Zigisg Portable Amp

[Deleted]

Spot on with the Neco, Frans. It isn't as loud. It is better with lower impedance, I think. I just seem to have hit a sweet spot with the AKG601.

I wish I could understand this power thing more because it is quite confusing. The Zigisg gives the impression of having enormous weight and power in comparison to many other portables and yet Zigis was quoting quite low gain.

So there is more in the matching of amp to impedance than I thought. I thought that the AKG K601 would be a very difficult load for it which is why I tried it and got the shock of my life. It's really powerful sounding.

So the Zigis is providing a good strong amount of voltage whereas others may supply more current? It's working it out that's difficult!!

[JohnnyBlue]

Ian

I have problems grasping all this, as well. I have an amp with specs giving 40mW output into 300 ohms, and another that allegedly gives 200mW into the same load, yet is not as loud!

I suspect Frans will despair of us: he's written this all up in his PDF about impedances and power, etc., but until we're thoroughly immersed in it, as he is, we're always going to struggle!

[Deleted]

John, I think it's more of a question of matching.

With ham radio, you can use any piece of wire as an aerial, but it won't transmit efficiently because it's not tuned or the correct length for the frquency you're transmitting on.

By making a 'tuning' circuit (with resistors and capacitors - preferably with a tunable capacitor) you can electrically 'match' the wire to the frequency that you're transmitting on so suddenly, the 'incorrect' length of wire becomes very efficient as an aerial.

To some extent, amplifiers and headphones work in a similar way but guys in hi fi call it synergy.

The signal is transferred more efficiently into certain loads and Frans is correct in that the Zigis drives the 120 ohm K601 extremely efficiently. It almost seems like a portable headphone on it!!

I guess it's more about the 'efficient' transfer of power without losing too much energy in the system.....

Now Frans will probably tell me off.

BTW, your amp is on its way. It'll arrive Monday. Many thanks John. The new Zigis is slightly better imo. Shorter signal paths and the capacitors gone seem to clean it up a bit. The earthing I'm not sure about how it affects the sound but I must admit, the sound of the K601 is way better with a simple little CMoy!!! How weird is that?

[Deleted]

By making a 'tuning' circuit (with resistors and capacitors - preferably with a tunable capacitor) you can electrically 'match' the wire to the frequency that you're transmitting on so suddenly, the 'incorrect' length of wire becomes very efficient as an aerial.

Hi Ian
I think you meant L not R. Ian is referring to the Standing Wave Ratio (S.W.R.) being optimised.
Kind Regards
Alex

[Deleted]

Feb 17, 2012 22:28:35 GMT JohnnyBlue said:

I suspect Frans will despair of us: he's written this all up in his PDF about impedances and power, etc., but until we're thoroughly immersed in it, as he is, we're always going to struggle!

X2



I actually printed out his impedance pdf and took it with me on holiday last year to read (and try to understand) by the pool. How sad is that ;D

And I'm still not sure I understand it fully.

It was written in english wasn't it?

Jeff

[Deleted]

Where did he stash the PDF?

[Deleted]

Antennae have to be matched for optimal power transfer (they transmit power, not voltage)
This is very difficult theory to grasp the antennae business and indeed with certain parts you can effectively 'elongate' antenna wires so they are effective at certain wavelenghts.

Audio amps give an output VOLTAGE and how much power is delivered depends on the headphone impedance.
The maximum output voltage it can give is determined by:
a: power supply voltage
b: circuit (topology)
c: output resistance
d: maximum current it can deliver

So in order to understand output power correctly all 4 quantities have to be 'looked at'.
How much power can be delivered (maximum) depends on the headphone impedance.

How LOUD one perceives the same amounts of power depends on the time of day.
This last part is the most confusing as during the day our hearing is 'dimmed' so we don't get swamped by sounds.
during the small hours the automatic gain control gets higher and we hear more sensitive.
Unless we have gone to a live rock concert or disco, in that case the volume control in our brains is at it's minimal setting.

Also how loud some thing is is determined by the efficiency of the headphone.
Unfortunately some numbers are given at 1V and others at at 1mW so not comparable.
Sometimes only the voltage or power is given to reach 90dB (or another value) or only the maximum SPL is given.

Another part is output power specifications that are given by vendors.
Everyone knows about small kids stuff with 200W PMPO on it right.
it has small 2W speakers in it and a trafo that doesn't even manage 10W.
Yet they probably don't lie and indeed the 200W PMPO can be measured.
PMPO is Peak Mono Power Output and is the combined power (left and right added) at maximum clipping level and measured during a msec or so, in essence the smoothing caps capacity and not sound.
Juggeling with figures it is and most vendors are doing just that in their manuals.

For specs of headphone amps it is slightly different as a vendor should specify which power in which impedance.
an amp that just says 200mW and doesn't specify the load impedance but merely states 16 Ohm to 300 Ohm may well give 200mW in a 32 Ohm headphone but this can be because of:
a: low output resistance
b: low output voltage
c: high current capability.
In a 300 Ohm headphone though there is not enough voltage to reach the 200mW in fact it manages only 21mW in 300Ohm.

On the other hand the Zigis (with 24V) manages 100mW into 300 Ohm but with only 1 channel driven 200mW !
the same amp with a 32 Ohm load manages 10mW in 32 Ohm.

the PA2V2 with it's power supply of only 2.4V (rechargeables) can only manage 30mW in 32 Ohm and 3mW in 300 Ohm.
When one realizes this amp (with portable equipment) is often considered 'powerful' it shows 10 to 30mW often will do in creating a pretty loud level.

Most amps have a peak in the maximum power output somewhere between the lowest and highest impedance of headphones.

So a specified power doesn't say much unless specified with
a: impedance of the headphone
b: specified distortion

if one amp is specified at 10% (yet not mentioned) and the other at 0.01% for instance the figures of the 10% version are more impressive.
Yet when we turn those up we stop when a certain amount of distortion is reached.
It may well be (topology reason) the one with the lowest power rating goes loudest simply because the 10% distortion amp leaves it undistorted area at a smaller power level than the lower spec'd one.



You do not need much power with some headphones to play loud.
KIng is possibly the DT1350 , yet it may play softer than less efficient headphones depending on output resistance of the amp and impedance of the headphone it is compared with.

Confusing.... isn't it.

In the end all can be easily explained.
yet it isn't synergy or power matching but the math.

Tell me which amps you meant and I will look into it but won't do that any time this question is asked.
It takes quite some time to find stuff out about amps and do the math based on used parts and voltages.

[JohnnyBlue]

Feb 18, 2012 8:20:38 GMT @iancraig10 said:

Where did he stash the PDF?

Ian, you have PM.

[JohnnyBlue]

Frans

Thank you so much for explaining all this so clearly, and I don't even know any more which amps it was for which I quoted those output powers. I was also thinking of amp specs where the quoted figures into different impedances don't match up mathematically in terms of the calculated output voltage.

Here's an example:

Matrix M-Stage
Impedance mW V
300 200 7.7
60 400 4.9

That's quite a difference in stated V output!

Also I'm intrigued by your comments on our hearing varying over the 24 hour day (what we Biologists call a diurnal rythym): do you have any links as to where you read about this? Or is it something based on your own observations, such as loud noises causing a (hopefully temporary) deafening?

[Deleted]

I think we all have days John, when our choice of equipment sounds below par.

I had my own theory that it was perhaps atmospherics that was causing this negative effect on SQ, but its probably wrong.

Mick.

[JohnnyBlue]

I'm totally familiar with hi-fi sounding good/awful at different times of day: I know after midnight my system sounds fantastic (when everybody's gone to bed and turned off their TVs, etc.) but then it's too late for me to enjoy it anyway.

I was interested in Frans' comment about the time of day:

"How LOUD one perceives the same amounts of power depends on the time of day.
This last part is the most confusing as during the day our hearing is 'dimmed' so we don't get swamped by sounds.
during the small hours the automatic gain control gets higher and we hear more sensitive."

[Deleted]

Own observations and by reading tons of articles on perception.
Can't really tell where they were..
I soke up info but can't really tell where I found it.

Ever gone to a disco/loud rock concert and went outside and couldn't hear the cars ?
a clock/watch you don't hear during the day, but can in the small hours ?
waking up and hearing how the 'volume' is turned up on waking up within 1 or 2 seconds ?

The most believable theories (to me) are:
To shut out irrelevant noises during the day and the evolution theory stating the humans must rely on hearing when it is dark (to be alert to predators).
This 'volume' adjustment is gradual, so we don't really notice.
Similar to the iris in the eyes, although these react fast.

Here is a fun experiment I did a couple of times:

Let people listen to audio equipment in TL lighting for some time.
Ask them how it sounds... mostly answered 'cold and analytical'
Then change to cosy and dimly lit circumstances (candles or flame lighting).
If asked again (same gear and music playing) and it sounds warm and musical.

This shows how the brain interprets sounds different simply by change of input on other sensors (eyes in this case)

really fascinating stuff the perception thing.
This and other experiments made me falling of my 'audio religion' as I was a devoted subjectivist in my early days of audio.
I should write an 'audiobiography' called 'loosing my (audio)religion' or something. ;D

[Deleted]

Yes i agree, late evening usually gives the best results, and yes, seems plausible that our hearing is more switched on at that time of the day, unless you work a night shift, then perhaps its reversed.

Mick.

[Deleted]

I should write an 'audiobiography' called 'loosing my (audio)religion' or something.

Frans
There is a software writer in C.A. that NOW goes by the name of
"losingmyreligion" but his would more likely be for the opposite reason to you. ;D
Alex

[Deleted]

I reckon it should be called, 'Losing that Magic'.

or

'The Science of Hi Fi'

or

'I just Want to Know Why'

or

'Let's Talk about CrossTalk'

or

'The Bable according to Frins'

[Deleted]

Feb 18, 2012 8:30:17 GMT @solderdude said:

How LOUD one perceives the same amounts of power depends on the time of day.
This last part is the most confusing as during the day our hearing is 'dimmed' so we don't get swamped by sounds.
during the small hours the automatic gain control gets higher and we hear more sensitive.

I'll give you a perfect example of how true this is.
I get up at 04:15 on an 'early shift' for a 06:00 start. I like to get my news fix first thing so the TV in the kitchen goes on to BBC news 24. I have set the default switch-on volume setting so it is loud enough to hear but not loud enough to wake my wife.
Switching on at any time during the day and I immediately have to increase the volume by a quarter at least to hear it.
Our hearing definately does seem to have an automatic gain switch which kicks in at night.

Jeff

[JohnnyBlue]

I recognise this phenomenon as well, except it's the radio in the kitchen, which invariably blares out when I turn it on first thing, before the others are up. I wonder how much of it is due to some 'AGC', as Frans suggests, or something else, like awareness and consideration of others around us.

I have to say, my whole headphone addiction/fetish has only developed in the last few years, in particular since my daughter (now 13) was old enough to resist the charms of Bob Dylan or Keith Jarrett through my Linn/Naim system and 'graduate' onto her own choice of music (Beyonce and Cheryl Cole) through her iPod...

[sobs]

[Deleted]

BTW, if anyone would like a K601 cheap, this is a bargain ......

www.thomann.de/gb/akg_k601.htm

£119.60 (approx)

Pretty flat response and very accurate sounding.

[Deleted]

Schematics drawn based on pictures posted.

Above older version (probably different opamp used)
below newer version (with charging circuit)

differences
1: the absence of input coupling caps (now DC coupled)
2: the charging/power supply circuit.
3: different opamp used ?
4: diifferent PCB (now dual layer with ground plane)

[Zigis]

Prefect reverse engineering, solderdude:)

1M, 1K, 4.7K, 30K for old amp,
100K, 1K, 3K, 30K for new amp, 75 ohm,LM317 for charger

If some one want to try yourself, I can even offer a board.

Power caps are 470uF x 16V, low ESR PanasonicFM, 2pcs, opamp are OPA2134 in standard amp (old and new), in "German HiFi forum pack" amp - LM4562.

If my amp sound slightly better then other CMoys (I am not compare myself, few different CMoys owners told me this), I believe it is because of compact board design, no long wires between pot and chip's input, and most important - large power caps as close as possible to chip's power legs. I learn this from CarlosFM at diyAudio forum long time ago.

In new amp double sided PCB/ground plane I believe make small improvement too.

Of course, I understand, this is not world's best amp possible, however for small portable 1 battery amp there is not too much to make considerably better.
I know about railsplitter downside and reed O2 story and all assays.

B.T.W. New rechargeable version of amp are tested successfully and available now!

p.s. solderdude, thanks for tip, schottkys ar in my next farnell order list.

[Deleted]

If my amp sound slightly better then other CMoys (I am not compare myself, few different CMoys owners told me this), I believe it is because of compact board design, no long wires between pot and chip's input, and most important - large power caps as close as possible to chip's power legs. I learn this from CarlosFM at diyAudio forum long time ago.In new amp double sided PCB/ground plane I believe make small improvement too.

I agree the PCB design (ground planes) and the way decoupling is done will have the most influence if there is.
Changing gains will also have 'psychological' influence on how it is perceived.
Not easy to discern what perceived difference comes from what change if there is more than one.
Technically the newer PCB can give (measurable ?) improvements

The values I will draw in when I have some time for it.

It's good VFM for sure.
Myself I would use a different rail splitter but would add to complexity, size and price.

For the charger circuit and the given current I came out on 78 Ohm and figured you would either use 68 or 82 Ohm (E12) but since you are using low tolerance resistors the 75 Ohm is much closer. Should have thought of that as all the resistors used are 1%

[Deleted]

It's a nice, clean listen and I fin that it matches the 120 ohm K601's really quite well, Zigis.

I have tried other CMoy amps and this one has a good 'feel' about it as well. The gain is sensible and not over the top so you can drive the K601's loud at 11 to 12 o' clock.

With some other CMoys that I have tried, they go suddenly loud at the bottom of the range which makes them difficult with more sensitive headphones. This one has a nice range and gives a good, solid amount of bass weight with the AKG's. (They're not particularly known for their bass)

I thought that perhaps I was hearing a difference between op amps at first since I directly compared the V1 with this one that I have and there is an improvement. It sounds more extended and a little more 'airy' than the first one.

[Zigis]

With different rail splitter you mean unity gain opamp or other buffer after TLE, or something different? Additional buffer can "eat" more battery power, this is not good, if someone really use it as portable.

To be honest this 75 ohm I simply "steal" from amb's miny3, long time used design, probably work good.

Yes, all resistors used are 1% metal film.

[Zigis]

In the original schematic from Chu Moy, gain was even 10, really too much.
It would be really good to know, what gain folks prefer with different phones and with different sources.
Someone who have "German HiFi pack" amp (old with metal DC socket and LM4562) - there is gain 2.
For me, with HD580, gain 2 is enough in almost any situation, maybe except on some very poor youtube tracks.

Other advantage of low gain - you can listen on higher volume pot position, 12 and higher. In logarithmic volume pots larger imbalance between channels are in the beginning of track.

[Deleted]

valid point on the current consumption and longevity of the battery.
When working on external voltage however (it could be more powerful in that case) the idle current wouldn't be a problem.
It's just a personal minor gripe (the TLE application) .
It has advantages and disadvantages which of those is considered most important for the application determines the usage.
From your viewpoint (portability) the TLE as is (with the added caps, makes a real difference) is the best choice.
Changing the design could increase output power for 16 and 32 Ohm headphones but at the same time increases current consumption due to higher power levels and idle current.

The LM317 current source, just like the Chu Moy circuit, is a standard application that is found in almost every datasheet.
a constant current also has dis-advantages but is simple and cheap.
One has to 'monitor' the charging time to get the maximum lifespan out of the battery.
Fortunately is is replace-able, but you can't use normal batteries anymore, only recharge-ables.
I don't consider it 'stolen' nor should a standard opamp circuit be named after someone who simply built what was already designed as a standard application anyway.
Chu Moy didn't invent or discover it.
He did get 'famous' with it and brought it to the attention of the hi-fi crowd.
Just like the gain-clone circuits were laughed away as a standard application by audiophiles until someone made a gimmick out of it and made it look like hocus pocus with some fancy 'marketing' and suddenly it was a hype and 'audiophile'.

How much gain you need depends on:
1: output level of the source
2: efficiency of the headphone (in volts)
3: preferred listening level

The volpot linearity in the lower settings and use-able volume range are indeed issues.
Having the pot between 10 o'clock and 3 o'clock is certainly best for L-R balance in the useable volume adjustment range
For most applications (where a headphone out signal is 'boosted') a factor between 2 and 4 is usually the best option.

perhaps when Chu Moy built it he needed a gain of 10 as his source might have given a low output signal or wanted to drive 600 Ohm headphones while being portable.