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Old 23rd February 2005, 06:40 AM   #1
Erukian is offline Erukian  United States
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Default Teac AL700P questions..

Hi, my first topic in these forums, and to be honest, the Tripath amps have really brought me into the DIY audio world. First, I did use the search function but it's been a pain in the *** for me to find specific information about the Teac T-Amp so I was hoping that I could just start a thread and have people throw in what they know.

So let me get to it!
1) How can taking out the center channel board help the sound? I figure if nothing's hooked up to it then nothing can draw load and the PSU isnt working harder.
2) I've read the popular thread on Sonic Impact Impressions -- in the guy's website he show's of the bass response falling off rapidly after 80hz, which is a big deal because my subwoofer's crossover really kicks in at 50hz, is this a problem with the Teac or is it a tripath problem? Is this a power-supply problem?

Like I said, i'd LOVE to learn more about the teac t-amp, the insides and outs, but i'm having a hell of a time finding info in here and would really appreciate any bones you can throw at this newbie.
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E-MU 0404 >> ratshack gold 1/4" RCA adaptor >> ratshack 'fusion' 3' cable >> Teac Tripath amp (unmodded) > monster xp cable > Hsu STF-2 Subwoofer > more speaker wire > Onix Reference 1 speakers.
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Old 23rd February 2005, 07:20 AM   #2
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Default Re: Teac AL700P questions..

Quote:
Originally posted by Erukian
[B]Hi, my first topic in these forums, and to be honest, the Tripath amps have really brought me into the DIY audio world. First, I did use the search function but it's been a pain in the *** for me to find specific information about the Teac T-Amp so I was hoping that I could just start a thread and have people throw in what they know.

So let me get to it!
1) How can taking out the center channel board help the sound? I figure if nothing's hooked up to it then nothing can draw load and the PSU isnt working harder.
While i don't have a AL700P, my understanding is that it's actually a 4 channel amp with only 3 channels connected. My guess is that removing the center channel would make no difference. The idle current consumption of the unused channels is probably negligible.

The only possible thing I can think of is that the tripath chips work by having each channel running at a different frequncy. If this is the case, and you have two identical channels (2 boards, 2 channels per board), you could have cross-talk injected from one board into the other.


Quote:
Originally posted by Erukian

2) I've read the popular thread on Sonic Impact Impressions -- in the guy's website he show's of the bass response falling off rapidly after 80hz, which is a big deal because my subwoofer's crossover really kicks in at 50hz, is this a problem with the Teac or is it a tripath problem? Is this a power-supply problem?

Like I said, i'd LOVE to learn more about the teac t-amp, the insides and outs, but i'm having a hell of a time finding info in here and would really appreciate any bones you can throw at this newbie.
Well the bass issues with the Sonic Impact are totally due to the way the input filter on that board is designed. The DC-blocking capacitor at the input is far too small in value, which results in early bass rolloff.

Whether or not this is a problem in the Teac is hard to tell, since I don't have one to look at their input filter. It's possible, since it was only designed for center-channel and surround duties, that they used a smaller value than ideal for the input. The only way to find out is to open it up and measure the value

I hope to pick one of these up, but I have too many other projects underway right now. Good luck! I'm sure other folks will be documenting it soon, since it seems like the quick and easy way to get a wall-powered tripath system.
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Old 23rd February 2005, 07:47 PM   #3
Erukian is offline Erukian  United States
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So nobody knows if the Teac rolls off too after 80hz?

What about the power rating on the Teac? From what I could see its 30Watts into 3 channels at 6 ohms, will it still work with my 8ohm speakers fine?

If i rip out the center channel board will it give the main two channels more headroom/power/curent?

What about the pots on the back of it? I'm having a real tough time finding pictures of the rear online, I was wondering if the pots are per-channel or if there's just one for the center and one for the stereo.

What sort of power supply is inside the Teac? Is it a 12V block?

hoping for some more answers
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E-MU 0404 >> ratshack gold 1/4" RCA adaptor >> ratshack 'fusion' 3' cable >> Teac Tripath amp (unmodded) > monster xp cable > Hsu STF-2 Subwoofer > more speaker wire > Onix Reference 1 speakers.
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Old 23rd February 2005, 08:29 PM   #4
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Quote:
Originally posted by Erukian
[B]So nobody knows if the Teac rolls off too after 80hz?

What about the power rating on the Teac? From what I could see its 30Watts into 3 channels at 6 ohms, will it still work with my 8ohm speakers fine?
It will work fine with 8 ohm speakers, but won't put out 30 watts.

Quote:
Originally posted by Erukian
[B]
If i rip out the center channel board will it give the main two channels more headroom/power/curent?
Most likely, the tripath chips are the limiting factor. If they're not, you can always upgrade the power transformer.

Quote:
Originally posted by Erukian
[B]
What about the pots on the back of it? I'm having a real tough time finding pictures of the rear online, I was wondering if the pots are per-channel or if there's just one for the center and one for the stereo.
No idea.


Quote:
Originally posted by Erukian
[B]
What sort of power supply is inside the Teac? Is it a 12V block?
Probably not. Tripath's higher power chips stat at 14.5V and go up from there.
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Old 23rd February 2005, 10:48 PM   #5
DougL is offline DougL  United States
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II was able to determine from the Tri-path site in the design wins press releases that the Chip is the 2050.

It is spec'ed for 50 watts into 6 ohms.
It is not bridged, and 4 ohm operation is not recommended by the chip manufacture due to current limit. YMMV.
quote:
What about the pots on the back of it? I'm having a real tough time finding pictures of the rear online, I was wondering if the pots are per-channel or if there's just one for the center and one for the stereo.

There are 3 mini pots, one for each input. Its designed to balance gain between speakers, not provide a volume control.
quote:
What sort of power supply is inside the Teac? Is it a 12V block?
The Sonic Impact only reaches 8W with a 4 ohm load with a "12 Volt" power supply. The 2050 is not bridged in the Teac, so common sense says itís a fair bit higher. Read the data sheet and the Application Note on the Tri-Path site.
That will answer most of your questions.


(edited for spelling)
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Old 24th February 2005, 12:36 AM   #6
Erukian is offline Erukian  United States
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From the impressions of the Teac vs the SI. I've read that some consider the SI more "edgy" in the highs and the teac smoother, but I haven't heard anything about the bass response.

Is the Teac pretty much avoided as a modding platform because the SI is _so_ cheap?

I'm _really_ new to modding, i do have a soldering iron, and I have limited use with it from high school physics. Do you guys think the Teac would be the best bang for my buck? If I could easily mod the SI to get rid of that bass drop, then i'd jump on it cause it'd save me a good $40 bucks or so.

Being a college student and all, money matters I don't wanna buy a SI and end up frying it. But nobody seems to know if the Teac suffers from the same issues in here.
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E-MU 0404 >> ratshack gold 1/4" RCA adaptor >> ratshack 'fusion' 3' cable >> Teac Tripath amp (unmodded) > monster xp cable > Hsu STF-2 Subwoofer > more speaker wire > Onix Reference 1 speakers.
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Old 24th February 2005, 02:48 AM   #7
DougL is offline DougL  United States
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According to this: Tri-Path App Note
The low frequency input pole is about 10 Hz in a typical design.
It is set by the value of the input cap and resistors.

Doug
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Old 24th February 2005, 03:04 AM   #8
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Audiocircle is probably the best source of info on the Teac units, although not with quite the same DIY/tech bent you get here.

The supply on the Teac is a switching supply, with the output bridge run at 28V, but also with 12V and 5V control signals. The 28V comes in directly from the supply, so I'm intenting to try clipping the leads and feeding it 24V of battery power.

The Tripath chip is actually labeled a TC2000 in mine, but it appears to be the same as the 2050.

I'm actually also surprised that the Teac isn't getting more attention from the modders out there. It's really a 4 channel amp, and there is tons of room inside for mods. The board and construction quality puts the SI to shame, and IMHO the case/appearance is great for a $100 amp. I suspect the cheapness of the SI is one factor, but also the simplicity - rip the board out, hook up a battery, and you're on your way. The Teac would require a bit more though/planning, particularly on the power supply side.
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Old 24th February 2005, 06:59 AM   #9
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Well, like I said, the Teac is on my to-do list. I think the big appeal for some audio guys for th SI is that it's battery powered. However, there's nothing to say you couldn't just make a battery PSU for the teac from a couple of series'd SLAs
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Old 24th February 2005, 03:51 PM   #10
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I have a heavily modded Teac and I am very happy w/ the quality of the sound. I am including a link to the thread from Audiocircle that covers most of these low tech modifications. http://www.audiocircle.com/circles/v...ic.php?t=11728
I asked VinnieR who is amember of this board to undertake a more intensive upgrade and the result is IMO a reference quality amp.
The switching power supply is of course the major obstacle to deal with. I use a balanced power transformer and isolate the Teac's power input from other devices.
There are two amplifier boards, one only uses a single channel so its removal lightens the load on the power supply and is a very cheap, simple and dramatic audible improvement. Removing the potentiometer riser and adding jumpers from the RCA inputs to the amp traces also is a fairly cheap mod with benefit. Many are only using a single channel on one of the amp boards which further reduces the load on the PS and some believe results in a better sound ("monoblocks"). Replacement of the capacitors on the PS board improves matters still further. Much of this is detailed in the link, unfortunately it is some 19 pages so you have to dig through it.
Battery power is a possible option but more complex in this case because of the multiple voltages required.
The range of speakers that become available would be greater than w/ the lower ouput 2024 Tripath chip but you pays your money and takes your choices.
Hope this helps.
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