mojo@kepler.UUCP (Morris Jones) (10/07/85)
I'd like to be able to play my CD through my friend's Onkyo receiver/amp.
Problem is the receiver has no other inputs besides the phono preamp
inputs. (Grrrrr.)
I figure I can either cannibalize the receiver and look for a line level
input to bring out to the case, or I can pad the output from the CD
down to phono preamp input level. I realize this is a bit of a crock,
but it'll be nice for her to be able to record some CDs, and to listen
to some of my favorites at her house.
Could one of you with spare time and access to the standards for stereo
input levels give me values for an H-pad or L-pad that would drop the
level and match the impedances?
--
Mojo
... Morris Jones, MicroPro Product Development
{ptsfa,hplabs,glacier,lll-crg}!well!micropro!kepler!mojordp@teddy.UUCP (10/08/85)
In article <281@kepler.UUCP> mojo@kepler.UUCP (Morris Jones) writes: >I'd like to be able to play my CD through my friend's Onkyo receiver/amp. >Problem is the receiver has no other inputs besides the phono preamp >inputs. (Grrrrr.) > >I figure I can either cannibalize the receiver and look for a line level >input to bring out to the case, or I can pad the output from the CD >down to phono preamp input level. I realize this is a bit of a crock, >but it'll be nice for her to be able to record some CDs, and to listen >to some of my favorites at her house. > >Could one of you with spare time and access to the standards for stereo >input levels give me values for an H-pad or L-pad that would drop the >level and match the impedances? > >-- Dropping the level to match the phone input is quite impossible. While we may be able to get the correct voltage levels, we must remember the fact that phono inputs (presumably this is a magnetic phono input) are heavily equalized to compensate for two things: 1) The output of a magnetic phono cartridge is velocity-dependent. This means that the output doubles for every doubling of frequency presuming the amplitude is kept constant. So built into every phono preamp is a 6 db/octave rolloff starting at about 20Hz or so. 2) Imposed upon the above curve is the RIAA equalization, a "shelf" starting at about 500 Hz or so and ending at about 2200 Hz. This is to reduce low frequency amplitudes on the records (allowing longer selection in a given amount of space due to the fact that you can pack more grooves/inch). Both of these factors prevent the use of an attenuator. It is possible to build a passive version of the pre-equalization network to do this all for you, and I have done such for testing preamp frequency response and transient characteristics, but you end up generating quite a bit of noise, as well as having to deal with whatever problems the unit's phono preamp presents you with. In short, the project you describe is possible, but quite impractical. Dick Pierce
john@gcc-bill.ARPA (John Allred) (10/08/85)
In article <281@kepler.UUCP> mojo@kepler.UUCP (Morris Jones) writes: >I'd like to be able to play my CD through my friend's Onkyo receiver/amp. >Problem is the receiver has no other inputs besides the phono preamp >inputs. (Grrrrr.) > >I figure I can either cannibalize the receiver and look for a line level >input to bring out to the case, or I can pad the output from the CD >down to phono preamp input level. I realize this is a bit of a crock, >but it'll be nice for her to be able to record some CDs, and to listen >to some of my favorites at her house. > >Could one of you with spare time and access to the standards for stereo >input levels give me values for an H-pad or L-pad that would drop the >level and match the impedances? > >-- >Mojo >... Morris Jones, MicroPro Product Development >{ptsfa,hplabs,glacier,lll-crg}!well!micropro!kepler!mojo Sorry, Morris, but there is a more significant problem here. In addition to being a much lower level input that normal, the phono has an equalizer circuit (RIAA) that compensates for the unusual was that records are cut (high freq. are recorded hot, while bass is reduced.) If you were able to match impedances, a CD going through the phono input would sound *bad*. -- John Allred General Computer Company uucp: seismo!harvard!gcc-bill!john
sjc@mordor.UUCP (Steve Correll) (10/08/85)
> I'd like to be able to play my CD through my friend's Onkyo receiver/amp. > Problem is the receiver has no other inputs besides the phono preamp > inputs. (Grrrrr.) > > I figure I can either cannibalize the receiver and look for a line level > input to bring out to the case, or I can pad the output from the CD > down to phono preamp input level. I realize this is a bit of a crock, > but it'll be nice for her to be able to record some CDs, and to listen > to some of my favorites at her house. > > Could one of you with spare time and access to the standards for stereo > input levels give me values for an H-pad or L-pad that would drop the > level and match the impedances? A magnetic phono input not only expects a much lower level signal (on the order of a couple of millivolts) than a line-level input (on the order of a couple hundred millivolts), it also expects a signal whose bass has been cut and whose treble has been boosted according to the RIAA equalization curve. Thus, you would need to add not only resistance (e.g. an L-pad) but also a network of precision (1% or better is the norm nowadays) resistors and capacitors to implement the inverse RIAA curve. Does the receiver really have no line-level input at all, or have you merely used up the ones it provides? In the latter case, you might investigate a cute little passive switching box which Radio Shack sells. It's meant for adding tape-to-tape dubbing capability to receivers which have only one tape input, but it also lets you plug 3 or 4 line-level sources into its inputs, and plug its output into a receiver's tape input (which is a line-level input). If your receiver does not even have an input for a signal from a tape deck, then cannibalizing it to add a line-level input sounds easier to me than trying to adapt to the phono input. Tapping in just before the volume or balance control (whichever is earlier in the circuit) usually works satisfactorily, since the impedance of such controls is usually 30k ohms or more. -- --Steve Correll sjc@s1-c.ARPA, ...!decvax!decwrl!mordor!sjc, or ...!ucbvax!dual!mordor!sjc
ark@alice.UucP (Andrew Koenig) (10/09/85)
> I'd like to be able to play my CD through my friend's Onkyo receiver/amp. > Problem is the receiver has no other inputs besides the phono preamp > inputs. (Grrrrr.) A receiver with no tape inputs? This is difficult to believe. It is possible, though a nuisance, to build a circuit that would allow a CD player to feed a phono input. The only real problem is that the frequency response of a phono input is nowhere near flat. Instead, it follows the "RIAA Equalization Curve," a standard agreed to by audio manufacturers. The reason for this non-flatness is complicated, but basically it allows a lot more information to fit on a record than would be possible otherwise. Thus, you must build an inverse RIAA filter, which, if done passively, will probably have about the right amount of signal loss. Then you must amplify that signal again (in the phono preamp), thus losing some of the CD's dynamic range. I suggest you not bother.
rfg@hound.UUCP (R.GRANTGES) (10/09/85)
[] A Ha! You said...so she would be able to record some CDs... This implies tape inputs and outputs on the receiver. Use them. They are "line level" and would work fine with a CD player. If you don't know how to use them, that's another question for another day, but I'm sure lots of places would be glad to sell you some switches that would help you to use them. -- "It's the thought, if any, that counts!" Dick Grantges hound!rfg
crandell@ut-sally.UUCP (Jim Crandell) (10/09/85)
In article <281@kepler.UUCP> mojo@kepler.UUCP (Morris Jones) writes: >I'd like to be able to play my CD through my friend's Onkyo receiver/amp. >Problem is the receiver has no other inputs besides the phono preamp >inputs. (Grrrrr.) > >I figure I can either cannibalize the receiver and look for a line level >input to bring out to the case, or I can pad the output from the CD >down to phono preamp input level. I realize this is a bit of a crock... Depending how big a crock you'll tolerate, how much digging you'd like to do, and how lucky you are, there just might be a very easy way out of this one. Some time around 1960, Sonotone introduced the ``hi-fi ceramic cartridge'', series 9T (it really did compete fairly impressively with some of the popular magnetic cartridges of its era). What is interesting about this is that since the idea was to encourage people to replace their old GE stereo VRs (for instance) with 9Ts, Sonotone also produced an optional accessory -- a pair of plug-in networks, with inline RCA connectors, to convert the ceramic cartridge outputs to something that a typical magcart preamp would be happy with. A ceramic cartridge, you may recall, is ordinarily used without equalization into a simple, high- resistance load and has an output level on the order of a half volt; i.e., a CD player should work nicely into a ceramic input. The first problem is locating a pair of these little dudes. My growing collection of audio memorabilia does include an old 9TAF cartridge, but I've never had any of the magnetic adapters. The second is that (I'm guessing) the adapters just might be made with composition resistors, and that could be bad news, particularly after this long a time. In all honesty, the best you could hope for in any case is a reasonable approximation, but it might be worth a try anyway. Does anyone else out there have a ``museum''? If so, got any Sonotone magnetic adapters? -- Jim Crandell, C. S. Dept., The University of Texas at Austin {ihnp4,seismo,ctvax}!ut-sally!crandell
wmartin@brl-tgr.ARPA (Will Martin ) (10/16/85)
> > I'd like to be able to play my CD through my friend's Onkyo receiver/amp. > > Problem is the receiver has no other inputs besides the phono preamp > > inputs. (Grrrrr.) > > A receiver with no tape inputs? This is difficult to believe. I've held off on entering this particular fray, but the dust seems to have settled (no traffic about it on net.audio for about 80 postings), so here goes... Let's try to analyze just what we have here. One factor that makes me wonder is that the original poster said that this was an "Onkyo" receiver. I consider Onkyo to be a solid middle-range maker, and did not think that they made (or used the Onkyo brand name on) low-end stuff like "cassievers" (cassette-deck-receiver combination units). Such a beast could have no input than a phono circuit, and no external tape facility. If this was a Lloyds or an Emerson, then this sort of thing is common; I never encountered such a beast in "Onkyo" clothing. If it is really a receiver, and if it has only a phono input and a set of tape-in and tape-out jacks, it is NOT a simple matter of plugging the external CD player into the tape-in jacks. Remember that the purpose was not to just *play* the CDs through the receiver in question, but *also* to record some tapes from the CD signal. (Unfortunately that reference is in another posting than the one I'm here following-up on.) On simple equipment with a single tape facility, remember that the circuits are designed so the tape INPUT cannot be fed to the tape OUTPUT. (You can usually only do this on gear with a "dub" switch and which is connected to two decks; you can get nasty feedback this way, so this is why they design the simple gear to not allow such a feedback loop.) So, if you plug the CD into TAPE-IN on the receiver, you can *hear* the signal if you switch on the tape-monitor, but you could NOT record it. The solution, in this case, is to unwire the existing tape deck from the receiver (remember we are now assuming a separate deck and receiver) and feed the CD signal into the tape deck and the tape deck's output into the receiver's TAPE-IN jacks, thus: ---------- ---------- --------------------- | out|->-->|in out|->-->|tape-in | | CD | | TAPE | | RECEIVER | | PLAYER | | DECK | |tape-out | ---------- ---------- --------------------- You leave the receiver's tape-monitor switch always "on" for the CDs. The tape deck is left in "record-pause" mode to just listen to the CD, when it feeds the input signal through to the output, and can be switched to really record anytime you want to dub from the CD to tape. Of course, you limit the CD signal quality by feeding it through the (presumably cheap) tape deck, but then you're limiting it by the cheap receiver, anyway :-). Now, doesn't this solve the needs of the original inquirer? Will
mojo@kepler.UUCP (Morris Jones) (10/18/85)
I started the whole thing with: >>I'd like to be able to play my CD through my friend's Onkyo receiver/amp. >>Problem is the receiver has no other inputs besides the phono preamp >>inputs. (Grrrrr.) In article <2191@brl-tgr.ARPA> wmartin@brl-tgr.ARPA (Will Martin ) writes: >Let's try to analyze just what we have here. One factor that makes me >wonder is that the original poster said that this was an "Onkyo" >receiver. I consider Onkyo to be a solid middle-range maker, and did not >think that they made (or used the Onkyo brand name on) low-end stuff >like "cassievers" (cassette-deck-receiver combination units). Such a >beast could have no input than a phono circuit, and no external tape >facility. If this was a Lloyds or an Emerson, then this sort of thing is >common; I never encountered such a beast in "Onkyo" clothing. ... then Will gives an excellent suggestion for feeding the CD through the tape deck into the amp. Thank you! But ... This is really a "cassiever." Surprise! And it really is an Onkyo, unless someone is counterfeiting the Onkyo name plate. So there is no external tape deck, no inputs for a second tape deck (no dubbing), and of course it's a lousy idea to try to use the phono input for the CD. What I'm going to have to try to do is bring an input out to the case ... perhaps I can lift the tuner input from the selector switches on the front and bring it out to my own switch, where I can feed the CD as alternative. Any other suggestions? I must say you all really came through on my original inquiry. Thank you very much for that! -- Mojo ... Morris Jones, MicroPro Product Development {ptsfa,hplabs,glacier,lll-crg}!well!micropro!kepler!mojo
kek@mgweed.UUCP (Kit Kimes) (10/23/85)
>I consider Onkyo to be a solid middle-range maker, and did not >think that they made (or used the Onkyo brand name on) low-end stuff >like "cassievers" (cassette-deck-receiver combination units). >I never encountered such a beast in "Onkyo" clothing. As a happy owner of a current model Onkyo receiver, I concur that there are definitely enough inputs for most normal users (probably even enough for some non-normal users :-) ). However, I have also been following Onkyo's products for several years now and I can definitely say that they did sell a 'cassiever' a couple of years ago. It is not in the current catalog and I don't know what the model number was. I threw out all the old catalogs and I don't know if this particular model had any aux inputs. Kit Kimes AT&T Information Systems Montgomery Works Montgomery, Il. 60538-0305 ..!ihnp4!mgweed!kek
jib@prism.UUCP (10/25/85)
If it is really a "cassette receiver", does it have microphone inputs?
If so, how about attenuating the signal and feeding it in there?
(you may still have problems monitoring the signal, and maybe even setting
record level -- depending on what type of VU meters you have).
(or have I missed something?)
---------------------------------------------------------------------------
Jim Block {cca, ihnp4!inmet, mit-eddie, wjh12, datacube} !mirror!prism!jib
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