Almi's Logitech Z-5500 Mod (High-End upgrade for the speaker system)

[A-Force]

The caps you used as i see in the pics are 63v. these you suggested are 160v. you think they are the same size or bigger? will they fit? for the control pod cap what is your recommendation?
To my second z5500 system the front left speaker stop working years ago. you think after the mod maybe it will work again? (you can barely hear it only when the speakers are full volume and the other speakers are disconnected. it has the volume of cheap headphones)  

 

[ramachandra]

The 160V a bit bigger, no problem. On the image you can see what capacitors i have used for the pod and also you find in the description under "You may need:".
Use Silmic II if you prefer warm analog sound or Cerafine if you like accurate with less coloratura. The best "upgrade" for the Pod is to live it out of business and use a direct cable connection to the Sub from the soundcard.
 
I think the OpAmp belong to the front left channel is is dead in the Sub (common problem) and the K73-16 will fix it. If not you may need to replace the TDA Amp near the thick yellow wire.

 

[jayjayuk]

has anyone noticed that on this sub... the rear speakers are variable with the pod? and also the center speaker.... but only when the center and rear's are set at about half volume are they level with the front speakers... like the front speakers have got more attenuation on them? last time i did this test i used RCA's and bypassed the pod and it was the same... so the attenuation is in the sub... i have also bypassed the op-amps for sat's and it is still the same so its not those either... i will check a little later on as i have just got up but there is one shunt resistor left right before the signal goes in to the non inverting input on pin 3 on the TDA7294 IC... my guess is that this shunt resistor is going to have a higher resistance than the rear and center speakers... but i will have to check this a little later on. how i see it is... if the rear and center can go louder and the board and drivers can handle it... then it is the exact same configuration on the board and divers except the attenuation... so i will try and get the front speakers back to the higher level like the others... or at least figure out three quarters and put them there so you can have extra boost on the front than factory but still be able to go past that with the rears and center... i will check back in with results... on my second board everything works apart from the sub (got parts on the way) so i can test this on there. got a mixer to fix right now that... bad PSU plus my good soldering iron has broken so waiting for another.
 
Cheers

 

[Abdiel]

Hello guys!
I've registered so I can discuss about Z-5500 modding.
 
I too have one system ripped apart at home and doing testing and whatnot with it.
My idea was to create entire new amplifier board with separate 6 amplifiers, using Control Center(pod) as a volume/input control and Dolby Digital encoder. The idea was also to make new speakers just for this upgrade, making the front speakers capable of delivering more low frequency. As I would recreate all speakers and amps for 5.1 system, I wanted to make a smaller 2.0 set which I would also control with the pod.
But, I guess that's not gonna happen...
 
I've created a new amplifier with TDA7294 and connected it to front left(or right) channel(before op amps in subwoofer amp plate) to check what kind of signals do I get. I used larger speakers, and sound was lacking bass. So I connected it to sub, and it was full of bass but also you can hear some voices...bad 150Hz crossover.
 
Anyone knows how to enable LFE for sub to go to front speakers and lower the bass cut-off frequency from 150Hz to 80-100Hz?
 
I've studied all chips on the pod board, CS42526 is an input selector, maybe it's doing some ADC(assuming all of this), NJW1150 is a volume controller and CS494003 is a DSP, which I guess is doing all the hard work around here(also cutting the frequency).
You can add more bass/treble with NJW1150 on front speakers(needs to be controlled over I2C, bypassing Zilog MCU(I've worked with Microchip, Atmel and ARM but not Zilog)) but the end product would be the increase of frequency of 150HZ and more.
 
Final option is to use few opamps and mix the sub output to front speakers. Not sure how well would that work or sound.
 
Anyways, if someone has an opinion on this, feel free to elaborate with me.
Currently I feel disappointed, even if I can control NJW, I can not get a full range frequency on front(or even all) speakers.
Anyone hacked into DSP? If yes, lemme know!
 
Greetings from Croatia!
Cheers

 

[jayjayuk]

@A-Force i am pretty sure your problem will be with the op-amp as mine went quieter than the others and when i put a new one in it fixed it.
 
@ramachandra i have done the op-amp bypass on my board and have it running... but for some reason i think when i turn the volume up before it had more power to give when the op-amps was in... i think this might be because the attenuation resistor just before the tda amp now does not have enough resistance for the direct connection... so it is shunting the voltage down to much for a direct connection from the input signal... what do think about this? i was thinking of changing the resistor for a higher value as to not let so much voltage drop... i will post back the results when i have tried it... but for now... i built that board i posted here to fix U15 and use wires to connect back to the main board with and everything is working fine again... been running for about to hours now... been sat on my bench in pieces for ages now so just enjoying it before i do anything else lol... inside that sub does not look pretty as there is alot of broken tracks and fixes here and there... i am just glad it is working again. i bought a bag of 50 x R4580i from ebay for £15 as i could not keep throwing OPA1612's in as they are expensive to keep popping... so went with the cheaper (original) option until things are smooth again... then i will by a couple OPA's to put back in the end. it is sounding pretty good... that hum i told you about seems to be gone... i have not changed main filter caps... maybe a bad ground or position of the cables inside like you said... but so far i am happy with it except for that i think that the overall power on the sats has dropped across the range so i will look into that

 

[ramachandra]

When i come up with the idea of the Third Mod i was afraid of this might happen and i tried it out on a front channel, and I left the other untouched. Than I have compared the two sides and i have not noticed any downside, the Pod was modified. Some of the SMD around the OpAmps can interfere i think, that is the reason i got rid of them completely. I'm interested when you progress further what will be your conclusion, i can be wrong. The cheaper OPA1602 sound more alive than the more expesive OPA1612.

 

[jayjayuk]

i will have to experiment with op-amps at a later date... i did not do the comparison you did as i was having problems with op-amps so i bypassed all in one go... if you say they are the same then i will accept your testing but i will continue to try and change the attenuation... i will try this ony my second board... i have all sats working just need to work on the sub area... i was also thinking (a big shot but i have been thinking alot about it) to get a board for the tda amp and use it in the same config as the sub (straight off the bootstrap to the inverting input) and then use that output as the negative for the sat speaker (just change the negative from the main ground to the inverting amplifier and it will give the sats an extra 50Watts (i think) but thats a mod for when i have tried other things... first i am going to try the attenuation resistors near the TDA's to boost the signal... this will only be a very small change in resistrance as i dont want to do it to much and the unit thermally shuts down... i want a bit more power but i still want constant use... which leads me to attenuation resistors or a sub tda board for an iverted negative to the sats... i will keep posting in every now and then with results... the sound is not greatly decreased i just mean when the volume is all the way up it seems like it had more to output when the op-amps was in... but the whole board and that end attenuation resistor was initially set for the op-amp in place so now the system is different and may need further modding of that resistor... tests will tell i do like the idea of powering the negative thought... that would boost this system very well i just need to find a suitable board on ebay so i can plan and place all the components on.
 
i also noticed that the front speakers (as stock) are attenuated to half the set volume of the pod's center and rears... so you have to set the center and rear speakers on the pod at half so they are the same as the front... this is done in the sub as i have used rca's on the sub (to bypass the pod) and the attenuation is still present so it is in the plate amp... and with the op-amp bypass there is only two components left before it goes to the non inverting pin on the tda amp... that is an smd capacitor and smd resistor both of with are connected to ground so it will be the resistor that is the attenuation (i need to check this though as if the resistors on the front are different values to the ones on the back and center then i can change them and get the same level) although i want to keep it slightly under the full level of the rear and center.
 
i will get back on this soon as i have a couple of mixers to look at and fix at the min.
 
Cheers

 

[Abdiel]

So, no feedback about crossover frequency?
I hope someone will comment about it, I would really like some opinions.

 

[andro6600]

  So, no feedback about crossover frequency?
I hope someone will comment about it, I would really like some opinions.

Hi,
about the HPF of the satellites, @ramachandra said to me before, that the filter is most probably in the volume control chip. But i don't have the knowledge to fix this. But anyway, i am not very sure, that the system has actually HPF. I tried satellites with test signal 20-20KHz, and i definitely can hear frequencies about the lowest satellites border, but they are somehow fading, but very slowly from about the 100Hz below. I mean, they are there, not cut, but with less gain that is suppose to. So, the only easy way to me was, to get the sats, that reproduce low mids very well, in other words, you need speakers that go down as low as possible, so they can remain very linear and accurate in the low range (also the Elna caps do helps a lot) This is not exactly the solution, but with right combination of mods, and sub placement, so that you can get impression that lows are coming from sats, not the sub, the result is impressive! But i also would like to know, if something can be done, for that problem, because, my sats, are quite decent, and can go very low, and it's a shame not to.
 
Cheers

 

[jayjayuk]

@Abdiel  sorry i am fairly new to electronics and have not looked into filters yet... although i can see my self getting right into them after i have finished playing with attenuation and possibly doubling the tda7294 chips as to have the same config as the sub but with no filter... i have a plan for this but looking hard to fit it all in. please if you can... send me the pdf documents/datasheets for the chips in the pod and i will take a look.
 
@ramachandra i got the second board fully working last night.... the only problem is i am missing a capacitor to ground which if logitech stuck to the datasheet components should be a 0.47uf 0603 to GND but i do not have one... it does not make a difference though... chip runs for hours and does not get hot or sound different to the other speakers or get hot any quicker so all is fine but i will be getting a cap to put back in... that was on the rear channel and the main broken tracks (to which i had to use a 680R metal film instead of a smd 681R) is on the rear channel so i left them and have started playing with the front channels for comparison.... heres what i am finding... i was initially wrong about the attenuation of the speakers (front/all others) the attenuation is done in the pod probabbly so the fronts dont over power all the other speakers and you have control over it. i had got some smd resistors in to make the board for U15 on my first board so i had alot spare.... the original resistor R500 (i think) is a 22.1K smd 0603 right before pin 3 to the tda7294 (non inverting input)... so i figured i would start by changing its value... to have less drop (audio drawn away) i wanted to increase this resistors value so less would pass through it to ground so i put a 31.6K resistor in there (spares that i had from around U15, R617 or R619 is 31.6K) and it changed it just slightly... i was looking for big sound attenuation difference or very slight visual (cone movement) difference... what happend was i can hear the sound is slighty above the unchanged channel i can also see that the cone is moving alot sooner... so if i start at low volume where i cannot see the driver move to the bass and slowly increase the volume until i can see the movement then the channel with changed resistor will be visable and audible first (although the second is not far behind) i am going to try something else a little later on (as i have spare chips so why not) i am going to try puttin a 90.9K in there and see if there is a big difference i will then try and leave this resistor out completely and see what happens...also on the tda7294 chips people can save on caps here as there is 2 22uF's for one tda amp... one of them is bootstrap but the other is either mute or standby (cant remember which) but it is seperate to the signal path... i think money can be saved on caps here as they dont enter the signal path.
 
More tests are coming... i only got this fully working last night and did one test but now i have two boards that fully work... i have an idea... snap all tda7294's out for the sats only... then cut pin 2 and 3 half way back... then solder wires on these pins and solder the chip in place as usual... but swap the wires over so pin 2 goes to hole 3 on the board and pin 3 goes to hole 2 (so the inverting and non inverting are swapped around) then i will have a plate amp that has the sub output as normal but all the sat speakers will be inverted so i have the negative... then i can mount another d-sub 15 pin connector on both plate amps and do the necessary wiring so standby and mute work and i will have two working together.... so i will have a 5.2 system where the original sats will have an extra 50-80W (not sure about the gain here) and i will also have an extra sub output... all of this i am pretty sure i could do... things like how to wire to both speaker output terminals i have not thought about but this will not be a problem if i sit and think about it... the main problem i am having is if i get all this to work (which i am pretty sure i can) i dont know how/where i can mount the second plate amp as there is no room on the box to do it and i dont want it separate from the sub box as this would make it so i can wire everthing internally and not use extra d-sub 15 connectors to connect the two together and everything will be neat and tidy... but i cant loose the plate either as the big heatsink will potentially run another sub driver and be inverting the sat speakers... so i need that plate with sinks on... more thinking on this is needed (possible another wooden box mounted/bolted to the top of the original so i can fit the plate amp on top and drill a big hole between the two boxes on the inside for the wires to pass through) i like this idea but its just getting everything together so it looks good....
 
more to think about and more to do... i will report back when i have more news...
 
Cheers. 

 

[Abdiel]

@jayjayuk
There are 3 main chips.
DSP: Cirrus Logic CS494003
Volume control/ADC: Cirrus Logic CS42526
Volume control: New Japan Radio NJW1150
 
DSP is licensed and you will not find any info about it.
CS42526 and NJW1150 are the things you can look into, but if you don't have no experience in electronics, there is a chance you will not find anything. You can download PDFs via google search.
If you do find out something, write it here. I've also asked some other people to help, so who knows, maybe we all find a way to enable real full-range on all speakers.
 
Also, doubling the amps will really get you nowhere, you don't need more than 50W per channel, for sub yes, but for all the rest, not. You could maybe change a transformer and give more volts to TDAs gaining more power, but you will get a higher THD and TDAs will heat more.
If you insist on doing it, maybe a best option would be to make a new amp plate. Also, change the transformer, original one is around 200VA, to 300VA or more, depending how much power you wish to achieve on all channels. Remember, original satellites only pull around 10W.

 

[A-Force]

my order arrived from mouser in just 3 days!!!! i am going to start the mod to the speakers and to the sound card!!!  can you tell me how can i bypass the control pod? i mean which cable to connect where? and what i need from equipment and stuff? i think that if i leave it out of business i am going to have less work to do instead of upgrading the original control pod and the sound is going to be better according to your conclusions. thx in advance!!!
 
p.s. the crossover for the speakers is in the original pod? i mean without it you can adjust the frequency with the sound card?

 

[Abdiel]

@A-Force
Yes, crossover is in control pod. There are some limitations to low frequency on TDA amp(used capacitors) and pre-amp is limiting some, but they are nothing compared to frequency cut which is coming from control pod. I suspect that DSP is limiting frequency, but currently i don't have time to investigate more, but I will soon.
 
Yes, if you bypass control pod and use sound card, you can somewhat bypass crossover frequency of the pod and set your own. But be aware that 3" tang bands used in satellites can't reproduce low frequency, the reason why crossover freq. is at 150Hz.
You can use cables which are sold on ebay, just search "z5500 bypass control pod cable" or similar search, you will find em.

 

[ramachandra]

You need a D-sub connector few jacks and the length of the cable(s) you prefer between your PC and the Sub. Try not to use cable where all the wires running together and only the outside have proper shielding (to avoid crosstalk). You can get jack extension leads cheap, and cut it on the middle. The 2W 22K resistors are not essential just recommended instead some sort of degrading volume control. Best if you get wirewound or at least metal film, more watts not a problem. If the space matter, you can use 1/4W metal film and hide them under the cover of the D-sub connector. The connection working without any resistors just too loud even on 10% in the Windows, so better to be careful in the beginning.
You need to use the bass redirect in the Creative software to set up the proper bass setting for your Sub. No resistor required for this channel.
 

 

[A-Force]

And if i want to connect the audio card to 2 z5500 systems?