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Old 29th April 2012, 01:26 AM   #1
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Hello Everyone,

I'm building an RH84 single ended amp for some friends. This couple are the epitome of tech savvy yuppies. (Tech savvy as in computers and 'mobile devices' as they call them.) So, how do I let them use an IPOD to drive the amp without having it sound like crap? I found a J-fet preamp that seems pretty simple. But If I can stay with old technology I'd rather. That is, is there tube technology that could deal with this wheezy input? A matching transformer would be the simplest way?

Last edited by mr2racer; 29th April 2012 at 01:30 AM.
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Old 29th April 2012, 01:55 AM   #2
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Assuming the "pod" does not produce enough volts to drive the RH84 to full power O/P, a simple common cathode gain stage DC coupled to a cathode follower should do the job. A couple of 14N7s (same triode as in 6SN7) would be fine. Not bypassing the gain triode's cathode bias resistor, along with a healthy resistive load should be highly linear, without yielding too much gain.

10M45S CCS load the CF. Don't forget a relatively modest B- rail for the CCSes.
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Old 29th April 2012, 02:25 AM   #3
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Use an iPod dock or cable to the dock connector to get the line out instead of using the headphone output. External DAC would be better yet, but that will be difficult to do with thermionic devices...
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Old 29th April 2012, 04:25 AM   #4
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Anyone had any experience with one of these?

http://www.edcorusa.com/p/89/ttpc600-10k

Last edited by mr2racer; 29th April 2012 at 04:32 AM.
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Old 29th April 2012, 04:50 AM   #5
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Quote:
Originally Posted by mr2racer View Post
So, how do I let them use an IPOD to drive the amp without having it sound like crap?
I have done exactly that. Heasphone out to RH84 sounds fine. Get a dock (i got an Apple) to get line out, gets a bit better.

The key thou is to ensure that the iPod has lossless files on it. Nothing is gonna fix an MP3.

dave
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Old 29th April 2012, 12:52 PM   #6
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Right Dave,

If these guys are willing to listen to MP3 then I let it be their problem. I'll put the RCA jacks on the front and let them figure out the rest. by the way, for all their money and sophistication they are still listening to a pair of Advent Prodigy bookshelf's placed on the floor. I found a pair of Advent Prodigy towers that I replaced the woofers in for them. Loud for them is 88db. 91db is rockin' the house.
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