On HD650s and speaker amps...

[JimP]

yup, 4-pin xlr female to bare speaker wire, no resistors. 840c will feed both almarro and b60r simultaneously (dac1 just happens to be in picture). For now keeping both dac1 and miniDAC -- both work credibly direct XLR out to the Senns (maybe one goes if I need to raise funds)

[Dusty Chalk]

Also helps if your amp can handle what is essentially an open load. (Oversimplification, I'll let others explain the details.)

[fierce_freak]

Quick question: what's the standard for wiring 4 pin xlr? as in, pin 1 would be Left-, 2 is Left+, etc.

[Salt Peanuts]

Quick question: what's the standard for wiring 4 pin xlr? as in, pin 1 would be Left-, 2 is Left+, etc.

Not sure if this is the standard, but following if the K1000 pintout -

Pin 1: Left +

Pin 2: Left -

Pin 3: Right +

Pin 4: Right -

[Duggeh]

If there is a standard, then its the K1000 configuration. The TakeT H2 swaps the pins on the right channel though.

[fierce_freak]

Thanks, guys.

[SonicDawg]

Just want to report that this method also works with K340s. And they benefit from it also tremendously!!

[catscratch]

Update:

I don't think I'll be using this system much longer, or at least on a constant basis. Not because I'm not happy with it sonically, but because the VP-20 can't handle the load without clipping occasionally. Now, this clipping is very rare and happens only during very dynamic passages - and even then isn't major - but given how much of a perfectionist I am, even that isn't good. Besides, I'm sure I can't be doing the amp any good in the long term.

So, I think I'm moving to an O2 MkII based system, with the Dared driving an SRD-7 Pro transformer.

I've had some talks with some hf members and it seems that the problem stems from the design of the Dared, where the input/gain stage lacks the voltage and current to drive the 6L6 output stage properly specifically when tasked with driving a sensitive 300ohm load. At least, that's how I understood it.

So, it's not a fault with the idea of driving a headphone with a speaker amp - but a fault with the VP-20 specifically used for the purpose. And even then, not a very major one.

I'll still probably whip the rig out every once in a while, since other than the occasional clipping issue, it does sound very good.

Just thought I'd post a heads up in case anyone was considering the VP-20 for the purpose.

[SonicDawg]

catscratch, what's the reported wattage on the amp? I am using a 60wpc amp with the K340s and they have never clipped.

[catscratch]

They're 18wpc, but it isn't the output stage that's clipping but the input/gain stage, or so I've been told. As I said, I don't believe that this is a problem with the concept of driving the HD650 with a speaker amp but a specific design problem with the VP-20.

Currently it's driving an SR-003 through an SRD-7 Pro and there is no clipping (that I can hear, I haven't specifically tested for it though).

I drove a speaker-reterminated Headphile K340 with the VP-20 and I don't remember any clipping there either. It sounded pretty good too, but I significantly prefer my stock K340 to that Headphiled pair, since the latter was seriously lacking in treble presense or extension - though of course my pair is 1/4" terminated and I couldn't drive it off the VP-20 for a direct comparison.

[Dusty Chalk]

Are you using the same source? If so, wouldn't that imply that it's not the input nor gain stages?

[ting.mike]

Hi. Resurrecting a one year old thread here. And this is my first post at Head-case.

I actually tried this as well, and have gotten really good results.

I don't use balanced cabling, so it goes: HD650 stock cable > Neutrix 1/4 Female w/ Canare starquad > Power Amplifier.

The Power Amplifier is an Adcom GFA 5802 which is a 300W/channel into 8 ohms.

Pre Amp is Adcom GFP 565. Source is CEC CD5300.

I really like the result, especially soundstaging is phenomenal, and like catscratch, also improved speed, detail, and low-end control.

The problem is there is a low noise, sort of like radio interference noise (like what you guys are also getting), and I wonder what can be done about it?

Also, have anyone tried to build the Joseph Grado adaptor? I'm still trying to source the 10W resistors, but I can't discern why he designed a 2 ohm resistor connecting the hot and cold cables.

[TheSloth]

Hi. Resurrecting a one year old thread here. And this is my first post at Head-case.

I actually tried this as well, and have gotten really good results.

I don't use balanced cabling, so it goes: HD650 stock cable > Neutrix 1/4 Female w/ Canare starquad > Power Amplifier.

The Power Amplifier is an Adcom GFA 5802 which is a 300W/channel into 8 ohms.

Pre Amp is Adcom GFP 565. Source is CEC CD5300.

I really like the result, especially soundstaging is phenomenal, and like catscratch, also improved speed, detail, and low-end control.

The problem is there is a low noise, sort of like radio interference noise (like what you guys are also getting), and I wonder what can be done about it?

Also, have anyone tried to build the Joseph Grado adaptor? I'm still trying to source the 10W resistors, but I can't discern why he designed a 2 ohm resistor connecting the hot and cold cables.

I'm also interested in this - never saw this thread when it was new.

Technically, what is a better solution, the Grado resistor technique or the ASL transformer technique?

[ting.mike]

I'm gonna try to build the Grado resistor one once I can find 10 watts resistors. ASL products is hard to find here.

I'm just using a cable with no resistors or impedance boxes and it works. So why is a resistor even needed? (other than for volume control maybe)

[deepak]

Using a Sennheiser cable terminated with a 4 pin male XLR connector, the K1000 tail adapter should work correct?

The K1000 adapter config (# corresponds to XLR pin number):

1 (white) L+

2 (black) L-

3 (red) R+

4 (blue) R-

[ting.mike]

Deepak: Assuming the wiring on the Sennheiser 4-pin XLR is identical to the K1000 tail adapter, I suppose it should work.

[TheSloth]

I'm thinking of making this adapter, and was wondering about the resistor values. If my physics isn't too off (it usually is...), do I understand from the 20 and 2 ohm resistor arrangement that the amplifier will 'see' a 2 ohm purely resistive load, and that the vast majority of the current will take the 'easy' route and be sunk straight to ground?

Would one not then want to adjust the value and relationship between the resistors to reflect firstly the ideal load for the amplifier, and secondly the amount of attenuation required to match the phones' sensitivity?

[n_maher]

All I'm really sure of is that the 2ohm and 20ohm resistors form a voltage divider on the output that will give you about 1/10th the output V. As far as the load the amp sees I would think that the 20ohm and 32ohm (nominal impedance of the Grados) would be in series for an effective resistance of 52ohm and that this resistance is also in parallel with the 2ohm resistor. Not sure what this accomplishes but I do believe that the amplifier will effectively see a 2ohm load (actually a little less) which hardly seems like a good thing to me.

A more informed opinion is definitely needed.

[aerius]

Actually the amp sees the 20 ohm load in series with the paralleled load of the 2 ohm resistor and the headphone. In the case of Grados this would work out to a bit under 2 ohms in series with 20 ohms.

I've built one of these doohickeys with 5W resistors way back in the day, my sources & 'phones weren't that great back then so I didn't really notice much of a difference, if any, between the adaptor output and the headphone output on my receiver.

[kelvinz]

Cool ting.mike, Smeggy, and I were having a conversation regarding this late lat night in chat.

Wanted to verify one thing. The consensus last night was re-terminating my hd800's to speaker/banana plugs and using the speaker amplifier section of my b22 wouldn't yield any extra power to the headphones vs. the headphone jack?

[dBel84]

I have built a simple version which uses an 8 ohm 5+W resistor to load the amp and a 100R in series with the headphones

Rod Elliot has a more thorough approach to balance power supply and impedance.

..dB

[TheSloth]

snip

Going back to my question, how did you choose those impedance values? What is the thinking behind the choice of different values?

[dBel84]

I chose a load that my amp would be happy with, 8 ohm seemed about right. Any additional resistance in parallel is going to be negligible. I wanted to attenuate the signal and 100 R seemed a good starting point and I had them sitting in my parts bin.

This was not a scientific process by any means but rather a scrounge through the parts bin to see what was available and what I could make work.

I am sure this has been mentioned in this thread but just a reminder not to try this with differential output amps ( ie bridged output ) - in other words , no amp that doesn't use a common ground for the output stage.

..dB

[Dusty Chalk]

But theoretically, you could do the same sort of thing (present loads between the two sides to ground, then run another resistor in series with the headphones), right? In fact, in that case, you'd run the two sides of each headphone against each other and not to ground.

[dBel84]

yes , you could load both sides of a differential amp, make sure you used a 4 pin xlr so that the headphones are driven balanced , you could probably just attenuate one side as the amp would see the same resistance of HP + resistor ( my anal symmetry freak side would want to put 1/2 R on each leg but that is my own nightmare ) .

Out of all the soultions, I like the transformer matching box the most ..dB