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flybigjet
18
Jul 24, 2017
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Ok-- color me confused.
I'm signed up for the Drop, but the whole DAC/Amp thing has boggled me.
I'm planning on using these with no DAC, no (mini-) Amp, but instead plugged directly into the headphone jack of a Marantz 2325 receiver-- it was Marantz's flagship in 1974 and was my father's. After he gifted it to me, I had a complete ground-up restoration done, and it's *perfect*-- 125 (true) watts per channel at 8 ohms.
Good plan? Bad plan? Right choice of headphones? Poor choice of headphones?
Thanks!
Jul 24, 2017
tessierpg
Jul 24, 2017
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flybigjetGreat vintage amp the Marantz. Great headphone the Sennheiser HD650. Do they match well together? It depends. I'm sure the power output is more than enough, but the important thing you should investigate is the output impedance of the headphone jack on your Marantz. Rule of thumb: your headphone's nominal impedance (300 ohms for the Hd650/Hd6xx) must be at least 8x the output impedance of your Marantz's headphone jack output., so max = 38 ohms. If it is the case, you should be okay. If not, the damping factor will be too low and the headphones will not play to their full potential. The bass and mid-bass will be increased by a few db because of that and it will be less controlled, more muffled, less tight. I will play loud enough, but musicality and transparency, balance between bass, mids and highs, will be negatively affected. You may or may not like the resulting sound, depending on your tastes. If your vintage Marantz doesn't cut it, you may buy an Objective O2 or Schiit Magni 2, that can be bought for around 100$, you plug it to the line out or tape out of your Marantz receiver and you're done! I did the same with my Onkyo Tx-NR646 Receiver (bought new in 2016), since the output impedance of the headphone jack is 390 ohms! It is common to see receivers from the 70s, 80s and more recent ones like mine to have very high output impedance off ther headphone jacks, because many receivers don't have dedicaded op amps for the headphone jacks, so they increase the resistance (impedance) at the output of the headphone jack so that the main amp may be used to amplify the headphones, and this creates the impedance mismatch I explained above. Receivers that have dedicated op amps for the headphone jack will normally offer a low impedance output which will be compatible with headphones such as the Sennheisers. Hope It answers it...
edit: I just googled "vintage receiver output impedance headphone" and I got this interesting thread from head-fi that corroborates what I've just wrote:
https://www.head-fi.org/f/threads/does-a-vintage-receiver-cut-it-as-a-headphone-amplifier.589415/
Jul 24, 2017
flybigjet
18
Jul 25, 2017
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tessierpgThank you very much for your response...... but now I'm even more confused than before!
I spent a good while today looking through the old Marantz materials I could find, both on my laptop and on the 'net, and the *only* thing I found re: the headphone jack was as follows:
"Headphones Output......................................................0.7V into 8 ohms at rated distortion"
Honestly? I don't even know what that means. However, a lot of the "vintage" threads seem to think that the amp is a jewel with pretty much any headphone, including the HD6xx series.
I had the amp completely rebuilt from the ground up in a "cost is no object" restoration, so I suppose I'll just have to operate on faith and give these headphones a chance, since I wasn't able to find any particular information on the Marantz 2325's headphone jack specifications.
Sigh. NOTHING is ever easy!
Jul 25, 2017
tessierpg
Jul 25, 2017
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flybigjetI would bet you a symbolic dollar that your vintage Marantz receiver doesn't have a dedicated op amp for the headphone jack and therefore has a very high (over 100 ohms) output impedance from the headphone jack, like it is the case for most (but not all) receivers of that time period. You could try it out but it does not respect the 8x rule and thus will have low damping factor and will not be optimized to your HD6xx. The good news is that you may still use your receiver as a preamp/input switch for your sources and you may add later a dedicated amp such as the ones suggested (JDS Objective O2 destop edition or Schiit Magni 2) and have it plugged in the "tape out" RCA output of your Marantz, this will cost you another 100$-140$ depending on the chosen model. This setup will then work out and be optimitized to your needs and to your HD6xx. Balloon tires (65) will work on your BMW coupe sports car, but low profile tires (45-55) are the way to go if you want to optimize your road handling... guaranteed!
Jul 25, 2017
blackbird13
3
Jul 28, 2017
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tessierpgThank you for your helpful answers to some of the same questions I have. These will be the most expensive headphones I've owned, and I want to do them justice. I have a Monoprice Desktop Amp/Dac that works great with my AudioTechnica 50x, but not so great with my Sennheiser HD555, which work better out of the headphone jack of my older model Denon stereo receiver. I'm assuming the 6xx will need a different option. I'm considering trying a tube amp, but the cheapest ones that I've read about that sound suitable are the Woo Audio WA3, which cost $600, or the $300 DIY Bottlehead Crack, but I'm not good the type of hands-on work a Bottlehead Crack would require. Any chance we'll ever see a Woo Audio drop here?
Jul 28, 2017
hagenhays
18
Jul 28, 2017
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flybigjetGood plan if in working order. i have a 2015 (1974 as well) works great for headphones. Haven't tried this exact model tho, but will :) december
Jul 28, 2017
ABitterLemon
1
Jul 31, 2017
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blackbird13If you want a tube amp, I would consider the Schiit Valhalla 2 ($350). I've heard that they go really well with the 650/6XXs.
Jul 31, 2017
Signal_operator
0
Sep 7, 2017
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tessierpghey so i have the same receiver and i bought the sennheiser-hd6xx. i tried to do hasty research to see if it would work but was able to find nothing (At the Time), so i ended up buying a Schiit Valhalla 2. Was that a good move or did i waste money?
Sep 7, 2017
tessierpg
Sep 7, 2017
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Signal_operatorIn my case I use the onkyo receiver as a Network receiver/DAC (the AKM AK4452 DAC included inside the receiver) and using the zone 2/line out of the receiver I plugged the Massdrop O2 headphone amp that drives my HD6xx. I do this because the output impedance of the headphone jack on the Onkyo receiver is way too high: 390 ohms! With my Onkyo line out plugged into my O2 amp, then the output impedance of the O2 amp is only 0.5 ohms, well okay for the 300 ohms Hd6xx headphones, which give a damping factor of 600 with my HD6xx plugged into the O2 instead of a damping factor of less than 1 if I plug the HD6xx directly from the Onkyo's headphone jack. So if you use and plug the Schiit Valhalla 2 in the same way i'm using the O2 with the Onkyo receiver (using it as a Network receiver/DAC), you should be okay. The only issue left is the somewhat low output power of the zone2/line out from the Onkyo receiver: which is maximum 1Vrms, similar to an iPad (A normal dedicated DAC would normally have a 2V or 2.1Vrms output.). But if your headphone amp has a gain switch and if you set it at high gain mode, then you should be fine. Then you don't really need a small dedicated DAC, although It could be usefull because more portable and smaller, depending on your setup.
Sep 7, 2017
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