I'm a firm believer in rechargeables. I use Panasonic Eneloop Pro 2450 mAh and love em! I get right around 8 hours of play time with those.
I've tested several brands and each one is different. It comes down to the type of cell and the capacity. A 1200 mAh battery won't last nearly as long as a 2450 mAh.
Also, make sure it's a high-drain battery and NOT Carbon-Zinc.
You're free to experiment with any that you choose.
My favorite is the Eneloops Pro 2450 mAh
I can only underline what Dave says. I've been using Eneloop rechargeable batteries for years now.
I've never had an issue. The ones I use are the 1900mA ones and they last for ages.
I use the 1900mA because I have loads of things that run on them so it made sense to stick with them.
I always have a second set with the ToneWoodAmp so I'm always covered.
I also use the Sanyo NC-MQR06W battery charger which is an intelligent charger.
It checks each battery individually and charges them accordingly.
You can use this charger for AA and also AAA batteries.
It's more expensive than many chargers but in my opinion the outlay is worth it.
Regarding other brands I can give you no advice.
As with Dave, I know that I can rely on Eneloop rechargeables.
Does that help?
I've bought 16 GP ReCyko+ Pro 2000mA for my TWA. these work well but I have to say they are very tight to insert and need force and a tool to extract. Hopefully that won't be very often. Also,the menu option described in the manual to select battery types is not present, bu I assume that will be corrected in the next firmware, which must now be imminent.
The very tight fit with the many rechargeables I have invested in is going to be real problem for me. I need a tool to get them out and even then it is not easy at all. It would be good not to have to return the unit to my supplier in the UK. Could you possibly send me the revised design top enclosure piece please which has the correct fit? I can easily fit it myself. I really hope you can help.
Some batteries are a bit tighter than others. You might want to loosen the screws on the bottom of your TWA a bit to help.
The battery option is only available in V2.50 and newer. If you want to update, submit a support ticket and I'll get you set up!
Something else you can do is tape the two batteries in the Negative terminal together so that when you remove one, it also pulls out the other.
I use Panasonic Eneloops, which are a bit on the large side, but they fit just fine and are easy to remove.
I've used some other brands previously that were too large to remove, each brand is slightly different and it may cause issues with smaller batteries if we revised our case again. It would be a better idea to try another battery that fits better with the TWA.
I've also never had an issue with my Eneloop rechargeables. They slide in and out with no problems whatsoever. They're also the best rechargeables I've ever had, and I've been using AA's for many years from several different manufacturers in many different devices. Since discovering the Eneloops I've never looked anywhere else.
I've had problems with other devices/instruments. E.G. my Godin Steel String SA guitar won't take all 9V blocks. It's the same with my Taylor T5. I've just had to accept the fact and use what fits. I'm still looking for a 9Vrechargeable block battery for both instruments. I've tried a few different ones but they didn't fit properly (too large). Until then I have to use what fits and to date that's only "normal" duracells which are my go to's for 9V batteries. It's a shame that manufacturers and specific dimensions for things don't always go hand in hand. Sometimes we have to learn to live with things. "Like it or lump it".
I find Dave's suggestion to be the most sensible in this case. "It would be a better idea to try another battery that fits better with the TWA." Just because we like a particular model of shoe which only goes up to size 10 doesn't mean that we buy them and try to squeeze our size 12 feet into them.
When all's said and done, when we make our bed we have to sleep in it. Either that, or we have to buy a new bed.
That's just my way of looking at things.
To quote the Jagger Man: "You can't always get what you want"
You can mix them as long as they are all the same specs, I usually prefer to use married sets, though. You may run into issues where the older batteries don't last as long as the new ones. The Battery type indicator is only available on most TWAs with V2.50 and newer. If you'd like to update, submit a support ticket and I can walk you through it.
That sounds like too much Input Gain. This can be adjusted from Global Settings> Gain %.
As you lower the input gain, you'll be able to boost the output volume and gain. Finding the sweet spot for that setting in the Master Gain menu is very important in the overall sound of the TWA.