Speaker amps for headphones
Sep 5, 2020 at 1:48 AM Post #3,316 of 3,707

AnaKinDV8

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Today, while being fully satisfied with the direct to amp connection of my Cantata DAC (and being ever so curious), I inserted my Stereocoffee LDR passive pre-amp in the chain and the Cantata was re-set to full volume. The LDR is a very transparent pre-amp that just lets the signal through using optocouplers to control volume. I did not prefer it in my stereo setup as it lacked gain to drive the X150.5 amp to full potential but in my headphone setup where my initial problem with the XP10 pre-amp was too much gain especially with balanced connections, this seemed like a good match...

IMG_20190831_164103.jpg

The LDR is an improvement over my Cantata directly driving the X150.5. Better transparency, more detail and overall a more realistic presentation. More on the plus side, I have again the luxury of having more input options to try out other DACS, and control of the volume with a knob! The Cantata had buttons and the remote, which was just not that convenient. I'm still amazed at how I was able to stumble upon this setup configuration for my 1266 TC's. Happy weekend!
 
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Sep 5, 2020 at 10:54 AM Post #3,317 of 3,707

Happy Camper

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Today, while being fully satisfied with the direct to amp connection of my Cantata DAC (and being ever so curious), I inserted my Stereocoffee LDR passive pre-amp in the chain and the Cantata was re-set to full volume. The LDR is a very transparent pre-amp that just lets the signal through using optocouplers to control volume. I did not prefer it in my stereo setup as it lacked gain to drive the X150.5 amp to full potential but in my headphone setup where my initial problem with the XP10 pre-amp was too much gain especially with balanced connections, this seemed like a good match...


The LDR is an improvement over my Cantata directly driving the X150.5. Better transparency, more detail and overall a more realistic presentation. More on the plus side, I have again the luxury of having more input options to try out other DACS, and control of the volume with a knob! The Cantata had buttons and the remote, which was just not that convenient. I'm still amazed at how I was able to stumble upon this setup configuration for my 1266 TC's. Happy weekend!
Remember that grin on your face when you brought up the volume for the first time? It stays with you.
 
Sep 8, 2020 at 12:56 PM Post #3,321 of 3,707

pataburd

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Dussun T6 [100 WPC] integrated driving the HEDDphone [volume at 2-out-of-10]:

IMG_20200908_124319966[1].jpg

. . . more refined and quicker than the Qinpu A-1.0X, but not as 3-dimensional and "natural-sounding" as the Sophia Electric Baby. [I miss the unexpurgated neutrality of the HEDD/Qinpu pairing.]

Mills resistors have arrived for the Sophia, so I swapped out the Dussun and tried the Sophia with the KEF iQ10 in the interim. Nice match with outboard speakers, too. The Sophia is surprisingly detailed, lively and dynamic.

: ).
 
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Sep 8, 2020 at 1:19 PM Post #3,322 of 3,707

pataburd

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Tried the [$1] 10 ohm resistors that I took off the Sophia with the [solid state] Dussun T6. [DakiOm A253 Feedback Stabilizer also in tow.]

Didn't get much more leeway with the volume knob [maybe 1/4 or 3/8 of an increment/unit extra], but--and am I imagining this?--detail seems richer [much richer]; images are bigger, more fleshed out [commensurate with an enlarged soundstage]; bass, though perhaps a bit less prominent, has better definition and texture; and layering sounds significantly improved. Game-changer: the Dussun now presents serious [ss] competition for the Sophia.


IMG_20200908_130444712[1].jpg

. . . or, maybe the Shakti Stone just kicked in! : )

Tidal Masters: America, The Complete Warner Brothers Collection 1971-1977, "Three Roses", sounds really, really nice.

Just put the ADX5000 and the ecp DSHA-3F up for sale. I don't think I can go back to "regular" headphone amps--at least not with the HEDDphone [the lone survivor].
 
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Sep 8, 2020 at 5:33 PM Post #3,323 of 3,707

typalder

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Tried the [$1] 10 ohm resistors that I took off the Sophia with the [solid state] Dussun T6. [DakiOm A253 Feedback Stabilizer also in tow.]

Didn't get much more leeway with the volume knob [maybe 1/4 or 3/8 of an increment/unit extra], but--and am I imagining this?--detail seems richer [much richer]; images are bigger, more fleshed out [commensurate with an enlarged soundstage]; bass, though perhaps a bit less prominent, has better definition and texture; and layering sounds significantly improved. Game-changer: the Dussun now presents serious [ss] competition for the Sophia.


IMG_20200908_130444712[1].jpg

. . . or, maybe the Shakti Stone just kicked in! : )

Tidal Masters: America, The Complete Warner Brothers Collection 1971-1977, "Three Roses", sounds really, really nice.

Just put the ADX5000 and the ecp DSHA-3F up for sale. I don't think I can go back to "regular" headphone amps--at least not with the HEDDphone [the lone survivor].
i have a question: is there anybody out there who wired a headphone to a speaker amp and went back to a "normal" headphone amp? cheers from cologne, oliver
 
Sep 8, 2020 at 9:08 PM Post #3,325 of 3,707

pataburd

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Oliver,
I still use a Fitz-upgraded/modded Bada PH-12 [1W] hybrid headphone amplifier [3x 6SN7 + 2x Toshiba K1529 MOSFET] with the HEDDphone, and the SMSL SP-200 THX AAA 888, which provides a great match for the Martin Logan Mikros 90.

Fitz-modded Bada PH-12.png


The Bada retains sentimental value, plus I put so much into that upgrade that I could probably never nearly recoup it in resale. It's a great little amp.

Cordially,
Patrick
 
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Sep 9, 2020 at 7:22 AM Post #3,326 of 3,707

beemerphile

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Tried the [$1] 10 ohm resistors that I took off the Sophia with the [solid state] Dussun T6. [DakiOm A253 Feedback Stabilizer also in tow.]
Didn't get much more leeway with the volume knob [maybe 1/4 or 3/8 of an increment/unit extra]

You misunderstand the reason for parallel resistors. Their impact is on the amp and they are needed for amplifiers that do not operate well into higher impedances, like many tube amps. Most SS amps act like voltage sources and deliver different currents into different loads without much negative impact until their current rating is exceeded. A parallel resistance lowers the overall circuit impedance seen by the amp and increases the wattage output at a given volume setting. Here are some numbers (per channel)...

Without the resistor, if you applied an average 14 volts to the 43 ohm impedance of your headphones, the amp would output 4.7 watts into the headphones. Since there are no resistors drawing current, the total load on the amp at 14 volts is 4.7 watts. If you add the parallel 10 ohm resistors, at the same volume control "clock" position (14 volts) the power absorbed by the headphones would still be 4.7 watts, however the resistor would absorb 20 watts making the total load on the amp 24.7 watts. At the 100 watt rating of your amplifier, the resistor is melting under its 80 watt load and the headphones have long since blown apart trying to dissipate 18.4 watts. These loads on the resistors should be your basis for determining the wattage of parallel resistor that is needed. I would recommend a 25 watt resistor in order for it to be within range for 5 watts output through the headphones.

The only thing you can do at the outputs of the amp that will give the volume control more swing and protect the headphones from indiscriminate use of the volume control is to add series resistance. This assumes that your SS amp is a perfect voltage source, which it is not. When the extra load of the parallel resistor is applied, there can be some sag in the voltage as it is drawn down by the added current of the resistor. This requires you to "clock up" the volume control a bit to get back to the prior voltage (thus volume) through the headphones - but maybe not so much, and with some amps not at all. This is why you should not expect a significant increase in volume control travel from adding parallel resistance. If I wanted to add volume control swing and protect the headphones from indiscriminate use of the volume control, rather than adding series resistors to the output I would start with about a 10K attenuator on the input side of the amplifier.

I will point out that there is no way to calculate or predict the behavior of the amp with the "DakiOm A253 Feedback Stabilizer" in the circuit. I don't know what it does or how it does it or what circuit is contained within it. However, unless the (-) speaker connections are common (in many amplifiers they are not) then the left channel is getting none of it (unless Kirchhoff's laws are invalid) because there is no connection to the left channel (-) connection. Power amplifier topologies exist with high and low feedback and some excellent ones are stable with none at all. Determining the amount of feedback needed to stabilize the circuit is part of the amplifier designer's job, and his job is not finished until the circuit is stable. For this device to have uniform applicability would mean that no amp designer is doing this job correctly and that one circuit addition fixes all of them. What it does to an amplifier that does not use feedback would be interesting to know.

... but--and am I imagining this?--detail seems richer [much richer]; images are bigger, more fleshed out [commensurate with an enlarged soundstage]; bass, though perhaps a bit less prominent, has better definition and texture; and layering sounds significantly improved. Game-changer: the Dussun now presents serious [ss] competition for the Sophia.

I can't find any specifics of the circuit topology used in the Dussun T6. I've not seen it, but I've heard of some SS amps that are reported to sound "flabby" unless some significant load is drawn on the amp. It is possible that the Dussun is one of these and the extra load of the resistor helps its output response.
 
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Sep 9, 2020 at 7:34 AM Post #3,327 of 3,707

Muataz

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What are a few affordable (sub 500$ used) amps (no need for dac) that would run the Abyss 1266 TC and the like with strong nice power?
Topping A90 will power 2 Abyss 1266 TC at the same time. The cleanest amp ever made in the history of audio industry.
 
Sep 9, 2020 at 8:18 AM Post #3,328 of 3,707

pataburd

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You misunderstand the reason for parallel resistors. Their impact is on the amp and they are needed for amplifiers that do not operate well into higher impedances, like many tube amps. Most SS amps act like voltage sources and deliver different currents into different loads without much negative impact until their current rating is exceeded. A parallel resistance lowers the overall circuit impedance seen by the amp and increases the wattage output at a given volume setting. Here are some numbers (per channel)...

Without the resistor, if you applied an average 14 volts to the 43 ohm impedance of your headphones, the amp would output 4.7 watts into the headphones. Since there are no resistors drawing current, the total load on the amp at 14 volts is 4.7 watts. If you add the parallel 10 ohm resistors, at the same volume control "clock" position (14 volts) the power absorbed by the headphones would still be 4.7 watts, however the resistor would absorb 20 watts making the total load on the amp 24.7 watts. At the 100 watt rating of your amplifier, the resistor is melting under its 80 watt load and the headphones have long since blown apart trying to dissipate 18.4 watts. These loads on the resistors should be your basis for determining the wattage of parallel resistor that is needed. I would reccomend a 25 watt resistor in order for it to be within range for 5 watts output through the headphones.

The only thing you can do at the outputs of the amp that will give the volume control more swing and protect the headphones from indiscriminate use of the volume control is to add series resistance. This assumes that your SS amp is a perfect voltage source, which it is not. When the extra load of the parallel resistor is applied, there can be some sag in the voltage as it is drawn down by the added current of the resistor. This requires you to "clock up" the volume control a bit to get back to the prior voltage (thus volume) through the headphones - but maybe not so much, and with some amps not at all. This is why you should not expect a significant increase in volume control travel from adding parallel resistance. If I wanted to protect the headphones from indiscriminate use of the volume control I would start with about a 10K attenuator on the input side of the amplifier.

I will point out that there is no way to calculate or predict the behavior of the amp with the "DakiOm A253 Feedback Stabilizer" in the circuit. I don't know what it does or how it does it or what circuit is contained within it. However, unless the (-) speaker connections are common (in many amplifiers they are not) then the left channel is getting none of it (unless Kirchhoff's laws are invalid) because there is no connection to the left channel (-) connection. Power amplifier topologies exist with high and low feedback and some excellent ones are stable with none at all. Determining the amount of feedback needed to stabilize the circuit is part of the amplifier designer's job, and his job is not finished until the circuit is stable. For this device to have uniform applicability would mean that no amp designer is doing this job correctly and that one circuit addition fixes all of them. What it does to an amplifier that does not use feedback would be interesting to know.



I can't find any specifics of the circuit topology used in the Dussun T6. I've not seen it, but I've heard of some SS amps that are reported to sound "flabby" unless some significant load is drawn on the amp. It is possible that the Dussun is one of these and the extra load of the resistor helps its output response.

beemerphile,
Thank you for taking the time to explain things in detail. Will go back over your text and review basic circuit design.

Will try the 25 watt resistors. Am also picking up some in-line attenuators [similar to the EVS Nude Ultimate Attenuators] to address the volume level vis-a-vis dial position.

Will try to find the white paper for Dr. Kim Dao's feedback stabilizers. His products went off-the-market approximately 5+ years ago. Have had good success [real or imagined?] with his headphone out device.

Your closing comments about certain amplifiers functioning better under extra load makes sense. Reiterating, I heard what I thought was a marked improvement from the Dussun with the resistors versus without.

At any rate, the Mills 10 ohm resistors are on the Sophia Baby, and HEDDphone listening is back to "normal".

Thanks again!


pataburd
 
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Sep 9, 2020 at 8:21 AM Post #3,329 of 3,707

beemerphile

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Will try to find the white paper for Dr. Kim Dao's feedback stabilizers. His products went off-the-market approximately 5+ years ago. Have had good success [real or imagined?] with his headphone out device.

This thread is probably not the place to run that rabbit. I only pointed it out with reference to its impact on determining the load response of the amplifier.
 
Sep 9, 2020 at 9:06 AM Post #3,330 of 3,707

pataburd

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OK. Chief.
Thanks again.
 

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