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



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PostPosted: Sun Jun 03, 2007 3:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeah some BBD stuff would be cool Smile
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doctorvague



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PostPosted: Sun Jun 03, 2007 4:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Jurgen
more greetings from Kansas Smile and thanks for being here! Wow, the demo of this thing sounds fantastic - I've never heard of it before myself. Love those sound sheets - wish I'd have saved mine from years past. Please put me down for a board and thanks for making them available. This is great news that you're thinking of doing boards for your projects. Lots of happy people contemplating that Very Happy

Phil
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jhaible



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PostPosted: Mon Jun 04, 2007 2:37 am    Post subject: Reply with quote  Mark this post and the followings unread

mediatechnology wrote:
I noticed that most of these designs use an output matrix. I did a stereo synthesizer design this way using an SAD1024 and later dropped in a pair of SSM2040s for an 8 pole dynamically-controlled phaser. I really loved that prototype. One of the cool things about matrixed outputs to derive stereo is that they fold down to mono.

There's a print here: http://www.ka-electronics.com/Images/stereo_synth_large.jpg


Nice current mirror output on the BBD!

I try to understand what matrix means in this context.
I see one channel with (dry + wet) signal, and the other with (dry - wet) signal. This means the effect will completely cancel when mixed to mono.
Normally you'd want to avoid this - but in your application (stereo synthesizer) it's intended. Create wide stereo, without any artefacts remaining in case it's being reproduced in mono. Is that the idea?

Quote:
The matrix in the above is on the right-hand side. I didn't use them in 1982 but for a matrix output today you might want to consider using THAT or SSM balanced line receivers. Their tight resistor matching for low CMR in line receivers, when used in a sum-diff network, can provide some very deep nulls. It just takes two.


For phasers and flangers, precise matching of wet and dry signal gain is important for deep notches. Normally this means trimming one of these gains; I can see how an internally matched instrumentation amp (or line receiver) could avoid trimming.
If the wet path has precise unity gain, that is.
Unfortunately, this is rarely the case over the whole audio range and CV range. One pleasant exception being opamp-based phasers with Vactrols or FETs as VCRs. OTA phasers for instance will always have a tiny LPF component in addition to their APF function. The Transistor Ladder used in the Tau / Aries / Quadra phasers is a quite bad offender here. With trimming, you get one notch close to perfect; the other ones won't be as deep. That's why these devices sound best with resonance / feedback added, where the peak/notch ratio is high despite a rather poor notch depth.

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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seaweedfactory



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PostPosted: Mon Jun 04, 2007 3:38 am    Post subject: I'm interested in a board... Reply with quote  Mark this post and the followings unread

Sounds like a great project! I'm interested in a board as well, depending on price. Also, are there any special components I will be needing? Thanks.

-Charles
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jhaible



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PostPosted: Mon Jun 04, 2007 4:35 am    Post subject: Re: I'm interested in a board... Reply with quote  Mark this post and the followings unread

charles.brodeur wrote:
Sounds like a great project! I'm interested in a board as well, depending on price. Also, are there any special components I will be needing? Thanks.

-Charles


Special components:
I've redesigned it to get rid of the obsolete dual FET.
You still need transistor arrays; I'll evaluate if the SNR is good enough with CA3046 / CA3086 (cheap), or if you need LM394 / SSM2210 (expensive).

If you don't have money but plenty of time, you can always hand-match BC550C transistors (or similar) - google for the Moog transistor matching circuit.

Opamps can be TL072. But I suggest using at least one OPA2134 (or similar low noise / high impedance dual opamp) for improoved SNR.

Capacitors: The biggest share is 40 (fourty) equal capacitors for the delay ladder. I'll determine the best value in simulation. (Right now, it looks like 15nF is a good value.)
The layout will accept both RM5 and RM7.5 cpacitors (5.08mm or 7.62mm spacing). Wima makes nice 5.08mm MKS types that are available in 5%.

Speaking of tolerances: The ARP version specifies 20% capacitors. I think the performance can be improoved with tighter tolerance. I'll probably select pairs of 1% tolerance for my prototype. It's good to know that the circuit will work with higher tolerances, though. I'd say 10% it should be at least. 5% is good. Tighter is luxury.

This is all preliminary - I'll know more when I've built my prototype.

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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jhaible



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PostPosted: Mon Jun 04, 2007 4:53 am    Post subject: Reply with quote  Mark this post and the followings unread

I have to add:

If you want temperature compensated 1V/Oct tracking, you need a tempco resistor.
The Tau used a 1.87k tempco resistor. I've redesigned it for a 560 Ohm tempco resistor (because I have a lot of them in the drawer). No problem to adapt it to more standard values like 1k, either.
If you don't want temperature compensation, a simple 560 Ohm resistor will do. (I don't expect the tracking to be MOTM-precice anyway, so the best would be a small fine tune / tracking pot on the front panel ...)

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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germaniac



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PostPosted: Mon Jun 04, 2007 10:57 am    Post subject: Re: I'm interested in a board... Reply with quote  Mark this post and the followings unread

jhaible wrote:

You still need transistor arrays; I'll evaluate if the SNR is good enough with CA3046 / CA3086 (cheap), or if you need LM394 / SSM2210 (expensive).


And 2SC1583? I've got a few of these around too. . . .

BTW, BBD projects, YES PLEASE!
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yusynth



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PostPosted: Mon Jun 04, 2007 11:04 am    Post subject: Reply with quote  Mark this post and the followings unread

2SC1583 won't do because they have their emitter connected together and this is not compatible with the ladder architecture.

If you get 2SC3381, this is what you need, no internal connection between emitters...

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germaniac



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PostPosted: Mon Jun 04, 2007 11:12 am    Post subject: Reply with quote  Mark this post and the followings unread

Ah, got it. Thanks Yves!
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jhaible



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PostPosted: Mon Jun 04, 2007 4:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

yusson wrote:
2SC1583 won't do because they have their emitter connected together and this is not compatible with the ladder architecture.

If you get 2SC3381, this is what you need, no internal connection between emitters...


Right: the 1583 doesn't work because of the tied emitters.
But I'm not so sure about the 3381 either. The Vbe offset specs are rather high (10mV max). I 'd have to make some worst case simulations to find out. But apart from that, the PCB layout is _not_ made for the 3381.

(I've built an all pass ladder from 3381s some years ago, and it did *not* work. But this may or may not have been because of Vbe tolerance: I also tried a couple more new ideas in this circuit, and never really investigated the reason of failure.)

JH.

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yusynth



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PostPosted: Tue Jun 05, 2007 2:54 am    Post subject: Reply with quote  Mark this post and the followings unread

jhaible wrote:
(I've built an all pass ladder from 3381s some years ago, and it did *not* work. But this may or may not have been because of Vbe tolerance: I also tried a couple more new ideas in this circuit, and never really investigated the reason of failure.)

It would be interesting to know, I have a bunch of 3381 that I purchased for building some Moog ladder stuffs... May be was it a bad idea then ? Embarassed
Would they be suitable for making discrete OTAs (associated to 2SA798 for instance) ?

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Dave Kendall



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PostPosted: Tue Jun 05, 2007 7:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi JH.


Looks like a very cool device. The demo record of the original is quite a thing, particularly at the end where it takes off ..... Smile

Put me down for a PCB !

cheers,

Dave
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jhaible



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PostPosted: Tue Jun 05, 2007 8:08 am    Post subject: Reply with quote  Mark this post and the followings unread

yusson wrote:
jhaible wrote:
(I've built an all pass ladder from 3381s some years ago, and it did *not* work. But this may or may not have been because of Vbe tolerance: I also tried a couple more new ideas in this circuit, and never really investigated the reason of failure.)

It would be interesting to know, I have a bunch of 3381 that I purchased for building some Moog ladder stuffs... May be was it a bad idea then ? Embarassed
Would they be suitable for making discrete OTAs (associated to 2SA798 for instance) ?


I used them in a Moog ladder, too.
I think it's not so critical there, because only the upper and the lower pair will define any bias points; the rest works with fixed base voltage and current-sourced emitter.
And you can always select these two pairs for low delta Vbe, or add a trimpot for offset compensation.

But in that All Pass Ladder the offsets might add. Or maybe not. I simply haven't investigated.

Also, 10mV (the max rating of the 3381) is most of what you normally have for signal amplitude for an undistorted audio. 10 ... 20mV, depending on what THD you are willing to tolerate. If you start at 10mV bias, a +/-10mV audio signal becomes 0 ... 20mV already. If you do that repeatedly, you run into limits.
Mind you, I can't say if there's a mechanism that all the offsets will effectively add up in the ARP / Tau / Aries ladder before I've run some simulations; but given that these are all emitter followers, DC-wise, I suspect the offsets will add up. If you're hitting something like 100mV, everything gets stuck.

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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yusynth



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PostPosted: Tue Jun 05, 2007 10:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Jurguen for these info...
I think the CA3046 will be the most sensible choice for the Tau ladder then. Using LM394 may seem a bit too expensive unless if one purchases them from Fulurlec (I bought a bunch of these for something like 2US$ each... which was a great bargain indeed)

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jhaible



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PostPosted: Wed Jun 06, 2007 8:27 am    Post subject: Reply with quote  Mark this post and the followings unread

yusson wrote:
Thanks Jurguen for these info...
I think the CA3046 will be the most sensible choice for the Tau ladder then. Using LM394 may seem a bit too expensive unless if one purchases them from Fulurlec (I bought a bunch of these for something like 2US$ each... which was a great bargain indeed)


I'll see how much the noise will build up with 3046's - that's a *lot* of pn junctions connected in series, running at tiny signal levels.

In the ARP version of this circuit, noise doesn't matter because of the compander system. This also changes the resonance behaviour, though.
(The ARP sounds more liquid, very pleasant, but doesn't give the brutal sound of the TAU demo record.)

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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vtl5c3



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PostPosted: Wed Jun 06, 2007 8:56 am    Post subject: Reply with quote  Mark this post and the followings unread

I wonder why there's this aversion to hand matching transistors. I used to not want to deal with it, but then one day I decided to try it. I used the (fixed) Moog matcher circuit and PCB layout posted on Old Crow's site. I was amazed how simple it was and how little time it took to find pairs that matched. Since thermal coupling is probably not an issue with a phaser, hand matched pairs seems like a good option to me. Just my 2 cents worth.

Romeo
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jhaible



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PostPosted: Wed Jun 06, 2007 9:24 am    Post subject: Reply with quote  Mark this post and the followings unread

vtl5c3 wrote:
I wonder why there's this aversion to hand matching transistors. I used to not want to deal with it, but then one day I decided to try it. I used the (fixed) Moog matcher circuit and PCB layout posted on Old Crow's site. I was amazed how simple it was and how little time it took to find pairs that matched. Since thermal coupling is probably not an issue with a phaser, hand matched pairs seems like a good option to me. Just my 2 cents worth.

Romeo


Thermal issues during the matching process.
Touch the transistor with your fingers, or open the door to the room, and you're several millivolts off.

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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frijitz



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PostPosted: Wed Jun 06, 2007 10:13 am    Post subject: Reply with quote  Mark this post and the followings unread

jhaible wrote:
Thermal issues during the matching process.
Touch the transistor with your fingers, or open the door to the room, and you're several millivolts off.
JH.

Indeed. That's why it's best to use a bridge circuit rather than the one-at-a-time Moog method. You can compare one (reference) unit against all the rest and pick the pairs with the same difference to the reference device. Cover with a cloth to eliminate drafts and wait for a stable reading to ensure equilibrium. With care you can measure mismatches down to 50 uV or so. Very Happy

Ian
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vtl5c3



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PostPosted: Wed Jun 06, 2007 10:26 am    Post subject: Reply with quote  Mark this post and the followings unread

I do my transistor matching in a dank basement. Smells like cat poo sometimes, but no airdrafts unless I open a window. Wink

What is this bridge matcher that you mentioned? Are there any schematics online?
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frijitz



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PostPosted: Wed Jun 06, 2007 12:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

vtl5c3 wrote:

What is this bridge matcher that you mentioned? Are there any schematics online?

There are now!

Sorry, it's just a pencil sketch, but it should be legible when printed.

Use the upper figures unless the device has tied emitters, in which case the lower ones must be used. So for individual NPN's, use the upper right figure.

To measure the offset between two devices it is necessary to swap the devices in the setup and to take half the difference of the reading, to cancel the residual bridge unbalance. (See the equations.) For comparing several devices to a standard this should not be necessary. You must match the 100k resistors very closely, though.

Have fun!


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jhaible



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PostPosted: Thu Jun 07, 2007 5:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quick update:

Prototype board has been shipped by Olimex, so it's already on it's way to me. (Can take more than a week, though.)

2:00 am - going to bed now - just cam back from Tori Amos concert in Munich - awsome music, but the concert was way too loud, even with earplugs. Sad

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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mono-poly



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PostPosted: Thu Jun 07, 2007 5:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

That's some good news!
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pdub



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PostPosted: Fri Jun 08, 2007 10:57 am    Post subject: Reply with quote  Mark this post and the followings unread

Just found this list. very cool! I would be in for 1 perhaps 2 PCB's. Thanks, Charles.
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Scott Stites
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PostPosted: Fri Jun 08, 2007 11:20 am    Post subject: Reply with quote  Mark this post and the followings unread

welcome Pdub. You've found at least one place where JH can make your wildest synth fantasies come true.


Quote:
There are now!

Sorry, it's just a pencil sketch, but it should be legible when printed.


I wouldn't care if it was drawn on a cocktail napkin - where has this been all my life? Thanks Ian!!

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PostPosted: Fri Jun 08, 2007 1:52 pm    Post subject:   Reply with quote  Mark this post and the followings unread

jhaible wrote:
Quick update:

Prototype board has been shipped by Olimex, so it's already on it's way to me. (Can take more than a week, though.)

2:00 am - going to bed now - just cam back from Tori Amos concert in Munich - awsome music, but the concert was way too loud, even with earplugs. Sad

JH.


Did you record it?
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