What?! Another headphone amp kit?! Smack me!
- Thread starter Doc B
- Start date
From what I have seen the people that are playing with "balanced" headphone output (which seems to be more concerned with supplying separate signal cold rails for each channel rather than balancing the output signal with respect to ground) are using a full sized 3 pin XLR connector for each channel. So that is what we are using. Not sure that I grasp the second question properly, but the single ended and balanced outputs are all switched from the output transformer, so there won't be a need for any additional transformers.
Actually, you answered my second question with your first answer. Balanced, not differential -- got it -- i.e. individual returns, not balanced with respect to ground.
A little poking around and I see that's what the headphone crowd referers to as balanced, where as the pro world has a somewhat different interpretation/execustion of that idea.
This too sounds to be another great bh product, and I suppose I'll just have to get one.
-- Jim
A little poking around and I see that's what the headphone crowd referers to as balanced, where as the pro world has a somewhat different interpretation/execustion of that idea.
This too sounds to be another great bh product, and I suppose I'll just have to get one.
-- Jim
Yeah, separate signal cold for each channel is what the emphasis is in the HP community. You can do that single ended like we do with separate Paramounts and K1000s. Of course that presumes the L and R signal cold is not common in the source or preamp ahead of the amp - not a very safe assumption. But Smack will be true balanced output with respect to ground, that is, it is transformer "decoupled" and there will be a grounded center tap.
Armaegis
Member
From what I understand, the cold on each side is an inverted signal from the hot, giving an effectively doubled voltage swing. As such, balanced headphone amps have twice as much circuitry because they're essentially amping 4 channels rather than two.
If you're feeding in an unbalanced source, it could be set up such that the cold on each side is essentially amping zero and the headphone operates as normal. Some balanced amps also have dual unbalanced outputs, with output 1 giving out hot left/right, and output 2 giving out cold left/right (and in a couple examples I've seen, use this as a default then use an adapter to hook up balanced headphones).
If you're feeding in an unbalanced source, it could be set up such that the cold on each side is essentially amping zero and the headphone operates as normal. Some balanced amps also have dual unbalanced outputs, with output 1 giving out hot left/right, and output 2 giving out cold left/right (and in a couple examples I've seen, use this as a default then use an adapter to hook up balanced headphones).
So are the amp manufacturers going to a single 4 pin XLR as well, or is this primarily a DIY movement? When I Google 'balanced headphone cable' images most shown have two three pin XLR plugs, though there are a couple 4 pin as well. Maybe the thing to do is sell the amp as I have designed it, with the chassis punched for a pair of XLR D type connector jack shells. That way one could use the standard pair of three pin XLRs or replace them with a single 4 pin XLR, or even a pair of TRS jacks in D style shells, depending upon what is on your headphone cable. We could make this an order option.
Looks-wise, imagine a S.E.X. amp but with no plate chokes on top and nine pin miniature 5687s rather than octal 6DN7s. And it will have the XLR sockets where the speaker binding posts are on a S.E.X. amp, at the back. We're going to see if we can cook up a special pre-order price today and let folks start queuing up, as I think we can have this ready to ship in about 4 weeks.
Looks-wise, imagine a S.E.X. amp but with no plate chokes on top and nine pin miniature 5687s rather than octal 6DN7s. And it will have the XLR sockets where the speaker binding posts are on a S.E.X. amp, at the back. We're going to see if we can cook up a special pre-order price today and let folks start queuing up, as I think we can have this ready to ship in about 4 weeks.
Armaegis
Member
RSA using a large 4-pin XLR for their full sized, and a small 4-pin square thing on their portables...
http://www.raysamuelsaudio.com/
iBasso has some sort of 6-pin connector on their portable balanced amp...
http://ibasso.com/en/products/show.asp?ID=70
and mini6 to large 4-pin adapter: http://ibasso.com/en/products/show.asp?ID=68
http://www.raysamuelsaudio.com/
iBasso has some sort of 6-pin connector on their portable balanced amp...
http://ibasso.com/en/products/show.asp?ID=70
and mini6 to large 4-pin adapter: http://ibasso.com/en/products/show.asp?ID=68
Well, as usual the industry has a big gun aimed at their foot when it comes to setting standards that make it easy for the consumer. I'm just gonna go with the most universal mounting holes we can offer. The D style mounting hole allows for XLR, TRS, RCA, Tuchel, Speakon, CAT-6 and probably a bunch of other styles of jacks. I'll let the cable guys make adapters for the oddball stuff.
It's single ended, just a single very linear triode gain stage for each channel. The other triode in each tube is the heart of the hybrid shunt regulator for the corresponding gain stage. SE is our area of expertise and IMO it sounds better than PP for these low power levels. You might take a look at the Paramount soft start driver stage upgrade kit. It's basically the same topology on the same PC board driving an output transformer rather than a 300B. But what you will see under the tube sockets will look very similar.
Rather than making a differential circuit the balanced output is derived at the output transformer secondary, a method that allows for great isolation of the left and right signals and, IMO, better retention of subtle spatial cues in the signal.
Rather than making a differential circuit the balanced output is derived at the output transformer secondary, a method that allows for great isolation of the left and right signals and, IMO, better retention of subtle spatial cues in the signal.
I think that the idea could work well as long as both sets of cans are the same sensitivity, like your two pairs of HD 600 concept. Otherwise, only let the person with the more sensitive cans set the volume! I have some 650s on the way so I can test the theory with my 600s and the 650s.
Paul Joppa
Moderator
I'm still refining the switching matrix, but here's some complicated details:
1) The switches will be on a board that mounts below the output transformer, under the chassis - so it's not for frequent switching, but no soldering requires to change the settings.
2) there are two impedance switches, giving four possible impedances. They'll be labelled LO, ML, MH, and HI, (16, 32, 64, and 128 ohms respectively) so the same switches can be used with the SEX amps and the Stereomour - they all have OPTs with the same topology, though different impedances.
3) There will be a third switch on the board, for balanced or single-ended output.
4) Here's the messy part - there are eight possible settings, and two kinds of output, as you can see. Total 16 combinations! I'll try to summarize - please understand, I'm on my second G&T (see other posts - family distractions going on) so this may not be accurate :^)
LO and ML impedance, balanced - the XLRs are balanced with 240 ohm resistors to ground from either balanced output; the 1/4" jack in front is IHF standard 120 ohms source impedance, like the stock SEX.
LO and ML impedance, unbalanced - the XLRs are grounded on the cold side, same as the 1/4" jack in front. The 1/4" jack sees the full voltage, same as the XLRs, with no extra series resistance.
MH and HI impedance, balanced - the XLRs are balanced with the transformer center tap to ground from either balanced output; the 1/4" jack in front is on one half of the output transformer (half the voltage of the balanced outputs).
MH and HI impedance, unbalanced - the XLRs are grounded on the cold side, same as the 1/4" jack in front. The 1/4" jack sees the full voltage, same as the XLRs
1) The switches will be on a board that mounts below the output transformer, under the chassis - so it's not for frequent switching, but no soldering requires to change the settings.
2) there are two impedance switches, giving four possible impedances. They'll be labelled LO, ML, MH, and HI, (16, 32, 64, and 128 ohms respectively) so the same switches can be used with the SEX amps and the Stereomour - they all have OPTs with the same topology, though different impedances.
3) There will be a third switch on the board, for balanced or single-ended output.
4) Here's the messy part - there are eight possible settings, and two kinds of output, as you can see. Total 16 combinations! I'll try to summarize - please understand, I'm on my second G&T (see other posts - family distractions going on) so this may not be accurate :^)
LO and ML impedance, balanced - the XLRs are balanced with 240 ohm resistors to ground from either balanced output; the 1/4" jack in front is IHF standard 120 ohms source impedance, like the stock SEX.
LO and ML impedance, unbalanced - the XLRs are grounded on the cold side, same as the 1/4" jack in front. The 1/4" jack sees the full voltage, same as the XLRs, with no extra series resistance.
MH and HI impedance, balanced - the XLRs are balanced with the transformer center tap to ground from either balanced output; the 1/4" jack in front is on one half of the output transformer (half the voltage of the balanced outputs).
MH and HI impedance, unbalanced - the XLRs are grounded on the cold side, same as the 1/4" jack in front. The 1/4" jack sees the full voltage, same as the XLRs
I can say that Red Wine Audio on the new Class A headphone amp module only uses the 4-Pin version. Also Ray Samuel has included the 4-Pin besides the dual 3-Pin on his units. The new Apex Pinnacle a $10,000 unit includes both versions, the Eddie Current ZDT and Balancing Act have a 4-Pin as well. Hope this helps.
OK, our production prototype (the one we photograph for the assembly manual) chassis is on order, and after a once over of PJ's design I will be ordering some of the output switching PC boards. These boards are quite versatile in that they will also fit the S.E.X. V2.1 and the Stereomour, allowing for switchable output impedance on those amps as well.
Did a bit of listening with our prototype today, which we have set up with rotary switches to allow switching between 32, 64 and 128 ohms output impedance. This rotary switch setup is a bit of a kludge that we did before having worked out the more refined and useful slide switch scheme that will be in the production model.
We listened to a range of headphones - HD600, HD650, K701, MB Quart QP400, Skullcandy Aviator and Ultimate Ears Triple Fi 10V ranging from 32 ohms impedance to 300 ohms. The switchable settings really work well, we found that each headphone seemed to work best at the impedance setting closest to its own impedance. The high impedance cans sounded really nice and the low and medium (K701) impedance cans that we more or less came up with the Smack to work with sounded great as well. Unfortunately I don't have an assembled Crack amp handy to A/B, but I think I would still put my money on Crack as the very best bet for 200 ohm+ headphones. For someone with a good sized collection of headphones who wants a single amp to use with them Smack is a great choice, though I think it's criminal to have many headphones and just one amp, myself. Smack and Crack together could give great performance from a whole lot of headphone types.
We listened to a range of headphones - HD600, HD650, K701, MB Quart QP400, Skullcandy Aviator and Ultimate Ears Triple Fi 10V ranging from 32 ohms impedance to 300 ohms. The switchable settings really work well, we found that each headphone seemed to work best at the impedance setting closest to its own impedance. The high impedance cans sounded really nice and the low and medium (K701) impedance cans that we more or less came up with the Smack to work with sounded great as well. Unfortunately I don't have an assembled Crack amp handy to A/B, but I think I would still put my money on Crack as the very best bet for 200 ohm+ headphones. For someone with a good sized collection of headphones who wants a single amp to use with them Smack is a great choice, though I think it's criminal to have many headphones and just one amp, myself. Smack and Crack together could give great performance from a whole lot of headphone types.
