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Old 23rd May 2004, 06:34 PM   #51
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Default Re: Re: Joke

Quote:
Originally posted by Peter K


He is BTW intending to stop this or next year.

Peter
That's what he is saying since he opened his shop I think it is this time serious though, he only opens on tuesdays and saturdays. After having been there finding a closed door for a few times now I ring before I go there. Too bad that he will stop, no good components for DIY electronics in the Netherlands without Piet Quakkelstein.

BTW I think he's equally worldfamous for RF and audioparts. For instance OSCON, MKP, Dale and MIL spec parts in large quantities for good prices. Not to forget his enormous supplies of new-in-box JAN tubes in the past.

For the dutch audio enthousiasts that don't know the shop, go there before he quits and don't forget to bring a sturdy case for carrying the stuff you find back home !
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Old 24th May 2004, 10:01 AM   #52
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Default Re: Re: Re: Joke

Quote:
Originally posted by jean-paul

For instance OSCON, MKP, Dale and MIL spec parts in large quantities for good prices. Not to forget his enormous supplies of new-in-box JAN tubes in the past.
All this at 10 min. walk from home?
I have this at several countries from home.
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Old 31st May 2004, 04:48 PM   #53
Peter K is offline Peter K  Netherlands
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Quote:
Originally posted by Pedja

Ok, here is something for which I would say can be made relatively fast starting from the circuit you are using now.

Signal should be tapped in that way the existing I/V resistors stay out of the working circuitry (simplest, disconnect both them and the first transistors). You could leave existing 100pF caps but you can try higher values as well. C1 (1n or something) you could add additionally. R3 should be the trimming pot of 4.7k or 10k and it should be tuned for zero DC at the Q2s emitter.

I think there is one practically the same circuit (without buffer) posted earlier on this forum as there are numerous suggestions for the improvement (addition of a current sink and a current source for the Q2, current source for the voltage reference (which can be a transistor connected in a few ways), addition of the folded cascode, current mirror). I have not built the circuit as shown below but I guess it can give the idea of how this kind of circuit can perform.

Pedja
Hi Pedja,

I have build the circuit you suggested, it worked at once without problems. Compairing to the original circuit (TNT audio) the sound of this circuit is cleaner, tighter bass and clearer high. Everything in between is there, the vocals are beautiful. Altrough it is difficult to give an exact desciption of the differences I prefer the sound of this stage above the original circuit.

I guess it is time to a little deeper into this and build Rudolfs I/V stage.

Thanks again,

Peter
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Old 31st May 2004, 04:57 PM   #54
Peter K is offline Peter K  Netherlands
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Quote:
Originally posted by Bernhard


Try it, costs only 5 minutes.

If the problem is somewhere else in the circuit you will have problems to compare sound of foil and lytic.

Bernard,

I have tested the caps, no problems found. The only thing I have found is some "silicone cooling stuff" that was between the capacitors pins on the IC socket. I removed it and the distortion problem disapeared. But to be honest I am not sure that the silicone stuff caused the problem. I might have made an other change in the system while I was working in it.

Question for the forum:
Can "silicone cooling stuff" that is on the (de-coupling) capacitor pins of a TDA 1541A cause distortion??

Peter
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Old 4th September 2005, 06:42 PM   #55
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Quote:
Question for the forum:
Can "silicone cooling stuff" that is on the (de-coupling) capacitor pins of a TDA 1541A cause distortion??
Was it conductive thermal compound or not?

I know some PC silicone grease IS conductive, and some is not.

An other question:
Why are OSCONs high priced?

MSI (average quality PC components manufacturer) put some Sanyo OSCONs on my GeForce 4 graphic card.

If MicroStar Intl. decides to put something like this, it HAS to be REALLY cheap.

A 27F cap is 2.27$ @ Mouser and my video card has some 100F.
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Old 30th January 2010, 10:22 PM   #56
tonimxp is offline tonimxp  Italy
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Hi!Peter k I realized the same PCB used by you :Facelifted no oversampling dual Philips TDA1541A DAC and 6C45π tube outputbuffer
, right now i have the same problem, noise at low levels of incision of the musical message.
Of course, when I extract one of two randomly tda1541 the problem disappears!
In desperation I tried to make a new layout of the PCB made with circad, but the problem remained the same!
Please keep me seemed to understand that ultimately you have solved, you could help me?
I own a Sony CDP-227esd with two tda1541 and the presence of double dac is felt.
I would solve the problem in order to finally complete the draft envi-site: Facelifted no oversampling dual Philips TDA1541A DAC and 6C45π tube outputbuffer
Please excuse my English translated by Google and tanks in advance by Antonio.













http://bygselvhifi.dk/images/nosdac/nosdacdac.jpg







Quote:
Originally Posted by Peter K View Post
Bernard,

I have tested the caps, no problems found. The only thing I have found is some "silicone cooling stuff" that was between the capacitors pins on the IC socket. I removed it and the distortion problem disapeared. But to be honest I am not sure that the silicone stuff caused the problem. I might have made an other change in the system while I was working in it.

Question for the forum:
Can "silicone cooling stuff" that is on the (de-coupling) capacitor pins of a TDA 1541A cause distortion??

Peter
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Old 1st September 2012, 02:58 PM   #57
wlowes is offline wlowes  Canada
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Default I too have the same problem

Strictly on the right channel and after playing 2 or 3 cuts. I have cleaned up some solder joints.

After reading this post, am convinced this is heat related. I have some heat producing shunt regs pretty close to the 1541a chip and there is not a lot of ventilation in the box. I am running with organic polymer caps soldered right on the decoupling pins (sound fantastic) and have a poorly implemented version of the Grundig 9000 DEM circuit. I think it is possible that I have damaged caps in either the DEM circuit or the decoupling caps with too much heat. Could be they leak and distort when overheated in my tight enclosure.

I have a lot of heat producing stuff crammed into a slim ARCAM box with tube output stage. The thing that has changed recently is the addition of a WaveIO USB - IS2 converter. I dissipates 500mW and may have tipped the thermal balance.

The distortion is consistent and predictable. I will first try running with an open case and see if this fixes it. I have seen other posts from long ago that tried changin the TDA chip only to see this reappear. I am wondering if running hot destroys the TDA or if it is the caps around it. Hope its the latter. I have had similar distortion with a bad solder joint on a decoupling cap, so here's hoping.
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Old 2nd September 2012, 02:49 PM   #58
wlowes is offline wlowes  Canada
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Default Problem solved

I have solved the problem by replacing the decoupling caps on one bank of tda1541a. I initially tried reflowing solder to all the caps. This seemed to help briefly, but problem would return as unit came up to temp. Ventilating the case did not resolve the issue.

I will not know if I had one or more capacitors that had been damaged and degraded over time, or if I simply had a bad solder connection. Either way the cap replacement has purged my system of this issue. I listened for about 3 hours with no hint of distortion. This at least confirms that in some cases at least, this age old problem of distortion on one channel of the 1541a is not due to failure of the chip, but to failure of the implementation around the chip.

In my experience, the 1541a seems to be a pretty bullet proof IC.
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Old 2nd September 2012, 08:09 PM   #59
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Quote:
Originally Posted by wlowes View Post
I have solved the problem by replacing the decoupling caps on one bank of tda1541a. I initially tried reflowing solder to all the caps. This seemed to help briefly, but problem would return as unit came up to temp. Ventilating the case did not resolve the issue.

I will not know if I had one or more capacitors that had been damaged and degraded over time, or if I simply had a bad solder connection. Either way the cap replacement has purged my system of this issue. I listened for about 3 hours with no hint of distortion. This at least confirms that in some cases at least, this age old problem of distortion on one channel of the 1541a is not due to failure of the chip, but to failure of the implementation around the chip.

In my experience, the 1541a seems to be a pretty bullet proof IC.
Not if it finds a negative voltage on one of its outputs, apparently.

I guess everything's been said about the TDA1541. All the same...

If the voltage at the output is the same as the ground used by the bit switches, then the decoupling caps' contribution is only to ground the noise from the 250kHz "dynamic element matching" switches. Low ESR at that frequency and its harmonics is important, and low leakage. Ceramics should be fine if the output is to a good virtual ground at 0V. Next would by lytics, but they don't last long. It certainly seems that high ESR films are not a good choice.

If the output voltage is not 0V, either DC or audio due to input resistance of I/V stage, then some of the decoupling caps switch at sampling frequency between ground and that varying voltage, depending on which bits are active. Current is diverted in consequence. The larger the output voltage, and the larger the caps, the greater the diverted current. Perhaps the resulting conflicting requirements are best met by C0G ceramics?

The effect on the audio output will be quite complicated.

I think perhaps the current can become great enough so the bit output stages begin to fail, one by one on in groups.

Perhaps the 10 least significant bits are less well protected?
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Old 3rd September 2012, 03:45 AM   #60
wlowes is offline wlowes  Canada
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For decoupling, I used smt organic polymer decoupling caps (ESRD Series 7.3 x 4.3 mm 16 V 8.2 uF Polymer Aluminum Electrolytic ) directly to the 14 pins of the TDA1541a.

Other members have told me that the leakage of these is too high. I must say however the sound quality with this approach is in a different league to what I replaced. This is on an Arcam audio board. Their stock board uses 10 220nf MKP caps and 4 440n tantalums. Crap by comparison to the polymer caps. Also light years ahead of the stock sound on my Rotel 855 cd. Not sure of the brand they use, but again good sized MKP if I am not mistaken.

I do intend to try the 1u SMT PPS stacked film caps recommended by ECDesigns. Right now too busy enjoying the Polymer caps.
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