Oops

Audio Power Amplifiers by Arto Kolinummi - figures error.

On page 233 in Arto's book, Figure 7.35 as shown in the book is incorrect. The correct figure 7.35 is here. On page 244, figure 7-48 as shown is also incorrect; this is the correct figure

My apologies to Arto and readers.

Volume 13

Corrected equations for Burkhard Vogel's Challenging BJT noise

Some typos crept in equation 3 and 4 of this article; here are the correct ones:

Equation (3) should be replaced by:

Equation (4) should be replaced by:

 

Corrections to An Electroascoustic measurement System by Mann and Vanderkooy and

A few undetected typos crept in this article. I have listed them in a downloadable PDF. These will be corrected in the downloadable article PDF.

Current driven Output-stage class AB power amplifier

An error crept into the final Current Source Driven amplifier, page 143, figure 4. The polarity of the output transistors should be swapped. A corrected figure can be downloaded here. Apologies to readers and to Ian for not spotting this in time.

Volume 12

Hans Polak book review 'Current Driving of Loudspakers' Vol 12

It was pointed ot to me that the references in the aricle ran through [24] but in the article itself the last one i [17]... My bad, apologies to Hans Polak, and here are the missing references:

[18]        AES E-Library, Investigation of Current Driven Loudspeakers. Authors: Schneider, Agerkvist, Knott and Andersen. (May 2015)

[19]        AES E-Library, Distortion Improvement in the Current Coil of a Loudspeaker. Authors: Pillonnet, Sturtzer, Rossignol, Tournier and Lemarquand. (May 2013)

[20]        AES E-Library, Comparative Analysis og Moving-Coil Loudspeaker driven by Voltage and Current sources. Authors: Bortoni, Noceti Filho and Seara. (October 2003)

[21]        AES E-Library, DSP in Loudspeakers. Author: Rumsey. (Jan 2008)

[22]        AES E-Library, DSP in Loudspeakers. Author: Staff AES (April 2004)

[23]        AES E-Library, Subjective Investigations of Inverse Filtering. Authors: Norcross, Scott, Soulodre, Gilbert and Lavoie. (October 2004)

[24]     http://www.diyaudio.com/forums/diyaudio-com-articles/158899-arpeggio-loudspeaker.html 
Author: Morgan Jones.

Volume 11

Error in Table for Douglas Self's The Devinyliser

A gremlin crept into Doug Self’s article in Vol 11 The Devinyliser. The table for case 3) at the bottom of page 94 is in error. The correct table is reproduced here. Thanks to John East for pointing it out to me.

My apologies to author Self.

   Desired    value

    Ra value

   Rb value

   Rc value

   Actual value

   Nominal    error

   Tolerance

       10k64

      30kΩ

      33kΩ

     33kΩ

      10k645

     +0.049%

     0.578%

       21k28

      33kΩ

      62kΩ

     1M8

      21k282

      +0.010%

      0.731%

 

Volume 10

Missing table for Scott Wurcer's article in Vol 10 on digital RIAA

Regretfully, one of the coefficient tables in the Appendix of Scott Wurcers article was mising from the issue; as a result, the remaining tables were numbered wrongly.

I have a full section of Scot's article in the Downloads area which contains not only the missing tables but also a large selection of test files, data as well as wave files (you need to scroll down a few pages to get to Scott's section).

With apologies to Scott.

Volume 9

Burkhard Vogel The RIAA Phono-Amp Engine II

Two errors crept into Burkhard's Engine II article in Volume 9. Figure 13b on page 138 should be replaced by this revised figure 13b. In the Appendix on page 147, equation (22) is incorrect. The correct equation should be: rce = (|VA| + |VCE|) / IC  (22)

With apologies to Burkhard.

The Low Parts Count Audiophile Power Amplifier

Update Aug 2015: there were a few more typos in the parts designation for the output power FETs. You would think that Exicon would prefix their parts with EXC, but alas - it's ECX... Here are the revised figure 3 and figure 9 for the article.

We’re sorry that an error crept into our final amplifier circuit, Figure 9, page 65.  Here is the new, corrected version. The only problem was that C4, 10uF, was improperly placed. It should have been in series with R5, to match C3 in series with R4.  Remember that the hum cancellation of the differential input is effective only if the output impedance of the driving preamplifier adds together with R4 to equal 1K.  As drawn, it is assumed that this output impedance is zero.  If both C3 and C4 are shorted out, the amplifier will be DC coupled but still has full differential character.

The authors also offer an LTspice simulation package, containing two LTspice simulation files, for you to check out the amplifier. The package also includes the spice models for the MOSFETs. One simulation file is the full amplifier with all components, while the second is a simplified version which has the power transformer secondary windings in the model. This allows checking power supply loading, turn-on behaviour, and hum characteristics. In each case the bias resistors will have to be changed to alter the MOSFET bias current.

Although the output stage is inverting, the overall amplifier is noninverting, as are most power amplifiers.  If you know the polarity of the rest of your audio system, then by wiring up your loudspeakers with the appropriate phase, the polarity of your whole system will be correct.

Volume 8

Ian Hegglun cube-law class A PCB footprint error

Each Volume 8 comes with a free PCB for Ian Hegglun's class A3 amplifier. Unfortunately, the silk screen footprint for the BC457/557 TO-92 transistors is reversed. The correct orientation is shown in the following pictures of the left and right board area. With apologies to Ian.

Volume 7

Joachim Gerhard Guest Editorial

Joachim Gerhard's Guest Editorial in Volume 7 about his G-pole development contains several hand-drawn figures. Although the figures in itself are correct, the references to them in the text are not always correct. The correct references are as follows:

  • Fig.1 is the standard stereo setup where L' and R´ create the unwanted aditional phantom image as shown;
  • Fig. 2A is the drawing Joachim made for Rick Beveridge as mentioned in the text;
  • Fig. 2B is an improved version of Fig 2A that can solve the beaming problem;
  • Fig. 3 is a typical implementation of a G-Pole. My apologies to Joachim for this confusion.

Volume 6

Corrections to Borbely/Ruschkowski Proteus phono preamp

Unfortunately, on one page of Erno Borbely and Sigurd Ruschkowski's article on the Proteus current inpout phono preamp, a few terms have disappeared during the layout process. Here is the corrected page 112. With apologies to Erno and Sigurd.

Volume 5

Bruno Putzeys offered a demo

In Volume 5, Bruno Putzeys offered a demo preamp project as part of his article The G-word, or how to get your Audio off the Ground. In the power supply section are four 2.2 ohms resistors, R25, R26, R27 and R28, as inrush limiters. The ressitors shown in the BoM however are not themselves inrush-resistant. The correct resistor type here is VISHAY BEYSCHLAG - MMA02040C2208FB300 - RES, MELF, 2R2, 1%, 250MW, SMD.

Volume 4

Marcel van de Gevel's article

Marcel van de Gevel's article in Vol 4 'A tube-based phono preamplifier' was concluded with a sidebar, starting on page 128, under the heading 'Phono amplifier with a +1 term'. Some of the time constant notations did not make it through the layout process unscathed. Here is the corrected section, with apologies to Mr. van de Gevel - ed.

Several typos crept into Ian Hegglun's article

Several typos crept into Ian Hegglun's Vol 4 article "Towards a reconciliation of measurements with listening tests".

Some of these, notably fig 6 and fig 10, have been addressed in Ian's reply to Burkhard Vogel's letter.

The remainder are listed below:

1. page 39, Fig.5: CCIR-468 weighting filter circuit: L1 should read 12.88mH and C2 26.82nF and L2 in nH.
2. page 41 Figure 8. Filter banks for evaluating twin and triple A-weighting using the Total Difference method: change: R3 to {RL}

Also note that Ian's Power Amplifier Kalkulator spread sheet PAK 1.0-NM along with the User Guide and the LTspice circuits can be obtained by email from Ian at ianhegglun01@gmail.com

Volume 1

Ovidiu Popa's article

Ovidiu Popa's article in Vol 1, `On the Noise Peformance of Low Noise Input Stages` contains an error. On page 150, middle of the page, the sentence: "The current noise decreases with the degeneration decrease....` should read ´The current noise decreases with the degeneration increase...`

Volume 0

Joachim Gerhard Down the Rabbit Hole - Adventures in the land of Phonostages

In the article by Joachim Gerhard in Vol 0, "Down the Rabbit Hole - Adventures in the land of Phonostages", some text between pages 38 and 39 was left out through an error of mine. The missing passage, with text before and after, is available as page 38a here. With apologies to Joachim!