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Loudness stage
Loudness stage
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Old 20th October 2020, 02:27 AM   #61
jfetter is offline jfetter  Costa Rica
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Loudness stage
I came across the Dual and Braun while looking for Dieter Rams designs. I think the packaging is excellent and if the outside is nice then following form/function the circuits must have sounded heavenly.. Simple and functional no more no less.
So I study the early designs. Braun, Dual , Telefunken, Philips and so on. I'll have to look at Grundig. Many companies attempted to copy Dieter Rams but it usually did look like a style copy, not quite correct. The early Sansui circuits are also interesting but not packaging. Some circuits I have adapted to valve-opamp hybrids. It is not difficult and the fft is exactly what I want.

The images are from BRAUN, BRAUN Hifi, Braun design, Thomas-Mathias Bock, Dieter Rams,Computer Graphic,
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Old 20th October 2020, 05:19 AM   #62
ubergeeknz is offline ubergeeknz  New Zealand
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Does anyone have a circuit to make use of a tapped volume control? I have an ALPS RK27 type (probably a clone) stepped attenuator with a loudness tap, I wouldn't mind trying a passive loudness circuit on it, so that it is active at lower positions only. Thanks in advance!
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Old 20th October 2020, 01:04 PM   #63
jfetter is offline jfetter  Costa Rica
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Loudness stage
Quote:
Originally Posted by nironiro View Post
This is 5 pin volume pot in Grundig SV 2000 amplifier.
Many Grundig models use that double loudness.
To copy/test the Dual loudness ckt a stepped attenuator can easily be made to operate as a 5 terminal volume control i'm thinking.

for ref here is sv2000 passive loudness volume ckt using Sziklai pair make-up amp. Its not switched so maybe less parts.
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Last edited by jfetter; 20th October 2020 at 01:28 PM. Reason: sch
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Old 20th October 2020, 01:12 PM   #64
nironiro is offline nironiro  Croatia
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Stepped attenuator must be simple to made for that, if resistors are easy accessible.
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Old 27th October 2020, 05:29 AM   #65
ubergeeknz is offline ubergeeknz  New Zealand
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OK so in my case the tap seems to have a resistance from the input pin as follows:

1-10 : 47.5k
11-22 : reduces by ~4k each step, ending in 5.8k at position 22 (it's a bit more gradual to start, then reasonably linear until it reaches step 22)

Question is, how do I use this tap to create a loudness control? I feel like I'm missing something obvious. This is a 50k log taper attenuator.

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Old 28th October 2020, 03:23 AM   #66
jfetter is offline jfetter  Costa Rica
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Loudness stage
my first try would be to use the grundig circuit on knee of your plot.
while the mirror knee gets the treble side.
if you do a plot from hi side of pot to wiper u see the mirror knee.
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Old 28th October 2020, 05:35 AM   #67
ubergeeknz is offline ubergeeknz  New Zealand
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Hmm @jfetter not sure that will work. As it is a volume attenuator with only one "tap", input, gnd, and wiper. And the main input/gnd/wiper is log/audio taper.
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Old 28th October 2020, 06:40 AM   #68
jfetter is offline jfetter  Costa Rica
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Loudness stage
its a bank of resistors, so move the switch to knee position and look at switch contacts.
that point is the loud tap.
of course a wire must be soldered and brought out for the loudness ckt.
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Old 28th October 2020, 08:40 AM   #69
Jonathan Bright is offline Jonathan Bright  Australia
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Dear all,
This will be a bit frustrating for many people but if you have access to the JAES or are prepared to buy this article the following would seem to be a very neat solution for most needs. Its from 1976. It has variable break points for the bass region. Elegant, simple, cheap and highly effective.
Cheers, Jonathan

AES E-Library >> Practical Loudness: An Active Circuit Design Approach

AES E-Library
Practical Loudness: An Active Circuit Design Approach
Document Thumbnail
"A loudness control fully compensated at mid and low frequencies has been designed for home use which can be aligned to match equal-loudness contours over about a 40-dB attenuation range. Using a linear potentiometer and an operational amplifier, the circuit can provide a smooth audio taper as well as a control of volume which is free of tonal balance coloration".

Authors: Newcomb, Jr., Arthur L.; Young, Richard N.
Affiliation: Langley Research Center, National Aeronautic and Space Administration, Hampton, VA
JAES Volume 24 Issue 1 pp. 32-35; February 1976
Publication Date: February 1, 1976 Import into BibTeX
Permalink: AES E-Library Practical Loudness: An Active Circuit Design Approach

Click to purchase paper as a non-member or login as an AES member. If your company or school subscribes to the E-Library then switch to the institutional version. If you are not an AES member and would like to subscribe to the E-Library then Join the AES!

This paper costs $33 for non-members and is free for AES members and E-Library subscribers.
Learn more about the AES E-Library
E-Library Location: (CD aes3) /jrnl6877/1976/7389.pdf
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Last edited by Jonathan Bright; 28th October 2020 at 08:43 AM.
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Old 28th October 2020, 10:10 AM   #70
ubergeeknz is offline ubergeeknz  New Zealand
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Figured it out now ... the amplifier is attached and it presents a low impedance relative to the 50k pot... hence it's throwing my measurements out. Of course it is just a center tap (at about 47.5k/2.5k). Which I can make sense of
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