DT 770 pro 80 or 250 ohms with a vintage integrated amplifier

[jop109876]

I recently bought a pair of Beyerdynamic DT 770 pro 80 ohms. I mainly use them for listening to music from my vintage Sansui AU-317 II integrated amplifier connected to a turntable and CD player.

My amp produces too much power so the lowest volume setting on the amp is already a little too loud. Because of this, I am considering switching to the 250 ohms version.

Will the 250s change much in the overall sound? I feel like the 80s can sound a little flat in the mid-range and vocals and read that this might get worse with the 250s.

What are you guys’ thoughts on this?
Should I switch to the 250s or look for different headphones all together?
I have also looked at inline attenuators or an extra volume control between the amp and the headphones.

 

[darrelb]

i also have the 250ohm dt770's, i have been using the schiit magni headphone amp amplifier and they est sound amazing together.
the schiit,s are cheapest at their web site.also i have been using their loki 4
band equalizer to fill the dip in the middle of the audio band and the loki gives
the dt770 the snap i was missing.
it does not make much sense to use the au-317 amp for a few milliwatts when
you can use a this great headphone amp .

 

[Chris Brown]

That sounds really odd. I have a pair of DT770-Pro 80ohm headphones and I have never had issues similar to what you describe with any receiver or preamp that I've tried them with. They aren't super efficient compared to other headphones or anything like that, and I've never noticed a huge difference in efficiency when switching between my DT770-Pro 80ohm and DT990-Pro 250ohm headphones.

I'd agree that a cheap headphone amp might be the way to go. You could run it from one of the Tape Outputs on the back of your Sansui. The Schiit Magni was suggested and that is a good model, but if you want to add a little warmth to the DT770 mids then you might consider a hybrid tube headphone amp such as the Schitt Vali or other brands such as the Little-Dot I+ (this is what I mainly use with my headphones and it works great with my DT770-Pro 80ohm).

 

[Caveman Carl]

Amps of that vintage were designed for high-impedance phones of the day, 600 ohms was not unusual. That being said I don't know if lower impedance is better but I often use a venerable Kenwood KR-6600 to drive 80-ohm Focal Elear with excellent results so who knows.

 

[lini]

My amp produces too much power so the lowest volume setting on the amp is already a little too loud. Because of this, I am considering switching to the 250 ohms version.

Well, Beyerdynamic lists a Kennschalldruck (= nominal sound pressure level) of 96 dB for all three DT770Pro variants (32, 80 and 250 Ohm). Unfortunately they don't tell, whether that's dB/mW or rather dB/V, but I'd deem dB/mW more likely. Well, and if I read the schematic for your Sansui correctly, the headphone output is driven by the power-amp section via 220 Ohm series resistors (one per channel), which hence would form a (somewhat variable) voltage divider together with the impedance of the headphone drivers (due to the actual impedance typically varying somewhat over frequency).

Now let's calculate: A certain volume control position would mean a certain output voltage (of course depending on the input signal voltage), but for simplicity let's assume that to be 1 V(eff.).

Now, in combination with the series resistor

- the remaining voltage share for the 250 Ohm model would be ca. (250 / (220 + 250)) x 1 V = ca. 0.532 V

- the remaining voltage share for the 80 Ohm model would be ca. (80 / (220 + 80)) x 1 V = ca. 0.267 V

- the remaining voltage share for the 32 Ohm model would be ca. (32 / (220 + 32)) x 1 V = ca. 0.127 V

And the corresponding powers (P = U² / R) would be ca. 1.13 mW, ca. 0.89 mW and ca. 0.50 mW. Well, and 1.13 mW to 0.89 mW would equal a difference of ca. +1.04 dB, while 1.13 mW to 0.50 mW would equal a difference of ca. +3.54 dB, and 0.89 mW to 0.5 mW would equal a difference of ca. +2.50 dB.

So (provided the assumption, that the Kennschalldruck is per mW, and both the 96 dB and the nominal impedances are reasonably correct) due to the voltage division with those series resistors the 250 Ohm variant could rather be expected to even be an all so tiny tad louder than the 80 Ohm version, while in combination with your Sansui the least loud one should be the 32 Ohm variant - although -2.5 dB compared to the 80 Ohm version would just be more noticable, but still not a really big difference. Hence going for one of the other two DT770Pro variants wouldn't seem a sensible solution for your "already a bit too loud at the lowest volume control setting" problem.

Greetings from Munich!

Manfred / lini

 

[seely]

No meaningful advice from me, but just wanted to say I nearly have the same issue using my early 80's 60wpc solid state Sherwood receiver with the 80 ohm DT 770 Pro's. The volume control on mine is "indexed", and the "jump" between volume settings is significant, so much so that it might be too quiet on one click and too loud on the next. Difficult to dial in a comfortable listening level sometimes.

 

[Caveman Carl]

Yeah click-stop may have a nice feel to it but it impedes precision. Happens with bass and treble on my Pioneer SX-650 and 950 but volume is not click-stop so there's always that lol

 

[pfsoft]

If you want you can read here:
https://robrobinette.com/HeadphoneResistorNetworkCalculator.htm
You can also try different values for the resistors and find the most suitable combination.