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Old 6th July 2013, 10:36 AM   #881
fas42 is offline fas42  Australia
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Originally Posted by owdeo View Post
Ok, it's not really a technical argument then, just a vague speculation that "low level distortion" is being injected due to supposedly faulty contacts.
Depends what you mean by technical ... any non-linear resistance where the design has assumed there to a correct continuity is liable to cause effects. As a mental exercise, consider the whole circuit, every component on the board, is connected on the board not by solder, but by a plug-in arrangement - what faith would you have that the performance in every area would match that of a fully soldered board?


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I can see how with say a power amp's speaker terminal connections a soldered contact might be better than crimp lugs due to the impedances and currents there and a small non-linear contact resistance being a significant proportion of the total.

But with a preamp we are talking ~kR impedances where any slight non-linear joint resistance is a tiny fraction of that of the linear parts. And you haven't even explained why a turned-pin gold plated IC socket will not make good connections to the IC pins.
Personal experience. Every time I reduced the number of non-soldered connections in a system the sound improved; I don't need a textbook to confirm the value of doing this. And, I very specifically don't like gold to gold, I spent quite a lengthy period confirming that unless the connection is truly gas-tight that electrically such a connection is not good enough, at least in the audio game ...

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Are you saying that you're 100% sure that the character of sound of this design and of opamps themselves is purely a result of poor connections? Would the major hassle of unsoldering all those sockets and soldering in the opamps 100% make the SQ of this design equal to that of the others? Surely you can see there's a logical flaw in that argument - swapping opamps produces a different sound but they are in the same sockets! Furthermore, the other opamp preamps I'm comparing it to contain the same dreaded socketed ICs and yet they are ok
All the preamps would probably improve in quality if the connections were soldered ... and there would still be differences due to variations in topology and component quality.

The opamps would vary in their susceptibility to less than perfect connections, hence variation in sound quality.

Personally, if I had the units, I would carefully solder the opamps to the sockets as is - removing the socket entirely would be of only marginal benefit.
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Old 6th July 2013, 10:56 AM   #882
owdeo is offline owdeo  Australia
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Originally Posted by sandyK View Post
Hi Frank
The problem here, as Owdeo has already pointed out, is that PCBs like this are not DIY friendly as regards modifications. Often as not, the copper lands are too small in most PCBs that are more suited to production line assembly. For DIY use, where modifications are a way of life, you need conservatively designed PCBs such as those from Silicon Chip magazine ,where you can play around if you are careful, without the risk of solder suckers etc. devouring fine copper pads, or the need to chop off components to avoid damage to a fragile PCB when removing them.
Hi Alex, Frank,

In this case it is a much better PCB than SC has ever produced, having been designed (I gather) by a professional PCB designer, though certain SC staff seem to be getting better. While the pads may be slightly smaller, being plated through the holes can withstand a lot more rework as they tend to stop the pads from peeling away. The problem is to de-solder an IC you need to cut the legs, thereby wrecking it in the process. Plus of course it's very time consuming with quite a few opamps involved.

Frank I would have no issue if you'd said your experience was that soldering ICs into designs where they were previously socketed had improved SQ on many occasions and you were sure of this because you had two of the same design, one with sockets and one without, to compare directly, especially if you admitted there was no clear reason why. But start by implying I'm a fool to have used sockets because you know better based on audiophile pseudo scientific speculation like "low level distortion" due to lack of integrity etc and I lose all interest. And your remarks on needing to let things settle reminds me of my audiophile friends who keep their system on 24/7 because they're convinced it takes 3 days to start sounding good after being switched on from cold. And that the type of wood their CD player sits on affects the sound massively. Etc etc. Sorry but I'm not interested in the whole mystical side, only the art and science
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Old 6th July 2013, 11:27 AM   #883
owdeo is offline owdeo  Australia
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Originally Posted by fas42 View Post
Depends what you mean by technical ... any non-linear resistance where the design has assumed there to a correct continuity is liable to cause effects. As a mental exercise, consider the whole circuit, every component on the board, is connected on the board not by solder, but by a plug-in arrangement - what faith would you have that the performance in every area would match that of a fully soldered board?
Plenty of faith if they were high quality connectors. I spend my days working on state-of-the-art medical imaging equipment that contains literally hundreds of connectors (with wires crimped into them too) with thousands and thousands of connections, and I'm quite sure their performance and reliability would not be improved by soldering every single connection. Not to mention how much fun servicing them would be then. And before you say anything I've rarely if ever seen any of this equipment fail due to the connectors. Now I know audio is a different beast as it involves our emotional response, but I don't see that's a good excuse to disregard physics and start inventing mysterious reasons for things.

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Originally Posted by fas42 View Post
Personal experience. Every time I reduced the number of non-soldered connections in a system the sound improved; I don't need a textbook to confirm the value of doing this. And, I very specifically don't like gold to gold, I spent quite a lengthy period confirming that unless the connection is truly gas-tight that electrically such a connection is not good enough, at least in the audio game ...
More Golden Rule (no pun intended ) dogma based on extrapolating one observation into a general principle - eg replacing an electrolytic capacitor in a particular part of one design improved the sound, therefore all electrolytic capacitors must degrade the sound in any part of any circuit (presumably as they also add low level distortion ). Having studied materials engineering at uni, I'm pretty sure I recall correctly that dissimilar metal joints are bad news in terms of corrosion. Hard to see why gold to gold would be so bad and a solder joint so much better. And as for gas tight, well electrons are pretty small. The part of the IC leg that's in contact with the socket hole, however small this area, is just as gas tight as a solder joint. That's how crimping works, right?

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Originally Posted by fas42 View Post
All the preamps would probably improve in quality if the connections were soldered ... and there would still be differences due to variations in topology and component quality.

The opamps would vary in their susceptibility to less than perfect connections, hence variation in sound quality.

Personally, if I had the units, I would carefully solder the opamps to the sockets as is - removing the socket entirely would be of only marginal benefit.
Oh so now you're saying the SQ difference is due to component and circuit differences after all, just that I can't observe this legitimately until I've soldered every single connection? But wait, if this only applies to opamps themselves that must mean another win for the legendary 5532 - it is so much more resistant to the effects of imperfect socket connections (solder joints always being perfect of course) than the LM4562.
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Old 6th July 2013, 12:09 PM   #884
fas42 is offline fas42  Australia
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We are really seeing things from two different angles here - I perceive worrying about the precise nature of the opamp as heading across to the audiophool camp, I've heard excellent sound coming through the most mangy of these little critters - provided I sorted out the other things that I've been mentioning ...

If you're happy that your IC sockets are gas-tight quality then probably best to leave this conversation at this point ...
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Old 6th July 2013, 12:32 PM   #885
owdeo is offline owdeo  Australia
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Well I can certainly respect and agree to that. I'm not saying I completely disbelieve this could ever make a difference to SQ, just that your pseudo-technical arguments as to why are unconvincing. You did make the original statement pretty bluntly after all. I would prefer to solder all the opamps in if I was sure I would never change them, and may still do so. But I'm very skeptical of hearing any difference as a result.

And you may note that I have never said or thought that the design isn't sounding good because of the opamps it uses so I'm not "worrying about the precise nature of the opamp". I think 5532s can sound pretty good and rather that it's some aspect of this design that is having the effect on SQ. Anway
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Old 6th July 2013, 12:38 PM   #886
fas42 is offline fas42  Australia
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Originally Posted by owdeo View Post
You did make the original statement pretty bluntly after all. I would prefer to solder all the opamps in if I was sure I would never change them, and may still do so. But I'm very skeptical of hearing any difference as a result.

And you may note that I have never said or thought that the design isn't sounding good because of the opamps it uses so I'm not "worrying about the precise nature of the opamp". I think 5532s can sound pretty good and rather that it's some aspect of this design that is having the effect on SQ. Anway
My apologies if my original statement came across as being too blunt!! Would be my Germanic heritage getting the better of me, then ...

Cheers, too,
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Old 17th September 2013, 02:56 PM   #887
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Default Self's Variable Tone Control Preamplifier

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Originally Posted by Carl_Huff View Post
Anybody interested in building Mr Self's latest preamp (with tone controls) that is features in the latest Linear Audio magazine?

A low-noise preamplifier with variable-frequency tone controls
Hi Carl,
I cannot find anyone on the forum actually answering your question (above). I have just ordered a copy of the Linear Audio Self article, so I am in the evaluation stage, but having built Self's original Advanced Preamplifier (still going strong) I am expecting his new design to be excellent.
Hence my question: Is anyone(or group) planning to build the variable tone control preamp and are there sources for PCBs for the project?
Are there any Forums addressing any of this?
Thanks for the help

George
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Old 17th September 2013, 03:24 PM   #888
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I have asked the man himself some weeks ago when I read Vol.5- being his IP.
He was uncommitted on the type of PCB design and whether it was viable for The Signal Transfer Co. If it turns out as a satisfactory arrangement and economical approach, I will certainly join the queue.
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Old 17th September 2013, 03:28 PM   #889
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Default Variable Tone Preamp

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Originally Posted by Ian Finch View Post
I have asked the man himself some weeks ago when I read Vol.5- being his IP.
He was uncommitted on the type of PCB design and whether it was viable for The Signal Transfer Co. If it turns out as a satisfactory arrangement and economical approach, I will certainly join the queue.
Based on my experience with Doug Self's designs, I shall be in the queue with you.
His Advanced Preamplifier design had switchable turnover points for the tone controls and I found them useful. Actually that Pre-amp is just 3 feet away.. I use it for ripping LPs onto myNAS. It has always worked perfectly.

Thanks fro that information

George
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Old 17th September 2013, 03:43 PM   #890
rsavas is offline rsavas  Canada
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Hi George, Carl, others.

Quote:
and are there sources for PCBs for the project?
Not that I am aware of.
I few years back I did a layout of the original, using SMT & THT, but never mfg the pre-amp, due to cost overruns. Since I have the design captured for layout and Pspice, it would not be too much work to re-visit the design again. I guess that i have to pony up to Jan D. & get the article however.
Recall it was a real rats nest to sort out. Lucky, I was doing the pcb in 4 layers so power/gnd was so much easier. Do not suspect people would wan ta 4-layer pcb however for a simple design like this one.
I have issue of usefulness of a stand alone pcb that only has one function and is not a complete system = market
I was contemplating doing it electronically, but gets involved. Probably using a CS3318, as TI PGA2311/4311 method requires more pkgs.
I realize however that tone controls do not necessarily need to be electronically controlled.
I also have a 4 channel parametric eq. design from 1978 that does a better job, if tone control is your thing. It used TL074 so it is screaming for an upgrade as well.
Rick
Attached Files
File Type: pdf Self Tone control 1996.pdf (327.8 KB, 61 views)
File Type: pdf Self Tone control 1996_top assy.pdf (246.2 KB, 44 views)
File Type: pdf SCHEMATIC1 _ Tone Control.pdf (16.7 KB, 61 views)

Last edited by rsavas; 17th September 2013 at 04:06 PM.
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