Idea of an simple mic pre.

[thor.zmt]

I'd guess some long way below 80dB.

I guess not. It will depend on the parts used. A lot of japanese "Audio Parts" (by now often no longer available even as SMT Versions sadly) overperform.

The amp part doesn't seem to have anything; no cascodes,

Cascodes do not change open loop gain.

an unbuffered VAS (let alone buffered with a darlington),

Likely with a Transistor with a typical beta of ~450.

no driver(s) and doesn't look like it's a Class A output stage.

Defo class A, for the loads it operates at.

And I'm not even sure we know what it's going to be driving,

According to the schematic, if no external effect is looped in ~ 100k and an open loop emitter follower.

BTW, J-Fet's are 2SK68AM with 12mA transconductance, so 6mA/V for a differential and the PNP VAS is 2SA725 with a beta of 500. And C6 is indeed 330uF polarised.

So Vas @ 0.6mA and 6mA/V input transconductance gives 66,000 OLG at DC or 96dB.

As said, solid, but not exceptional.

Thor

 

[thor.zmt]

I'm truly at a loss to understand how anyone can find LTspice unfriendly.

I do. I have tried a few times and just gave up each time. PSpice or TINA are just SO MUCH more usable to me.

I think it's utterly brilliant. I've used it for ~ 15 years and don't often have to go to the User group until things gets very specialised indeed.

I never have to do anything like this.

Funnily enough I finally downloaded Tina-free just last week to see if their models of some parts worked better natively, and I totally hated it. I couldn't even draw a point to point line without a spiral of squiggles at the closing end, let alone plop a component over a track and have it realise that it wasn't intended to be in parallel with a perfect short.

Funny, I have no such issues.

Moreover, from the number of complaints I read, Altium appears to have been ruined and is now a pricey cash cow. Just as LTspice is now the de facto professional standard, KiCAD (and its integration with FreeCAD) appears to be becoming the same for layout.

Don't get me started on KiCad. I have a customer (consultancy) who uses it. It is utter Tish. Never encountered such a useless EDA. He constantly get's into all sorts kind of problems a professional EDA would never permit.

I haven't tried it yet, but I'm told the schematic editor in KiCAD has become very good indeed.

Not good enough to stop stupid mistakes.

Thor

 

[thor.zmt]

??? I think that sentence may have got a bit mangled along the way ?

* not sure...

But apart from that I should have said I also use TINA-TI and also like that. Do you have the full commercial TINA or the free TI version ?

For some early versions of TINA-TI the program was too crippled. So I had an "evaluation" version installed in 2100 instead. Now TINA-TI seems to lack any limitations compared to the full version, so Tina-Ti.

Also Altium integrated SIM from some years ago. That's good but I find it only really copes with segments of a moderately complex circuit. Current versions likely more powerful ?

Altium will simulate FPGA's and analogue circuits at the same time. I find it for now overpowered to use for my piddly little sim's and more comfortable in TINA. If I have spare time on a rainy day I might engage with Altium's sim more.

Thor

 

[ct.waveform]

I do. I have tried a few times and just gave up each time. PSpice or TINA are just SO MUCH more usable to me.



I never have to do anything like this.



Funny, I have no such issues.



Don't get me started on KiCad. I have a customer (consultancy) who uses it. It is utter Tish. Never encountered such a useless EDA. He constantly get's into all sorts kind of problems a professional EDA would never permit.



Not good enough to stop stupid mistakes.

Thor

How recent is your experience with KiCAD? I would have agreed with you a couple of years ago but I'm told it's far, far better now. And its integration with 3D modelling is very attractive and that can then be used for 3D printing; which is probably why the maker people are using it. It's going to be a few months until I use it in anger so I'm not really the best person to comment on it just yet. What I would like is something where I don't have to do new schematics and can just hoik one over from LTspice. But that's kinda laziness because there's nothing that I do that's of any real complexity.

 

[ct.waveform]

I never have to do anything like this.

The user group is actually a huge asset. The documentation to LTspice is pretty succinct and there are quite a number of undocumented features, both of which are annoying. I found no problem picking it up, but a number of levels deeper and you started running into places where it was sometimes not obvious how to do a something. I'm afraid I can't remember what these were as it's so long ago, but I do remember they could be a bit intransigent in how they did things. That hasn't been an ongoing problem and I'd guess that I probably wasted only about 5-7 days in total across the time I've used it. More recently I have only had to go to the user group with a problem over the PWR() function (or one of the several possibilities for it) which had then been a recent change. For that I'd already decided to do it longhand. Another was to find out how to put up a label for the DC output voltage on a regulator I was doing. Not their fault, but I was sometimes getting great AC graphs for rejection but the reason was that almost nothing was coming out of the regulator. So instead of, say, 15V, it would have been a volt or so. So I needed a label to tell me this had happened without having to hover over the node or look in the Error log. I don't think that was documented and me not realising what was going on had cost me a fair bit of time.

 

[thor.zmt]

How recent is your experience with KiCAD?

Weeks. It was an older version. Upgrading to the latest version broke the whole customers project totally and he had to roll back.

He has a very complex, industrial control for a complex system (robotics essentially) and poor sod is "open sauce" enthusiast and thus by policy only uses open source software. The wasted effort and money from that is epic already.

He as agreed finally that in future we migrate everything on demand to professional closed source tools. Only took 3 years and 10's of thousands of dollars wasted.

I consider KiCad an educational toys, not a serious tool to do real work with. It's fine for hobby, side projects. But please don't ask me to USD it if the results should work first time.

Thor

 

[thor.zmt]

The user group is actually a huge asset.

It is only needed because LTSpice is singularly unintuitive and was never intended to be a general purpose simulator.

The need for a user group to be useful illustrates the fact that it is a poor tool. So the user group is an asset that partially makes up for fundamental failings, I'd call that a liability, not an asset.

Good tools will be intuitive to use and draw you naturally into more advanced things.

Thor

 

[ct.waveform]

Weeks. It was an older version. Upgrading to the latest version broke the whole customers project totally and he had to roll back.

He has a very complex, industrial control for a complex system (robotics essentially) and poor sod is "open sauce" enthusiast and thus by policy only uses open source software. The wasted effort and money from that is epic already.

He as agreed finally that in future we migrate everything on demand to professional closed source tools. Only took 3 years and 10's of thousands of dollars wasted.

I consider KiCad an educational toys, not a serious tool to do real work with. It's fine for hobby, side projects. But please don't ask me to USD it if the results should work first time.

Thor

Interesting; and rather worrying that an upgrade broke it. I can honestly say that no LTspice upgrade has ever broken anything I've worked on. There was a period where they decided to follow Windows conventions for where you saved your projects and that caused whole files to be lost (and you couldn't be sure they'd be there on backups). But that's a long time ago. CERN seem to have had a fairly patchy interest in KiCAD, so having decided only fairly recently to properly commit to it, it isn't a complete surprise that it's not backward compatible. I'm now rather grateful to have uninstalled earlier versions on all my PCs. I would have assumed that they'd be compatible, so thanks for that!

 

[ct.waveform]

It is only needed because LTSpice is singularly unintuitive and was never intended to be a general purpose simulator.

The need for a user group to be useful illustrates the fact that it is a poor tool. So the user group is an asset that partially makes up for fundamental failings, I'd call that a liability, not an asset.

Good tools will be intuitive to use and draw you naturally into more advanced things.

Thor

Haha! I just don't compute how anyone can find it unintuitive. Before LTspice arrived (or then SCAD3) I had spent years writing my own software. You think I'd be reluctant to give up on something so tailored but it was quite the opposite. I've barely even looked at my own software since.

 

[thor.zmt]

Interesting; and rather worrying that an upgrade broke it.

As said, it was completelx project with a lot of component block reuse (down to layout level) etc.

It would not be a problem for a simple circuit and PCB. But modern systems are complex and often repetitive and need EDA that handles this.

KiCad cannot, through upgrades. It did a poor job to start with, compared to professional tools.

It's not something you need for a single channel mic pre, but useful for a 48 in 16/8/4/2 Bus mixer, that nobody uses any longer.

Thor

 

[user 37518]

Incorrect. There is a 1.5k emitter resistor and ~ 22k load.

The VAS thus only offers 15V/V gain.

Lets look at both the scenarios you propose, that is, if the cap is either 330p or 330u. If it is 330u, the 1.5k resistor is bypassed by a capacitor, in this case the transconductance of the VAS is gm=0.5mA/26mV = 19.23 mA/V and the Gain is Av = -gmRL = 19.23mA/V * 22K = 423 V/V, but this is not entirely true, I estimated an Early voltage of 50V from the 2SA970 datasheet, which would mean that the gain is more like 19.23mA/V*22k||100k= 347 V/V, if the cap is 330pF, the gain is a bit lower than 22k/1.5k = 15 V/V, lets say 13.

Actually like 225pF. So slew rate with miller loop closed looks like 4.5V/uS and the low VAS Gain means modest input skewing may not saturate the the VAS.

Miller effect on the capacitor is given by C(1-A), where A is the gain, but, since the gain is inverting and its value is 347 as I mentioned, then the cap is 15p(1+347) = 5.22nF, if the emitter cap is 330p, then the Miller cap is 15p(1+13) = 210 pF. It is important to note that this is a small signal effect. SR, which refers to a large signal effect depends on that cap absolute value and the maximum current it can be provided to it, which in this case is the tail of the diff pair, which is 1 mA. The current through a capacitor can be expressed as i = C dv/dt, hence dv/dt = i/c = 1mA/15pf = 66 V/usec, the actual figure will be lower than this, though. If, as you mention, Tascam had low TIM, then this unusually high value of SR would make sense.

These are likely 2SK170 or 2SK369 or equivalent duals. So the Transconductance of the differtial Amp is probably around 15mA/V.

The 2SK170 has an Idss between 2.6 and 20 mA, let's say 10mA since this is one of the values of the plots reported in the data sheet, it also has a pinch-off voltage of around -0.5 V, its intrinsic transconductance is gm0 = 2IDSS/|Vp| = 40mA/V. The schematic shows a VGS = -0.3V, hence the transconductance of each transistor is gm0(1-VGS/Vp) = 16 mA/V, so yes, your 15 mA/V is a good guess.

Assuming 2SA970 for the VAS (another standard "Japan audio part"), the load for the input stage is likely around 400 * 1.5k or 600k, leading incidentally to a similar 80dB open loop gain estimation with around 18kHz -3dB Point.

Regarding the value you estimated for the load resistor: 1.5k*400 (I am assuming you are using beta=400). If the 1.5k resistor is bypassed by the 330u cap, the load is more likely 400*(26mV/0.5mA)=20.8k AKA rpi in the standard pi model, if it is 330p then it is 600k as you say. Then the gain of the first stage is 16mA/V*20.8k = 333 V/V, this is the DC gain of course, however, as I will show next this value is actually 16mA/V*20.8k||400k = 316 V/V, the 400K resistor (which I obtained from simulation) being the 'Early' resistor of the 2SK170, and that is assuming the BJTs have a beta = 400, considering a beta = 200, which is the lowest specified by the datasheet then the gain is 162. If however, the cap is 330p, the resistance is indeed 600K, however, being paralleled by the 400k resistor gives a dc gain of gm*600k||400k = 3840. All of these unusually high values of gain for the diff input pair makes sense, since the transistors are not degenerated by any resistor.

The total DC open-loop gain with 330uF would then be 316*347= 109.6 kV/V = 101 dB or 162*347 = 56.2 kV/V = 95 dB. If the cap is 330p as you say, then the gain is roughly 3840*13 = 49.9 kV/V = 94dB. Of course, this is considering that they indeed used the parts we are assuming they used.

I plotted the 2SK170 IV curves on a simulator, and estimated a lambda = 0.005/V (output resistance parameter). With the 0.5 mA of drain current, this would yield roughly an Early resistance of 400K.

Regarding the -3dB Open loop Bandwidth. We see that in the case of the 330u cap, the OLBW is essentially 1/(2pi*400k||20.8k*5.22n) = 1.5 KHz, and with 330p it is 1/(2pi*400k||600k*210p) = 3.16 kHz. Now, lets look at the unity gain frequency, in the case of the 330u cap, assuming a gain of 101 dB this happens at 168 MHz, with the 330p cap and a gain of 94dB, it happens at 158 MHz. There is, however, another 15p cap in parallel with the 12k resistor, which would limit the frequency response to 884 kHz in closed loop.

Bottom line: in either case (whether the cap is 330u or 330p) the results are similar, I don't like that the input diff pair stage has no degeneration, if indeed the cap is 330u, it would mean that there is practically zero local feedback being used. On the other hand, if the cap is 330p, there is local negative feedback on the VAS due to that 1.5k resistor. Secondly, the lack of a Darlington or cascoded VAS is also not something I am very fond of. If I were to modify this amp, I would start by adding an emitter follower between the diff amp and the PNP common emitter.

 

[user 37518]

I'd guess some long way below 80dB.

No

 

[thor.zmt]

Lets look at both the scenarios you propose,

I got the service manual and clarified.

All of these unusually high values of gain for the diff input pair makes sense, since the transistors are not degenerated by any resistor.

They are J-Fets, which have different behavior from BJT's. Degeneration is commonly not needed.

The total DC open-loop gain with 330uF

Would be the same as without... On the other hand AC gain above ~ 10Hz would be increased.

I don't like that the input diff pair stage has no degeneration

They are J-FET's it will be fine.

Secondly, the lack of a Darlington or cascoded VAS is also not something I am very fond of.

Reading too much D. Self I presume.

If I were to modify this amp, I would start by adding an emitter follower between the diff amp and the PNP common emitter.

I'd suggest replacing the PNP BJT with a small signal P-MOS.

I'll put it into TINA tomorrow when I need a break from other.

Thor

 

[user 37518]

I got the service manual and clarified.



They are J-Fets, which have different behavior from BJT's. Degeneration is commonly not needed.



Would be the same as without... On the other hand AC gain above ~ 10Hz would be increased.



They are J-FET's it will be fine.



Reading too much D. Self I presume.



I'd suggest replacing the PNP BJT with a small signal P-MOS.

I'll put it into TINA tomorrow when I need a break from other.

Thor

I don't know why you have to be so pedantic. I meant well and did all the computations as an intellectual exercise, hoping to get some dialogue. And I really tried not to respond viscerally to your arguments, but your dismissals and delusions of grandeur are becoming really annoying

No, jFETs get benefited by a small amount of degeneration, they require less than BJTs, but they are not immune to gain variations vs input signal which produce non-lineariities, they are still non linear, if the gain of the diff pair is so high, it would definitely benefit from some small degeneration resistors. This cascoding or VAS Darlington idea is not idiosyncratic to D. Self.

You are correct about what I said regarding the DC gain with the 330uF cap, I meant the very low frequency gain. But you know what I meant, you are just being smug about it.

I honestly don't care about that preamp, and I didn't say you were wrong about the cap, I wanted to make assumptions and see what answer seemed more convicing, and discuss, however, you somehow turned it into a pissing contest. Not interested.

 

[thor.zmt]

you somehow turned it into a pissing contest.

Not a pissing contest. I made the calcs for the same reason as you did, using much simpler math than you and we both ended up with more or less similar results.

Nevertheless, you and others have roundly dismissed the circuit as complete rubbish, because it doesn't have this or that specific feature, something I consider prejudiced and narrow-minded.

HOWEVER I stand to be corrected, hence I will put the circuit I to a simulator with slightly more modern parts and then see the real performance and what effect the suggested "improvements" including my own actually have and if there is something we all can learn from the debate.

Thor

 

[user 37518]

I made the calcs for the same reason as you did, using much simpler math than you and we both ended up with more or less similar results.

What can I say, I love math. I just enjoy taking out my HP calculator with RPN and writing circuit equations; it is what I do for a living.

HOWEVER I stand to be corrected, hence I will put the circuit I to a simulator with slightly more modern parts and then see the real performance and what effect the suggested "improvements" including my own actually have and if there is something we all can learn from the debate.

Thor

Fair enough. BTW, I don't think the circuit is complete rubbish, I just thought it could've been better with some minor changes.

 

[ct.waveform]

What can I say, I love math. I just enjoy taking out my HP calculator with RPN and writing circuit equations; it is what I do for a living.

Fair enough. BTW, I don't think the circuit is complete rubbish, I just thought it could've been better with some minor changes.

I'm sorry to say that I do think the circuit is rubbish, and though I only put my finger in the air re. gain, I'll be v surprised if it comes out as high as you say - especially if it has a load affecting the gain. (Are you really sure it's going to be 100k and not 600R?) Anyway, after the mic has had its 50 or 60dB of needed gain, I don't think there's going to be much left over. Even if budget limited, none of these is where I would put the component money. This has been covered by numerous people, including the BJT vs JFet debate, not just back when Doug Self was learning as he went along.

This page has 5 or 6 examples that are a bit more like it. I can't remember what the output stages are, or if they all have one, but you can add a push-pull and a current sink if needed. All the work has been done for you already. Mic Amp Design

 

[user 37518]

I'm sorry to say that I do think the circuit is rubbish, and though I only put my finger in the air re. gain, I'll be v surprised if it comes out as high as you say - especially if it has a load affecting the gain. (Are you really sure it's going to be 100k and not 600R?) Anyway, after the mic has had its 50 or 60dB of needed gain, I don't think there's going to be much left over. Even if budget limited, none of these is where I would put the component money. This has been covered by numerous people, including the BJT vs JFet debate, not just back when Doug Self was learning as he went along.

This page has 5 or 6 examples that are a bit more like it. I can't remember what the output stages are, or if they all have one, but you can add a push-pull and a current sink if needed. All the work has been done for you already. Mic Amp Design

I do think the amp needs to have a good amount of gain at low frequencies. The manual says the amp has 60-63dB of gain. With the resistors shown (12k and 75 ohm), the closed loop gain is around 44 dB, the rest must be provided by that transformer, which, judging from the 100k at the gate of the JFET, if the reflected impedance to the primary is 1-2K-ish, I would say the trafo is around 1:8; giving it the extra 18dB required to reach the specified gain of 62dB or thereabouts.

If the amp is providing a max gain of 44 dB, it must have lot more gain than that near DC (I am choosing my words more carefully now). So, lets make an intellectual exercise just for the sake of it, suppose that the closed-loop gain at 20kHz is 44dB (we are running the amp at max gain), now lets assume that the TEAC engineers left some extra open-loop gain at that frequency, for instance, lets assume it has 20dB of feedback left, namely, an open-loop gain of 64dB@20kHz. Considering a slope of 20dB/dec, that means that it still has 84dB at 2kHz, now assume that 2kHz is close to the 3dB point, lets add 3dB, we reach 87dB of open-loop gain at low frequencies. This is, of course, just an exercise but it is not far fetched from the values Thor and I computed using the transistors he suggested. I know nothing about the amp but that snippet of a schematic inkster posted, so I have no clue which transistors are actually being used or if the cap is 330p rather than 330u. Thor said he checked the service manual and there is not reason not to trust him.

P.S. I checked that link you provided, the author seems like he is quite a character..... specially his photo page where he refers to his wifes as "1st ExWife", "2nd ExWife" and his current one as "3rd Partner".

 

[ct.waveform]

I do think the amp needs to have a good amount of gain at low frequencies. The manual says the amp has 60-63dB of gain. With the resistors shown (12k and 75 ohm), the closed loop gain is around 44 dB, the rest must be provided by that transformer, which, judging from the 100k at the gate of the JFET, if the reflected impedance to the primary is 1-2K-ish, I would say the trafo is around 1:8; giving it the extra 18dB required to reach the specified gain of 62dB or thereabouts.

If the amp is providing a max gain of 44 dB, it must have lot more gain than that near DC (I am choosing my words more carefully now). So, lets make an intellectual exercise just for the sake of it, suppose that the closed-loop gain at 20kHz is 44dB (we are running the amp at max gain), now lets assume that the TEAC engineers left some extra open-loop gain at that frequency, for instance, lets assume it has 20dB of feedback left, namely, an open-loop gain of 64dB@20kHz. Considering a slope of 20dB/dec, that means that it still has 84dB at 2kHz, now assume that 2kHz is close to the 3dB point, lets add 3dB, we reach 87dB of open-loop gain at low frequencies. This is, of course, just an exercise but it is not far fetched from the values Thor and I computed using the transistors he suggested. I know nothing about the amp but that snippet of a schematic inkster posted, so I have no clue which transistors are actually being used or if the cap is 330p rather than 330u. Thor said he checked the service manual and there is not reason not to trust him.

P.S. I checked that link you provided, the author seems like he is quite a character..... specially his photo page where he refers to his wifes as "1st ExWife", "2nd ExWife" and his current one as "3rd Partner".

I'd forgotten about the transformer. I can see I'm going to have to put this into LTspice at some point in the foreseeable future (which is no bad thing as I have some original 2SK170s here which I've been hoping to experiment with). Staying off the top of my head though, that 3 Stage Lin topology is something I'm familiar with as it's pretty much the blueprint for 90% of hi fi amps today - and it doesn't have much gain. And we do everything we can to up the gain, not much of which is done here (though I haven't looked at it since yesterday - actually the day before, now). I suspect we're going to find that the priority here was noise; and that explains the choice of a transformer - and maybe why not so much went into the amp part beyond standard, abbreviated, thought.

I like what I've seen of that website so far, but I haven't looked at his biography yet. Sounds fun! I agree with him and some of his offbeat conclusions in areas I know about, and he seems to have some good ideas. I like that he's a fan of the CFP, but I suspect some of those dazzling figures will collapse somewhat when he puts models of actual components into his simulation. That's often an alarming experience.

 

[ct.waveform]

I'd forgotten about the transformer. I can see I'm going to have to put this into LTspice at some point in the foreseeable future (which is no bad thing as I have some original 2SK170s here which I've been hoping to experiment with). Staying off the top of my head though, that 3 Stage Lin topology is something I'm familiar with as it's pretty much the blueprint for 90% of hi fi amps today - and it doesn't have much gain. And we do everything we can to up the gain, not much of which is done here (though I haven't looked at it since yesterday - actually the day before, now). I suspect we're going to find that the priority here was noise; and that explains the choice of a transformer - and maybe why not so much went into the amp part beyond standard, abbreviated, thought.

I like what I've seen of that website so far, but I haven't looked at his biography yet. Sounds fun! I agree with him and some of his offbeat conclusions in areas I know about, and he seems to have some good ideas. I like that he's a fan of the CFP, but I suspect some of those dazzling figures will collapse somewhat when he puts models of actual components into his simulation. That's often an alarming experience.

I forgot to mention that I completely follow your reasoning and wasn't meaning to suggest I'd put it into LTspice to disprove you. I'm quite surprised at the 87dB figure, but move the pole lower and that figure just gets higher. I'll have a considered look at it tomorrow (as it's 2.30am here).

 

[user 37518]

that 3 Stage Lin topology is something I'm familiar with as it's pretty much the blueprint for 90% of hi fi amps today - and it doesn't have much gain. And we do everything we can to up the gain, not much of which is done here (though I haven't looked at it since yesterday - actually the day before, now). I suspect we're going to find that the priority here was noise; and that explains the choice of a transformer - and maybe why not so much went into the amp part beyond standard, abbreviated, thought.

Yes, at first, the fact that it uses a very simple Lin topology made me believe that the gain wouldn't be very high. To be honest, I think that is due to the fact that most Lin topologies have a very heavily degenerated BJT input stage, gains of 15-30 for the input stage are common and those topologies rely mostly on the VAS to provide most of the gain. Here, however, the fact that the input stage is not degenerated and that, even if the VAS is not a Darlington arrangement, the BJT of the VAS has a very high beta; allowing the first stage to have a very large gain. Even if the mysterious cap were 330 uF, the high beta of the BJT (and relatively low collector current) still presents a somehow large load to the drain of the JFET.

I think you are also right regarding noise being a priority, if that cap is 330p (and I am not denying it), the first stage has a whopping 3840 V/V of gain, probably less in practice, but still a huge amount of gain, which would definitely make sense in terms of noise.

I forgot to mention that I completely follow your reasoning and wasn't meaning to suggest I'd put it into LTspice to disprove you. I'm quite surprised at the 87dB figure, but move the pole lower and that figure just gets higher. I'll have a considered look at it tomorrow (as it's 2.30am here).

Don't worry about it, I know you mean well. It should be wise to put it into a sim, up to now it has all been paper-and-pencil computations.

 

[thor.zmt]

Are you really sure it's going to be 100k and not 600R?

According to the service manual, yes, BWTFDIK?

Anyway, after the mic has had its 50 or 60dB of needed gain,

Of which 20-30dB are in the input transformer.

I don't think there's going to be much left over.

If OLG = 100dB (those of us who calculated this end up around there), total gain 50dB and transformer step-up 20dB we get 70dB NFB.

True, it's not a lot to people who make multi-loop circuits cascading two Op-Amp's with over 100dB OLG and use the result in unity gain (what does 200dB+ of NFB sound like?).

But I think in the context it's fine.

not just back when Doug Self was learning as he went along.

Mr Self is surprisingly biased and sets out to prove that "generic 0815 is the best" and always failed to do so, so we get the advocating of many parallel cheap OPA or ridiculously oversized generic coupling capacitors, failing to note that he merely matched the "exotic" components (to Mr Self most generica is "exotic") and totally blew the budget to smithereens, never mind extra complexity, size, weight etc.

Mr Self pretends to promote "appropriate technology", when in fact he mostly propounded what I consider "inappropriate technology".

I mainly read Mr Self's Articles and books for the extensive data, not the conclusions and also to know how not to do things.

Cordell, Borbeley and Groner are much better sources for "how you should do things".

This page has 5 or 6 examples that are a bit more like it.

Not "like it", but according to what I shall charitably call your preference, which you are entitled to, of course.

All the work has been done for you already. Mic Amp Design

Interesting guy. I both match him in a lot of ways and differ sharply in others.

Thor

 

[thor.zmt]

Staying off the top of my head though, that 3 Stage Lin topology is something I'm familiar with as it's pretty much the blueprint for 90% of hi fi amps today - and it doesn't have much gain.

You are thinking classic self blameless topology into speaker loads.

Most modern Op-Amps are 3stage LIN as well.

And we do everything we can to up the gain,

Except using suitable devices with superior performance designed for audio use, as these are considered suspect, snake oil and "exotic".

I like that he's a fan of the CFP,

Another one? I like him more.

Try a CFP with 2SK269 and BSS84 for input stages, or better extend to cascomp...

You will not Adam and Eve the relative levels of noise, transconductance and linearity with ultra high input impedance, if you are used to "Self" ish stuff.

Then repeat with BSS84 and STD1N60K as second differtial stage VAS.

Then add a BiMos Output stage, Exicon or Renesas lateralMOSFET follower as driver for RET Output transistors, drivers biased ~100mA, outputs biased for Class A/B with lowest amount of upper harmonics.

Then scratch your head and wonder why anyone ever bother(ed) with lesser parts.

Mind you, Class D is the field of endeavor now...

Thor

 

[thor.zmt]

Interresting guy. I both match him in a lot of ways and differ sharply in others.

Also divorced two wives, one a BAME background small time model.

British mainly by choice, not the old school tie(s) but German by origin.

Further, right now I sit under the stars five minutes from the beach and the Gulf of Siam by the side of my 10 x 5m Pool, next to my 200 sqm two floor villa, with Disco lights and Radio FG Paris "Classics" playing on the "First Universal Cybernetic Kinetic Ultra Petablaster" (peta beats mega) blasting tunes.

"F.U.C.K.U.P." is a hifi ghetto blaster with LDAC 96/24 Bluetooth using an ESS 9018 DAC, a 2 x 80W RMS class D Amplifier (modded) 150WH/22.2V LiPo battery pack and a pair of 6.5" Polycone Midbass plus coaxial inverted titanium dome tweeter.

Think mid 90's high end speaker or passive monitor and naturally Discolights that beat the Vala Disco Light blaster from that Madonna video a lot ( go crazy or go home)

...

Sitting with me is a girl almost young enough to be my granddaughter, 5'5"/110 brown eyes, smile like the sunrise...

To quote "LG":

Life's Good

Thor

 

[user 37518]

Mr Self is surprisingly biased and sets out to prove that "generic 0815 is the best" and always failed to do so, so we get the advocating of many parallel cheap OPA or ridiculously oversized generic coupling capacitors, failing to note that he merely matched the "exotic" components (to Mr Self most generica is "exotic") and totally blew the budget to smithereens, never mind extra complexity, size, weight etc.

Mr Self pretends to promote "appropriate technology", when in fact he mostly propounded what I consider "inappropriate technology".

I mainly read Mr Self's Articles and books for the extensive data, not the conclusions and also to know how not to do things.

Cordell, Borbeley and Groner are much better sources for "how you should do things".

I've read most of Mr. Self's work, in my opinion he has very good ideas, and he is brilliant in many ways, but there is no one in the world for Mr. Self except for Mr. Self; his last name is most appropriate to describe him. He believes he has written the final word on amplifiers, and whomever dares to publish something different is attacked by him. I somewhere read that some guy tried to publish an amp design and Self was not only overly harsh but even rude. Even Cordell, who I think is one of the most polite and gentle persons in the audio world, has had some confrontations with Self (Self is to blame in my opinion; he started posting his disagreements, or rather provications, in a thread about Cordell's book) I think you can still read the exchange over at the diyaudio.com forum.

 

[user 37518]

Mr Self is surprisingly biased and sets out to prove that "generic 0815 is the best" and always failed to do so, so we get the advocating of many parallel cheap OPA or ridiculously oversized generic coupling capacitors, failing to note that he merely matched the "exotic" components (to Mr Self most generica is "exotic") and totally blew the budget to smithereens, never mind extra complexity, size, weight etc.

Mr Self pretends to promote "appropriate technology", when in fact he mostly propounded what I consider "inappropriate technology".

I mainly read Mr Self's Articles and books for the extensive data, not the conclusions and also to know how not to do things.

Cordell, Borbeley and Groner are much better sources for "how you should do things".

I've read most of Mr. Self's work, in my opinion he has very good ideas, and he is brilliant in many ways, but there is no one in the world for Mr. Self except for Mr. Self; his last name is most appropriate to describe him. He believes he has written the final word on amplifiers, and whomever dares to publish something different is attacked by him. I somewhere read that some guy tried to publish an amp design and Self was not only overly harsh but even rude. Even Cordell, who I think is one of the most polite and gentle persons in the audio world, has had some confrontations with Self (Self is to blame my opinion; he started posting his disagreements, or rather provications, in a thread about Cordell's book) I think you can still read the exchange over at the diyaudio.com forum.

 

[murrayatuptown]

5'5"/110.

I'm glad I saw the non-metric y-axis dimension on my small screen phone...

...so I realized the -y gravitational constant was not kg.
;@)

Murray

 

[thor.zmt]

5'5"/110.

I'm glad I saw the non-metric y-axis dimension on my small screen phone...

...so I realized the -y gravitational constant was not kg.

I am nostalgic for imperial units. Metric is better for universal use, but...

One hundred sixtyfive, fifty, brown eyes

Ain't have the lilt of

Five five, oneten and brown eyes.

Imperial makes for better lyrics

Thor