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 Forum index » DIY Hardware and Software » Jürgen Haible designs
Interested in Tau Pipe Phaser / Flanger boards ?
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numbertalk



Joined: May 05, 2008
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PostPosted: Mon Dec 15, 2008 12:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

numbernone wrote:
Speaking of Bill and Will...where have they gone?

All the links are dead, and I cannot find any further info by googling.

I would love to revisit their info prior to finalizing these babies.


They changed the paths to their pages for some reason:

http://dragonflyalley.com/index.htm
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guitarfool



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PostPosted: Mon Dec 15, 2008 9:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

Well, I finally got both of my Tau phasers working nicely together. I used CA3046 chips throughout (for the expo converter as well) and they seem to track pretty well over several octaves. I had to reduce R4 from 220k to 160k in order to get them to self-resonate well, and adjusted R5 so that they start to really resonate with the resonance panel control at "9" with full self-oscillation when it's fully CW. With self-oscillation, the scale tune adjustment was done the same as for a VCO Very Happy

The scope shot shows what the Tau's output looks like when self-oscillating. In the third sound file, the 1V/oct input is being fed from my MFOS Quantizer being fed from a triangle LFO. This does not cover the Tau's entire range - it can go a lot higher and lower.

The second sound file is basically the same, but the resonance control is set just below "9", and the input is fed with an animated sawtooth drone.

The first sound file is 2 Tau phasers, slightly detuned with their internal LFO's set at different rates, and very little depth. Resonance is still the same, and both inputs fed the same animated sawtooth drone. It sounds much better in stereo! I haven't gotten set up to record stereo on my PC yet Embarassed

All 3 sound files are "raw" - Tau output -> soundcard. No reverb or any post-processing


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neandrewthal



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PostPosted: Mon Dec 15, 2008 10:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

That first clip is amazing! Long stand the Twin Tauers!
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jhaible



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PostPosted: Mon Dec 15, 2008 11:55 pm    Post subject: Reply with quote  Mark this post and the followings unread

neandrewthal wrote:
That first clip is amazing!


Absolutely.

Great demo!

JH.

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"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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numbertalk



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PostPosted: Thu Dec 18, 2008 10:56 am    Post subject: Reply with quote  Mark this post and the followings unread

jhaible wrote:
numbertalk wrote:
Plus is there supposed to be a volume drop when you switch to vibrato mode? I'm starting to wonder if it's one of my chips.


Should be no volume drop in vibrato mode.


Where would this suggest I start looking (the volume drop in Vibrato mode)? I see that vibrato mode opens part of the circuit where the phaser setting closes that part, but I don't quite understand this part of the circuit and why I would get or where to inspect a volume drop in vibrato mode.

Thanks again for the help.
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jhaible



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PostPosted: Thu Dec 18, 2008 12:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

numbertalk wrote:
jhaible wrote:
numbertalk wrote:
Plus is there supposed to be a volume drop when you switch to vibrato mode? I'm starting to wonder if it's one of my chips.


Should be no volume drop in vibrato mode.


Where would this suggest I start looking (the volume drop in Vibrato mode)? I see that vibrato mode opens part of the circuit where the phaser setting closes that part, but I don't quite understand this part of the circuit and why I would get or where to inspect a volume drop in vibrato mode.

Thanks again for the help.


Phasing = all pass filtered (APF) signal + dry signal
Vibrato = APF signal

APF signal should be approximately the same level as dry signal before summing point.
Maximal increase of level from summing is +6dB. In practice, less that that, because you don't sum in-phase for each frequency.

If your APF signal isn't roughly the same level as the dry signal before summing, I guess you have a wrong resistor value somewhere in the driver circuit or pickup amp for the ladder.
(APF path in Tau = driver circuit + ladder + pickup amp)

JH.

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"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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numbertalk



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PostPosted: Thu Dec 18, 2008 12:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thank you - this is very helpful. Will start looking at resistor values there.

jhaible wrote:
numbertalk wrote:
jhaible wrote:
numbertalk wrote:
Plus is there supposed to be a volume drop when you switch to vibrato mode? I'm starting to wonder if it's one of my chips.


Should be no volume drop in vibrato mode.


Where would this suggest I start looking (the volume drop in Vibrato mode)? I see that vibrato mode opens part of the circuit where the phaser setting closes that part, but I don't quite understand this part of the circuit and why I would get or where to inspect a volume drop in vibrato mode.

Thanks again for the help.


Phasing = all pass filtered (APF) signal + dry signal
Vibrato = APF signal

APF signal should be approximately the same level as dry signal before summing point.
Maximal increase of level from summing is +6dB. In practice, less that that, because you don't sum in-phase for each frequency.

If your APF signal isn't roughly the same level as the dry signal before summing, I guess you have a wrong resistor value somewhere in the driver circuit or pickup amp for the ladder.
(APF path in Tau = driver circuit + ladder + pickup amp)

JH.
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numbertalk



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PostPosted: Thu Dec 18, 2008 9:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Just checked every resistor on the board and they're all correct Confused If one of my LM394s were shot I wouldn't get any audio from the APF, right?
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jhaible



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PostPosted: Fri Dec 19, 2008 2:49 am    Post subject: Reply with quote  Mark this post and the followings unread

numbertalk wrote:
Just checked every resistor on the board and they're all correct Confused If one of my LM394s were shot I wouldn't get any audio from the APF, right?


Not sure.

Have you used sockets?

JH.

_________________
"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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numbertalk



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PostPosted: Fri Dec 19, 2008 8:02 am    Post subject: Reply with quote  Mark this post and the followings unread

I did. Should I go through and replace each one by one and compare? I did a voltage drop check on the pins for the transistor junctions in each chip and they *seemed* ok.

EDIT - just for the sake of full disclosure, I'm using your resonance mod with a push/pull resonance pot - 180K in place of the 220K on the board and a 20K wired in series off the CW lug of the pot to the switch. I see others have lowered this resistor value (and if anything I would guess having a lower resistor would boost the volume but just to give a more complete picture of what I'm working with).

jhaible wrote:
numbertalk wrote:
Just checked every resistor on the board and they're all correct Confused If one of my LM394s were shot I wouldn't get any audio from the APF, right?


Not sure.

Have you used sockets?

JH.
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jhaible



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PostPosted: Fri Dec 19, 2008 9:11 am    Post subject: Reply with quote  Mark this post and the followings unread

numbertalk wrote:
I did. Should I go through and replace each one by one and compare? I did a voltage drop check on the pins for the transistor junctions in each chip and they *seemed* ok.

EDIT - just for the sake of full disclosure, I'm using your resonance mod with a push/pull resonance pot - 180K in place of the 220K on the board and a 20K wired in series off the CW lug of the pot to the switch. I see others have lowered this resistor value (and if anything I would guess having a lower resistor would boost the volume but just to give a more complete picture of what I'm working with).

jhaible wrote:
numbertalk wrote:
Just checked every resistor on the board and they're all correct Confused If one of my LM394s were shot I wouldn't get any audio from the APF, right?


Not sure.

Have you used sockets?

JH.


If the voltage drop is "regular" on the transistor pairs, I wouldn't expect one to be faulty.

Resonance resistor won't make a difference in APF level (when resonance is at ccw end).

Just to be certain: How *much* of a level drop are we talking about?

have you maximized th elevel with the Gain trimmer?

Are the capacitor values in the pre- and deemphase circuits right?

JH.

_________________
"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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numbertalk



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PostPosted: Fri Dec 19, 2008 10:04 am    Post subject: Reply with quote  Mark this post and the followings unread

jhaible wrote:
Just to be certain: How *much* of a level drop are we talking about?


To make sure I'm doing this right, I'm putting the red probe of my meter at the base and then putting the black probe at the collector and measuring, then moving the black probe to the emitter (leaving the read at the base) and measuring.

I am noticing something odd but am guessing that either in the context of the circuit I should be getting this, or else this will tip us off to a problem somewhere leading into the ladder. For every B-E B-C junction in the ladder I'm getting a voltage drop of between .53-.58 V *except* the first chip in the ladder (I think it's the first - the most upper right LM394 if you have the board oriented so that the header output/input connections are at the bottom, with the power input at bottom right) - the voltage drop I'm getting for B-C for *both* transistors in that chip is .068V. Is that what is expected? The B-E voltage drop for these transistors is .538V. When I remove this chip from the circuit and measure I get a B-C voltage drop of .5V, so the chip itself seems ok.

jhaible wrote:
have you maximized th elevel with the Gain trimmer?


I have this trimmer set full CW.

jhaible wrote:
Are the capacitor values in the pre- and deemphase circuits right?


They seem to be - the ones whose markings are still visible are correct. I can't read the markings on a few of the ceramic ones with the board populated but I'm very careful about component placement when building and would say I'm 99% certain they are correct. To my knowledge I've never fried a cap when soldering in either, but these are mounted very low to the board. Seems unlikely though.

Doubt this would be the culprit for either issue (clicking or the volume drop), but for the 10n cap at the upper left of the board right before the ladder starts I'm using a 5% Panasonic ECQ-B Polyester cap - is this ok here? I measured it before soldering it in and it looked like it was exactly 10n.

Thanks.
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jhaible



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PostPosted: Fri Dec 19, 2008 10:09 am    Post subject: Reply with quote  Mark this post and the followings unread

numbertalk wrote:
jhaible wrote:
Just to be certain: How *much* of a level drop are we talking about?


To make sure I'm doing this right, I'm putting the red probe of my meter at the base and then putting the black probe at the collector and measuring, then moving the black probe to the emitter (leaving the read at the base) and measuring.

I am noticing something odd but am guessing that either in the context of the circuit I should be getting this, or else this will tip us off to a problem somewhere leading into the ladder. For every B-E B-C junction in the ladder I'm getting a voltage drop of between .53-.58 V *except* the first chip in the ladder (I think it's the first - the most upper right LM394 if you have the board oriented so that the header output/input connections are at the bottom, with the power input at bottom right) - the voltage drop I'm getting for B-C for *both* transistors in that chip is .068V. Is that what is expected? The B-E voltage drop for these transistors is .538V. When I remove this chip from the circuit and measure I get a B-C voltage drop of .5V, so the chip itself seems ok.

jhaible wrote:
have you maximized th elevel with the Gain trimmer?


I have this trimmer set full CW.

jhaible wrote:
Are the capacitor values in the pre- and deemphase circuits right?


They seem to be - the ones whose markings are still visible are correct. I can't read the markings on a few of the ceramic ones with the board populated but I'm very careful about component placement when building and would say I'm 99% certain they are correct. To my knowledge I've never fried a cap when soldering in either, but these are mounted very low to the board. Seems unlikely though.

Doubt this would be the culprit for either issue (clicking or the volume drop), but for the 10n cap at the upper left of the board right before the ladder starts I'm using a 5% Panasonic ECQ-B Polyester cap - is this ok here? I measured it before soldering it in and it looked like it was exactly 10n.

Thanks.


Here's the overlay with values not obscured by components:
http://www.jhaible.heim.at/tau/jh_tau_component_overlay_with_comments.pdf

DC voltage drop should be approx. the same for all transistors in the ladder.

I meant, how much is the drop in level (APF vs. dry)?
Just a few dB? 20 dB ?

JH.

_________________
"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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numbertalk



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PostPosted: Fri Dec 19, 2008 12:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

jhaible wrote:
DC voltage drop should be approx. the same for all transistors in the ladder.


So what I'm seeing in the B-C voltage drop for the transistors in that first chip seems wrong then. What would cause there to be less of a voltage drop there - what components leading into the ladder could be the culprit?

Quote:
I meant, how much is the drop in level (APF vs. dry)?
Just a few dB? 20 dB ?


Going by the db meter on my Mackie mixer it's in the neighborhood of 6db *between vibrato and phaser*. I don't have bypass configured for my module to compare the APF signal directly to the dry signal. Outside the circuit, when I run the signal driving the Tau directly into my mixer and compare to the vibrato signal from the circuit, it seems a little less then 6db difference (my mixer level meter indicates at 6db intervals - I can't as easily run this into my computer at the moment to see more precisely). But if you'd like audio samples of the comparison I can do this (I recently had a flood in our basement which *was* my studio - have moved most of the stuff upstairs but not my audio interface).
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jhaible



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PostPosted: Fri Dec 19, 2008 12:55 pm    Post subject: Reply with quote  Mark this post and the followings unread

numbertalk wrote:
jhaible wrote:
DC voltage drop should be approx. the same for all transistors in the ladder.


So what I'm seeing in the B-C voltage drop for the transistors in that first chip seems wrong then. What would cause there to be less of a voltage drop there - what components leading into the ladder could be the culprit?


No, if something is wrong here, the transistor pair should be replaced.
It's all the same current running thru all transistors ...


Quote:
Quote:
I meant, how much is the drop in level (APF vs. dry)?
Just a few dB? 20 dB ?


Going by the db meter on my Mackie mixer it's in the neighborhood of 6db *between vibrato and phaser*. I don't have bypass configured for my module to compare the APF signal directly to the dry signal. Outside the circuit, when I run the signal driving the Tau directly into my mixer and compare to the vibrato signal from the circuit, it seems a little less then 6db difference (my mixer level meter indicates at 6db intervals - I can't as easily run this into my computer at the moment to see more precisely). But if you'd like audio samples of the comparison I can do this (I recently had a flood in our basement which *was* my studio - have moved most of the stuff upstairs but not my audio interface).


Oh, I thought it was more!
Something between 3dB and 6dB is to be expected.

JH.

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"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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numbertalk



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PostPosted: Fri Dec 19, 2008 1:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here are a couple samples of a raw saw wave through the Tau - let me know if this sounds like a normal volume difference to you. The stereo is the main out to left and aux out to right. The mono is main out. In the stereo it's phaser first then about 1/2 way through I switch to vibrato. In the mono sample I switch back to phaser again after switching to vibrato.


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jhaible



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PostPosted: Fri Dec 19, 2008 2:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

numbertalk wrote:
Here are a couple samples of a raw saw wave through the Tau - let me know if this sounds like a normal volume difference to you. The stereo is the main out to left and aux out to right. The mono is main out. In the stereo it's phaser first then about 1/2 way through I switch to vibrato. In the mono sample I switch back to phaser again after switching to vibrato.


The level difference is more than I'd expect, but the phasing doesn't sound bad, does it?

On the stereo sample, I noticed a lot of odd noises on the "weaker" channel.
Either there's an intermittent contact, or some HF oscillation.

JH.

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"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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numbertalk



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PostPosted: Fri Dec 19, 2008 2:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

jhaible wrote:
The level difference is more than I'd expect, but the phasing doesn't sound bad, does it?


The phasing sounds great.

jhaible wrote:
On the stereo sample, I noticed a lot of odd noises on the "weaker" channel.
Either there's an intermittent contact, or some HF oscillation.


Could this mean some of my SMD bypass caps aren't soldered correctly (if there's HF oscillation)?
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jhaible



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PostPosted: Fri Dec 19, 2008 2:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

The opamps need to be bypassed with teh SMD caps to prevent HF oscillation, yes.

JH.

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numbertalk



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PostPosted: Fri Dec 19, 2008 2:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

The volume drop between phaser and vibrato is much less dramatic on the Aux output. Does this mean maybe there's not such a difference between the APF signal & the dry signal but perhaps more a problem somewhere around the Main out? I'm not exactly sure what the aux out is, so beyond checking the bypass caps for the noise, where might I look for this volume drop to be happening on the main out? All the component values seem correct and I checked continuity all around the board as well and everything seemed to check out ok.

Also I replaced that chip in the ladder and get the same weird voltage drop difference in that same spot. Since the vibrato coming through the Aux signal is significantly stronger than on the Main channel, wouldn't this mean the APF is fine? I changed the output IC U4 with a different chip and still have the same problem. Could HF oscillations effect the volume difference on the main channel (and also would it not effect the Aux out) or is this likely 2 separate issues?

Thanks again. Feel like we're getting there.
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PostPosted: Fri Dec 19, 2008 4:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

numbertalk wrote:
The volume drop between phaser and vibrato is much less dramatic on the Aux output. Does this mean maybe there's not such a difference between the APF signal & the dry signal but perhaps more a problem somewhere around the Main out? I'm not exactly sure what the aux out is, so beyond checking the bypass caps for the noise, where might I look for this volume drop to be happening on the main out? All the component values seem correct and I checked continuity all around the board as well and everything seemed to check out ok.

Also I replaced that chip in the ladder and get the same weird voltage drop difference in that same spot. Since the vibrato coming through the Aux signal is significantly stronger than on the Main channel, wouldn't this mean the APF is fine? I changed the output IC U4 with a different chip and still have the same problem. Could HF oscillations effect the volume difference on the main channel (and also would it not effect the Aux out) or is this likely 2 separate issues?

Thanks again. Feel like we're getting there.


If there is HF oscillation, you should first get rid of that. May cause all kinds of secondary effects.

JH.

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numbertalk



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PostPosted: Fri Dec 19, 2008 6:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

What exactly is it you are hearing in that sample? Just want to make sure I can tell if it improves (or even what to look for in any build that might suffer from this). Might get rid of the SMDs and try ceramic caps like Yves Usson did.

Also I'm using 100nf SMDs rather than 47nf - could that be a problem? More than likely I just did a shoddy job with the SMDs.
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PostPosted: Sat Dec 20, 2008 1:32 am    Post subject: Reply with quote  Mark this post and the followings unread

numbertalk wrote:
What exactly is it you are hearing in that sample? Just want to make sure I can tell if it improves (or even what to look for in any build that might suffer from this). Might get rid of the SMDs and try ceramic caps like Yves Usson did.

Also I'm using 100nf SMDs rather than 47nf - could that be a problem? More than likely I just did a shoddy job with the SMDs.


I don't hear high frequency oscillation, of course.
What I hear is an intermittent noise which might indicate there's HF oscillation in the circuit. It's on the left channel at the beginning of your stereo sample, and on the right towards the end. (I wonder how you can not hear it - it's very prominent!)
As I said, it's not necessarily HF oscillation - could be some intermittent contact problem (bad solder joint etc.). Which, in turn, would give a good explanation for a low level, too.
It's really hard to make a remote analysis for that kind of stuff. I mean, I can give some hints what could be wrong, but you are sitting in front of the circuit, and can attach a scope probe to opamp outputs to check for oscillation (1:10 probe, not 1:1 !), or can knock on your PCB to check for intermittent contacts ...

JH.

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"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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numbertalk



Joined: May 05, 2008
Posts: 992
Location: Austin, TX
Audio files: 5

PostPosted: Sat Dec 20, 2008 6:33 am    Post subject: Reply with quote  Mark this post and the followings unread

I understand and yes, now I do hear it. Was so focused on the volume drop didn't listen closely enough but yes, it's a very prominent intermittent static sound. Embarassed

One question on checking the op amp outputs with the scope - how do I identify HF oscillations mixed with the audio signal on the op amp outputs when looking with my scope? Sorry, I'm not sure where these oscillations would come from (e.g. the power supply, etc...) so not sure if I could check this with no audio connected.

Thanks again.

jhaible wrote:
numbertalk wrote:
What exactly is it you are hearing in that sample? Just want to make sure I can tell if it improves (or even what to look for in any build that might suffer from this). Might get rid of the SMDs and try ceramic caps like Yves Usson did.

Also I'm using 100nf SMDs rather than 47nf - could that be a problem? More than likely I just did a shoddy job with the SMDs.


I don't hear high frequency oscillation, of course.
What I hear is an intermittent noise which might indicate there's HF oscillation in the circuit. It's on the left channel at the beginning of your stereo sample, and on the right towards the end. (I wonder how you can not hear it - it's very prominent!)
As I said, it's not necessarily HF oscillation - could be some intermittent contact problem (bad solder joint etc.). Which, in turn, would give a good explanation for a low level, too.
It's really hard to make a remote analysis for that kind of stuff. I mean, I can give some hints what could be wrong, but you are sitting in front of the circuit, and can attach a scope probe to opamp outputs to check for oscillation (1:10 probe, not 1:1 !), or can knock on your PCB to check for intermittent contacts ...

JH.
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jhaible



Joined: May 25, 2007
Posts: 2014
Location: Germany
Audio files: 24

PostPosted: Sat Dec 20, 2008 8:41 am    Post subject: Reply with quote  Mark this post and the followings unread

numbertalk wrote:
I understand and yes, now I do hear it. Was so focused on the volume drop didn't listen closely enough but yes, it's a very prominent intermittent static sound. Embarassed

One question on checking the op amp outputs with the scope - how do I identify HF oscillations mixed with the audio signal on the op amp outputs when looking with my scope? Sorry, I'm not sure where these oscillations would come from (e.g. the power supply, etc...) so not sure if I could check this with no audio connected.

Thanks again.

jhaible wrote:
numbertalk wrote:
What exactly is it you are hearing in that sample? Just want to make sure I can tell if it improves (or even what to look for in any build that might suffer from this). Might get rid of the SMDs and try ceramic caps like Yves Usson did.

Also I'm using 100nf SMDs rather than 47nf - could that be a problem? More than likely I just did a shoddy job with the SMDs.


I don't hear high frequency oscillation, of course.
What I hear is an intermittent noise which might indicate there's HF oscillation in the circuit. It's on the left channel at the beginning of your stereo sample, and on the right towards the end. (I wonder how you can not hear it - it's very prominent!)
As I said, it's not necessarily HF oscillation - could be some intermittent contact problem (bad solder joint etc.). Which, in turn, would give a good explanation for a low level, too.
It's really hard to make a remote analysis for that kind of stuff. I mean, I can give some hints what could be wrong, but you are sitting in front of the circuit, and can attach a scope probe to opamp outputs to check for oscillation (1:10 probe, not 1:1 !), or can knock on your PCB to check for intermittent contacts ...

JH.


With a scope you see a "band" instead of a line when watching audio signals.
This band then becomes a sine oscillation when you look at it with a short time base (like, 1us).

JH.

_________________
"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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