Tape Project Forum
Tape Machines => Tape Tech => Topic started by: jorsan on October 06, 2008, 07:33:10 PM
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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.
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nobody?
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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.
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would you elaborate pease? Im VERY interested. thanks
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I'll publish the circuit after I come back from RMAF. It will be valid for every R2R set for an NAB EQ.
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Highly interested Tubes n tapes. Will be waiting your return and your post.
Thanks
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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.
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Please post the link when the article is ready. Thanks
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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.
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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!
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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.
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Perfect so now I need someone who could build this in a nice box and Im ready.
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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
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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.
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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
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Someone could post a place in internet where I can buy all the stuff that is needed to build this unit? thanks
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You will have to shop around for everything , but a good spot to start is here
http://www.partsconnexion.com/partscomponents.php
http://www.percyaudio.com/
I pick them for good service rather than the lowest cost...
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Great suggestions Ben. Unless you need a lots of parts in which case Digikey or Mouser will save you a little cash. Percy and Parts Connection are limited to less common brands and the more esoteric parts so if you just need any old generic box or switch, you'll have a better selection with the big guys.
I always try and give Michael Percy and Parts Connection business when I can though. Both of their shipping is insanely fast (when I get something from either of them I'm usually shocked that it's arrived already). I can send a personal check to them and have the parts in my hand about a week quicker than using the instant payment from PayPal with most other guys.
http://www.digikey.com/?WT.term=digikey&WT.campaign=1448&WT.content=text&WT.medium=cpc&WT.source=google&cshift_ck=1057840886cs506115095&WT.srch=1
http://www.mouserelectronics.com/
BTW For some temporary stuff (like little project boxes or little boards for proto work) don't forget your local Radio Shack. Some of this stuff is so cheap that you can toss it (into the proper recycling bin of course) when you're done with little or no guilt.
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Thanks for your help and happy weekend.