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Audio-gd discrete op-amps reviewed: OPA-Earth, OPA-Moon, OPA-Sun v.2 - Page 7

post #91 of 393
Quote:
Originally Posted by Ron.id View Post
Base headamp PCBs
One schematic tells more than a thousand pictures! Open loop/closed loop? Resistor values? Grounding?

Quote:
Sound is so good, powerful, dynamics, tight, wide.... in short, I love it!
It would be nice if you could develop this a bit, like compared to what etc.
post #92 of 393
Quote:
Originally Posted by NelsonVandal View Post
One schematic tells more than a thousand pictures! Open loop/closed loop? Resistor values? Grounding?
It's a 3 channel headamp with buffers, class-A bias at gain stage, Jung multiloop.





Quote:
Originally Posted by NelsonVandal View Post
It would be nice if you could develop this a bit, like compared to what etc.
Hmmm... i didn't compared it head-to-head with other headamps yet, so I based my statement only with this headamp previous settings, and my memory when i have a chance to compare it with others in the past. In the past I have compared this headamp with this (mine is third from the bottom):



My friend has version 2 of this headamp (slight modification in the schematic), as you can see it on top of Lisa III, which use a better parts than me (mostly the opamps), ranked the second best below Lisa III.

And... going to full discrete - if my memory served me well - this headamp jump much higher than that v2.

I don't know how good is this discrete against Lisa III coz my experienced is too short with this headamp. As i remember, one thing that definitely makes Lisa III stay ahead of all headamps at that photograph is the soundstage. I hope at our local meet at the end of this month someone will bring Lisa III so I can compare it.
post #93 of 393
Thread Starter 
This schematic is not optimal. First - it is designed the way that the L/R channels have two stages and it makes no sense as the second stage is nowhere more efficient in terms of current. Just op-amps again. Second thing is that parallel connections of outputs decrease detail a bit - just due to some very slight but existing phase shifts between the two parallel stages. All in all, the amp is not very current efficient - just like INA134 by half. I saw the LISA III schematic and it makes much more sense but NelsonVandal's discrete amp makes even more IMHO.
post #94 of 393
Hi all...

Since Ron.Id has posted the schematics here, I might as well explain it a bit...

Yes, probably it's not optimal, but given the purpose of the design is:

"To build a multiloop amp, with parts available only on local stores around me"

Now, if you live in my country, well, to get a good op-amp is really difficult, the same also with buffer chip like the popular BUF634 is almost impossible to get in local stores around, the best I can find is only LM4562 and OPA2134...

Yes we can get parts from internet, but I usually just use what available around me...

So why does the L/R have two stages, with the 2nd stage just acting as follower and yes, it's nowhere more efficient in terms of current...

Because to use the multiloop topology we need buffer (or in this case follower), and since I need bigger current output to drive low impedance headphones, so a quick hack is just to parallel the 2nd stage L/R (the follower) with another op-amp ~ a l a A47

So why don't I just use single op-amp and follow it with discrete diamond buffer? Since it's easy to get general purpose BJTs around?

Simple, because I want it to be able to swap buffer (as long as it works inside the feedback loop)

first the use of dual op-amp (for both stage) on the L/R makes it easy for me to just use the U1 DIP8 socket as an "expansion" socket, just like Ron.Id do with his Diamond buffer module which is plugged in directly to the U1 socket

and second, because the U2 op-amp is in parallel, whenever there's an "expansion" module inserted to U1 socket, I can just ignore it completely by not plugging any op-amp on the U2 socket...

And the last, the use of INA134 as rail splitter, it's just simply because I can't get TLE2426 around, and this is the only chip I found that states inside the application note that it can be use as a virtual ground...

I hope it explains well about the schematics

Regards...
post #95 of 393
Thanks for the explanation psychaudio

Now, as we're talking about discrete op-amps, specifically Audio-gd OPA's, yesterday I have an opportunity to compare it with several headamps as I received an invitation to test a brand new IE Series from Sennheiser (IE6, IE7, IE8).

This is the humble headamp setups for these HDAMs:



Two OPA Moon and one OPA Sun v2 at the gain stage, followed by discrete diamond buffers. No ICs at all in this headamp, all discrete.



The result is: discrete op-amps easily beats down all his rivals, to name it: virtually all iBasso series, The Hornet, TTVJ Millet, as well as version 2 of this headamp with expensive components and ICs. The huge dynamics is a wow factor here with discrete op-amps, among the other things.
post #96 of 393
Nice work Ron.id. Pity it's too big to go in one's pocket.

What made you decide to choose the Moon and Sun respectively?
post #97 of 393
They are quite a bargain in comparison to the Burson 100 dollar OpAmps eh?

Ron that is one of the most interesting Amps I've seen, very cool looking. For casing, I think be awesome, what someone did for the DAC-100, have holes in the top casing to so the HDAMs can be seen.
post #98 of 393
I finally got my earth and moon that i ordered over 2 weeks ago and installed the moon in my ef1 on fri. everything seemed to be working ok. I used 2 8pin socked adapters stacked on top of original op amp socket. ive been burning in moon since then. then this morning i went to try earth becuase i thought it might synergize better with denons d5000 i had on loan. I was sorely dissapointed there was horendous distortion in right channell with certain higher frequency. I checked the sockets and they were tight and still worked fine with moon. then i discovered if i touched one side with my finger distortion went away. and here comes the weired part, if i just put my finger by the otherside without touching it the distortion would get worse! its like my finger is passing through a magnetic field or something.

Have you guys ever run across this before? any way to fix? I am hoping i dont have to send back. these almost got lost by the post office getting here, dont know if i trust it to get back in one piece.

thanks for the help.
post #99 of 393
Quote:
Originally Posted by Currawong View Post
Nice work Ron.id. Pity it's too big to go in one's pocket.

What made you decide to choose the Moon and Sun respectively?
Thanks Currawong. Yeah this headamp surely too big to put into the pocket, but still portable enough, coz i run it with a portable NiMH external battery

I choose the Moon just to know how it sound, because I already have 1 piece of SUN v2 before bought the Moons.

Quote:
Originally Posted by mbd2884 View Post
They are quite a bargain in comparison to the Burson 100 dollar OpAmps eh?

Ron that is one of the most interesting Amps I've seen, very cool looking. For casing, I think be awesome, what someone did for the DAC-100, have holes in the top casing to so the HDAMs can be seen.
Yes it is.... the price is good.

Thanks for your compliments. I thought the same thing with casing, with a hole on top of it to show these HDAMs. But after some considerations, I prefer a closed one because I want to put another casing on top of it that contains capacitors since I use this headamp with modified iPod (DIYmod).

Quote:
Originally Posted by theBigD View Post
then i discovered if i touched one side with my finger distortion went away.
Have you ground the Earth? LOL ...how to ground the earth anyway LOL

I mean, have you connect the ground lead of OPA Earth to the ground of your PCBs? Hope this could help... although I'm not so sure about it.
post #100 of 393
Thread Starter 
Connecting the ground helps all OPA's IMHO. Do it as close to the output as possible for best results. I connect the ground to the ground pin of the socket for wiring the RCA outputs.
post #101 of 393
yes i grounded to the rca ground in back. this was kingwas suggestion. unfortunenetly didnt fix the earth. but i have moon grounded there now and it may be responsible for the much improved attack and speed of it, although sennsay says it is part of burn in. I have around 56 hours on it now and plan to get at least 200.

audio-gd is sending a new earth as replacement and hopefully this will fix the issue. kingwa is very good to do bussness with. he has responded very quickly to help me with this problem.

if you guys can think of any other thing i could be doing i sure appreciate it. the contacts seem to be well connected and work better than the extension lead i was using before.

and the moon is working great right now. in the same arrraingement.

here are some pics before i moved ground to proper spot.
LL
LL
post #102 of 393
The effect I noticed from grounding the HDAMs to the RCA output in the Zero DAC I could best describe as sounding like the power circuit had been upgraded and had better control, if that makes any sense.
post #103 of 393
Quote:
Originally Posted by theBigD View Post
I finally got my earth and moon that i ordered over 2 weeks ago and installed the moon in my ef1 on fri. everything seemed to be working ok. I used 2 8pin socked adapters stacked on top of original op amp socket. ive been burning in moon since then. then this morning i went to try earth becuase i thought it might synergize better with denons d5000 i had on loan. I was sorely dissapointed there was horendous distortion in right channell with certain higher frequency. I checked the sockets and they were tight and still worked fine with moon. then i discovered if i touched one side with my finger distortion went away. and here comes the weired part, if i just put my finger by the otherside without touching it the distortion would get worse! its like my finger is passing through a magnetic field or something.

Have you guys ever run across this before? any way to fix? I am hoping i dont have to send back. these almost got lost by the post office getting here, dont know if i trust it to get back in one piece.

thanks for the help.
i've been opamp rolling in an asus xonar essence sound card which uses 3 dual dip-8s. at the suggestion of a former national semiconductor engineerwho was on the team which came out with the 497xx series of opamps, i put in 3 49720s, in the to-99-8 metal can version, i first put them in sockets to preform the leads, then put them, socketed, into the sockets on the cards.

this lead to some of the same kind of distortion you mention, so i pulled them, and put them directly into the card's sockets. distortion went away.

more recently, i put a pair of 49710s (the single version of the 49720) also metal cans, into the output position, using a browndog adaptor which converts a pair of single dip-8s to one dual dip-8.

the small box-shaped caps surrounding the opamp socket prevent the adaptor from going al the way in, and there is a hint of that same distortion, unless i push it in as far as it will go.

lead-length seems crucial in these applications, and that may be what you are running into.

hope that helps,

best,

Mark
post #104 of 393
I can't see how the gd-opamps could function properly unless you connect them to ground where it's specified.
post #105 of 393
yeah with the hdams the connection has to be absolutely solid. i did get the earth to finally work in my ef1. I really like the wide involving soundstage of the earth and moon. I have yet to hear an op amp that sounds this natural and dynamic. but then i havent yet tried the ad797brz or the other opamps that markl likes better yet. i do plan on trying them soon.

my ef1 is on the fritz right now. so i went back to by go vibe v5s with 24volt elpac. didnt like the sterility of the op627 i had in it so. i plugged the earth into it and wow! huge spacial improvement not to mention a more extended bass response better tonal representation.

i have to say the hdams seem like a step in soundstage between the op amp and tube like sound.
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