Amps with Crossfeed circuit?

0 Members and 1 Guest are viewing this topic. Read 977 times.

dB Cooper

Re: Amps with Crossfeed circuit?
« Reply #20 on: 4 May 2018, 01:43 pm »
BTW, Tyll Hertsens of Innerfidelity just did a report on something called the 'Smyth Realizer' which is probably the state-of the-art in headphone spatial presentation. He raved about it. It's a hybrid DSP/hardware solution, apparently. Downsides are high cost and possibly separate costly calibrations required for each headphone (not for 'headphone rolling') (the article isn't clear on this but IIRC it was mentioned by Mark Waldrep in one of his blog posts.)

Video mentioned in the article, describing the 'Smyth Realizer' system

In the meantime, until there is a cost breakthrough in this technology, I'll continue to use crossfeed most if not all of the time. It's not perfect, but it usually does improve the 'headstage'.

By the way, if you watched the video... One of the many parameters controllable in the Canz3D plugin is head circumference. Since HRTF is critical to the presentation, and everybody's will be different, having someone measure your noggin and plugging in the result may be very helpful to the presentation. This is a perfect example of something that would be difficult to impossible to implement in the analog domain.

adydula

  • Full Member
  • Posts: 1565
Re: Amps with Crossfeed circuit?
« Reply #21 on: 4 May 2018, 04:48 pm »
I built this amp severl months ago:

http://www.diyaudio.com/forums/headphone-systems/304684-ampcasq-opa1622-integrated-headamp-project.html

Here is Chris's intro....I was interested in the new specifically designed OPA 1622 TO chip the was designed for Headphone amps..
Chris wanted to experiment with crossfeed, so I got to build it and try this implementation of crossfeed for myself.

If you go to the link there is a link to the actual Xen Audio cross feed circuit and design as well as a description of how it works.
It definitely added to the cost with the switching stuff....

"Hi All,
Like some of you I followed with great interest the thread 'New Audio Op Amp - OPA1622' by TI’s Johnnc124. I wasn’t initially specifically interested by headamps but as the OPA1622 was simple to implement and was supposed to provide good results I decided to setup a project with it. More than building an headamp this project was aimed to confirm I could achieve designing a PCB with a CAD software and also soldering SMD devices, including ones in DFN or QFN package.

I’have finally been through all steps, I’m happy with the result (OPA1622 sounds very good !) and I’m now confident to move to projects that will require complicated PCB and good soldering capabilities.
Now, I have to finish assembly and testing of a Salas DGC3 in order to do some comparisons!

The main requirements for AmpCasq where :
It should stand in a small aluminum box, in order to sit on desk
It should be powered by an AC adapter I had, which provided 17VDC
It should have a volume control
It should have RCA and jack 3.5 inputs
It should have jack 3.5 & 6.35 outputs
It should allow me to experiment crossfeed
Final price should stay under control

About the schematics:
Regulators:
Ampcasq was designed in September 2016, at this time LM27762 was announced but not available. So, I did stay with LM27761 for -5V and LP38798 for +5V; LP5907 was a bit short on current. The 7805 lifted by R17/R12 was added to limit LM27761 input voltage to 5.5V, its max value. 7805 allow Ampcasq to be powered by any DC source from 10V to 35V, 300mA max.
Power Input:
D1 to protect against bad connection.
D2, R23, R10, R11, C24 to manage the Enable pin of the OPA. Objective was to avoid noise in the can at power up/down. This partly works: mute the output when enable Low (<~0.8V) but can’t avoid noise in can when power supply capacitors are discharching and OPA1622's supply getting out of tolerance. On power off with SW1, OPA1622 is muted as C24 is quickly discharged through R23, D2 and SW1. D2 is a Schottky, not for speed but for low drop (Vf close to 0.3V).
Crossfeed:
It is based on an Xen-Audio (EUVL) paper: Xen Audio cross feed.
There’re three positions for the switch: Low Xfeed – No Xfeed – High Xfeed. Low Xfeed is Ok, High is exaggerate: there’s too much bass boost. After some listening sessions I finally do not use the Xfeed.
Gain + out
Not much to say."

So I built the amp and have a thread here on the circle with the build and listening results.

The net of it was the crossfeed had three settings, high, med and low.
I heard no real world difference in any of the positions with my set of headphones.

It was very subltle if any changes auduble etc...I then removed it and used the space on the pc board to build three selectable gain settings instead.

YMMV...
Alex


https://www.audiocircle.com/index.php?topic=150546.msg1610824#msg1610824

macdane

  • Jr. Member
  • Posts: 97
Re: Amps with Crossfeed circuit?
« Reply #22 on: 4 May 2018, 05:38 pm »
Most if not all of the HeadRoom amps, desktop and portable, had switchable crossfeed; in fact, it was their 'calling card'. There were (are? haven't looked lately) a variety of them.

I think part of the reason I'm surprised at the relative lack of crossfeed options is that both Headroom and Meier were major players in the market last time I went through this process. At the time, I ended up buying the Meier Cord Prehead and I'm still enjoying it immensely.

What are your sources? My listening is almost 100% from computer, do I do crossfeed in software. (I use a Mac so the following may not be helpful to you, but...)

My primary source at home is a MacBook Air with a Meridian DAC, but headphone duties there are under control thanks to the Prehead. What I'm looking for now is a good portable solution. A local coffee shop serves as my "office" and I like to listen in my own world while working there. To that end, I have a pair of Opposite PM-3s with the Opportunity HA-2SE DAC/amp and I've also played with a friend's Dragonfly Red. In both cases, my most significant complaint is the lack of a crossfeed option. In this setting, I sometimes use my MacBook Pro as a source and sometimes my iPhone, so I think an amp with crossfeed makes the most sense.

Thanks,
Dane

macdane

  • Jr. Member
  • Posts: 97
Re: Amps with Crossfeed circuit?
« Reply #23 on: 4 May 2018, 05:40 pm »
Wow, the Leckerton amps are very reasonably priced (starting at $219 for a portable DAC/amp?!?  :o  )
That might take the HeadRoom used amps out of contention unless the price is really right. Thanks hayden.

Agreed ... these look like a real possibility.


macdane

  • Jr. Member
  • Posts: 97
Re: Amps with Crossfeed circuit?
« Reply #25 on: 4 May 2018, 06:03 pm »
I believe some of the iFi portable gear has something called 3D which they say is better than crossfeed eg. https://ifi-audio.com/portfolio-view/micro-idsd/, https://ifi-audio.com/portfolio-view/nano-ican/

I've seen these but, frankly, I don't find their claims very persuasive. They offer essentially no explanation of what they're doing other than that it's not just a rehash of the techniques used by Bauer and Linkwitz. Since the Meier circuit works really well for me, I'm leery of trying something different that's described so vaguely.

Dane

macdane

  • Jr. Member
  • Posts: 97
Re: Amps with Crossfeed circuit?
« Reply #26 on: 4 May 2018, 06:14 pm »
I know these two with integrated crossfeed + more 
I own both of them  8)
the minidsp HA-DSP for travelling
https://www.minidsp.com/products/dsp-headphone-amp/ha-dsp

Thanks Juergen. Is the HA-DSP as complicated as the manual makes it seem? While I appreciate the array of options offered by an approach like this, I'm not looking for a new hobby. I'm starting to wonder if my best bet will be to look for one of Meier's old portable amps with crossfeed ... I'm not sure, but I think he had some at one point.

Dane

wagnju

Re: Amps with Crossfeed circuit?
« Reply #27 on: 5 May 2018, 06:09 am »
Hi Dane
The HA-DSP is not a easy plug and play unit. It sounds very good but I have to admit that you need some patience to set-up the huge amount of options . I have the unit since 4 months now and I'm still playing with different setups .
So I wouldn't say the unit is complicated but it is challenging to find the right setup that fits your taste . Just too many choices for setup , maybe a little bit too much for me , maybe heaven for somebody else  8)
« Last Edit: 5 May 2018, 02:28 pm by wagnju »

FullRangeMan

  • Volunteer
  • Posts: 10325
  • All Tweeters look like a target, then shoot them!
    • Never go to a psychiatrist, adopt a straycat or dog. On the street they live only two years average.
Re: Amps with Crossfeed circuit?
« Reply #28 on: 5 May 2018, 06:29 am »
The owner manual dont suggest settings?

adydula

  • Full Member
  • Posts: 1565
Re: Amps with Crossfeed circuit?
« Reply #29 on: 5 May 2018, 03:16 pm »
I went to the HA DASP site and read the 40 page manual.

This device is a DSP for sure with many, many variables, settings and adjustments....your going to have to be a rocket scientist to really understand its complex design and settings....IMO this is not an easy device to use by folks that just want tp press some buttons to change the sound.

It looks like it can be a really nice tool in the hands of someone that really understand audio processing, recording etc...

There is a simple plug and play mode...but the power of the DSP IMOP cant be unleashed unless you read and understand the various setups and interactions.

My guess most people would become confused and most likely screw up stuff and get frustrated...so again IMO if you buy this device understand what your getting into and what you want to do...and will this device allow you to accomplish that??

Alex

EkW

  • Jr. Member
  • Posts: 4
Re: Amps with Crossfeed circuit?
« Reply #30 on: 8 May 2018, 04:12 am »
I too read through the long manual but could not find a single mention of crossfeed in it. The Leckerton units look nice but they provide no info on how they implement the crossfeed. I have an old Meier Porta-Corda amp and really like the crossfeed. Not sure why Meier doesn't make a portable unit any more.
Many years ago I rigged up a potentiometer to reduce the channel separation. It kinda worked; using a good audio taper pot would have helped. My old Apt-Holman preamp had knob that provided L+R when turned clockwise and L-R when turned CCW.
I wonder if it would be possible to implement a passive crossfeed circuit inline with the headphone cable?

macdane

  • Jr. Member
  • Posts: 97
Re: Amps with Crossfeed circuit?
« Reply #31 on: 8 May 2018, 05:25 am »
I too read through the long manual but could not find a single mention of crossfeed in it.

It's in there ... sorta. There are several pages on FIR filtering, of which I think crossfeed is a part, but no specific mention of it or instructions regarding *how* to do it. For someone who wants to do a lot of fiddling, I can see where this would be a good tool. Personally, I want zero fiddling.

The meier crossfeed just plain works for me and it's a simple matter of turning it on. Well, ok, my Prehead offers a choice of off/low/medium/high crossfeed, so it's slightly more complicated than just turning it on, but barely. And virtually 100% of the time, *any* level of crossfeed is better than "off."

If I didn't know it'd end in certain disaster, I'd buy the Porta Corda kit from the Meier site; I'm envious that you have one!

adydula

  • Full Member
  • Posts: 1565
Re: Amps with Crossfeed circuit?
« Reply #32 on: 8 May 2018, 05:04 pm »
I mucked with the XEN Audio implementation in several ways and never found it to be worth it or that it really made a whole lot of difference.
I find that finding well recorded (mic'd) material hjas a more pronounced affect of the listening experience.

So if you indeed find a crosfeed circuit implemetation that you like..it may work you with some material and be even worse on other material.

Audio source material is so different across the board, I constantly look for recordings that are done well up front....I have several recordings of
a particular song, some sound like CRAP and others sound awesome....

YMMV
Alex

macdane

  • Jr. Member
  • Posts: 97
Re: Amps with Crossfeed circuit?
« Reply #33 on: 8 May 2018, 05:33 pm »
I mucked with the XEN Audio implementation in several ways and never found it to be worth it or that it really made a whole lot of difference.
I find that finding well recorded (mic'd) material hjas a more pronounced affect of the listening experience.

I'm not familiar with XEN, but I think one lesson here is that preferences and priorities vary from listener to listener ... otherwise there'd be no need for the vast array of options in the marketplace.

I think it's a given that well recorded material is a plus, but sometimes that's not an option. There are certainly some recordings that I only have because of their sound quality; most often, though, my priority is on the music.

So if you indeed find a crosfeed circuit implemetation that you like..it may work you with some material and be even worse on other material.

The reason I said "virtually 100% of the time" is that I necessarily have a large handful of mono recordings — perhaps 5% or so of my library? — and for those I switch the crossfeed circuit off. Other than that exception, I'd have a hard time pinning down a stereo recording that in *my* experience doesn't benefit from the Meier crossfeed.

As I said earlier, I'm leaning more and more toward looking for an old Meier portable amp as the solution to my particular issue, since I know their crossfeed implementation works for me.

Dane

adydula

  • Full Member
  • Posts: 1565
Re: Amps with Crossfeed circuit?
« Reply #34 on: 8 May 2018, 09:55 pm »
Dane,

What headphones do yoiu use?

Alex

macdane

  • Jr. Member
  • Posts: 97
Re: Amps with Crossfeed circuit?
« Reply #35 on: 8 May 2018, 10:43 pm »
Dane,

What headphones do yoiu use?

Alex

At home (with the Meier Prehead) I alternate between DT-880s and K-501s, with the AKGs getting perhaps 70% of the time on my head. Well, 70% of the relatively little time I spend listening to headphones, since I'm primarily a 2-channel speaker guy. I like certain things about each of those but have never been super happy with either, and to that end I'm considering adding ... something to the mix.

Most of my headphone listening is done at a local coffee shop that serves as my office most days. So here I need a closed-back set and the best balance of price-sonics-mobility I've found is the Oppo PM-3. My source is ALAC files served by either my laptop or my phone, and then fed into the Oppo HA-2SE DAC/amp.

I've had two gripes with that mobile rig. First, my ears get really hot when listening to the Oppos. Second, the HA-2SE doesn't have crossfeed ... which is why I'm here!

Dane

maty

  • Full Member
  • Posts: 954
    • Nauscopio Scipiorum
Re: Amps with Crossfeed circuit?
« Reply #36 on: 9 May 2018, 09:41 am »
https://headfonics.com/2018/04/rme-adi-2-dac-review/2/

Quote
Crossfeed

I love crossfeed. I use it all the time. My first serious head-amp was the Meier Corda Jazz because it had crossfeed. Usually, recordings are mixed for speakers in a stereo setup. This results in strong channel separation that can cause fatigue when listening over headphones.

RME gives you 5 options to remedy this. The 2nd option is actually based on Jan Meier and thus is a DSP emulation of the hardware crossfeed found on Corda amps. The 4th option is supposed to emulate a stereo speaker placement in 30 degrees at a 3m distance.

The experience is definitely not as strong as some gimmicky head tracking or surround emulations, but for that, they stay clean and precise. Except for the 5th option, I haven’t noticed any mud or lack of resolution introduced. As I often see false information: These are not equalizer settings! Crossfeed considers the time domain and treble adjustments of the opposite channel. Also, crossfeed is not the same as crosstalk. The latter is information with the wrong polarity, effectively damaging the signal.

adydula

  • Full Member
  • Posts: 1565
Re: Amps with Crossfeed circuit?
« Reply #37 on: 9 May 2018, 01:09 pm »
I read the headphonics link just posted and it was interesting and helpful in understanding what the design and engineering side of this subject is.

If the article is correct in that most cd's music etc are made (recoreded/mic'd) for 2 cha stereo systems then IMO your going to need a seperate set of crossfeeed settngs or circuits for potentially each cd you have.

In my thousands of cd's they are all over the place in quality and recording and how they were mic'd..

So many of us look for heeadphones that have large soundstages, differing frew response curves etc..and many varing types of dace, amps, cables, tubes , opamps etc....and now your adding a crossfeed variable...

Seems like this had gotten to a point where things hae become very complex......???

I have always tried to keep all but the minimum "stuff" between the source and the transducer....a system that can discern a good recording from a mediocre one...and I am at that point.

These IMO "magic" boxes that tinker with crossfeed are indeed intriguing but seem to require a bit of tinkering....I guess that maybe a few settings might be used with a majority of your cds or material....just dont know.

In a perfect world it would be nice to have a intelligent processor in these crossfeed boxes that would detect how to set up the materail based on how its recorded to emulate a 2 ch stereo system iin your headphones...

But headphones are not speakers and this may not ever be totally possible, but its neat stuff for sure...

Alex

macdane

  • Jr. Member
  • Posts: 97
Re: Amps with Crossfeed circuit?
« Reply #38 on: 9 May 2018, 02:37 pm »
https://headfonics.com/2018/04/rme-adi-2-dac-review/2/

That's cool, but looks like another way-too-complicated solution for my needs. And among RME's dizzying array of products, I haven't yet found anything that looks portable. Thanks for the info, though.

Dane

maty

  • Full Member
  • Posts: 954
    • Nauscopio Scipiorum
Re: Amps with Crossfeed circuit?
« Reply #39 on: 9 May 2018, 02:48 pm »
It is desktop DAC I have selected to buy if someday I find an amplifier that satisfies me.

Review and Measurements of RME ADI-2 DAC

https://audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-rme-adi-2-dac.2582/

These measurements do not detract from those that appear in the manual, highly recommended reading.

And it has a very important characteristic to me: it uses super low noise regulators -> very clean power to the circuits. With the own external SMPS -> it does not problem with DC at mains (I have a lot).

By the way, DC at mains is problematic with the phono too and not only with big amplifiers. Well, if you want to listen very good records or to make very good vinyl rips.