SLA battery sounds better than A123?

[ggking7]

My Wavelength Proton USB DAC (which also serves as my preamp) is usually powered by an 8Ah SLA battery by way of this USB isolator:

Ultravox - SGD70.00 : Welcome to the diyparadise e-store!

I tried connecting NiMH batteries in place of the SLA battery but they sounded much worse. Today I connected this A123 battery pack in place of the SLA battery:

EP Buddy 3S1P 9.9V 2300mAh LiFe battery pack USA A123 - eBay (item 230442131487 end time Jan-20-11 16:40:21 PST)

I'm very surprised to find the bass and mid-bass sorely lacking compared to SLA. Does anyone know why SLA is outperforming A123 here?

[steve jones]

Just a guess.

The SLA is 12-13VDC and the LifePo4 stack is 9.9VDC and is right at the working edge of the voltage compliance of the onboard regulators on the Proton?

[qusp]

yep, something is wrong with your setup, most likely as mentioned above, your voltage is too low. the lower impedance and MUCH higher current capability of the LiFePo4 batteries should if anything provide much BETTER bass.

also did you charge them before using? because most likely they were shipped in a 50% charged state, meaning the voltage would be even lower. your battery life will be quite a bit shorter of course, but you knew that.

sorry thats about all I can say from this information

[ggking7]

Both the SLA and A123 pack go through a 5V linear regulator on the Ultravox actually. But strangely the A123 pack been getting steadily better until now it sounds about the same as the SLA. Burn-in maybe?

EDIT: qusp, what type of connectors do you use? I'm using Deans.

[ggking7]

When I first got the battery I caused a quick short. Could that have damaged it in any way? I always charge it in balance mode.

[qusp]

OK well this is not really the best way to tell any differences if both are then regulated by the same reg, the whole point of using A123 over the SLA is it has very good transient response, low output impedance and low noise, none of these make much/any difference if its then regulated afterwards, as the regulators performance will dominate. not even sure I understand the point of using either battery unless portable if you are just going to regulate it with stock onboard regs.

the 9v output of the A123 combined with regulator X at 5v out, may mean you are scraping close to the regulators dropout voltage at low battery (at low they will be around 9v for the pack)

I use various connectors depending on the application, of the RC connectors, the deans are good, I use the deans heavy duty one and their micro connector, but I mostly use either HD15 dsub type connectors, or for more demanding applications I use hybrid high current Dsub connectors from amphenol, or hardwired with a dsub for the charging circuit. in a pinch you could use a neutrik speakon or powercon multipin; hell for a 3 cell pack you could use 4 pin XLR. of course any of these means you have to make your own charge/balance connector/cable assembly to connect to the charger.

perhaps could have damaged the cells with that arcing, but unlikely to have been too bad unless it was significant. bet that gave you a fright, these things put out some pretty serious current into a short, not the sort of thing you usually expect from a battery, first time gave me a fright, never happened again.

nah your problem will be that reg ridding you of any benefit, unless its PSRR is atrocious

[ggking7]

OK well this is not really the best way to tell any differences if both are then regulated by the same reg, the whole point of using A123 over the SLA is it has very good transient response, low output impedance and low noise, none of these make much/any difference if its then regulated afterwards, as the regulators performance will dominate. not even sure I understand the point of using either battery unless portable if you are just going to regulate it with stock onboard regs.

Here's the thing. I started with this SLA and it sounded great. I wanted something that would be a quicker charge so I gave NiMH a try and they sounded awful. Now I'm trying A123 and the charge time is incredible but after a lot of listening I think the SLA sounds better. If I try to analyze it it's a slight difference, but the SLA feels a lot more enjoyable to listen to. It seems more effortless and smoother.

the 9v output of the A123 combined with regulator X at 5v out, may mean you are scraping close to the regulators dropout voltage at low battery (at low they will be around 9v for the pack)

Is that a typo? If the pack is at 9V when low it will be above the 7V required by the LT1085 linear regulator.

perhaps could have damaged the cells with that arcing, but unlikely to have been too bad unless it was significant. bet that gave you a fright, these things put out some pretty serious current into a short, not the sort of thing you usually expect from a battery, first time gave me a fright, never happened again.

The first one was minor but it happened again yesterday and it will never happen again. It was a bad one. I was prying apart the Deans connection between the charger and the pack with a tiny metal screwdriver. That connection is way too tight and I need something to enable me to pull it apart. I've carefully used the screwdriver many times but I wasn't paying enough attention yesterday.

[qusp]

hmm well I cant comment there, because it really doesnt make much sense that the 2 batteries sound any different under these circumstances; as long as dropout is covered, but i'm not going to argue with what you hear, it just doesnt make any sense to me.

wasnt a typo, I had no idea what regulator you are using (or missed it in your post) and 4v dropout is not uncommon with discrete regulator designs, so I didnt rule it out. the fact you are using the LT1085 makes it even more confusing to me that you hear a difference, as their PSRR is very good. all specs of the SLA are inferior to LiFePo4, I dont get it.

for me the tight large gauge connection is what makes the deans so good, I suggest loosening it up a bit by repeated connect/disconnect, or get yourself some nylon/polymer tools for the prying in future haha no more zappy zappy

[ggking7]

At this point I'm thinking either my pack is damaged from the shorts or maybe it generates greater micro-vibrations than the SLA. The SLA is definitely a lot heavier. The micro-vibrations could be transferring to the isolator and/or DAC and affecting audio performance that way.