Subject: attenuator - response summary From: =?ISO-8859-2?Q?Pawe=B3_Ku=B6mierek?= <pawel.kusmierek@xxxxxxxx> Date: Sun, 20 Nov 2011 20:26:51 -0500 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>--0015175cbae6a3a13204b23496cf Content-Type: text/plain; charset=ISO-8859-1 Hello everyone, thanks to everyone who replied to my question about attenuators. Some responses were off-list, and some were "off-off-list" (I asked elsewhere), so here is the summary. To remind you, I was looking for a "commercially available precise digitally controlled (i.e., repeatable) attenuator with fast and quiet attenuation changing. Preferably, but not necessarily controlled via RS232." The RS232 was suggested because I want it to be controlled from CED Spike2/Power1401 system or from NBS Presentation, or from similar systems, and RS232 looked like a sensible (although pretty old) solution. Basically there were two suggestions. 1. TDT PA2 advantages: - wide attenuation range of ~120 dB (0 to - 120dB), - small gain step (0.1 dB), - high accuracy (0.05 dB), - good noise/distortion figures - manual control possible - attenuation value is displayed - ready to use disadvantages: - price: $725 for a single channel device, but additional control/power/PCI cards, etc. hardware and software are needed, which drives the price of a single-channel attenuator to ~$2,500. I think that the second channel can be added for additional $725 only, but still it is not cheap - control: via an AciveX control, I am not exactly sure if (and how) I could do this from CED or NBS systems. A person suggested TDT RX5 and I was not able to find what it is. However, RX6 and RX7 appear to be powerful DSP devices, so RX5 is probably too much capability-wise and price-wise than I need. Please correct me if I am wrong here. 2. A "digital potentiometer" chip. Specific models suggested were Dallas Semiconductors DS1801, Cirrus CS3310 (or 3308 for 8 channels) and Texas Instruments PGA2320. advantages: - low price - the chip itself is in $5-$20 range, for a 2-channel device - wide attenuation range ~127 dB for the CS and PGA (~63 dB for the DS) - pretty small gain step/accuracy (CS: 0.5/0.05 dB, PGA 0.5/0.1 dB, DS 1/not sure) - good noise/distortion figures - control via three serial TTL lines (more may be needed if certain features cannot be set to enabled or disabled permanently) - this could be achieved from NBS Presentation via LPT printer port or NI I/O board, and from CED Spike2 via the 1401 interface - zero-crossing mode - the chips may be set to attempt to change atttenuation on analog zero-crossing to reduce artifacts disadvantages: - a device has to be built around the chip - power supply (PGA: +5V, +15V, -15V, CS: +/- 5V, DS: +3 or + 5V), connectors, possibly buffers. This will increase the total price, but definitely it will be still well below TDT PA5 price, even with labor factored in. - for CS and PGA the 127-dB attenuation range is NOT 0 to -127dB, it is +31.5dB to - 95.5dB, which may have clipping implications - no manual control and no way to read back the set value (unless special steps are taken) One person warned me that "digtal audio attenuators" typically do not have 1 dB steps, but fine steps at high levels and coarser steps at lowe levels. However, the chips that were suggested to me have 0.5 or 1 dB steps over their attenuation range. He also proposed using and old SoundBlaster SB16 or AWE32 as an attenuator. These cards need a computer with ISA bus, which are not available for me (and frankly, I doubt there are many operational machines from these days around). Thanks again to everyone for your suggestions, Pawel ** * * --0015175cbae6a3a13204b23496cf Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable <div>Hello everyone,</div><div>=A0</div><div>thanks to everyone who replied= to my question about attenuators.</div><div>=A0</div><div>Some responses w= ere off-list, and some were "off-off-list" (I asked elsewhere), s= o here is the summary.</div> <div>=A0</div><div>To remind you, I was looking for a "commercially av= ailable precise digitally controlled=A0(i.e., repeatable) attenuator with f= ast and quiet attenuation changing. Preferably, but not necessarily control= led via RS232."</div> <div>The RS232 was suggested because I want it to be controlled from CED Sp= ike2/Power1401 system or from NBS Presentation, or from similar systems, an= d RS232 looked like a sensible (although pretty old) solution.</div><div> =A0</div><div>Basically there were two suggestions.</div><div>=A0</div><div= >1. TDT PA2</div><div>=A0</div><div>advantages:</div><div>- wide attenuatio= n range of ~120 dB (0 to - 120dB), </div><div>- small gain step (0.1 dB), <= /div> <div>- high accuracy (0.05 dB),</div><div>- good noise/distortion figures</= div><div>- manual control possible</div><div>- attenuation value is display= ed</div><div>- ready to use</div><div>=A0</div><div>disadvantages:=A0</div> <div>- price: $725 for a single channel device, but additional control/powe= r/PCI cards, etc. hardware and software=A0are needed, which drives the pric= e of a single-channel attenuator to ~$2,500. I think that the second channe= l can be added for additional $725 only, but still it is not cheap</div> <div>- control: via an AciveX control, I am not exactly sure if (and how) I= could do this from CED or NBS systems.</div><div>=A0</div><div>A person su= ggested TDT RX5 and I was not able to find what it is. However, RX6 and RX7= appear to be powerful DSP devices, so RX5 is probably too much capability-= wise and price-wise than I need. Please correct me if I am wrong here.</div= > <p>=A0<br>2. A "digital potentiometer" chip. Specific models sugg= ested were Dallas Semiconductors DS1801, Cirrus=A0CS3310 (or 3308 for 8 cha= nnels) and Texas Instruments PGA2320. </p><div>advantages:</div><div>- low = price - the chip itself is in $5-$20 range, for a 2-channel device</div> <div>- wide attenuation range ~127 dB for the CS and PGA (~63 dB for the DS= )</div><div>- pretty small gain step/accuracy (CS: 0.5/0.05 dB, PGA 0.5/0.1= dB, DS 1/not sure)</div><div>- good noise/distortion figures</div><div> - control via three serial TTL lines (more may be needed if certain feature= s cannot be set to enabled or disabled permanently) - this could be achieve= d from NBS Presentation via LPT printer port or NI I/O board, and from CED = Spike2 via the 1401 interface</div> <div>- zero-crossing mode - the chips may be set to attempt to change attte= nuation on analog zero-crossing to reduce artifacts</div><div>=A0</div><div= >disadvantages:</div><div>- a device has to be built around the chip - powe= r supply (PGA: +5V, +15V, -15V, CS: +/- 5V, DS: +3 or + 5V), connectors, po= ssibly buffers. This will increase the total price, but definitely it will = be still well below TDT PA5 price, even with labor factored in.<br> - for CS and PGA the 127-dB attenuation range is NOT 0 to -127dB, it is +31= .5dB to - 95.5dB, which may have clipping implications=A0</div><div>- no ma= nual control and no way to read back the set value (unless special steps ar= e taken)</div> <div>=A0</div><div>One person warned me that "digtal audio attenuators= " typically do not have 1 dB steps, but fine steps at high levels and = coarser steps at lowe levels. However,=A0the chips that were suggested to m= e have 0.5 or 1 dB steps over their attenuation range.</div> <div>He also proposed using and old SoundBlaster SB16 or AWE32 as an attenu= ator. These cards need a computer with ISA bus, which are not available for= me (and frankly, I doubt there are many operational machines from these da= ys around).</div> <div>=A0</div><div>=A0</div><div>Thanks again to=A0everyone for your sugges= tions,</div><div>=A0</div><div>Pawel<br>=A0<br>=A0<br>=A0<b><font size=3D"5= " face=3D"Arial"><font size=3D"5" face=3D"Arial"></font></font></b></div><b= ><font size=3D"5" face=3D"Arial"><font size=3D"5" face=3D"Arial"><div> =A0</div></font></font></b><font size=3D"5" face=3D"Arial"><font size=3D"5"= face=3D"Arial"></font></font> --0015175cbae6a3a13204b23496cf--