[Jan Meier]

Dear headfellows,

just a technical note:

With most amplifiers the input signal is first attenuated with the use of a potentiometer and next it is fed into an output stage with fixed amplification factor. The higher this amplification factor, the higher the noise that is contributed by the output stage.

The concept of the STEPDANCE and QUICKSTEP models is different. The input signal is not attenuated but the amplification factor of the output stage is changed with volume. This implies that at low volume settings the noise of the output stages also is much lower than on conventional designs.



Jan

 

[zilch0md]

That's brilliant Jan!  
 

 

[Axcelon]

Hey guys,
 
Has anyone had problems with the XP8000?  Mine has failed completely.  The first time I reached for it after the warranty period it was dead.  I'm considering building a battery pack out of 2 LiPo 9V and running that into the willy.
 
Any ideas?
 

 

[zilch0md]

Hey Axcelon,
 
Quote:

Hey guys,
 
Has anyone had problems with the XP8000?  Mine has failed completely.  The first time I reached for it after the warranty period it was dead.  I'm considering building a battery pack out of 2 LiPo 9V and running that into the willy.
 
Any ideas?
 

 
That's a bummer.  Precisely which LiPo 9V batteries are you thinking about using?  
 
Both the XP8000 and the larger XP18000 contain a 5-cell LiPo pack, totaling 21.0V when fully charged, at 4.2V per cell.  
 
Thus, a five-cell, 18.5V LiPo pack would be the best thing to use with the XPAL Willy WI15 inline regulator cable, as a substitute for the XP8000.
 
You may be wondering why I'm recommending an 18.5V pack when I just finished saying that a 5-cell pack totals 21.0V when full charged...
 
RC LiPo batteries are rated at their nominal voltage - assuming 3.7V per cell - but when fully charged, they deliver 4.2V per cell, thus a battery like this...

 Gens Ace 2200mah 5S1P 18.5V 25C Lipo battery pack   Currently $26.42 at HobbyPartz.com

 
...which has a "5S1P" designation (5 cells in series, with no parallel connections), can deliver 21.0V when fully charged (4.2V x 5 cells), despite being labeled as an 18.5V battery (3.7V x 5 cells.)  
 
But you'll also need a charger.  I use this one:
 
Thunder AC6 Smart LiPo Balance Charger/Discharger w/ AC Adapter for 1-6 Lipo/ 1-15 Nimh + USB to PC Software
 
Currently $39.95 at HobbyPartz.com.

 
These LiPo packs can deliver A LOT OF AMPS.  The C rating of a LiPo battery can be used to calculate the number of Amps it's capable of delivering continuously.  The 2200mAh battery pictured, above, has a 25C rating.  To calculate the number of amps that can be delivered with a continuous load (peak current is typically 50% higher still), just multiply the C rating by the mAh rating and divide by 1000:
 
25 * 2200 / 1000 = 55 Amps! 
 
I'm concerned about your XPAL Willy Cable WI15 handling this much current capacity.  It's only rated at 3 Amps.  It's a given that the Stepdance will pull less than one Amp, for sure, but there's the matter of whether or not the WI15 can sit in front of a battery capable of delivering 55 Amps without arcing or shorting.  
 
Ideally you would have a current limiter in addition to a voltage regulator, but I've not figured out a way to do that with these LiPo batteries.
 
I don't use a voltage regulator between the LiPo pack and the Stepdance.  I just allow the voltage to decay as the battery pack discharges.  This means that Stepdance performance falls as the supply voltage falls, but you get a lot more play time per charge cycle.  
 
Here's a PDF I created a while back, showing two LiPo pack solutions for the Stepdance - using either a 12.5V (3-cell) pack, or a 16.8V (4-cell) pack. 
 
More than you wanted to know, perhaps, but there's a lot of convenience bundled into an XP8000.   A DIY equivalent requires patience.
 

 
Mike

 

[Axcelon]

The reason I bought the XP8000 was to not spend the time engineering a power supply . . . oh well . . .
 
The reason I'm thinking 9V LiPo is because I already have em, and the charger . . .
 
I don't think over-current protection is necessary in this circuit--or with a willy circuit.  The willy makes noise, suggesting a pulse width modulated system feeding either a rectifier or just caps.  So, the transistor might allow very brief high-current moments--but I don't think that would be a big deal.

 

[Armaegis]

@ zilch0md
 
Although a bunch of batteries in series like in that LiPo pack will add up their internal impedances, which *might* have an effect on sound quality. 
 
I'm also starting to wonder about those adapter cables. After all, a regulator isn't necessarily noise free. 

 

[zilch0md]

The reason I bought the XP8000 was to not spend the time engineering a power supply . . . oh well . . .

The reason I'm thinking 9V LiPo is because I already have em, and the charger . . .

I don't think over-current protection is necessary in this circuit--or with a willy circuit.  The willy makes noise, suggesting a pulse width modulated system feeding either a rectifier or just caps.  So, the transistor might allow very brief high-current moments--but I don't think that would be a big deal.

Axcelon,

It has only just now sunk in that you must be talking about rechargeable 9V batteries that can be used inside the Stepdance in lieu of standard 9V alkaline batteries. I was way off track thinking you were talking about RC batteries like I use.

Yes, you probably won't hurt anything wiring two of those batteries in series, then regulating them with the WI15. It will either work or it won't, but you're not likely to break anything.

Mike

 

[zilch0md]

@ zilch0md

Although a bunch of batteries in series like in that LiPo pack will add up their internal impedances, which *might* have an effect on sound quality. 

I'm also starting to wonder about those adapter cables. After all, a regulator isn't necessarily noise free. 

Indeed! But the Stepdance is somehow immune to the very low level hum generated by the WI15 regulator cable, even with ultra-sensitive IEMs.

See the last two paragraphs of my recent post (or read the whole post.)

http://www.head-fi.org/t/507835/meier-audio-quickstep-now-shipping-stepdance-and-2stepdance-discussion-and-impressions-thread/2055#post_8897030

 

[LogicalDisconnect]

A quick question for someone with a 2Stepdance or for Mr Meier himself: Some very faint sound is still audible through my 2Stepdance when the volume pot is switched off. Is this a fault or is it normal? It's being used with an XP8000 + WI15 and in high gain mode if it matters. There doesn't seem to be any issue with sound quality when the volume is turned up.

EDIT: I should say it's not hiss or noise - when nothing is playing the amp is pitch black. It's just when music is actually playing through the DAP and the volume pot is switched off that the music is still faintly audible. I'm thinking it might just be residual voltage in the capacitors that might discharge after a short time if the battery is unplugged/removed?

 

[cooperpwc]

Do not worry. That is normal. Even with the amp turned off, the sound will leak through the circuitry.

 

[rasmushorn]

Quote:

A quick question for someone with a 2Stepdance or for Mr Meier himself: Some very faint sound is still audible through my 2Stepdance when the volume pot is switched off. Is this a fault or is it normal? It's being used with an XP8000 + WI15 and in high gain mode if it matters. There doesn't seem to be any issue with sound quality when the volume is turned up.

EDIT: I should say it's not hiss or noise - when nothing is playing the amp is pitch black. It's just when music is actually playing through the DAP and the volume pot is switched off that the music is still faintly audible. I'm thinking it might just be residual voltage in the capacitors that might discharge after a short time if the battery is unplugged/removed?

This is normal. I hear the same with my Quickstep and my 3Move. A lot of amplifiers have it the same way. It depends on the design of the circuit. 

 

[LogicalDisconnect]

Thanks so much for the quick replies. I thought it was normal but just wanted to be sure.

 

[pietcux]

Quote:

Hey guys,
 
Has anyone had problems with the XP8000?  Mine has failed completely.  The first time I reached for it after the warranty period it was dead.  I'm considering building a battery pack out of 2 LiPo 9V and running that into the willy.
 
Any ideas?
 

My XP8000 from 05/2012 died 09/2012 it worked fine till it died. But it kind of got pumped up so that the housing first got a crack or better a cleft on the underside. Then after my summer vacation of two weeks @ 32 degree Celsius it died after the housing looked more bloated from day to day. As it died it also began to emit some serious stink. But for me the warranty worked, I got a brand new unit. One thing that I remember is that the first XP8000 could never charge my IPOD classic, but the replacement can do that.
 
 
 
 
 

 

[maguire]

So what other options do we have for a better quality Battery pack? Seems XP8000 isn't reliable.

 

[Armaegis]

I don't think you have much cause for concern...  If you read pietcux's post, he said he bumped it and cracked the case, then after a few weeks it bloated and started to smell. Most likely, that bump damanged one (or more) of the cells inside. Know what happens to a damaged battery? the acid leaks out, causing swelling and odour/gas as it corrodes the other components.