From the experiments I've done many of the differences in sound from attenuators comes from the parasitics. Not all, but many.
I took a Jensen JT-MB-CPCA input transformer, connected a pot to the secondary, placed a R in parallel to the pot to get the correct R loading on the xfmr, set the wiper to max clockwise and listened.
I then started to strip parts off the pots, as many parts as I could and still get the pot to work. The more parts missing the better the pot sounded. I did this with Bourns 51, 91, Alps, Panasonic. I then used a stepped att with a Greyhill switch. The switch beat all pot comers.
The circuit is a mic pre.
I then repeated the above using a Braumer Phanther mic and SM57 for the input signal. The same results could be heard.
The Jensen was used specifically because any changes in parasitic loading would be heard. They are touchy as to what is on the secondary. I didn't pay attention to what the signal looked like on a scope as parts were removed. I didn't want to and much of the listening tests were done in studio. I don't have a AP system 2 so I use other methods...
John
I spoke to Bourns at AES in October 08. They still haven't done much to improve tracking of their multi ganged pots. According to Bourns, the way they make pots they don't care or pay any attention to tracking. They make individual sections, the sections all "go in a box" and then the sections are pulled and assembled to make a multi-channel pot. No matching is done.
And in talking to THAT Corp at the show, they commented that one of the reasons their new VCA was done was because of this very issue.
These comments are not made to discount or dis-credit any of the previous posts. Only to say that IMO, there is much more to the attenuator issue than just what material is used or how that material is applied to a substrate.
I took a Jensen JT-MB-CPCA input transformer, connected a pot to the secondary, placed a R in parallel to the pot to get the correct R loading on the xfmr, set the wiper to max clockwise and listened.
I then started to strip parts off the pots, as many parts as I could and still get the pot to work. The more parts missing the better the pot sounded. I did this with Bourns 51, 91, Alps, Panasonic. I then used a stepped att with a Greyhill switch. The switch beat all pot comers.
The circuit is a mic pre.
I then repeated the above using a Braumer Phanther mic and SM57 for the input signal. The same results could be heard.
The Jensen was used specifically because any changes in parasitic loading would be heard. They are touchy as to what is on the secondary. I didn't pay attention to what the signal looked like on a scope as parts were removed. I didn't want to and much of the listening tests were done in studio. I don't have a AP system 2 so I use other methods...
John
I spoke to Bourns at AES in October 08. They still haven't done much to improve tracking of their multi ganged pots. According to Bourns, the way they make pots they don't care or pay any attention to tracking. They make individual sections, the sections all "go in a box" and then the sections are pulled and assembled to make a multi-channel pot. No matching is done.
And in talking to THAT Corp at the show, they commented that one of the reasons their new VCA was done was because of this very issue.
These comments are not made to discount or dis-credit any of the previous posts. Only to say that IMO, there is much more to the attenuator issue than just what material is used or how that material is applied to a substrate.
Pavel -- The Caddocks which Sigurd mentioned are wonderful but expensive. I would have needed a bank loan to buy 64 of them for my power amps. The Vishay/Dale LVR series are very good and what I am using now. A little over $1 from Mouser. Up to 5 watts they are metal strip as opposed to metal foil and non-magnetic. The terminals are copper. But they are limited in resistance range from 0.005 to 0.25 ohm.
Many years ago we used to submerge the high voltage divider strings for mass spectrometers in a 55 gal barrel of oil and keep them at constant temp.
Many years ago we used to submerge the high voltage divider strings for mass spectrometers in a 55 gal barrel of oil and keep them at constant temp.
1audio said:
The graph shows -70dB for a 10Meg resistor if at .1W this is 1000V so yes normalized to power density such a graph makes sense. If I biased a FET input preamp with a 10Meg input resistor my performance is not limited to -70dB (.03%) at the low frequency pole.
Funny thing speaking of capacitors and the CLT-1 I found this:
"Levels of the 3rd harmonic to carrier ratios for some types of ceramic and micaceous capacitors
measured with CLT 1 apparatus by Radiometer Copenhagen Company are compared. At working
voltage 30V are the U3/U1 ratio for USSR capacitor K15 U- 2200 pF/3 kV –160 dB, for Tesla mica
capacitor WK 702 17 3300 pF/4 kV –150 dB, for Tesla ceramic capacitor NPO TK755 750 pF/250 V–
130 dB. The 3rd harmonic level was below the apparatus sensitivity threshold for the vacuum capacitor
KP 1-8 100 pF/5kV and air capacitor R-920 20 pF, both of USSR production. The 3rd harmonic to
carrier ratio for all voltages (up to 200 V) was better than 160 dB."
Apparently the capacitors are mostly off the scale in linearity.
Yes, I am familiar with that winding technique - they are pretty much the only kind of resistors I use. The only reason I can think of that would explain how a non-inductive (or "normal") wirewound resistor would have less inductance in a larger value is that there is a change in the composition and/or gauge of the wire used.
John
Classic Records remasters most of the RCA classical recordings you are probably interested in. SpeakersCorner makes a specialty of remastering Decca SXLs, which are generally better recorded than RCA Living Stereo. They also do Philips High-Fi Stereo re-issues. I don't listen to John Denver and have never heard of Esquivel, although Elvis can be fun from time-to-time.
John
Scott is putting forth DA as a form of non-linear distortion, BUT it is really a form of LINEAR distortion, (as he knows full well, because he helped us measure it, initially, over 25 years ago). Linear distortion is also a major component in what is wrong with resistors, due to their thermal capacitance and tempco. Work it out on a calculator, if you don't believe me.
I should go further on this topic. DA is usually measured between .001% and 10% . Mica might measure .05% for example. DA is not COMPLETELY linear, but it is modeled that way for easy understanding. Therefore, the same mechanism that makes DA can make SOME non-linear distortion, BUT that is not what we usually measure or care too much about, because it is at such a low level. For example, .001% or -100dB 3rd harmonic distortion should NOT be detected in virtually any audio situation that I can think of.
However, DA of .05% (-86db) seems to be audible in many situations.
However, DA of .05% (-86db) seems to be audible in many situations.
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