hifimediy T2 mods?

I just ordered a hifimediy T2 amp plus accompanying Meanwell 27v SMPS. Thanks to hifmediy for building these amps, and to Nick for making them so readily available.

I know there is already a long D class forum thread on hifmediy's amps, but it emphasizes the TK2050 boards.

If I understand correctly the 2050s are no longer available, and the T2 now has a TC2000 controller with two sta505 power chips.

I know folks in the other thread have talked about various mods to input caps, pots, and toroids. What I want to do with this thread is see if there is enough interest to discuss mods applying to this specific amp. I would love to benefit from anyone's experience before I begin.

Thanks!

Bruce Bender
Santa Fe, New Mexico, USA
 
I know there is already a long D class forum thread on hifmediy's amps, but it emphasizes the TK2050 boards.

If I understand correctly the 2050s are no longer available, and the T2 now has a TC2000 controller with two sta505 power chips.

Ah, the TK2050 ... Such confusion. The thing is that the Tripath TK2050 chip-set is made up of two chips: A TC2000 controller, and an output stage chip, canonically the TP2050. The STA505 is exactly the same as the old TP2050 output chip.

So all the old mods apply. There are some differences in the output filter components - inductors, caps, and resistors - according to what load impedance the board is designed for. 8 Ohms or 4 Ohms. Most everything else that is 'tweakable' is the same across these amps.
 
Sorry for the trolling comment, I felt like you were dissing both the manufacturer and my choice of product - a bit hasty on my part!

The T2 is one stereo board, with a volume control on it, so you can just hook up a power supply plus ins and outs and you are good to go. Specifically recommended for 4ohm speakers, and I have some Focals that dip way down there in the midbass. Priced about US$40. Meanwell S-350-27 is recommended as the power supply.

The T3 is higher power, but one channel per board. You need a total of four boards, two T3s and two accompanying power supply filter boards for the two channel system equivalent to the T2, and there are no pots. So it takes more layout to get it operating. Price US$about 100. Meanwell S-350-48 is recommended as the power supply, plus the use of the filter boards.

Hifimediy|Hifimediy T3 [email protected] Amplifier set

I suspect if I like the T2 I will be unable to resist playing with the T3. I am a tube guy, and all this stuff seems very inexpensive to play with to me, especially if it sounds good.

I have two Class D high-power bass guitar amps, and they sound very good, so I have high hopes.

(For the record, I am a newby to Class D stuff, and have no affiliation with hifimediy, just chose them based on extensive web surfing.)
 
It's my personal opinion but almost any Tripath based amp sounds a far cry better than any other class-D amp so you should be in for a treat.

I just noticed in another thread that hifimediy will make a T4 which is basically a TC2000 controller with a ST317B output driver working in stereo which would basically make what I said about replacing the STA505 with the STA517B so hifimediy does recognize the sound quality difference between the 2. That's very good since they measure almost identically, and one that would only look at the engineering numbers would naturally go for the lower priced part.
 

trevmar

Member
2011-01-10 8:36 pm
My T2 just arrived and it is a nice, clean, Tripath implementation. I saw nothing unusual when I had it on the bench, the characteristic Tripath meandering of the PWM signal as the sinusoid reaches 100% was the primary negative observation on the 'scope.

I did notice that the heatsink gets quite warm when stressed into 4 ohms at about 2/3 rail voltage. I guess the extra power transistor dissipation is necessary to ensure low output distortion, as the power switches are outside the TC2000 feedback loop. I didn't bother to measure dead-time, etc...

I decreased R1 and R4 to 10K, as the standard gain was a bit low for me. The T2 seemed to be set up for full output at 0.9VRMS, and I prefer to keep my preamplifier signals about 6dB below that.

At the risk of you all laughing uncontrollably, I am currently testing the subjective audio quality with my two superb Peerless 2 inch 830983 widerange speakers in Linkwitz-inspired omnidirectional enclosures. My old TA2024 just didn't quite have enough power to handle the amplitude-compensation applied by my miniDSP :) The T2 sounds clean and clear.. (speaker photo below)

These speakers form the basis of my traveling kit - HiFi for the frequent traveler :) I intend to replace the T2 with a lighter-weight TDA7492 amplifier when it arrives :)

I am running the amp nicely at 20V bypassing the bridge rectifier, as I like to live dangerously :) I did test the T2 at higher voltages on the testbench...

Anyway -- great job guys, I will have to try some other HifimeDIY products :)
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TheDealer

Member
2008-04-05 3:49 pm
So Folks, excuse me when my comment appears a bit rough:mad:. As long as any of us is not an experienced guy/girl in electronics, we should firstly ask the designer which mods are allowed and senseful. I am nearly sure that some risky mods lead into damage of the board and instead the modder tells the truth, he/she makes such a "defect" delivered board public and forces the designer here to make a good face to a bad game. Such behavior I find extremely asocial.

Nevertheless,this should not be a general critic on the thread title.
 
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trevmar

Member
2011-01-10 8:36 pm
Dear The Dealer,
Members watching this thread will have many levels of competence, although it is to be expected that anybody who visits here will either understand the risks involved in modding, or understand the technology to the point that any risks become minimal. Perhaps some might understand more about how the various PWM chips function than the board designers, who knows?

Personally, I think it should help the board designer to look at the questions he/she is being asked about the product, and the deficiencies which 'modders' perceive in the product.

I come to diyAudio to get the direct perspective of the board designers, so I can figure out which of them knows what they are doing, and those who are not so confident. I would urge cristi, ljw_ljw, hifimeDIY and the others to give us as much info as they can about the design concepts behind their products. Discussing 'modifications' should provide an excellent way for them to do this.

Of course, there are always issues a board designer would not want to buy into. Let's hope they remember these discussions when they design their next product revision :)
 

TheDealer

Member
2008-04-05 3:49 pm
Hi Trevmar, of course are such threads a welcomed opportunity for the designer and the consumers to learn more and more about the possibilities to make things better.

Eventually the designer should start modding threads himself and contribute a list of senseful and senseless changes on the board.

Very important I find meanwhile the issue of gain setting which is the latest article of Michael Mardis on the start page of this forum. My critics are not aimed to the experienced users who know very well what they do.
 

trevmar

Member
2011-01-10 8:36 pm
Maybe I didn't read carefully enough, but I thought the original post was focused on "input caps, pots, and toroids," In the T2, the input caps are huge 3.3uF poly, the pots trim the output voltage offset, and toroids might well saturate, or otherwise change the distortion characteristic of the amplifier.

Gain, on the other hand, is set by the input resistor network. IMO the change I made was routine. A quick check of the data sheet for the TC2000, just to make sure, and I changed the resistors R1 and R4. If you are unfamiliar with how to desolder chip resistors, or do not have some 10K chip resistors on the shelf, I suspect you would not have followed the same path as I did :)

Anyway, just to make sure I didn't mislead any newbies: "if you change the input gain resistors, like I did, you are likely to damage the board from desoldering and resoldering, and you are reducing the amount of negative feedback, which may well increase the harmonic distortion."

The problem seems to be that I posted in a thread where the board developer is not actively helping newbies to size up the risk. I guess I will just have to make mods for myself in future, and not share with the diyAudio members what worked for me, and what didn't :)
 

TheDealer

Member
2008-04-05 3:49 pm
Maybe I didn't read carefully enough, but I thought the original post was focused on "input caps, pots, and toroids," In the T2, the input caps are huge 3.3uF poly, the pots trim the output voltage offset, and toroids might well saturate, or otherwise change the distortion characteristic of the amplifier.

Gain, on the other hand, is set by the input resistor network. IMO the change I made was routine. A quick check of the data sheet for the TC2000, just to make sure, and I changed the resistors R1 and R4. If you are unfamiliar with how to desolder chip resistors, or do not have some 10K chip resistors on the shelf, I suspect you would not have followed the same path as I did :)

In this case this should mean that you optimize the board for one source, or not ? The sure-board has these 4 position switches for gain setting. Is this a acceptable flexible solution for you or is a good pre-buffer even though much more expensive (like the burson buffer) the better choice ?

The problem seems to be that I posted in a thread where the board developer is not actively helping newbies to size up the risk. I guess I will just have to make mods for myself in future, and not share with the diyAudio members what worked for me, and what didn't :)

Share with us please the things that have worked for you:). I think it is a correct behaviour of each modder to take responsibility for himself and indeed for the community by comparing his acts with his know-how. O.K. my thoughts above should be understood as a small attention for the kamikaze members here.

So let's change now to daily programme and discuss the possibilites to optimize the board for different powersupplies. I think this is one of the most important steps for a well constructed amp.
 

trevmar

Member
2011-01-10 8:36 pm
The sure-board has these 4 position switches for gain setting. Is this a acceptable flexible solution for you
We are talking about the T2 board, at this URL:

Hifimediy|Hifimediy T2 2*[email protected] amplifier STA505 Nichicon KG 10000uf

which has a potentiometer (volume control) to allow higher input-level sources to drive the amplifier :confused:

I used a 24V 5A switching power supply I bought at the SEG market in Shenzhen for $5 last February. It looks like a 'Meanwell,' but is branded only with Chinese characters. Nevertheless, the output voltage adjusts to a rock solid 27V. The Nichicon capacitor on the T2 would help smooth out transients, in any case.
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TheDealer

Member
2008-04-05 3:49 pm
Really ??!:eek:

which has a potentiometer (volume control) to allow higher input-level sources to drive the amplifier :confused:
I know the T2 boards well. Also the first V2.0 version and some others of hifimediy. Not sure what you exactly mean. It is important to match the output voltage of the source with the input voltage of amp. A vol. pot. is not the ultimate tool in modding.:(
 

trevmar

Member
2011-01-10 8:36 pm
A vol. pot. is not the ultimate tool in modding.:(

Indeed, there is noise picked up in the T2 input circuits when this control is in its mid position. I have mined turned fully up, which is just right to interface with my MiniDSP preamp's output (AFTER I increased the gain with R1 and R4)...

As for the "modding world," I lived through the transition from Vinyl to CD, and understand there will always be folk who can hear the difference between a 3.3uF MKP input cap and a 4.7uF MKP cap. I am not one of them
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