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Author Topic: eq options .... external device?  (Read 14536 times)

Offline jorsan

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eq options .... external device?
« on: October 06, 2008, 07:33:10 PM »
Hi,
I have a Tandberg 20A SE with the standard american eq. Honestly I dont want to tuch this unit internally so, is there an external device in the market that could let me choose between the two eq.? Thxs in advance.
« Last Edit: October 07, 2008, 05:27:43 AM by jorsan »

Offline jorsan

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Re: eq options .... external device?
« Reply #1 on: October 09, 2008, 04:13:20 AM »
nobody?

Offline Tubes n tapes

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Re: eq options .... external device?
« Reply #2 on: October 09, 2008, 08:49:54 AM »
Jorsan,

I don't think there is an existing device available, but a simple circuit consisting of 6 components that you can put in series with your output interlinks will do the trick, if you are interested.
Arian Jansen.

SonoruS Audio.
VP of technology of the Los Angeles and Orange County Audio Society (LAOCAS).
ESL/OTL builder and modest Studer/ReVox collector.

Offline jorsan

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Re: eq options .... external device?
« Reply #3 on: October 09, 2008, 07:37:24 PM »
would you elaborate pease? Im VERY interested. thanks

Offline Tubes n tapes

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Re: eq options .... external device?
« Reply #4 on: October 09, 2008, 11:22:09 PM »
I'll publish the circuit after I come back from RMAF. It will be valid for every R2R set for an NAB EQ.
Arian Jansen.

SonoruS Audio.
VP of technology of the Los Angeles and Orange County Audio Society (LAOCAS).
ESL/OTL builder and modest Studer/ReVox collector.

Offline jorsan

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Re: eq options .... external device?
« Reply #5 on: October 15, 2008, 09:03:15 AM »
Highly interested Tubes n tapes.  Will be waiting your return and your post.
Thanks

Offline Tubes n tapes

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Re: eq options .... external device?
« Reply #6 on: October 17, 2008, 05:32:56 PM »
Jorsan,

I'm just back from RMAF and another trip right after. I will write a short article on this circuit and publish it on the website of the LA and OC audio society. The article is in the planning for this weekend, so it should be live on the web by next week.
Arian Jansen.

SonoruS Audio.
VP of technology of the Los Angeles and Orange County Audio Society (LAOCAS).
ESL/OTL builder and modest Studer/ReVox collector.

Offline jorsan

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Re: eq options .... external device?
« Reply #7 on: October 19, 2008, 10:02:52 AM »
Please post the link when the article is ready. Thanks

Offline jorsan

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Re: eq options .... external device?
« Reply #8 on: October 21, 2008, 08:03:51 PM »
Great, the article is out:

http://laocaudiosociety.net/tech/NABtoIEC.pdf

The problem for me now is that my knowledge in this area is close to cero (ok,ok, ... cero...) so will be great if someone could build and put this circuit in a box for a fair price, I think several of us will buy it. My deck has only RCA's (tandberg 20A SE) and looks like the best option is the -10db (flattest response) so for me this will be the option, if Arian do not say the opposite of course.

Offline ironbut

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Re: eq options .... external device?
« Reply #9 on: October 21, 2008, 09:12:31 PM »
Another award winning (or should be) write up on that adapter Arian! Man, you put my clunky efforts to shame. Many thanks for your work and for sharing you knowledge. You're tops in my book!
steve koto
 Sony scd 777es(R. Kern mods)> Vpi Aires>Dynavector XX-2mkll>Bent mu>CAT ultimate>CJ premeir 140>Magnepan 1.6qr(Jensen xover)Headphone Eddie Current Zana Deux>AT ad2000,HD800 ,Metric Halo ULN-2 (battery powered),
 HE Audio Jades

Offline Tubes n tapes

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Re: eq options .... external device?
« Reply #10 on: October 21, 2008, 11:20:41 PM »
Steve, Thanks for your encouraging comments.

Jorsan, You can use the -10dB circuit for RCA as well as. You just need to turn your volume up a bit more.
Arian Jansen.

SonoruS Audio.
VP of technology of the Los Angeles and Orange County Audio Society (LAOCAS).
ESL/OTL builder and modest Studer/ReVox collector.

Offline jorsan

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Re: eq options .... external device?
« Reply #11 on: October 22, 2008, 06:10:42 AM »
  Perfect so now I need someone who could build this in a nice box and Im ready.

Offline Kenkirk

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Re: eq options .... external device?
« Reply #12 on: October 22, 2008, 10:39:46 AM »
Excellent write up!  And I think you are the one who could figure out how to make another passive circuit that would roll in the IEC curve and an inverse RIAA curve to feed a tape head directly into a nice phono stage! Can it be done???

Thanks,

Ken
Ken Kirkpatrick
Cat Ultimate preamp, Basis Debut Vacuum, Basis Vector tonearm, Urishi,Walker motor drive, Cat JL-1 amps, Sony XA9000Es SACD, Wadia 860,Yamaha CT 7000, Nak Dragon, RX 505, 2 REL Stentor II's, Sonus Faber Amati's, Cardas Golden Cross and Siltec cables, Otari MX 5050 B III, Teac X2000R

Offline Tubes n tapes

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Re: eq options .... external device?
« Reply #13 on: October 22, 2008, 02:01:54 PM »
Ken,

There is a little bit of good news and a lot of bad news. The good news is: Yes it can be done.

The bad news is: It won't be practical. IEC has one corner frequency of 4500Hz, while RIAA has three corner frequencies 50Hz, 500Hz and 2122Hz. That means that you have to do four different compensations to make it flat. To do a reasonable compensation for the 50Hz corner you will lose 10dB (similar to the NAB to IEC converter), however to compensate for the flat area between 500Hz and 2122Hz, you will lose another 13dB. So, the total loss of the passive converter circuit would be at least 23dB.

A second,  even more important problem is that the exact frequency characteristic of a repro head is not universal. It differs quite a bit between manufacturers. The R2R manufacturer needs to compensate for the head specific deviations in their repro electronics and melt in the EQ at the same time. So if I would design a RIAA to IEC converter circuit for a Revox head, it would not work correctly with your Otari and it would again be different for your Teac.
Arian Jansen.

SonoruS Audio.
VP of technology of the Los Angeles and Orange County Audio Society (LAOCAS).
ESL/OTL builder and modest Studer/ReVox collector.

Offline Kenkirk

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Re: eq options .... external device?
« Reply #14 on: October 23, 2008, 01:28:30 PM »
Thank you Arian for the information. I figured it would get messy, and all of those parts would start to mess with the overall sound as well. I am not so concerned with the 23db loss as I was going to use my Cat Ultimate phono stage which is a M/C phono stage and will need padded down anyway to compensate for the higher output of a tape head. But it sounds like it would turn into a trial and error project with the time better spent just building a Seduction or something else.
Thanks again!

Ken
Ken Kirkpatrick
Cat Ultimate preamp, Basis Debut Vacuum, Basis Vector tonearm, Urishi,Walker motor drive, Cat JL-1 amps, Sony XA9000Es SACD, Wadia 860,Yamaha CT 7000, Nak Dragon, RX 505, 2 REL Stentor II's, Sonus Faber Amati's, Cardas Golden Cross and Siltec cables, Otari MX 5050 B III, Teac X2000R