I've been looking for a service manual for the Marantz SA14S1 so I can figure out the output impedance(I've got a picky tube pre-amp which doesn't like anything over 200ohms single ended).
The above website is the only one I've found which has it available but the site seems kind of shady and they want a lot of personal information before letting you download the .PDF.
I found a manual for the SA15S1 but I can't confirm if it's the same design or not. I'm not sure if I'm reading it correctly but it looks like the output impedance is going to be 100ohm for the single ended outputs?
Thanks for your time!
The above website is the only one I've found which has it available but the site seems kind of shady and they want a lot of personal information before letting you download the .PDF.
I found a manual for the SA15S1 but I can't confirm if it's the same design or not. I'm not sure if I'm reading it correctly but it looks like the output impedance is going to be 100ohm for the single ended outputs?
Thanks for your time!
Yep! You were exactly right and I was reading it backwards! It's actually the line output for the CD Player. 47ohms output impedance seems quite low compared to others I've seen but at least it means there won't be any attenuation with the weirdly low input impedance on my tube pre-amp.
The designers decided to split the input transformers into balanced and single ended windings along with other circuit choices which results in a measured input impedance of only 770ohms at 10kHz. Which resulted in a -4dB attenuation at 10Khz with my current SACD player which has an output impedance of 540ohms. Given that they spec the input impedance at 100kohm(the highest it actually reaches is 24Kohm at 300Hz) it took me a while to figure out what was going on!
Thanks for your help.
47 Ω is pretty common. The resistor is added to make sure the preamp doesn't start to oscillate with a capacitive load such as a long interconnect cable.
Tom
Tom
Alright, 47ohm is the lowest I've seen from a CD Player or DAC but I've only seen that spec on maybe a dozen different units. I've normally seen 100/200ohms being the most common. The 540ohm on my Yamaha CD-S2100 is the highest I've run into so far.
Can you tell whether changing the resistor in the Yamaha output below to a lower value could negatively affect the performance? Or would I be okay with substituting a lower value so that I could have a lower output impedance? I don't have the full circuit diagram for this one.
I don't know. That's a question best directed at Yamaha.
I suppose I could simulate the preamp and look at how its stability changes with capacitive load, but then again so could you... 😉
Tom
I suppose I could simulate the preamp and look at how its stability changes with capacitive load, but then again so could you... 😉
Tom
Considering they wouldn't even provide me with the output impedance when I asked I somehow doubt they'll consult with changes in the design!
Well...you're talking to a guy who read the schematic backwards a mere 8 hours ago so that's a bit outside my wheelhouse. However, I have the interest and I have the ability to learn so now is as good a time as any to increase the breadth of my knowledge. If you hear a large bang from the east that's my head exploding.
Right now I'm currently distracted by my brand new Quant QA403 audio analyzer so it might have to wait a bit! I found a 5dB discrepancy in the SNR of my 300B monoblocks that isn't explained by the tubes themselves so I'm psychologically obligated to figure out why and how to fix it! Even though it's still below the audible range.
Thanks for your time. I appreciate the help. Have yourself a good week.