[Headdie]

Hi guys,
 
I'd like to try a better PSU than the wall wart included with my Firestone Cute Curve amplifer. The wall wart included is 24v 500mA. I've tried some laptop PSU that I have in here. With a 19v 4A PSU, the sound was a bit softer. With a 24v 4A, the bass appears to be stronger... Now, there's this one here,
 
http://www.ebay.com/itm/250806526350?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649#ht_4362wt_1270
 
Do you think it's nothing else than a standard laptop PSU ? Would expect a real improvement from it ?
 
Any advice would be welcome.
 
Regards,

 

[Headdie]

After more listening, I guess what I've felt as smoothness with the 19v PSU was just slighlty reduced volume or dynamics. I could also purchase a 30v PSU for my amplifier, instead of the 24v included. Does more voltage simply equate with more volume or dynamics ?

 

[Mad Max]

You will kill your amplifier with more than 24V.  19V is underpowering the amplifier.
You must get a power supply of no less and no more than 24VDC output and at least 500ma current output.
 
Also, forget laptop bricks.  If specs are mentioned on the product page, you want to go for a power supply with lower ripple current, voltage noise, and I forgot what else.  50mv ripple or less should be the kind of upgrade you should look for, I think.
 
Edit: Why not go for the Firestone Supplier psu?

 

[Headdie]

Thanks for your input. It's really appreciated, because I'm still puzzled by many things about power supply/adapters.
 
I'm effectively considering the Firestone Supplier, but it's only 300mA...
 
Regarding voltage, Firestone tells me that I could go for a high as 30v. Some people pretend that op-amps would sound better with 30v, so I wonder...
 
That being said, I've listened to three PSUs this week (see the first post). The 19v PSU is under powered, but it's a regulated switcher (LTE-60E). That's why I've tried it.
 
I've compared all three of them with the phone jack of my NAD receiver and my battery powered Thunderbolt phone amplifier, the later is supposed to be a perfect power supply...
 
Conclusion :
 
1. My NAD receiver (C720BEE) gives the best sound of the lot
2. I can't here no noise or whatever coming from the three PSUs used with the Firestone, compared to my battery powered head amplifier
 
So I wonder,
 
a. Could I bring the Firestone to the level of my NAD with a better PSU and rolling the main op-amp eventually
b. What's the fuss about normal/laptop AC/DC adapters, if I can't hear a difference compared to batteries (the ideal power source)
 
Am I mistaken...What do you think ?

 

[DefQon]

Quote:

So I wonder,
 
a. Could I bring the Firestone to the level of my NAD with a better PSU and rolling the main op-amp eventually
b. What's the fuss about normal/laptop AC/DC adapters, if I can't hear a difference compared to batteries (the ideal power source)
 
Am I mistaken...What do you think ?

 
The changes will be subtle not night and day difference. Op-amp rolling will give it a boast and a better PSU just mean's no more background noise (depending on the PSU, regulated vs non-regulated, linear vs triode).
 
There's a fluctuation with laptop AC/DC adapters reason why they are not ideal is because of the slight hum they produce sometimes s it's from the rippling affect of the capacitors inside. A filtered regulated PSU will get the best possible sound production out of your system if your using it with your amp, something like the Sigma DIY kit or so.
 
And also, laptop AC/DC adapters easily burn out or pop sometimes. There's plenty of threads citing around the internet on other boards with them popping or giving out with a bit of magic smoke or burnt smell.

 

[Mad Max]

Opamp-rolling can improve the sound a bit, but upgrading the PSU will have a bigger impact than any opamp, a possibly lower noise floor is just one of the effects.
The supplier PSU is designed for Firestone products, so I suppose that the Cute can do with just 300ma of current, unless they told you otherwise.

 

[Headdie]

Ok, I've put many more hours yesterday comparing these three :
 
1. Firestone Cute Curve headamp with the included 24v-500mA switching PSU
2. Firestone Cute Curve headamp with a 24v-4A switching PSU (laptop adapter)
3. NAD C720BEE receiver phone jack
 
The listening test was done with Beyerdynamic DT990-250ohms.
 
Here's what I can say :
 
- No noise issue with any of those
 
- Number 1 is the worst.
 
- Number 2 is better with more bass. Maybe because it's a better PSU or it can push more current, I don't know... 
 
- Number 3 gives the best sound. Bass is strong, sound is round with more details than the previous two. Perhaps because it's a better amplifier, it has more voltage or current in reserve, or a better match with the DT990-250...
 
I'll repeat the test with a Denon D2000 to see if the headphone impedance change a thing in the results.
 
To be followed,

 

[Headdie]

Test over.
 
The Firestone Cute Curve headamp with the included 24V-500mA switching PSU is not in the game, with Beyerdynamic DT990-250ohms or Denon D2000-25ohms.
 
The Denon D2000 with Cute Curve and the 24V-4A switching PSU (laptop adapter) provides more details than thru the NAD C720BEE receiver phone jack. The NAD seems to offer more space and finesse, but definitly lacks in the details. It may be an impedance mismatch effect, who knows...
 
I conclude that the Firestone can compete with the NAD with lower impedance headphones and that a better PSU definitly help in that way.
 
My next step will be to get an even better PSU, with higher current and voltage. Something like a regulated 30V-1A.
 
Any feedback/suggestion is welcome. I'll let you know when I'll get it...

 

[DefQon]

Quote:

 
 
My next step will be to get an even better PSU, with higher current and voltage. Something like a regulated 30V-1A.
 
Any feedback/suggestion is welcome. I'll let you know when I'll get it...

 
I would not recommend getting a bigger rated PSU for the Firestone if its rated at 24v. Most likely inside the Firestone amp, all the components used i.e. capacitors used for power filtering or separation for the opamps and any nearby mosfet's will be rated at something like low farades but 24v rating. Sometimes having a bigger rated PSU does not equate to providing more power headroom instead burnout components because the circuit isn't used for higher rated {V}.

 

[Coltrane]

What are you using to ensure level matching when switching between the different components?

 

[Headdie]

When I swap a 24v PSU for a second 24v PSU on the Firestone, I just unplug and replug... It takes about 2 seconds and doesn't change much the level, if at all.
 
When I compare the NAD and the Firestone, both are on the same DAC with separate volume pots. I just set them to comparable level.
 
No rocket science level matching.

 

[Mad Max]

Unless he underpowers his amp or something, there won't be a difference in volume level.

 

[Headdie]

Here's something new for you.
 
It maybe weird, but the best sound I actually get from the Firestone Cute Curve is from my Denon D2000 powered by a 19V laptop adapter... and it's very good indeed !
 
So I got the idea to compare four 19V power adapters of mine, to see if I can hear a difference...
 
The contenders:
 
1. Delta Power Sharp, ADP-45GB Rev: E 3, 19V-2.4A (coming with an old Acer laptop)
2. Lite-On Technology, PA-1121-08, 19V-6.3A (coming with an old Toshiba laptop)
3. Prudent Way, PWI-AC120LE, 19V-6A (variable laptop PSU)
4. Li-Tone Electronics, LTE60E-SW-1, 19V-3.42A (coming with a Firestone Big Joe II Class D amplifier)
 
Results:
 
They all sound exactly the same to me. The only difference is for noise.
 
Here's how I test for noise,
 
a. I play a song with Foobar and I put it on pause (if I stop the song, the amp is totally silent)
b. I turn up the volume to max
c. I listen for noise
 
Contender number 4 had a bit of noise. Then I realized it was alone with no ferrite core. So I put a ferrite core on it and it became silent as the others.
 
Conclusions:
 
i. Or these power adapters are quite good, even if they are switchers
ii. Or the Cute Curve has the ability to filter/reject the noise coming from them
 
Anyway, I don't think I'll put much money on my next 30V adapter, considering all those budget adapters give good sound, with no flaw I can hear...
 
Have you ever done the same experiment? What are your conclusions...

 

[Headdie]

Regarding noise, you have to pay attention to all those wires and cables running behind your desktop. They can pickup noise if you don't respect good wiring principles and you could think the problem is one of your components... By the way, the collection of Marantz Hi-End Audiophile Test Demo SACDs are great for testing 

 

[Headdie]

Conclusion :
 
I finally got a 30V 900mA filtered power adapter. It's perfect, but no more than a 19V or 24V psu... The Firestone Cute Curve doesn't seem very insensitive to the input voltage...
 
On a different note, I've rolled in the CC an LME49860 in the place of the OPA2604. now the sound is top level to me.
 
Regards,