LC Audio Dual Mono RIAA - Light MC Headamp

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mlloyd1

mlloyd1

Member
Joined 2001
would either of you who actually built Borbely EB-804-419 post some pictures and comment on the schematic? i'm not asking for component values or anything like that. i like to study Borbely's designs and have never heard or seen a good description of EB-804-419.

algar_emi: what is your final ranking? sounds like :
1. SVP
2. Xono
3. LC Audio

?

thx,
mlloyd1
 
K

kamis

Member
Joined 2006
mlloyd1 said:
would either of you who actually built Borbely EB-804-419 post some pictures and comment on the schematic? i'm not asking for component values or anything like that. i like to study Borbely's designs and have never heard or seen a good description of EB-804-419.

algar_emi: what is your final ranking? sounds like :
1. SVP
2. Xono
3. LC Audio

?

thx,
mlloyd1
Click to expand...
I will send a picture as soon as possible. Two parts article with detailed description is available on Internet.
 
K

kamis

Member
Joined 2006
It was the simplest Borbely phono stage with two stage RIAA and low noise All-Fet regulators.Similar to famous Vendetta phono.I built PCB with 70 microns copper.
 

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plexi0

Member
Joined 2014
I just tried out the MM version of this. Quite nice. very natural, open. My only quibble is a a bit uncontrolled bass. The MM uses AD844 and AD 743 chips.... Maybe someone could suggest a mod to help define the low end. It's a bit bulbous as if there was no filter? An earlier post suggested 100n caps instead of 100n.

An externally hosted image should be here but it was not working when we last tested it.
http://s13.postimg.org/r1nri7b8n/image.jpg
 
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abraxalito

abraxalito

Member
Joined 2007
Undefined low-end is often the result of too much LF PSU noise. I'd suggest decoupling the AD844 better, plenty of low ESR high value 'lytics across the supply, along with inductors in place of the 2R2 supply series resistors. The supply is just too saggy with those 2R2s to get decent bass.
 
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plexi0

Member
Joined 2014
the other issue is a bit of grain in upper mids/lower treble. I'd like to get a bit more body and resolution throughout the mids and treble. I suspect I'm not going to get it out of this topology however...what this does well is a nice open sound with good dynamics. It doesn't excell at the finer points.....using with shureV15 III MR
 
abraxalito

abraxalito

Member
Joined 2007
Across pins 4 & 7 I wrote - they are -ve and +ve power, respectively.

I noticed the AD844 is working in this circuit without feedback, so the graininess will in large part be a function of the loading you have on its output. Do you have a pot being fed from the output of the AD844? If so, what's its value?

An experiment you can do to check if its the PSU noise causing the grain is to increase the feedback impedance around the AD743. Currently that's got 10k and 470R, so try changing those two resistors to 47k and 2.7k respectively. It might be a bit noisier but listen out for the graininess.
 
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S

slybean

Member
Joined 2009
I've just come around building my phonostage. I've order the complete board and two voltage regulator from LC audio two years ago. I've experience two problems.

the first was with my ZYX catrigde on complexe passage i had tracking problem. But than change the cart for a Denon 103 and everything was fine. Is the damping not enough for the ZYX?

The second problem I experience a hum (60Hz). I've wired the toiroid transfo to the regulator directly and then directly to my phonoboard. Without grounding to a star ground. If i look closely to Algar-emi photos he did the same. Is this ground sheme causing my problem? Hum...? lol
 
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