AudioDigit's new 100W T-Amps

[quicklizard]

Hi Jon 30, seeing as I have built this amp and we are freinds I am somewhat surprised you did not choose ask me these questions?

I have even offered to build it for you and perform some extra performance tweaks too.

However if you would like to go it alone I wish you the very best of luck

[klm1]

Try going to the Tubes section, read the section about"Tube learning for newbies", also "safety practices"; both sticky threads.

Everything you want to know; never be afraid to ask!!!

[holdent]

OK - I've now received the Class T-Amp 100 kit and I'm not sure how to wire it up.

I assume the power terminal block is by the rectifer - yes? If so which is positive and which is negative? (Nothing is marked on the board). Can the amp be damaged by reversing the polarity?

I'm also guessing that the speaker terminal blocks are the two to the left. Is the far left one for the left channel? Which side of each of these blocks is positive and which is negative?

---

Note that the board is advertised on the AudioDigit web site as 12 x 6 cm which is correct but doesn't account for the permanently bonded heatsink. With the heatsink the dimensions are actually 12 x 9.3 cm.

[holdent]

Got a very quick response for my questions from AudioDigit!

About the power input:
"the power input is near the rectifier. Polarity is not important, you enter into the rectifier chip which is a bridge, so
wiring will be OK in any case."

About the speaker outputs:
AudioDigit e-mailed the board layout but I can't figure out how to post it. However, holding the board so the power terminal block is on the right, the speaker ternimals are to the left. Logically the far left one is for the left channel and the right channel is on the right. The positive side of each channel is on the left, negative on the right.

[starn02]

I my help you with the transformer.
Here in Europe we have 230 VAC, in the usa I believe it's 115V AC.
The transformer here are produced with 2 primary windings of 115 V AC each. The scope is being able to wire the transformer to be used at 230 and 115.

When you need 230 you have to put the two primary windings in series, so that you have 115 + 115 = 230. That's the bottom figure in the pfd. The "central connection" (wires violet and gray) are connected together, insulated with tape, and left floating .... it's just the connection in series from the first winding to the second one. You use the other two wires (blue and brown) to connect to the mains.

When wiring the transformer for 115V you have to put the two primary windings IN PARALLEL, so that the primary current flows in both of them. Wiring in parallel leaves you with 115V AC, as if you used only one primary, only the transformer will be capable to give you more output power (to be exact about half the primary current will flow in each winding). So you connect together blue and violet on one side, and you get the first terminal, and on the other side you connect together gray and brown, and this is the second terminal.
You can now connect the two terminals you have to the mains.

Hope that helps! It's really simple once you think in terms of series and parallel: in series the voltages are summed, in parallel the voltage remains the same but the current capability is doubled.

Let us know if you feel safe now!

[starn02]

Hey, did you see the 8 channel amplifier (and diy module)?
Wow, 100 w x channel! And really a good looking case ....
http://www.audiodigit.com/?section=84

[cpu8088]

anyone knows if the back of the assembled amp is using IEC connection type or figure 8 cable to the wall socket power point?

just that the photos in the website nor the specs not very clear

[Tekko]

100 watts in 50% distortion ? Sounds like a bad amp to me.

And how the heck are u supposed to do connections unless u have a babys fingers ??

Are there no heatsink on the IC´s ??? Even tho it is class D/T it will get hot and melt without any form of heatsink.

[Eva]

They are using car-radio ICs on that amplifier, and power is rated in the very same way as it's done for car-radios.

100 watts is the maximum peak power that a single channel fed with the maximum allowed supply voltage can produce into the minimum allowed load impedance for one second without blowing. Practical power rating as per conventional Hi-Fi criteria with all channels driven and a sagging power supply will be not higher than 20W rms per channel into 4 ohms, or 12W rms per channel into 8 ohms.

At these power levels, I would rather use linear car radio amplifier ICs. Almost any DIYer can build a similar 8 channel amplifier from scratch around these...

Most manufacturers still can't develop their own class D stuff, so everybody seems to be sticking to these chips now (and it's better that way because their own designs would be much worse).

[holdent]

Almost all Class-D amps have their actual power over-rated -- this is no surprise. This amp probably should've been more realistically called a 50W amp.

Although the pics on the AudioDigit site don't show them, these amps will have heatsinks (they'll have to). The heat sinks clearly aren't attached to the ICs but there is a number of ventilation slots both below and above the area were the heatsinks would be. The chips are efficient enough that if they were directly attached to the metal case it would be adequate as a heat sink. Remember we're talking about efficient Class-D operation and not Class A!!!

I not sure if Eva intended to sound dismissive of the chips by saying "they are using car-radio ICs on that amplifier". These are genuine audiophile ICs that can also be used (like all Class D amps) in car-radios because they are small and efficient.