Zigisg Portable Amp

[Zigis]

For changing battery need to removing back panel (4 screws), partly unscrewing 2 upper front panel screws and slide top cower



Not handy job for every few days, so rechargeable battery and build in charging schematic will be better.

Next problem - for 3x9v=27V battery charging at least 35V-40V required. Hard to find ready made PS with so high voltage at reasonable price.
Solution - Voltage multiplier with 555 chip. Now with external standard 12V PS on the multiplier output is about 40V, enough for charging. Then 16mA CCS on LM317 and red LED in series with battery. LED(on back panel) indicate reall battery charging.



You can partly see voltage multiplier/charger in side of amp, behind my cheap testing batterys.

Amp is build on protoboard and as you can see, most of space take batterys

[Zigis]

Here is amp's schematic





Hi Ian, at the moment only one amp is built on protoboard, however I am currently drawing double sided PCB for amp.
If there will come enough interest from people for PCBs or amps, I am going to order boards. About 20 boards need to order for reasonable price, I myself need maybe 2 at the moment.
Let's see. I post about amp here too:

www.head-fi.org/t/610650/my-new-3x9v-cmoy

There is amp's owner reply too.

[Deleted]

One thing is for sure... that blue LED won't be emitting much light connected the way it is drawn...

[Deleted]

May 24, 2012 5:05:53 GMT @solderdude said:

One thing is for sure... that blue LED won't be emitting much light connected the way it is drawn...

Neither should an LM4562 be operated directly into a cable capacitance without a series resisitor.It may even become unstable.

[Deleted]

From the LM4562 datasheet:

This Audio Operational Amplifier achieves outstanding AC performance while driving complex loads with values as high as 100pF.
Capacitive Load Drive Overshoot 100pF = 16 % in essence: (+1.3dB) @ 10MHz

Most HP caples will be around 100pF/m so you can 'safely' attach one meter of cable.

The LM4562 is designed to drive loads higher than 600 Ohm (about 300 Ohm absolute minimum)
Because a high output voltage amp is only needed for 300 and 600 Ohm headphones it can just cope.

driving 32 to 120 Ohm headphones is still 'possible' but not recommended for these opamps nor do the impressive specs still apply as the current limiter kicks in.
How audible the degradation is remains to be seen as hundreds if not thousands of hifi enthusiasts with these standard application designs are using these opamps even on 16 Ohm IEM's and no-one complains about the SQ.

a series resistance is recommended though when driving cables longer than 1m.

[Deleted]

Frans
A typical headphone cable length is closer to 3 M, not 1M.
Of course if used with only IEMs that would be different.

hundreds if not thousands of hifi enthusiasts with these standard application designs are using these opamps even on 16 Ohm IEM's and no-one complains about the SQ.

Millions listen to low bit rate MP3s through IEMs too.
They aren't exactly what I would class as HiFi enthusiasts either. ;D

Regards
Alex

[mrarroyo]

The LM4562 has been used in various headphone amps, some right here in this forum have recommended them in the past. Why is it not good now?

[Deleted]

May 24, 2012 10:15:44 GMT mrarroyo said:

The LM4562 has been used in various headphone amps, some right here in this forum have recommended them in the past. Why is it not good now?

Hi Miguel
As stated, it isn't designed to work directly into such a low output impedance, and it doesn't like working into capacitances higher than 100pF. In most other amplifiers it was followed by a discrete output stage, or several LM4562s were used to drive the load.
Alex

[Zigis]

May 24, 2012 5:05:53 GMT @solderdude said:

One thing is for sure... that blue LED won't be emitting much light connected the way it is drawn...

Thanks, solderdude, now it shine again

Theoretical discussion about LM4562 are interesting, everyone has right to his own viewpoint.
Anyway, opamp is on socket.

[Deleted]

In your final design I assume you use 3 batteries of the same capacity.
In the picture there is one with 200mA/h and 2 with 250mA/h rating.

I take it this was just for the picture or testing purposes.

In the schematic the battery symbol is reverse polarity also ... the + and - that are displayed are correct though.
The + is usually depicted by the longer bar.

With only 2 times gain and connected to an ipod for instance, with max 1V_RMS the output voltage will never be higher than 2V_RMS. (6V_PP) in this case a single 9V battery will be enough.
This is LOD output voltage and non E.U. HP-out.
To reach clipping levels (with 3 batteries) 24V_PP a gain of 8x would be needed.

In the EU versions of the ipod the output voltage is restricted to 0.3V_RMS (= 1V_PP) at the HP-out socket and if that is used as a source the max output voltage would be 0.6V_RMS and to reach clipping levels with 3 batteries a gain of 24x would be needed.

When driven from redbook CD out 4x would be needed to reach 2V_RMS= 6V_PP in to reach 8V_RMS = 24V_PP.

A CDP would be able to fully drive a headphone without even reaching clipping levels on 2 of those 9V batteries with the current gain setting (4V_RMS = 12V_PP)

[Zigis]

Yes these Chinesian batteryes are fanny. I buy thees for very cheap in internet shop, where I buy LEDs for good price (and good quality). I don't believe battery are 250mA, I don't believe even 200mA and I don't believe there is any difference between both, except labels of course:)
Ordering 1 type of labels are twice cheaper, than ordering 2 type of labels. I think this is the reason why they gluing same label on both battery sides. On one side polarity is right, on the other side - not so right, sorry:)
I use batterys only for testing amps.

In theory your gain calculations are right. However at higher voltage chip simply sound better. I listened to portable amp with 1 battery with HD580, at low level far from clipping. Then I connect external 24V PS, sound improves are large.

LM chip and gain 2 is what in this one amp are used. Person, who ordered amp, used my Desktop amp with same chip and gain (German HiFi forum pack) long time, with high quality 30V PS. Then he wanted same sound quality for portable.

If PCBs will be made, any chip and any gain can be used

[PinkFloyd]

Yes these Chinesian batteryes are fanny. I buy thees for very cheap in internet shop, where I buy LEDs for good price (and good quality). I don't believe battery are 250mA, I don't believe even 200mA and I don't believe there is any difference between both, except labels of course:)Ordering 1 type of labels are twice cheaper, than ordering 2 type of labels. I think this is the reason why they gluing same label on both battery sides. On one side polarity is right, on the other side - not so right, sorry:)

Hi Zigis,

That is NOT a good look If they are glueing meaningless "labels" onto the batteries then that would lead me to believe that the batteries, themselves, are far from "kosher" when it comes down to quality construction, reliabilty, safety, longevity, specififications and quality control.

I wouldn't feel confident using ONE of these in an amp, let alone THREE.... how long before they start bulging at the seams and turn into Chinese fire crackers?

Frans is correct (as always)..... no need to have three crap batteries when all you need is ONE quality battery to do the job (or even one crap battery, until it explodes).

What are you selling here exactly? The "I don't believe the specs of the parts but they are cheap" type thing or "I am confident in the parts and your amp will last many years" type thing?

You seem to be going down the "I don't know what I'm doing but I will keep digging the hole" type route.... all good shit and amusing to witness but, come on man, we are trying to help you here......

The design may be flawed (according to the schematic) but don't "add" insult to injury and tell us that your battery supplier is so fekkin' wild west that the batteries he is supplying are "variable" and may not be what the label states.....

Eh? What part of THAT would make me think "I know what... I want one of those Zigi amps"?

I'm not having a go at you, just letting you know how this thread will be perceived by readers.... your "build" quality is superb, just a bit of fine tuning in the battery, choice of components / implementation of components.....

I haven't even heard one of your ZIGI amps and am questioning if I WANT to hear one.... purely down to your honesty, schematics and bad choice of battery supplier.

I always use my ears at the end of the day (after verifying my house won't go on fire thanks to bogus batteries) if you'd like to send me over a Ziggy I will be happy to give it a "totally" unbiased review

Pinkie.

[Zigis]

Pinkie,
I think there is misunderstanding due to my weak English.
All I wanted to say in my previous post about battery in photo - I agree, battery are cheap, very low quality and I don't trust any word, they printed on labels.

Fast photo was made only to see, how it fit and size comparison (I haven't any other rechargeable at home).

Of course amp was sold WITHOUT battery.

What I wanted to say about PS voltage and gain, I understand all calculations and one 9V might be sufficient in most cases.
However I clearly hear sound difference between 9V and 24V even at low listening level (with any chip). And I believe, I am not the only one. Headroom maybe?

On the more constructive atmosphere about amp - what flow you see in schematic (except LED polarity typo, I fixed)? What should be changed in your opinion?

I am always open to constructive criticism and listen to any good advice. Sorry, if it is misunderstood.

Zigis

[Deleted]

Another free tip to improve your product....

The biggest problem for rechargeable batteries is a deep discharge.
This SEVERELY limits lifespan especially for NiMH batteries, all rechargeables I might add.

The 'problem' your design currently has is that there is virtually no possibility to check how far the batteries have discharged other than an 'estimation' by how bright the LED is.
Most people will deplete their batteries in portable gear UNTIL the unit stops working.
Since the opamp in question still works O.K. on 5V and in most cases will never be driven to clipping levels this means you won't be warned by 'deteriorating' sound quality.

At that voltage (5V) this means one or two of the 9V batteries already may be as low as 1 or 2V or even gone negative.
9V Batteries (in low drain sitations like these amps) should not fall below 7V.
So with 3 of those 9V batteries in series should NOT drop below 21V !
9V batteries that have gone below 5V may soon be ready for the dust bin after just a few 'recharges'.
In this case the damage has been done already.

This you can solve by adding a zener in antiseries with the front LED so it goes off when the battery voltage is below a set treshold.
There is a snag, however, which is that in this case it's easy to accidentally leave the amp on (unknowingly) as it appears to be off (no LED) destroying the rechargeables for sure.

A solution could be to mount a small resistor in parallel to the zener so it lights DIM when the batteries need recharging and is relatively bright when the batteries are full.

The easiest solution is to leave out the charging circuit/batteries and use 'normal' 9V batteries.

[Deleted]

Just thinking out loud here, with no real knowledge

Is there a simple of way of setting the circuit so that when the voltage of the batteries is OK a bi-colour LED is green.
When the voltage falls towards recharge-time, the green leg is switched off and the red leg triggered on?

Maybe a small relay affair?

[Zigis]

Thanks again for advice, solderdude, looks like some battery status indication are really essential.
I find in other forum this schematic:



It might work with bi color LED. There are two types of bi-color LEDs, with three legs, with common cathode and two legs- both diodes in parallel, but in opposite direction.
What scred me in this schematic - too many components and not many free space on board, hard to push in.
Your idea with simple zener might be better in this situation, I need to think about, how to upgrade it to work with bi-color LED.

[Deleted]

I found what I had in mind (cmos), I don't know if you can use this for the desired effect.

Attachments:

[Deleted]

This is another amp I was VERY interested in. A nice oomphy portable.
I recently enquired with Zigis and he said the idea had been shelved for now but doable.

I'd like to see this one perfected as per the thread and be up for grabs.

[Deleted]

Me too Chris. I really like the simplicity and power of the Zigis Cmoy and would love to have a three battery rechargeable amp. It would probably put the price up quite a bit though. The ordinary 9v Cmoy is SUCH good value. I was really surprised when mine arrived.

The bigger voltage option is really attractive since I still haven't found a decent power supply for it that doesn't cause it to hum although it's very low level.

[Zigis]

Well, if there is so large interest in 3x9V amp, this will be my next project to finish.
Things to do:
1. battery status indication testing, if everything works good,
2. finishing and ordering PCBs

Currently I am working on tube hybrid amp, somehow similar to Indeed, Bravo, but "upgraded" with good quality parts and better (in my opinion) enclosure. here you can see early prototype:
www.head-fi.org/t/402067/a-super-simple-6dj8-headphone-amp/390
There is Alps "Blue Velvet" volume pot, EvoxRifa polypropylene input caps, Panasonic FM 1000uf 35V output caps and CRC power filter, separate for each channel.
Enclosure is made from piece of aluminum U frame 100x40x3mm, it work as heat sink. Unlike prototype, amp will be black powder coated, with wood side panels.
Wen the amp is finished, I post some photos. Currently 1 amp is ordered, but I make 6 enclosures.

[mrarroyo]

Zigis, how much are you asking for the new hybrid amp? Thanks.

[Deleted]

Well, if there is so large interest in 3x9V amp, this will be my next project to finish.Things to do:1. battery status indication testing, if everything works good,2. finishing and ordering PCBs

I would be interested but on RG, I'm not sure. The interest in the Aune T1 hybrid was a bit low which I felt was a shame.

It's the pure simplicity of the design that I like - no fuss, just works well.

I'm blowed if I can find a power supply for the little CMoy that doesn't hum on one side though.

The 3 rechargable battery unit I saw looked a lot more substantial and it would indeed be a nice touch to stop the batteries discharging too far.

That's often overlooked in rechargable amps, leaving us unsure of how long to leave them on charge without overcharging. Some don't stop at full charge and continue which is a little bit dangerous.

[Deleted]

Don't know whether I'm helping here but if a LED battery status light is still required there is a bloke (actually has a doctrate in a relevant subject) that sells such a thing for 12v batteries. If of interest I'll try to dig up some contact info.
Dave.

[Deleted]

I think it's all in hand, Dave. Zigis has designed the circuit and is in the process of designing one. In fact, I know he sold one to someone on Headfi working on three 9v batteries. I can't remember if they were rechargeable or not but it's just a really useful thing to have some kind of indicator to enable the checking of any remaining power so that they don't go into a deep discharged state, so shortening battery life.

That's something that the Neco could have done with actually, since it is difficult to know exactly what charge is left.

Also, because you don't know how much has been used, you don't know how long to leave it on charge as well so you could overcharge them.

When you fly helis all over the place like I do, you soon learn the dangers of taking too much power out and overcharging.

The lipos that fit in helicopters go up like a bomb. I've done it (on purpose) just to see for myself exactly how dangerous these things can be. Also, how easily they can be damaged.

I think Zigis has some arrangement sorted out now.

[Zigis]

mrarroyo, hybrid amp will be about $220, good aluminum/wood enclosure and good quality parts increase costs a lot.

Ian, what do you mean with RG ?

Dave, any additional information or schematic about battery status are welcome.

Wen I built first amp, to be honest, I did not even imagine this battery problem, before solderdude point me.