I've heard that too, but I don't understand why? Can you explain a bit on the subject? I've heard that big solid state monoblocks could have an effect at startup which needs to be controlled by a soft-start, but I don't understand why would that be needed on a very efficient Tripath based solution? Do you think these amps have dangerous loads at startup?
And it was mentioned that many guys have killed their T-Amps by running them from car batteries. But why? That amp requires so little power!
AND: what if we just put a fuse between the battery and the amp? Can a fuse in the power input modify the sound? The mentioned commercial product uses a fuse too. Doesn't it have any side effect?
Any experience with T3 soft-start?
Hi Scott, have you looked at the T3a board that comes with the hifimediy T3? Sounds like it could help solve this issue. As it stands, a high current smps can also fry the switch if it's not big enough...
How about the amp boards themselves? Anything to fear there? It's always easy enough to get a BIG on/off switch... and will we get a nasty 200 W pop from just using a single switch?
I have not experimented with these options on my boards... call me chicken if you must.
Hi Scott, have you looked at the T3a board that comes with the hifimediy T3? Sounds like it could help solve this issue. As it stands, a high current smps can also fry the switch if it's not big enough...
How about the amp boards themselves? Anything to fear there? It's always easy enough to get a BIG on/off switch... and will we get a nasty 200 W pop from just using a single switch?
I have not experimented with these options on my boards... call me chicken if you must.
spark
i'm just judging by the size of the the spark that is thrown when I slam the last terminal down on the battery post. With 2 car batteries in series, 25v, the spark is humongous. I played with 3 batteries briefly even though it is slightly over the safe design spec of my amp at 38v and the spark is down right dangerous. And this was with the stock tank caps of 3600uf before adding an additional 10,000 that I use now. The surface mount caps on the Sure amps are very fast to start, as are the amp's circuit. This giant spark will burn a switch.
i'm just judging by the size of the the spark that is thrown when I slam the last terminal down on the battery post. With 2 car batteries in series, 25v, the spark is humongous. I played with 3 batteries briefly even though it is slightly over the safe design spec of my amp at 38v and the spark is down right dangerous. And this was with the stock tank caps of 3600uf before adding an additional 10,000 that I use now. The surface mount caps on the Sure amps are very fast to start, as are the amp's circuit. This giant spark will burn a switch.
soft start
Of the Hifime amps, I would be most interested in the mono T3.
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SMPS are current protected so they always start just as they want to.
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It might be possible to build a simple manual soft start for use with batteries using the first switch with a series resistor and a second switch wired straight through if you didn't want to mess with a timed relay.
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Of the Hifime amps, I would be most interested in the mono T3.
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SMPS are current protected so they always start just as they want to.
.
It might be possible to build a simple manual soft start for use with batteries using the first switch with a series resistor and a second switch wired straight through if you didn't want to mess with a timed relay.
.
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Spark? Dangerous?
Dangerous? Well, maybe if you have an open canister of gas in your audio room... that's one way of getting some BOOM in the bass registers
I once lost about a 1/4" chunk from the tip of my screwdriver with an automotive battery... made me reluctant to try it that way on amp... i think i'll do a 3 step manual soft-start thing with these a123 batt-packs
Dangerous? Well, maybe if you have an open canister of gas in your audio room... that's one way of getting some BOOM in the bass registers
I once lost about a 1/4" chunk from the tip of my screwdriver with an automotive battery... made me reluctant to try it that way on amp... i think i'll do a 3 step manual soft-start thing with these a123 batt-packs
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A123 cells for T2-TK2050?
In looking closely at the a123 I realized that although the source impedance is very low, the capacity is only 2.3Ah (2300mAh). This would give a fairly short run-time, probably only 2 hours or so with the TK2050.
The RedWine pack is a 25.6V/10Ah and powers my Virtues for about 10 to 12 hours continuous play at moderate volumes. So it's probable we would want at least 7Ah for the T2 w TK2050 and 10Ah for the T3
For the T2, this now takes the number of a123 cells to about x24: 3 paralleled sets of 8 series cells = 24 cells for a +26.4V supply.
That gets expensive... but it also reduces the source impedance even more, now the DC source impedance becomes less than 80 mili-ohms per leg, for a total source impedance of under 27 mili-ohms... and the AC source impedance, at less than 64 mili-ohms per leg, will end up under 21 miliohms... that's close to 0.02 Ohms which is phenomenal... in theory peak instantaneous current would be near 1300 Amperes! Now THAT should handle any sudden amplifier demands!
For the T3 which uses the STA517B in parallel, the operating voltage is between +30V to +60V... To get about 200W output into 4 ohms, the supply needs to be at about +36V, maybe +40V
And we'd need at least 10Ah, so given the available battery management systems and chargers, it might make more sense to drive the T3 with 4 sets of 12 cells in series, and then the drive voltage gets up to be about +40V/9.2AH and under 0.025 ohm source impedance.
If we use flatpack cells at 10Ah like RWA does, it's probably something like 8 of these:
High Power LFP Polymer Cell: 3.2V 10Ah (8790160-5C) 32Wh, 50A rate UN Approved (DGR)
At $50+ per cell, that gets expensive fast! Use 8 of them, then add to that the battery management module and the charger and a case + connectors + shipping cartons and it's easy to see why the RWA sells for $800
I like your idea of "parallel pirating" some of the voltage to power the DAC. etc. Battery supply is REALLY great for DACs!
In looking closely at the a123 I realized that although the source impedance is very low, the capacity is only 2.3Ah (2300mAh). This would give a fairly short run-time, probably only 2 hours or so with the TK2050.
The RedWine pack is a 25.6V/10Ah and powers my Virtues for about 10 to 12 hours continuous play at moderate volumes. So it's probable we would want at least 7Ah for the T2 w TK2050 and 10Ah for the T3
For the T2, this now takes the number of a123 cells to about x24: 3 paralleled sets of 8 series cells = 24 cells for a +26.4V supply.
That gets expensive... but it also reduces the source impedance even more, now the DC source impedance becomes less than 80 mili-ohms per leg, for a total source impedance of under 27 mili-ohms... and the AC source impedance, at less than 64 mili-ohms per leg, will end up under 21 miliohms... that's close to 0.02 Ohms which is phenomenal... in theory peak instantaneous current would be near 1300 Amperes! Now THAT should handle any sudden amplifier demands!
For the T3 which uses the STA517B in parallel, the operating voltage is between +30V to +60V... To get about 200W output into 4 ohms, the supply needs to be at about +36V, maybe +40V
And we'd need at least 10Ah, so given the available battery management systems and chargers, it might make more sense to drive the T3 with 4 sets of 12 cells in series, and then the drive voltage gets up to be about +40V/9.2AH and under 0.025 ohm source impedance.
If we use flatpack cells at 10Ah like RWA does, it's probably something like 8 of these:
High Power LFP Polymer Cell: 3.2V 10Ah (8790160-5C) 32Wh, 50A rate UN Approved (DGR)
At $50+ per cell, that gets expensive fast! Use 8 of them, then add to that the battery management module and the charger and a case + connectors + shipping cartons and it's easy to see why the RWA sells for $800
About battery capacity: its so easy when you think in Wh units.
The one pack version of the RedWine is 12.8 V * 10 Ah = 128 Wh
The two pack version of the RedWine is double that = 256 Wh.
The price difference between them is 300 USD, which means the RedWine batteries cost about 2.34 USD / Wh.
The prismatic (flat) cell you linked is 32 Wh and 56 USD, which means its 1.75 USD / Wh.
100 batch of 2300 mA A123 cells from here is 780 USD and its 3.3 V * 2.3Ah * 100 = 759 Wh, which means 1.02 USD / Wh.
A123 has a new prismatic cell too, its called: AMP20. Its 20 Ah * 3.3V = 66 Wh. Here is a detailed specification which says that they are actually 64.6 Wh. Look: two of these modules are exactly one RedWine module (128 Wh). And these modules just started to be available for the public (they are made for the electric vehicle market!). I'm 99% sure that RedWine uses something like two of these packs exactly, but rewires (is it possible with prismatic cells?) them them to set the voltage required.
Oh, you will like it:
And its not even expensive: for example here its 60 USD, which means its 0.9 USD / Wh! Thats quite good for an A123 cell!
Here is a big thread praising them and about how hard it is to aquire a first class one.
Endless-sphere.com • View topic - A123 20AH cells source?
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Going without a protection circuit isn't worth it. However, I'm confident that there are external protection circuits that work with A123 packs, or chargers that attach to a balancing harness.
The main point with the protection circuit is the charge-balancing: It bleeds power off of cells that have higher charge than the other ones in the battery, so that the charger doesn't leave one of them stranded in undervoltage land. Breaks the cell, breaks the pack.
Thank you for all thee inputs. Very helpful.
Yes, it's a way hot... I never realized it until the curiosity about T amps arose...
I've had another look at the techsheets. The preamp has a max gain of 16dB, wich would correspond to a 12V output with a 2V line source.
It's really a lot for a preamp.
The 220 Ohm on the output are indeed very impressing.
Yesterday I've found a thread of user Rabbitz. He had the same issue and found a sulution with a simple voltage divider before the power amp in. I think I'll go the same way:
http://www.diyaudio.com/forums/solid-state/129236-nad-106-pre-gain-changes.html
Thank you Jack for the detailled explanation. As a drummer I'm used to high dB but the clarity and detail of t amps (the well designed ones) blew away all my assumptions on older architectures.
Maybe, before melting a hifimediy or helder amp iI'll try with a cheaper sure board.
Will keep you updated.
12 V ???
Yes, it's a way hot...
I never realized it until the curiosity about T amps arose...I've had another look at the techsheets. The preamp has a max gain of 16dB, wich would correspond to a 12V output with a 2V line source.
It's really a lot for a preamp.
The 220 Ohm on the output are indeed very impressing.
Yesterday I've found a thread of user Rabbitz. He had the same issue and found a sulution with a simple voltage divider before the power amp in. I think I'll go the same way:
http://www.diyaudio.com/forums/solid-state/129236-nad-106-pre-gain-changes.html
Thank you Jack for the detailled explanation. As a drummer I'm used to high dB but the clarity and detail of t amps (the well designed ones) blew away all my assumptions on older architectures.
Maybe, before melting a hifimediy or helder amp iI'll try with a cheaper sure board.
Will keep you updated.
The voltage divider won't cost much time or effort or materials, so if you're still worried about that go ahead and put one in.
But before you do anything read the following: both the hifimediy and Helder seem to benefit from a pre-amp with a little more gain, especially with tracks that are recorded way below the "0dB" level indicator on the recording system. The Sure at max gain setting has a little more gain than the hifimediy and Helder.
As an example, I have a CD called "Misa Flamenca" which must have been recorded at -20dB for the peaks and maybe -40dB average, or even less. It's very interesting music, and I like it a lot, but it can be very frustrating to listen to it: with a normal line level input into the T-amp, I can barely get this song to play at quiet conversation levels in the room!
The +16dB gain on your NAD would be a great addition for extreme situations like this. And, if you happen to use an extremely low output moving coil phono cartridge, you will definitely want more system gain. That's why the extra gain is there!
I guess the bottom line is that the volume control on your pre-amp is useful... turn it up or down according to the level on your recordings and you'll be fine. I highly doubt you'll be melting anything on your amps by using it just as it is, in stock form.
BTW, I was looking at the Burson pre-amp, that one will put out 25V !! Seems like overkill, but if you ever try one of those ultra-low moving coils phono cartridges, you'll quickly learn to appreciate it.
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Warning about A123?
There are several statements to the effect that a123 systems have completely discontinued selling to retail outlets and vendors and are focusing only on large scale industrial sales.
...along the lines of this one:
"A123 just published in March a warning about pirated cells 26650 "B" (lower grade) cells that someone has been re-wrapping and passing off as "A" grade cells"
So, it's looking like a virtual CERTAINTY that what is being sold on ebay is NOT brand new functional A123 product, it is either fake or old worn out cells, or cells that did not pass QA and are being dumped on unsuspecting users.
Time to find some other alternatives. Back to the LiFePo4 batteries.
Maybe something like this 24V 10A unit from Ping Battery:
24V 10AH LiFePO4 Electric Scooter E Bike Ping Battery! | eBay
or for the 36V type suitable to drive the T3:
36V 10AH LiFePO4 Electric Scooter E Bike !Ping Battery! | eBay
We'd need to find out what kind of source impedance these units exhibit...
On many of the Racing Car sites (RC) there is a whole lot of complaining about the a123 cells sold on ebay being fakes or worn out cells repackaged by unscrupulous vendors.
There are several statements to the effect that a123 systems have completely discontinued selling to retail outlets and vendors and are focusing only on large scale industrial sales.
...along the lines of this one:
"A123 just published in March a warning about pirated cells 26650 "B" (lower grade) cells that someone has been re-wrapping and passing off as "A" grade cells"
So, it's looking like a virtual CERTAINTY that what is being sold on ebay is NOT brand new functional A123 product, it is either fake or old worn out cells, or cells that did not pass QA and are being dumped on unsuspecting users.
Time to find some other alternatives. Back to the LiFePo4 batteries.
Maybe something like this 24V 10A unit from Ping Battery:
24V 10AH LiFePO4 Electric Scooter E Bike Ping Battery! | eBay
or for the 36V type suitable to drive the T3:
36V 10AH LiFePO4 Electric Scooter E Bike !Ping Battery! | eBay
We'd need to find out what kind of source impedance these units exhibit...
About source impedance...
Vinnie at RWA has mentioned that his 25.6V LFP-V packs have a source impedance of under 0.02 Ohms... that's under 20 miliOhms... that's a VERY low Zs.
As an example, the very highly regarded Burson low noise regulators have <15miliOhm for their 12 V reg.
Extrapolating from this, if we can get under 30miliOhm for a 24V batt-pack, or under 45 miliOhm for a 36V pack we're ahead of some of the very best regulators.
Vinnie at RWA has mentioned that his 25.6V LFP-V packs have a source impedance of under 0.02 Ohms... that's under 20 miliOhms... that's a VERY low Zs.
As an example, the very highly regarded Burson low noise regulators have <15miliOhm for their 12 V reg.
Extrapolating from this, if we can get under 30miliOhm for a 24V batt-pack, or under 45 miliOhm for a 36V pack we're ahead of some of the very best regulators.
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But the same sites say that epbuddy for example is genuine, but a bit more expensive, and there are other sellers which are genuine, but a bit more expensive then the ebay ones.
Yeah but...
The question for us as potential users is how can WE know for sure? If I'm going to spend $300 on batteries, I really do want to be know that I'm getting the real thing!!
A123 Systems has published warnings about fraud and piracy taking place, as well as re-labeling of B-stock as A-stock.
So I just called ep Buddy and found out they sell B-stock cells which they get directly from the manufacturing factory in China. These are not "authorized" A123 batteries.
They said that on these units the self-discharge rate did not meet QA, because the shelf-life would be shorter. Ep Buddy warranties the batteries for 1 year, but these come without any form of pcm for charging.
I don't get a real good feeling about buying units that did not pass QA. Draw your own conclusions, but for me it looks like it may be better to look elsewhere.
And that's a shame, as I really like those ultra-low source impedance figures on the A123 cells...
The question for us as potential users is how can WE know for sure? If I'm going to spend $300 on batteries, I really do want to be know that I'm getting the real thing!!
A123 Systems has published warnings about fraud and piracy taking place, as well as re-labeling of B-stock as A-stock.
So I just called ep Buddy and found out they sell B-stock cells which they get directly from the manufacturing factory in China. These are not "authorized" A123 batteries.
They said that on these units the self-discharge rate did not meet QA, because the shelf-life would be shorter. Ep Buddy warranties the batteries for 1 year, but these come without any form of pcm for charging.
I don't get a real good feeling about buying units that did not pass QA. Draw your own conclusions, but for me it looks like it may be better to look elsewhere.
And that's a shame, as I really like those ultra-low source impedance figures on the A123 cells...
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OK, then the best option is to buy DeWalt pack and take out the batteries. Those must be genuine. A quick search in endless-sphere forums turned out these:
10 for $90:
Endless-sphere.com • View topic - DeWalt 36V Battery Pack (10 A123M1 cells)
20 for $175:
Endless-sphere.com • View topic - DEWALT DC9360 Batteries + 1 HR Dewalt Charger
naked cells sourced from DeWalt packs with spot welding and pack building service:
http://www.nabatteries.com/ANR26650M1-A.php
A123 ANR 26650 M1A LiFePo4 3.3V 2.3Ah Battery Cell on eBay.ca (item 300534224788 end time 05-Jun-11 18:48:48 EDT)
But you need to invest in a good quality balanced charger which can charge the cells separately, as well as could tell you which cell is bad/overcharged/over-discharged in a pack.
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How good is battery management inside the Dewalt?
I'm leaning more and more toward getting a Dewalt pack to power a quad of T3's for my powered bi-amped speakers.
Assumptions:
1) Since it's a batt-pack intended for very frequent and heavy use, I'm thinking (guessing? hoping?) that along with the A123 cells it would have some pretty decent battery charge protection modules already built-in.. yes?
2) Also, since power tools require huge currents for high torque at start up, I would think those modules are already designed with high instant current capabilities, much higher than need for the T3 amp boards. Overkill is good! Overkill is good! Overkill is good!
Has anyone here opened one up? Any opinions on the Dewalt batt mgt modules? Or do we have to rely on the RC crowd to find out... unlikely they would know, they strip 'em down to the bare cells and must recharge individually.
If assumptions 1 and 2 are any where near correct, then what's to keep us for using them in their standard un-opened case and thereby not void the 3 year warranty and possible re-sale value?
Betcha their connectors can handle it!
I think I'll pick one up new from Amazon and try it out on a pair of T3 + T3a soft-start boards... If it works well, I'll report back here.
Oh well, here goes another $300... one Dewalt 36V batt-pack & charger + 2x T3 amps...Battery powered T3, here we come!
I'm leaning more and more toward getting a Dewalt pack to power a quad of T3's for my powered bi-amped speakers.
Assumptions:
1) Since it's a batt-pack intended for very frequent and heavy use, I'm thinking (guessing? hoping?) that along with the A123 cells it would have some pretty decent battery charge protection modules already built-in.. yes?
2) Also, since power tools require huge currents for high torque at start up, I would think those modules are already designed with high instant current capabilities, much higher than need for the T3 amp boards. Overkill is good! Overkill is good! Overkill is good!
Has anyone here opened one up? Any opinions on the Dewalt batt mgt modules? Or do we have to rely on the RC crowd to find out... unlikely they would know, they strip 'em down to the bare cells and must recharge individually.
If assumptions 1 and 2 are any where near correct, then what's to keep us for using them in their standard un-opened case and thereby not void the 3 year warranty and possible re-sale value?
Betcha their connectors can handle it!
I think I'll pick one up new from Amazon and try it out on a pair of T3 + T3a soft-start boards... If it works well, I'll report back here.
Oh well, here goes another $300... one Dewalt 36V batt-pack & charger + 2x T3 amps...Battery powered T3, here we come!
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Ping Battery
Even if it has decently low source impedance, the Dewalt 36V LiFePo4 pack delivers only 2.3AmpereHours... if the T3 burns an average of 20W/Hr as has been stated elsewhere in this thread, it means it's drawing about 0.55Amps per hour, so playtime between charges will only be around 4 hours.
So then we'd need to use TWO of these per channel to get 8 hours of playtime... that's gettin' expensive!
So, in looking around some more, it appears Ping Battery has a good reputation among the electric scooter crowd. Their base 3.2V cell has under 10mili-Ohm source resistance, Li Ping said it's more like 6 to 7 Mili-ohm typical, pretty comparable to the A123 cell, but with TWICE the stored energy at 5AH vs. 2.3
And Ping can outfit these with the special high current discharge Battery Management Modules.
For example, a pack that would be ideal for the TK2050 is this one: 24V 10AH V2.5 LiFePO4 Battery Pack
Even if it has decently low source impedance, the Dewalt 36V LiFePo4 pack delivers only 2.3AmpereHours... if the T3 burns an average of 20W/Hr as has been stated elsewhere in this thread, it means it's drawing about 0.55Amps per hour, so playtime between charges will only be around 4 hours.
So then we'd need to use TWO of these per channel to get 8 hours of playtime... that's gettin' expensive!
So, in looking around some more, it appears Ping Battery has a good reputation among the electric scooter crowd. Their base 3.2V cell has under 10mili-Ohm source resistance, Li Ping said it's more like 6 to 7 Mili-ohm typical, pretty comparable to the A123 cell, but with TWICE the stored energy at 5AH vs. 2.3
And Ping can outfit these with the special high current discharge Battery Management Modules.
For example, a pack that would be ideal for the TK2050 is this one: 24V 10AH V2.5 LiFePO4 Battery Pack
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