[fishski13]

Quote:

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.   

 

[gurubhai]

Quote:

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:

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:

 
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 ?

edit : replaced the pic with the correct one.

 

[fishski13]

looks good.

 

[jdkJake]

What is the advantage of using the shunt?

 

[gurubhai]

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

 

[les_garten]

Well Homes, I think you have it wired backwards.
 
 
http://www.world-designs.co.uk/forum/showthread.php?t=5795
 
Quote:

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

 

[fishski13]

Quote:

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.

 

[les_garten]

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

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

 

[fishski13]

Quote:

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

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

 

[gurubhai]

Quote:

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)

 

[BebopMcJiggy]

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

.

 

[gurubhai]

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

 

[BebopMcJiggy]

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?

 

[johnwmclean]

The specs of most of in-direct heating tubes specify +/- 10%, your 7V is 1% over tolerance @ 111%.
 
Personally I wouldn’t worry...

 

[adamus]

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