[murrays]

Quote:

Originally Posted by crapback /img/forum/go_quote.gif I was a bit worried about EMI/RFI issues with the long leads but I can turn the volume all the way up with winamp/medimonkey/foobar paused and there is just a slightly audible bit of hiss that is even in both channels.

You say you are getting background hiss and the modules are running warm/hot - these are 2 symptoms of HF oscillation. Sometimes the audio will sound OK as 'phones and ears can only process the lower audio frequencies. However, the amps could be oscillating in the MHz range, effectively creating an AM radio broadcast. This can use up a lot of power (hence the heat) and can go as far as destroying components.
At the higher frequencies (MHz) those long leads provide all sorts of unwanted couplings between inputs, outputs, feedback loop, power, etc that can provoke oscillation.

One thing that may be saving your bacon, and someone else who knows better may be able to step in here to confirm/deny

, your modules may be tailored to only work at audio frequencies and may be deliberately rolled off below the HF range. Certainly most chip op amps will have a usable bandwith up to at least 1 Mhz or beyond. I have personally seen such chips oscillating continuously while still providing audio output. Presumably an AM transistor radio would pick up signals in the MW band?

Quote:

Originally Posted by crapback /img/forum/go_quote.gif I thought there might be a bit of hum from the transformer's magnetic field but there was no hum at all. I would love to be able to come up with a better arrangement than the use of the long extension leads but I drive a truck for a living and for me to be able to bring my zero with me I need to be able to keep it closed up. If I could leave the top of all the time i'd probably just stack a couple dip sockets till the hdams could clear the caps on the HA. I'm a bit of a noob in electronics so i'm not quite sure what you are talking about bypassing. All I know is there are a pair of bypass caps on each module and I have bypass caps on all the electrolytic caps of the frankenzero mod plus a few. Are you saying that the length of the leads is decreasing the effectiveness of the bypass caps on the modules? This is all a fun learning experience for me so all advice is appreciated.

Yes, bypassing requires very short leads to eliminate inductance and self-resonances in the HF ranges. It is good that there are caps on the modules, as well as the ones on the main board. A short, direct earth return is a requirement in many cases, though. These modules may be different enough from chip op amps that what you are doing is OK, whereas it wouldn't be with a standard chip op amp on the end of such long extensions. I will admit to having no experience with those discrete modules - others may be able to fill in the details here...

 

[crying]

Quote:

Originally Posted by wsatia /img/forum/go_quote.gif How do you guys find the AD845's? I kinda like them in the P3 with certain headphones. And thanks SpudHarris and ROBSCIX for the help! I'll be checking out my options and reporting back when I've gotten new opamps/buffers. Just wish I had someway to get my hands on the Hi-C 634's. But even normal BUF634's would be better than the bypassed buffers or stock buffers for the P3 right?

The AD845KN is a quite good sounding opamp, IMO. It's natural and colorful...

Too bad it doesn't come SMD and doesn't like too low supply voltages.


BTW, the LT1057 is nice but overrated. Take the LT1678 or the LT1122 instead (the latter is single, and FET input like the LT1057, but faster, better and newer). Or take the LT1364.

 

[crying]

Quote:

Originally Posted by wsatia /img/forum/go_quote.gif But even normal BUF634's would be better than the bypassed buffers or stock buffers for the P3 right?

The BUF634 is a very nice buffer, but it depends on how you set its bias... with the lowest bias it sounds rather coarse, while if you put a 220 ohm (or lower) resistor between pins 1 and 4 it sounds much better...

That said, I have no idea how the discrete little buffer (two transistors?) supplied with the P3 should sound...

 

[wsatia]

Quote:

Originally Posted by crying /img/forum/go_quote.gif The AD845KN is a quite good sounding opamp, IMO. It's natural and colorful... Too bad it doesn't come SMD and doesn't like too low supply voltages. BTW, the LT1057 is nice but overrated. Take the LT1678 or the LT1122 instead (the latter is single, and FET input like the LT1057, but faster, better and newer). Or take the LT1364.

Quote:

Originally Posted by crying /img/forum/go_quote.gif The BUF634 is a very nice buffer, but it depends on how you set its bias... with the lowest bias it sounds rather coarse, while if you put a 220 ohm (or lower) resistor between pins 1 and 4 it sounds much better... That said, I have no idea how the discrete little buffer (two transistors?) supplied with the P3 should sound...

Pardon my ignorance but what's FET input? And what other kinds of input are there? And hmm I'll check those out.

Anyway I was wondering what the two types of slots for opamps actually do in the P3? Does anyone know? I think the L/R slots work like normal but what do the 3/4 slots (as called in the manual) actually do? Does anyone know?

And I guess I'll have to find someone to help me do up the resistor on the 634.

 

[SpudHarris]

wsatia, the resistor between pins 1 & 4 on a Buf634 is ''Hi-C'' and sounds considerably better than the standard 634's and also the ibasso transister buffers. That said, I prefered the ibassos over the standard 634's.

I make the Hi-C adapters on DIP sockets (I'll post a pic later) so the 634's can be used as standard in other applications if need be.

The 3/4 slots in your P3 are ''Ground channel'' and you can only use single opamps here, also both sockets need to be occupied giving 4 channels. With the P3+ you can bypass one if you like to give 3 channels.

Regards

Nigel

 

[wsatia]

Quote:

Originally Posted by SpudHarris /img/forum/go_quote.gif wsatia, the resistor between pins 1 & 4 on a Buf634 is ''Hi-C'' and sounds considerably better than the standard 634's and also the ibasso transister buffers. That said, I prefered the ibassos over the standard 634's. I make the Hi-C adapters on DIP sockets (I'll post a pic later) so the 634's can be used as standard in other applications if need be. The 3/4 slots in your P3 are ''Ground channel'' and you can only use single opamps here, also both sockets need to be occupied giving 4 channels. With the P3+ you can bypass one if you like to give 3 channels. Regards Nigel

Damn I had no idea I could only use single opamps in the Ground channel sockets. I've always used dual opamps in them

Hmm okay a picture would be good so I can show someone who can solder/do it up for me

Oh and when should I use the bypassed buffers and when should I use a dedicated buffer? Is there any requirements or something or is it just based on what sounds better?

 

[SpudHarris]

There are a few that people will recommend such as the AD8397 but I think what ever sounds good.

Here are Hi-C adapters I made for use with the Buf634's. Do you have any 634's yet?

 

[wsatia]

Nope no 634's yet but I can get them from my local Farnell anytime.

 

[SpudHarris]

Get them and PM me your address and I'll post you a couple of adapters......

 

[SpudHarris]

Quote:

Originally Posted by wsatia /img/forum/go_quote.gif Damn I had no idea I could only use single opamps in the Ground channel sockets.

My bad, sorry been such a long time since I rolled with the P3

....You can use duals in the centre configuration, it was obviously the buffer positions I was thinking of. I usually use singles in L/R & G because I use Class A adapters to squeeze a little more from them which you can't do with duals.

 

[ROBSCIX]

@Spudharris:
Can you elaborate why you cannot use a similar idea with a dual channel module?

I am just curious though, I like your adapter and idea.

 

[ecclesand]

Quote:

Originally Posted by leeperry /img/forum/go_quote.gif my LT1057ACN8 never came either...I think they don't have them in stock or sumthing, as my LT1677/78 came very quickly several weeks later

They have them in stock. I just bought 3 of them and got them in 3 days. And yes, I did say bought. Perhaps they're not sending any out as samples anymore.

 

[SpudHarris]

I just ''Bought'' one also from Farnell. Should be here tomorrow and I will see if there is a successor to the AD797's....

 

[ecclesand]

Quote:

Originally Posted by SpudHarris /img/forum/go_quote.gif There are a few that people will recommend such as the AD8397 but I think what ever sounds good. Here are Hi-C adapters I made for use with the Buf634's. Do you have any 634's yet?

Hey Nigel...
What resistor are you using for your adapter? Also, can you tell me what pins it should be soldered to?

EDIT: DOH! I should have read your earlier post. Never mind.

 

[crapback]

Quote:

Originally Posted by murrays /img/forum/go_quote.gif You say you are getting background hiss and the modules are running warm/hot - these are 2 symptoms of HF oscillation. Sometimes the audio will sound OK as 'phones and ears can only process the lower audio frequencies. However, the amps could be oscillating in the MHz range, effectively creating an AM radio broadcast. This can use up a lot of power (hence the heat) and can go as far as destroying components. At the higher frequencies (MHz) those long leads provide all sorts of unwanted couplings between inputs, outputs, feedback loop, power, etc that can provoke oscillation. One thing that may be saving your bacon, and someone else who knows better may be able to step in here to confirm/deny , your modules may be tailored to only work at audio frequencies and may be deliberately rolled off below the HF range. Certainly most chip op amps will have a usable bandwith up to at least 1 Mhz or beyond. I have personally seen such chips oscillating continuously while still providing audio output. Presumably an AM transistor radio would pick up signals in the MW band? Yes, bypassing requires very short leads to eliminate inductance and self-resonances in the HF ranges. It is good that there are caps on the modules, as well as the ones on the main board. A short, direct earth return is a requirement in many cases, though. These modules may be different enough from chip op amps that what you are doing is OK, whereas it wouldn't be with a standard chip op amp on the end of such long extensions. I will admit to having no experience with those discrete modules - others may be able to fill in the details here...

The hiss is much less than the stock zero. At normal listening level with no signal there is no noise at all. It isn't until the volume is at about it's last 10% or so to max level that there is any audible hiss. With my lowest gain music in my library, I can't turn the volume past the 10 o'clock position without it starting to hurt my ears.

As far as the heat generated by the hdams, I wouldn't say they are any warmer than the stock opamps get. I believe that there were actually changes made to the board design of the zero to accomodate the ground wire for the hdams. I can't remember which thread I read that in though. I've tried removing the extension wire for the dac hdam to see if it generated less heat but I couldn't tell any difference other than it's still much cooler than the mosfet heatsinks. I tried not attaching the ground wire like in the zero intro thread and they seemed to get a little less warm, but they didn't sound right. In all honesty, I've had a bit of a heat paranoia with electronics since my athlon 1700 overclocking days so I will email kingwa to ask him if they should be getting warm.

As for the sound I think they work great in the zero's el cheapo circuit. They may not be much of an improvement or even a step down in better gear, but I like them so far and will be enjoying my little mutant until my bank account recovers from my sister's wedding this weekend.

There has to be some kind of topical cream for upgraditis, right?

I recieved an answer to my email to Kingwa:

Date: Mon, 14 Sep 2009 09:19:18 +0800
From: audio-gd@126.com
To: that really awesome guy that all the women love@hotmail.com
Subject: Re:

Dear Sir,
The OPA are work on class A, power supply is more than normal chips (like OPA2604) 5X times, so it get warm, around 45C, this is very safe .
The OPA don't roll off at 20KHz, it depend on the outside circuits design, like the ZERO, its analogy filter is apply -12DB roll off design, so maybe let 20KHz roll off around 1DB to 4DB, even you apply OPA2604.
Kingwa


在2009-09-14，"og og" <and wears underoos cause he's a real superhero, not just cause they look awesome@hotmail.com> 写道：

Hello again Kingwa,

I recently ordered a number of your opa's and I have a question about them. I have an '09 tianyun zero with 3 opa earths in it. Are the opa's supposed to get warm? If they are, about how warm should they get? compared to say, the mosfet heatsinks? Also, is there a high frequency rolloff with the opa's to prevent any issues with oscillation affecting their performance?

Thanks again, Joel