Abstract
Concerning electronic noise, we cannot compare the world of valves with the one of the solid-state world. Whereas the latter offers a rather narrow bandwidth of noise voltage tolerance, respectively, valves come along with a very broad tolerance noise voltage bandwidth. Sometimes the noise voltage difference between a selected low-noise type and a non-selected, “normal” one can reach up to 20 dB in the audio band. That is why the calculation of the audio band noise of a valve gain stage requires exact operating data of the chosen valve.
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Notes
- 1.
However, evolution doesn’t sleep and creativity efforts on old-time things can lead to astonishing new results: see “A new low-noise circuit approach for Pentodes”, Frank Blöhbaum, Linear Audio, Vol. 0, 2010, ISBN 9 789 490 929015.
- 2.
“Telefunken Laborbuch” (Laboratory Handbook), Vol. 3, 2nd edition 1966.
- 3.
See Footnote 2.
- 4.
It is not only 1/f-noise (or flicker noise). Quite often, we find additional noise artefacts with a 6 dB/octave slope and a separate corner frequency that can be lower than fc. I do not want to over-complicate things: that is why I will focus on 1/f-noise and its corner frequency only. The consideration of other and noise impacts lower than fc will not touch the noise calculation equations of this chapter negatively.
- 5.
Concerning 1/f-noise in Sect. 7.7 and in Chap. 17 I will give additional noise calculation hints.
- 6.
EIN = equivalent input rms noise voltage in B20k, referenced to 774.6 mVrms or 1 Vrms.
- 7.
On the home page of this web-site please search: “Rauschmessungen an Roehren”; The whole text is written in German; however, I guess the many measurement graphs are self-explanatory. Because of its – supposedly – insignificant contribution it is mentioned that excess and white-noise of the plate resistor was not taken into account. On the other hand the triode graphs show white-noise voltage density levels >10 kHz close to the calculated ones.
- 8.
“Measurement filters” see Chap. 23.
- 9.
The “c” after rN should indicate the 1/f-noise dependency and the average rN value in a given audio bandwidth.
- 10.
See also Chap. 14 of HTTG, see Appendix 6.
- 11.
Details see Chap. 17.
- 12.
“Valve Amplifier”, Morgan Jones, see Appendix 6.
- 13.
Don’t be surprised about the strange numbering of the resistances. I’ve gone through the measurement and calculation of many different gain stages and I didn’t want changing the numbering. Hence, in every case, the same resistance in the various circuits gets the same number.
- 14.
JJ Electronic, A. HLinku 4, 02201 Cadca, Slovac Republic, www.jj-electronic.com
- 15.
For noise calculations only the phase relationship of a gain stage is not important and needs not to be taken into consideration.
- 16.
Additional useful valve formulae for all triodes: \( {r_a}\,{g_m} = \mu. \)
- 17.
Idle gain for pentodes: \( {G_p} = \left| { - {g_{m.p}}\,{R_a}} \right|\,\,\,({r_{a.p}} \,> \,> {R_a}). \)
- 18.
See HTTG or the author’s “Glowing GainMaker” series, 10 short articles on triode gain-stages in EW 06-2010–03-2011.
- 19.
It makes sense to “fix” the average temperature T inside a valve pre-amp case at 315 K (see also (Chap. 17); after 30 min and in a distance of 2 cm from the valve my temp-meter always showed values like this.
- 20.
All details: see Chap. 12, Worksheet 12.12.
- 21.
- 22.
All details: see Chap. 12, Worksheet 12.12.
- 23.
See respective equations in Sect. 7.13 ff.
- 24.
More details on the different types of gain stages: see Chaps. 17 and 18.
- 25.
CF = cathode follower.
- 26.
Morgan Jones’ “Valve Amplifiers”, see Appendix 6.
- 27.
See Sect. 7.16.
- 28.
Nevertheless, Worksheet 12.12 shows the equations in dependency of a source resistance R0.
- 29.
Worksheet 12.13 gives all details of the presented equations with a dependency of a source resistance R0.
- 30.
In 2003 the third edition entered the markets.
- 31.
Worksheet 12.14 offers a double triode (E88CC) example calculation for both versions. It shows the equations with a dependency of source resistance R0 and it includes the calculation of Cc1 too.
- 32.
See Glowing GainMakers EW 02-2011.
- 33.
The new EL84T would be a very interesting candidate for a test.
- 34.
See: HTTG Chap. 4 or EW 2010-08: “Glowing GainMaker Part 3”.
- 35.
Details of the equivalent noise bandwidth concept ENB see Chap. 23.
- 36.
It will work with a very low 1/f-noise content only!
- 37.
See Worksheet 12.13 in Chap. 12.
- 38.
© stereoplay 2006-07, courtesy of Motor-Presse International Verlagsgesellschaft, Stuttgart, Germany.
- 39.
© stereoplay 2006-07, dto.
- 40.
Mr Brüggemann, SST Brüggemann GmbH, Frankfurt, Germany, got a lot of positive practical knowledge on that issue in the past when designing and building-up many German valve driven radio station studios.
- 41.
- 42.
Details see Worksheet 12.12 of Chap. 12.
- 43.
See Sect. 11.16.
- 44.
See Chap. 30 for further info on the Jensen Transformers JT-346-AXT.
- 45.
See Chap. 10 and the respective application notes from the transformer manufacturers.
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Vogel, B. (2011). Noise in Valves (US: Tubes). In: The Sound of Silence. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-19774-1_7
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