Ok I am getting a little steamed!
I connected all the components in the Soundtraxx recommended circuit shown below, so that I could experiment with plugging the Soundtraxx DSX into a stereo as suggested on their website. I used the exact parts shown. I rebuilt this several times.
Well, the sound is there in my 2" test speaker, but nothing, nada, bupkis when plugged into my stereo inputs. I plugged it into the aux., cd, tape in, etc. etc.
The sound is minimally present. Not at all what is intended. What gives?
The decoder also becomes too hot to touch within a minute or so. Smells hot.
I think the circuit design is faulty or I am missing something. But the website says it is the circuit needed to plug the DSX into a stereo to run the audio through large speakers.
The sound is actually clearer and louder if I bypass this circuit and connect to my little test speaker, but nothing results from jacking it into a stereo, and the decoder heats up just as much.
Anyone out there has ever jacked a DSX into a stereo amplifier (as Soundtraxx suggests is possible) and gotten good results? How did you do it?
I am also going to run this by Jarrett at Soundtraxx tech support and Soundtraxx/Yahoo, but this forum is often very good.
You have a computer with soundcard. Use the line/aux in on the sound card. Open the mixer (double click on Windows speaker icon) and adjust your line in volume (preamp). Hope this gets you further.
I found another crcuit, same function and same output transformer. They did not use the 5K audio taper pot. it worked for them. They were extracting audio from the 8 OHm output of a synthesizer.
Hope you are using the proper primary and secondary connections of the O.T. ?.
UpNorth wrote: Hope you are using the proper primary and secondary connections of the O.T. ?.
Thanks. I hope so. I don't have the input and output reversed if that's what you mean.
However, does it matter which coloured leads of the inputs and outputs go where? This is how I have it set up now:
I will try it with my soundcard
No it makes no difference as long as your decoder is wired to the 8 ohm side and the amp is on the 1K side as you indicate and you are not using the center tap of the output. Color code should be indicated in the instructions from R.S.
Like I wrote, the similar circuit I found on the web did not use the V/R (taper pot) in the circuit. Might be an idea to try it without V/R.
Thanks.
Well, I don't know what the circuit is for, exactly. But when I jacked the decoder speaker leads directly into the microphone input on my computer sound card, success! I have heard from another hobbiest that does this...no circuit involved.
From there I fed the signal out to the big stereo and subwoofers. It can really rumble now.
The decoder also stays cool.
So what could the circuit be for? I will just have to wait and perhaps Jarrette at Soundtraxx tech can explain.
Also, the sound to even the regular 2" test speaker would only work by removing the capacitor shown in the circuit. Seems like this is a theoretical circuit that no one actually checked out, because it only seems to block the signal.
Soundtraxx say not to attach DSX decoders direct and give a different circuit for the DSD and DSX. Go figure. The Output transformer is just to put an 8 OHM load to protect the decoders amp section from running with no load and blow it.
Lets await for a responce from Soundtraxx and see.
Otis wrote: UpNorth wrote: Hope you are using the proper primary and secondary connections of the O.T. ?.Thanks. I hope so. I don't have the input and output reversed if that's what you mean.However, does it matter which coloured leads of the inputs and outputs go where? This is how I have it set up now:I will try it with my soundcard
On the diagram you show the amplifier input off the right side of the impedance matching transformer but you also show two 14 ga wires going to a speaker. Is this correct ? Is there really a speaker connected to those 14 ga wires ? If so, that will cause the problem and it should be disconnected In that scenario you have taken an 8 ohm load and placed it in parallel with the 1k ohm load of the transformer. That will effectively reduces the load 7.9 ohms and corresponding output voltage will be significantly reduced, thus you won't be able to hear it.
In simple terms the transformer has a 1:125 impedance match winding that is degined to drive a 1k ohm load and provide an 8 ohm load to the sound decoder. By adding an 8 ohm load to the secondary, that is reflected back across the 1:125 winding as a .06 ohm load and the sound decoder cannot drive a load that small.
As for plugging the output of the sound decoder right into your stero input, that should work as long as you take into consideration a couple of things. First, use the capacitor provided. Many modern stereos are true DC amplifiers and any DC input offset voltage from your decoder will be amplified and sent to your speakers. DC applied to speakers can cause voice coil heating and burnout. Second, the sound decoder is meant to drive a low impedance load and you are plugging into a high impedance input. The result is that a small change in the volume on the sound decoder can have a major change in input voltage to your stereo and over drive your stereo and speakers. Most stereo line inputs are designed for about 1V RMS to drive out 1 watt of power at the speakers (not exactly but close enough for this discussion) and have a maximum input of a few volts RMS. Cranking up the sound decoder may over drive the input limits for the stereo amp. That is the purpose of the impedance matching transfromer. You can get by without it but the potentiometer may be needed to help match the signal levels.
Engineer Jeff NS Nut Visit my layout at: http://www.thebinks.com/trains/
Thank you, Engineer Jeff.
No, I used the speaker wire to jack into the various inputs of the stereo amplifier....the aux in, cd in, tape in etc. I didn't get any results. I am no engineer as you can tell, but I think I needed to jack it into a preamplifier first.
Is that what I am doing when I jack it into the computer soundcard input, which is then connected to my stereo aux in? (I listen to music on the stereo played from the computer so that latter connection is always there for me.)
Thanks for the info re: the use of the circuit and capacitor in jacking into the soundcard. I will try that next.
Otis wrote: Thank you, Engineer Jeff.No, I used the speaker wire to jack into the various inputs of the stereo amplifier....the aux in, cd in, tape in etc. I didn't get any results. I am no engineer as you can tell, but I think I needed to jack it into a preamplifier first.Is that what I am doing when I jack it into the computer soundcard input, which is then connected to my stereo aux in? (I listen to music on the stereo played from the computer so that latter connection is always there for me.)Thanks for the info re: the use of the circuit and capacitor in jacking into the soundcard. I will try that next.
The AUX IN, CD IN and Tape IN are all line level signals that are in the range that I mentioned above. The sound decoder should be able to drive a signal easily to a line level input but you'll need the poteniometer if you want to have adjustable volume (since you'll have bypassed the preamp). My comment about the capacitor is if you don't want to use the circuit and you want to plug the output of the sound decoder straight into your sound card or stereo. Use the capacitor to avoid the chance of injecting a DC offset into the input. Also make sure you have volume controls set a minimum and bring them up slowly. With the impedance mismatches you can over drive the amplifier.
Otis wrote: I don't know what the circuit is for, exactly. But when I jacked the decoder speaker leads directly into the microphone input on my computer sound card, success! I have heard from another hobbiest that does this...no circuit involved.
Also, the sound to even the regular 2" test speaker would only work by removing the capacitor shown in the circuit.
I'm, no engineer but your diagram was clear to me, you wired it right. The CD, AUX, Tape are Line level inputs. You require a preamp input, IE: phono, mike or the likes of. Best bet is a computer sound card because your sure to have a preamp section.
The computer sound card has a mike input port, the mixer I spoke in my post is a PREAMP.