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| Gariver Joined: N/A |  Message [#1] posted on: 12-12-2001 04:51 PM CST (US).   |  |  Hi ppl: You suggested the use of the AD-845 as a superior replacement for the OPA-132 and the OPA-134. So I want to try an AD-845. However, Analog Devices has two very similar AD-845 opamps in 8-DIP plastic packages (from Newark.com). One ends with "KN," and the other with "JN." I'm not sure which one to order since these two opamps are almost the same (almost twins). Which one do you suggest I buy for a CMoy amp? Thanks in advance for your help! AD-845KN = $7.84 The same applies to other Analog Devices opamps, such as: AD-744 (single) and the AD-746 (dual). Sometimes one encounters the "KN" and "JN" options at Newark.com. In this respect, I'd like to know which is best to buy. You say the AD-744 is very similar to the OPA-627! That, of course, makes the AD-744 very desirable. AD-744KN = $6.50 [Edited by Gariver on 12-13-2001 at 03:07 AM.] |
ppl  Headphone Council Joined: Jul. 28, 2000 | Message [#2] posted on: 12-12-2001 11:49 PM CST (US). | | The Difference is in the Grade and the Better grades have closer matched parameters sutch as DC offset ect. I would not use the AD-744 or AD-746 in a cmoy since it's 20 ma output current is not what i would use to drive headphones with, use a Buffer. However the AD-845 is perfect for this because of it's 50 ma output current and sound quality and performance are light years ahead of the OPA-134's |
| G HeadWizer Joined: Apr. 2, 2001 | Message [#3] posted on: 12-13-2001 01:47 AM CST (US). | | ppl is the AD845 a direct drop-in replacement for the OPA134 in the Cmoy pocket amp? G |
cmoy Administrator Joined: Apr. 13, 1999 | Message [#4] posted on: 12-13-2001 03:57 AM CST (US). | |
While the AD845 does have a better current drive spec, its power supply range is not as wide. The minimum recommended supply for the AD845 is +/-4.5V, which means that a single 9V battery will be able to power the opamp within spec only for a short time - maybe a hour or so. The OPA134 has a minimum power supply of +/-2.5V and will run for several days on a single 9V battery. [Edited by cmoy on 12-13-2001 at 08:00 AM.] |
| Gariver Administrator Joined: N/A | Message [#5] posted on: 12-13-2001 04:41 AM CST (US). | | Thanks for the fast and enlightening response! Can't go fast on this, right? |
| ppl Headphone Council Joined: Jul. 28, 2000 | Message [#6] posted on: 12-14-2001 01:12 AM CST (US). | | cmoy is right the min operating voltage of the AD-845 is not as low as the OPA-134 but the Performance and most importent the Sound quality of the AD-845 is more than worth the extra battery, and the AD-845 has a High output stage Bias current so the Current Drain is alot Higher than the OPA-134. |
| Gariver Headphone Council Joined: N/A | Message [#7] posted on: 12-14-2001 09:15 AM CST (US). | | The question is: Is the AD-845 the best choice from Analog Devices for a portable amp? Maybe there's another AD opamp that is more efficient and doesn't eat-up batteries so fast. Another question: How long will an 8 AA battery-pack last with an AD-845 portable amp? If you can, give me an estimate here to get a general idea. I realize this is not an easy question. So I don't expect a precise answer. TIA for the effort! |
aos HeadWizer Joined: Jun. 15, 2008 | Message [#8] posted on: 12-14-2001 09:51 AM CST (US). | | AA batteries of NiMH type can be had with 1600mAh rating. If, say, your amp draws 16mA, it would last roughly 100 hours. These are all raw estimates but they give you a ballpark figure. Find how much AD845 needs from its datasheet. When working it will need more than that of course, as much as your headphone needs. I'd think 8AA batteries can power portable amp for quite a while, but then they're bulky and heavy and costly if not rechargeable so it's only logical they'd last longer. |
| ck42 HeadWizer Joined: Oct. 28, 2001 | Message [#9] posted on: 12-14-2001 10:40 AM CST (US). | | Ya'll have got me thinking again. My first amp looks like it's gonna turn out to be a 'stay at home' version. Since I'm not concerned about batteries, what would be the best opamp to use PERIOD (drop-in replacement for OPA134)? |
| Gariver HeadWizer Joined: N/A | Message [#10] posted on: 12-14-2001 11:28 AM CST (US). | | Thanks, aos! You made it easy for me to calculate battery power requirements. FWIW, I've been looking at the new NiMH batteries over at the Thomas Distributing site. The GP AA rechargeables pack lots of power. Price? It's $14.97 for 4 AAs with 1800mAH power! Wow! Very interesting! I also liked the 9v NiMH rechargeable Plainviews. Take a look... cr42: [Edited by Gariver on 12-14-2001 at 03:44 PM.] |
| ck42 HeadWizer Joined: Oct. 28, 2001 | Message [#11] posted on: 12-14-2001 06:07 PM CST (US). | | Gariver: Actually, I went to the AD site to look at the AD845 and then clicked on Purchase only to find a list of 11 different versions of the 845. Anyone know which one would be best? |
| G HeadWizer Joined: Apr. 2, 2001 | Message [#12] posted on: 12-14-2001 08:18 PM CST (US). | | Try this link for Analog Devices chips. G [Edited by G on 12-15-2001 at 08:06 PM.] |
| aos HeadWizer Joined: Jun. 15, 2008 | Message [#13] posted on: 12-14-2001 10:03 PM CST (US). | | AD845JN or AD845KN is what you want (DIP). K is higher grade but that likely doesn't matter. |
| Gariver HeadWizer Joined: N/A | Message [#14] posted on: 12-14-2001 10:35 PM CST (US). | | ck42: These Analog Devices opamps are from Newark.com! Both the AD-845KN (high grade) and the AD-845JN (lower grade) come in 8-DIP. You don't want the others at all. The absolute best? It's the AD-845KN, and it's the only one in stock at the moment! So get a pair if you really want to give 'em a try. Here's Newark's prices... Search without the hyphen (AD845)... [Edited by Gariver on 12-16-2001 at 07:16 PM.] |
| ppl Headphone Council Joined: Jul. 28, 2000 | Message [#15] posted on: 12-15-2001 12:31 AM CST (US). | | Ya'll have got me thinking again. My first amp looks like it's gonna turn out to be a 'stay at home' version. Since I'm not concerned about batteries, what would be the best opamp to use PERIOD (drop-in replacement for OPA134)? -------------------------------------------------------------------------------------------------------------------------------------------- Ck. if the Best op amp PERIOD as a drop in replacement for the OPA-134 for an AC operated Amp that is using at least +15 & -15 volt rails then I would sugest the AD-843. The Best Opamp i have heared but IT IS NOT FOR A BATTERY POWARD AMP, because of the High 13 Ma Icq. and you dont want to operate this Opamp anywhere the Clipping point or it will Misbehave because of Phase reversal. but when operating on +/-15 to 18 volt rails and a small heatsink is used Those Glue on ones for Dips. then the 36 MHZ unity gain stable bandwidth and 250Volt per uSec Slew rate combined with 140 Ma. Output Current gives Both Performance and sound quality that is Great for an fet input Opamp. [Edited by ppl on 12-15-2001 at 04:33 AM.] |
| ck42 HeadWizer Joined: Oct. 28, 2001 | Message [#16] posted on: 12-15-2001 05:18 AM CST (US). | | oh boy....845KN or 8443......845KN or 843..... Glad I hadn't already bought the 12V power supply I was planning on...sounds like I'm gonna need to go with 15V-18V now regardless. Anybody else want to throw their 2cents on which of these two opamps? |
| Gariver HeadWizer Joined: N/A | Message [#17] posted on: 12-15-2001 08:05 AM CST (US). | | Not me! I don't know that much. So when ppl gives his opinion on opamps, you better listen. He is our Opamp Master in Residence here, and he's tried them all (ie: lots of experience). |
| ck42 HeadWizer Joined: Oct. 28, 2001 | Message [#18] posted on: 12-15-2001 09:52 AM CST (US). | | Well...while looking for sources for the AD843, I ran across THIS site. VERY interesting. Tempted to just order the pcb and build one up myself. Would LOVE to hear comments on the actual amp design. Anyone know of anywhere besides Newark(93 day B-O'd) that has the AD843 in stock? |
| Gariver HeadWizer Joined: N/A | Message [#19] posted on: 12-15-2001 10:19 AM CST (US). | | Congratulations ck42! You just found a new headphone amp kit! The price of the kit is very reasonable, and I bet it sounds terrific with those AD-843s. I wonder what ppl has to say about this kit? AD-843 and EL-2009... Sourcing the AD-843... |
| Gariver HeadWizer Joined: N/A | Message [#20] posted on: 12-16-2001 11:56 AM CST (US). | | Allied Electronics carries and sells Analog Devices opamps! Here's some examples with Allied part numbers, the number in stock, and price of the opamp... AD845KN (630-2045 with 1,118 in stock): $7.90 Question on the pins of the AD845KN and AD843KN... [Edited by Gariver on 12-16-2001 at 04:10 PM.] |
| ck42 HeadWizer Joined: Oct. 28, 2001 | Message [#21] posted on: 12-16-2001 03:21 PM CST (US). | | ...so, before I order, can I get confirmation that the AD843 *is* a drop in replacement? BTW, Gariver, thanks a bunch for the AD843 source! |
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