Super PAs-4

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Teknofossil58

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Super PAs-4
« on: 3 Dec 2014, 03:55 am »
Hello all. I am new to this forum. I have a rather elderly but very good condition Super PAS4. This uses the AD843 opamp as the output driver (buffer). After reading the Versa-Kit thread from 2011 and the posting of a Super PAS-3 output buffer addition (http://www.audiocircle.com/index.php?PHPSESSID=ffrc6ckej6lg39las8cag4s3a7&topic=96041.0) I am now curious as to whether there may be a better device / circuit to replace the older AD chip. Any thoughts out there? Mr Van Alstine, could you comment? -T

Lefty052347

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Re: Super PAs-4
« Reply #1 on: 4 Dec 2014, 12:52 am »
The quick answer yes we can (and have) replace the AD chip, with the LME 49600.  It's a kluge but with excellent sonic results.  (Attaching a 5 pin surface mount device into a 8 pin IC socket.)

Regards,
Dean

Teknofossil58

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Re: Super PAs-4
« Reply #2 on: 4 Dec 2014, 03:20 am »
Thank you for the response. I will look into that chip.
-T

Teknofossil58

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Re: Super PAs-4
« Reply #3 on: 14 Dec 2014, 06:04 pm »
Thank you for the response. I will look into that chip.
-T
I took a look at the LME 49600. That is an extremely fast buffer IC. I noticed that there is a bandwidth pin which, depending on the resistance value between pin1 and the -V rail, will set the upper limit of the response of the buffer. Can you offer any suggestions as to what value should be connected to this pin or should it be directly connected to -v?

Thank you!

avahifi

Re: Super PAs-4
« Reply #4 on: 14 Dec 2014, 08:18 pm »
We leave the bandwidth pin disconnected.  We did provide for the adjustment resistors in the first generation of the boards we designed for this amazing part but heard no difference with or without the extended bandwidth and thus prefer stability over enhanced bandwidth.  It is super blazing fast in any event.

Frank

Teknofossil58

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Re: Super PAs-4
« Reply #5 on: 14 Dec 2014, 08:36 pm »
Thank you for responding Mr V! I didn't expect a response from "The Man" himself. My concern about the wide bandwidth was due more to the RF interference from the community collage radio station (which is not too far from our house). At different times we have had this low wattage FM station causing interference problems. Happened more frequently some years ago but lately it is minimal or gone altogether. Perhaps some beer saturated students on the station night shift are having fun with all the brightly colored buttons.....

avahifi

Re: Super PAs-4
« Reply #6 on: 14 Dec 2014, 08:48 pm »
If you decide to replace the ICs with LME49600s, you will need to add 47uF 25V NP capacitors in series with the output resistors to eliminate DC offset.

By the way, we will do it for you for $300, parts and labor.  Musically, it is well worth the money.

Frank

Teknofossil58

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Re: Super PAs-4
« Reply #7 on: 16 Dec 2014, 04:58 pm »
If you decide to replace the ICs with LME49600s, you will need to add 47uF 25V NP capacitors in series with the output resistors to eliminate DC offset.

By the way, we will do it for you for $300, parts and labor.  Musically, it is well worth the money.

Frank
Now THAT sounds like a good deal. What typically is the turn around time after AVA receives the unit (assuming the PAS4 does not require some level of repair)?
-T

avahifi

Re: Super PAs-4
« Reply #8 on: 17 Dec 2014, 02:47 pm »
Our turnaround time right now is under 30 days.

Contact me directly at avahifi@comcast.net for more information about this upgrade or call me at 651-330-9871

Merry Christmas

Frank Van Alstine

Teknofossil58

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Re: Super PAs-4
« Reply #9 on: 18 Dec 2014, 10:53 am »
Our turnaround time right now is under 30 days.

Contact me directly at avahifi@comcast.net for more information about this upgrade or call me at 651-330-9871

Merry Christmas

Frank Van Alstine
I will be in touch soon. Thank you and have Merry Christmas!

Teknofossil58

  • Jr. Member
  • Posts: 17
Re: Super PAs-4
« Reply #10 on: 28 Dec 2014, 07:37 pm »
I have another question that recently came up about the Pas4. Was the Pas4i basically the Super Pas 3 circuit but with output buffers and a head phone amplifier (and a new PC board)?

Thanks.