon_wink.gif)
I am still occasionally surprised and warmed by human generosity.
This is probably a good thing
![Wink ;)](./images/smilies/icon_wink.gif)
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- floppybootstomp
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#15
There was a big slow down somehwere, caused me to make double post so I have deleted it.
If you give it a short, sharp, shock.... hey
If you give it a short, sharp, shock.... hey
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