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Cavalli EHHA Embedded Hybrid Headphone Amp - Page 113

post #1681 of 1816
Quote:
Originally Posted by gurubhai View Post

Can you point me to some detailed info on 'shunt' mod. I have alps 'blue velvet' 100k pot.


 

 

sorry, i don't have a pic.  

 

on a pot:

Input = input signal from RCA

W = wiper

G = ground

 

connect W and G together for each channel.  place a 100K resistor in series from the RCA to Input on the pot to each channel.  from the Input after the 100K resistor, connect to the signal inputs on each channel.  the ground from each of the RCAs to should connect at their respective channels on the pot at W and G.  connect the W and G of each channel on the pot to their respective input ground on the boards.  

 

instead of the signal being across the wiper and conductive material,  the signal is "only" across the in-series input resistor.  in this configuration,  the potential divider is adjusted on the ground leg and not the input leg.   

post #1682 of 1816
Quote:
Originally Posted by ujamerstand View Post

out of curiosity, which transistors are you using to replace 2SC2705/2SA1145 in your EHHA? Also, is it just me or are those 6GM8s are awfully bright?

Using the BC556/BC546.

You caught me on the 6GM8s. Just the regular tubes with the LEDs in the background.
 

Quote:
Originally Posted by fishski13 View Post




i forget what the quiescent current of the EHHA is, but the o22 is rated for 1A continuous with the recommend heatsinks per AMB's BOM. .  i used the recommended 1.5" Avid Therm. for a +/-30V o22 powering a 3-board B22, with each board drawing 200mA.  my o22 heatsinks barely get warm.     


These are the 1.5" heatsinks, only the branches aren't as spread out as in some of the other pics I have seen.

The mosfets on S22 are getiing only lightly warmed up but the BJTs on EHHA are getting a bit hot.

 

Quote:
Originally Posted by fishski13 View Post



 

sorry, i don't have a pic.  

 

on a pot:

Input = input signal from RCA

W = wiper

G = ground

 

connect W and G together for each channel.  place a 100K resistor in series from the RCA to Input on the pot to each channel.  from the Input after the 100K resistor, connect to the signal inputs on each channel.  the ground from each of the RCAs to should connect at their respective channels on the pot at W and G.  connect the W and G of each channel on the pot to their respective input ground on the boards.  

 

instead of the signal being across the wiper and conductive material,  the signal is "only" across the in-series input resistor.  in this configuration,  the potential divider is adjusted on the ground leg and not the input leg. 

Thanks. This is how I understand it - shunt ( on top) as against normal (bottom ) connection. Is it ok ?

shuntpotvol2.gif

edit : replaced the pic with the correct one.


Edited by gurubhai - 11/1/10 at 10:02pm
post #1683 of 1816

looks good.

post #1684 of 1816
What is the advantage of using the shunt?
post #1685 of 1816

I did the shunt mod & but now the volume decreases on turning the pot clock-wise & vice-versa. What am I doing wrong ?

post #1686 of 1816

Well Homes, I think you have it wired backwards.

 

 

http://www.world-designs.co.uk/forum/showthread.php?t=5795
 

Quote:
Originally Posted by gurubhai View Post

I did the shunt mod & but now the volume decreases on turning the pot clock-wise & vice-versa. What am I doing wrong ?

post #1687 of 1816
Quote:
Originally Posted by les_garten View Post

Well Homes, I think you have it wired backwards.

 

 

http://www.world-designs.co.uk/forum/showthread.php?t=5795
 


that's the pic i was looking for.  yes, you probably have the pins on the pot reversed.

post #1688 of 1816

It would work perfectly in the Anti-Universe...
 

Quote:
Originally Posted by fishski13 View Post




that's the pic i was looking for.  yes, you probably have the pins on the pot reversed.

post #1689 of 1816
Quote:
Originally Posted by les_garten View Post

It would work perfectly in the Anti-Universe...
 


i hope we get beyond the theory and i can buy a ticket to get there.

post #1690 of 1816
Quote:
Originally Posted by les_garten View Post

Well Homes, I think you have it wired backwards.

 

 

http://www.world-designs.co.uk/forum/showthread.php?t=5795
 


That diagram explains it.Signal wire is being connected to terminal 1 (ground in the default config)

post #1691 of 1816

Started building one of these but after seeing that dude who threw Alan Rickman from the Nakatomi building's beautiful case work I am gonna be embarrassed to show what I'm working with.  Most of the parts are still in transit anyhow frown.gif.

post #1692 of 1816

For people who have fiddled with NFB/OLG  by changing R22/23, what is the value you have preferred for best sound quality ?

post #1693 of 1816

Is it going to be a problem if my heater supply is putting out 7 VCT instead of 6.3? ;p  Should I replace it with a weaker filament transformer?  I haven't really got room in the case for much else... should I scrap the case and use a regulated 6.3v supply?  Expand my build to 4 channel and hope the voltage droops a bit? ;p  Ignore it?  And yes that is 7 volts while it is on and hooked up to 2 ehha boards.  Is it going to do anything besides slightly reduce the lifespan of my tubes?

post #1694 of 1816

The specs of most of in-direct heating tubes specify +/- 10%, your 7V is 1% over tolerance @ 111%.

 

Personally I wouldn’t worry...

post #1695 of 1816

i would worry, and use a couple of resistors to drop the extra  V. you know the current draw (tube datasheet), you know the drop you need.... ohms law does the rest

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