I agree that board is a good one .
perhaps noise can come from the inbuilt potentiometer.
On TDA7498 input impedance is 69k and, if i remember, on that particular board potentiometer is 50kB, should be better to fit 10kA to reduce impedance mismatch.
also there is no 1nf cap on input going to ground like on ST schematics, perhaps something to do here.
on mine i sorted the dual 50k pot, the two 1Uf ceramic cap going to inputs (shorted), an soldered a pair of 1uF+1nf film cap directly on the old pot pinout.
perhaps noise can come from the inbuilt potentiometer.
On TDA7498 input impedance is 69k and, if i remember, on that particular board potentiometer is 50kB, should be better to fit 10kA to reduce impedance mismatch.
also there is no 1nf cap on input going to ground like on ST schematics, perhaps something to do here.
on mine i sorted the dual 50k pot, the two 1Uf ceramic cap going to inputs (shorted), an soldered a pair of 1uF+1nf film cap directly on the old pot pinout.
What is the trimmer box for in the corner. Is it for supplying power to a fan for cooling?
Supposedly it is to vary the output of the adjacent 2 pin connector from 0 to 13v, from memory.
You tried to turn several times clock-wise and several times counter clockwise and the voltage didn't change?
What is the marking on the black IC next to the trimmer? LM2575S?
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Yeah sometimes with those box shaped trimmers turning them both ways doesnt do much but after awhile in one particular direction they start to show an effect. If its stuck at 8V then i feel that is the max output for it but it should be possible to reduce it to a lower value, might need to turn for sometime in either direction till the V reading changes on the DMM.
I did a quick search for cpu cooling fans & it seems there are quite a few of those availble that run at 12V dc, so i believe that extra voltage outlet on these boards above is for an external fan to run.
I did a quick search for cpu cooling fans & it seems there are quite a few of those availble that run at 12V dc, so i believe that extra voltage outlet on these boards above is for an external fan to run.
I agree very much with you. Apart from supplying the fan-circuit, I guess it also serves to step (the up to) 39V input voltage down to the input of a linear 3.3V regulator used for control inputs. Such a 3.3V linear regulator will hardly appreciate up to 39V at the input.
Yes, these multi-turn trimmers do not always react right away.
Sorry, I mixed up the 7498 board you have with the 7498E board using a 5-pin SMPS IC.
For your board, it is an SMD LM317 linear regulator. With the three leads pointing towards you, the most left pin is the reference pin. If you turn the trimmer many turns counter-clockwise and then many turns clockwise, You do not at any moment see a change in voltage on that reference pin measured with ground ("-") as reference?
For your board, it is an SMD LM317 linear regulator. With the three leads pointing towards you, the most left pin is the reference pin. If you turn the trimmer many turns counter-clockwise and then many turns clockwise, You do not at any moment see a change in voltage on that reference pin measured with ground ("-") as reference?
Hi FauxFrench, I made some calculations based on the explanation you had provided to me earlier regarding the tpa3118 & this time the calculations i made myself are regarding a TDA7498E. Could you correct me if I've done it wrong.
at Veff=32V, Vrms = 21.3V:
----------------------------------------------
Load @ 16ohm
Max output power = 28W
Max peak output current = 2A
Max P.S.U. Power Capacity = 35W
-----------------------------------------------
Load @ 8ohm
Max output power = 56W
Max peak output current = 4A
Max P.S.U. Power Capacity = 70W
-----------------------------------------------
So a 32V 2A (~64W) power supply should work fine with lots of headroom for the TDA7498E board I guess for 16 ohm load?
The descriptions for these boards mention 8ohm as best for speaker impedance at 32V. These are the safe operating values I think they have mentioned on the products page. I found the overcurrent protection limit value for this chip little confusing, does the datasheet mean 11A in BTL(160W) mode & 14A in PBTL(220W) mode?
at Veff=32V, Vrms = 21.3V:
----------------------------------------------
Load @ 16ohm
Max output power = 28W
Max peak output current = 2A
Max P.S.U. Power Capacity = 35W
-----------------------------------------------
Load @ 8ohm
Max output power = 56W
Max peak output current = 4A
Max P.S.U. Power Capacity = 70W
-----------------------------------------------
So a 32V 2A (~64W) power supply should work fine with lots of headroom for the TDA7498E board I guess for 16 ohm load?
The descriptions for these boards mention 8ohm as best for speaker impedance at 32V. These are the safe operating values I think they have mentioned on the products page. I found the overcurrent protection limit value for this chip little confusing, does the datasheet mean 11A in BTL(160W) mode & 14A in PBTL(220W) mode?
at Veff=32V, Vrms = 21.3V:
----------------------------------------------
Load @ 16ohm
Max output power = 28W
Max peak output current = 2A
Max P.S.U. Power Capacity = 35W
-----------------------------------------------
Load @ 8ohm
Max output power = 56W
Max peak output current = 4A
Max P.S.U. Power Capacity = 70W
-----------------------------------------------
Flawless calculations! You do well.
So a 32V 2A (~64W) power supply should work fine with lots of headroom for the TDA7498E board I guess for 16 ohm load?
Njaaah, you just calculated that each channel needs 35W of supply. Then, a board with two channels needs 2x35W=70W.
Taking a bit of music crest-factor into account, it will work with music.
The descriptions for these boards mention 8ohm as best for speaker impedance at 32V. These are the safe operating values I think they have mentioned on the products page. I found the overcurrent protection limit value for this chip little confusing, does the datasheet mean 11A in BTL(160W) mode & 14A in PBTL(220W) mode?
You are right, what if we use PBTL? I believe you interpret "3.4, Iocp" (datasheet) a bit your own way. I read: the current limit for an output is typically 11A, at least 10A but maximum 14A. But, can we just double that value for PBTL? Probably not! More than 20A in these small chip leads appears unhealthy. I would still assume the 11A (typical) and 14A maximum.
The 220W are at 10% distortion, thus, with a rather distorted sine-wave. Let's use the 170W at 1% THD instead. 170W in 4 Ohm means an RMS current around 6.5A. That is a peak current below 10A. We do not need the 14A to get the 170W.
These maximum current values are often ambiguous as you also conclude.
----------------------------------------------
Load @ 16ohm
Max output power = 28W
Max peak output current = 2A
Max P.S.U. Power Capacity = 35W
-----------------------------------------------
Load @ 8ohm
Max output power = 56W
Max peak output current = 4A
Max P.S.U. Power Capacity = 70W
-----------------------------------------------
Flawless calculations! You do well.
So a 32V 2A (~64W) power supply should work fine with lots of headroom for the TDA7498E board I guess for 16 ohm load?
Njaaah, you just calculated that each channel needs 35W of supply. Then, a board with two channels needs 2x35W=70W.
Taking a bit of music crest-factor into account, it will work with music.
The descriptions for these boards mention 8ohm as best for speaker impedance at 32V. These are the safe operating values I think they have mentioned on the products page. I found the overcurrent protection limit value for this chip little confusing, does the datasheet mean 11A in BTL(160W) mode & 14A in PBTL(220W) mode?
You are right, what if we use PBTL? I believe you interpret "3.4, Iocp" (datasheet) a bit your own way. I read: the current limit for an output is typically 11A, at least 10A but maximum 14A. But, can we just double that value for PBTL? Probably not! More than 20A in these small chip leads appears unhealthy. I would still assume the 11A (typical) and 14A maximum.
The 220W are at 10% distortion, thus, with a rather distorted sine-wave. Let's use the 170W at 1% THD instead. 170W in 4 Ohm means an RMS current around 6.5A. That is a peak current below 10A. We do not need the 14A to get the 170W.
These maximum current values are often ambiguous as you also conclude.
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Thanks FauxFrench.
I was able to order the board Yatshushiro had linked. The other board jimk04 had linked to was cheaper but the shipping was costlier, almost half the price of the board, so I went with this one:Aiyima TDA7498E 160W*2 High Output Power Digital Amplifier Board Dual Channels Audio Stereo Amplifiers-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
Anyways, are the differential inputs on this board for pro audio stuff, like XLR/TRS type of connections where there is +ve, -ve & ground terminals for each left & right input connections? It does have a single ended input too but I was going to put this board in an aluminium enlcosure & figured I could add XLR/TRS sockets for the inputs as well along with the RCA type socket since I have some laying around in my parts bin not getting used for a long time.
Also how does one use this board in PBTL mode? On the tpa3116 & other tda7498 boards there are jumper points on the bottom of the board. This one has some markings but its not very specific as to what they are for. I'm inserting a link of a pic of the backside of it. There's mono out mentioned on the bottom with WL+/- & WR+/-, can't tell what its for.
I was able to order the board Yatshushiro had linked. The other board jimk04 had linked to was cheaper but the shipping was costlier, almost half the price of the board, so I went with this one:Aiyima TDA7498E 160W*2 High Output Power Digital Amplifier Board Dual Channels Audio Stereo Amplifiers-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
Anyways, are the differential inputs on this board for pro audio stuff, like XLR/TRS type of connections where there is +ve, -ve & ground terminals for each left & right input connections? It does have a single ended input too but I was going to put this board in an aluminium enlcosure & figured I could add XLR/TRS sockets for the inputs as well along with the RCA type socket since I have some laying around in my parts bin not getting used for a long time.
Also how does one use this board in PBTL mode? On the tpa3116 & other tda7498 boards there are jumper points on the bottom of the board. This one has some markings but its not very specific as to what they are for. I'm inserting a link of a pic of the backside of it. There's mono out mentioned on the bottom with WL+/- & WR+/-, can't tell what its for.
Hi Stevie,
I would have purchased the same board under these circumstances. I have a red board so I cannot easily give you a reply. I need to study the design before I give it a guess. As you say, it is not obvious with these few hints. I will try to give a suggestion tomorrow.
Seems to be a nice board, you just have to be careful about thermal things, when enclosed it can be quite hot when playing loud.
subsidiary question to FauxFrench (RealFrench ?).
TDA7498E datasheet says "differential input impedance = 69k"
if i remember is ok :
when output is not saturated , input impedance is equal to R1+R2.
so in unbalanced mode input impedance should be 69K/2 = 34.5k
can you confirm i'm right about that ?
best regards.
subsidiary question to FauxFrench (RealFrench ?).
TDA7498E datasheet says "differential input impedance = 69k"
if i remember is ok :
An externally hosted image should be here but it was not working when we last tested it.
when output is not saturated , input impedance is equal to R1+R2.
so in unbalanced mode input impedance should be 69K/2 = 34.5k
can you confirm i'm right about that ?
best regards.
Semi French. French (south) in the look of my cars but "made" somewhere more north. Married to a genuine Francaise. I also want to see the sun in my lifetime, some 180 Km from your place. Sunny today.
Your OP-AMP example is interesting and not as straight forward as just the sum of R1 and R2. Honestly, I started doubting and had to consult the Internet. The link: Overlooking the obvious: the input impedance of a difference amplifier - Precision Hub - Archives - TI E2E Community (Figure 2)
But, you are not sure if the TDA7498E inputs are designed like that. Would you have a differential input stage with 69K between the two base/gate terminals, you would have an input impedance of 69K both if you use the two inputs differentially or you tie one to ground and use the other as input.
Your OP-AMP example is interesting and not as straight forward as just the sum of R1 and R2. Honestly, I started doubting and had to consult the Internet. The link: Overlooking the obvious: the input impedance of a difference amplifier - Precision Hub - Archives - TI E2E Community (Figure 2)
But, you are not sure if the TDA7498E inputs are designed like that. Would you have a differential input stage with 69K between the two base/gate terminals, you would have an input impedance of 69K both if you use the two inputs differentially or you tie one to ground and use the other as input.
yes you're right, we do not know how it's made.
is it inverting input or not ? is it designed like those opamp or not ? who know...
I'll try to calibrate my LDR volume with a bit lower Z just to try.
that arduino LDR Volume, you can find the project in "sources > analog line level" section is really excellent , I can recommend to anyone needing a volume control.
I can also encourage any red sanwu owner to change inductors to sagami styled one, it's way better.
I never thought it could change SQ like it did !
Thanks a lot for your reply.
is it inverting input or not ? is it designed like those opamp or not ? who know...
I'll try to calibrate my LDR volume with a bit lower Z just to try.
that arduino LDR Volume, you can find the project in "sources > analog line level" section is really excellent , I can recommend to anyone needing a volume control.
I can also encourage any red sanwu owner to change inductors to sagami styled one, it's way better.
I never thought it could change SQ like it did !
Thanks a lot for your reply.
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