john65b said:
Its funny you mention the price jump of the Entech. I was just looking on ebay before I returned to this thread an noticed it myself. I actually have 4 of them. I bought the last one for $43 shipped. So I actually got all of them for around $150.😀
I know exactly which DAC your talking about......
http://cgi.ebay.com/DAC-IN-THE-BOX-...ryZ64593QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
I was looking at that DAC before I bought the Entechs; but the Entechs happened to be cheaper at the time so I went with them instead.
I'm looking forward to your comparison of the two.
Yup, that's the one. I hope it has real CS8416/CS4397 chips in it instead of the fake crap we have been hearing about coming out of China. You never know - if it looks to good to be true...
If it is real, and sounds sweet, and I am able to cirmcumvent those high-end-audio companies out there charging $500 - $5000 for the same DAC setup, well, I think it would be worth the $59 gamble...Hey, it happens, just look at the $3000 Gaincard and the its nearly identical $49 Gainclone (got three of these too - ah, Gainclones that is).
I like the blub on the eBay DAC auction "UNIT HAS A SEAL ON THE CHASSIS BOX AND THE WARRANTY IS VOIDED IF THE SEAL IS BROKEN"....BAH!
On another topic - that separate DSP board in the DCP-501 with all the cheesy, crappy electrolitics in the signal path - why are they all there if the input to the amp already has dc blocking caps? Can't we just jumper those caps if the signal eventually gets to the "amp caps" before amplification?
Just thinking out loud here...
If it is real, and sounds sweet, and I am able to cirmcumvent those high-end-audio companies out there charging $500 - $5000 for the same DAC setup, well, I think it would be worth the $59 gamble...Hey, it happens, just look at the $3000 Gaincard and the its nearly identical $49 Gainclone (got three of these too - ah, Gainclones that is).
I like the blub on the eBay DAC auction "UNIT HAS A SEAL ON THE CHASSIS BOX AND THE WARRANTY IS VOIDED IF THE SEAL IS BROKEN"....BAH!
On another topic - that separate DSP board in the DCP-501 with all the cheesy, crappy electrolitics in the signal path - why are they all there if the input to the amp already has dc blocking caps? Can't we just jumper those caps if the signal eventually gets to the "amp caps" before amplification?
Just thinking out loud here...
john65b said:
I never bothered tracing the full route from the DSP to amp board. I'm sure some of the caps could be removed, but I have no way to check.
I threw out the rest of the parts a few weeks ago. I have enough clutter as it is; it drives me insane.
Hey John,
I'm not sure if you have seen this thread, but it is about the DAC you just purchased.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=92830
I'm not sure if you have seen this thread, but it is about the DAC you just purchased.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=92830
Thanks john65b and theAnonymous1 for the information!
I do have one other question. I'm looking at cases and was wondering what the thinnest case I could use is? Or rephrased, what is the thickness of the largest part (the toroid?) so I can stuff it all in a case?
I've got a tracking number on my DCP, so it shouldn't be more than a week before the fun begins!
Thanks again for the help!
-PGPfan
I do have one other question. I'm looking at cases and was wondering what the thinnest case I could use is? Or rephrased, what is the thickness of the largest part (the toroid?) so I can stuff it all in a case?
I've got a tracking number on my DCP, so it shouldn't be more than a week before the fun begins!
Thanks again for the help!
-PGPfan
I plan on rehousing the DCP-501 amp in an old Parasound Amp Chassis that went belly up. The amp board is vertical in the DCP, but I plan on laying it on its side, so the toroid Trannie will govern height - I would say 3 to 4" high - min.
Also, I remember the amp board was kinda long (over 14" I think), so a standard Rac case of 17" should suffice...
Also, I remember the amp board was kinda long (over 14" I think), so a standard Rac case of 17" should suffice...
Member
Joined 2003
I will be purchasing a rackmount chassis shortly to house my stripped DCP501. I have measured that the absolute minimum depth for a 2U chassis would be 11.5" for this amplifier. The amp board actually fills the width of a rack chassis quite nicely.
What I am planning to do with this power amp project is to experiment with the amp in bridged mode. The TDA3020 datasheet shows an odd (maybe not that odd, I haven't really looked at bridged amp modes before, but it looks odd) bridged configuration in which the signal is fed through the inverting input of the amp which applies gain. The output of this stage is fed to the inverting input of the other channel which applied no gain (just inverts the already inverted signal). See figure 6 on page 23 of the TDA3020 datasheet.
I am planning to not modify any parts on the DCP501 amp board besides the input coupling caps, and set the amp to work in bridge mode externally. I will have an input buffer which will invert the signal and simply send an inverted signal to one channel, and a non-inverted signal to the other channel. This should work just fine should it not? I was a bit confused when I saw the bridged mode example in the datasheet, as I have read many amps are not very stable at unity gain. Then again, this is what I have read about Class AB amps (like the LM3886), I have not heard this about class D amps and am just assuming.
What I am planning to do with this power amp project is to experiment with the amp in bridged mode. The TDA3020 datasheet shows an odd (maybe not that odd, I haven't really looked at bridged amp modes before, but it looks odd) bridged configuration in which the signal is fed through the inverting input of the amp which applies gain. The output of this stage is fed to the inverting input of the other channel which applied no gain (just inverts the already inverted signal). See figure 6 on page 23 of the TDA3020 datasheet.
I am planning to not modify any parts on the DCP501 amp board besides the input coupling caps, and set the amp to work in bridge mode externally. I will have an input buffer which will invert the signal and simply send an inverted signal to one channel, and a non-inverted signal to the other channel. This should work just fine should it not? I was a bit confused when I saw the bridged mode example in the datasheet, as I have read many amps are not very stable at unity gain. Then again, this is what I have read about Class AB amps (like the LM3886), I have not heard this about class D amps and am just assuming.
DcibeL,
If you plan on bridging you will need to change the value of the over-current resistors. You can do this by simply soldering a 20k resistor over the 15k thats already there. These are marked R11A, R11B, R11C, R11D, R11E, and R11F on the PCB.
I have tested this amp bridged. It put out some serious power, but I was only using one bridged channel and it really stressed out the power supply. Don't expect a full doubling of power using two bridged channels unless you plan on getting a new transformer.
Using an external inverter to bridge is fine, but if you don't want the added components in the signal path it is possible to just use a SPDT switch to go from stereo to bridged using the method described in the data sheet. I would try to explain exactly how to do it, but it would probably be easier for you to just figure it out on your own.
Also, correct grounding is very important with this board. If your grounding scheme is wrong the amp won't fully turn on. I'll hold off on a drawing on how to do it until someone asks; too much work for me at the moment.
If you plan on bridging you will need to change the value of the over-current resistors. You can do this by simply soldering a 20k resistor over the 15k thats already there. These are marked R11A, R11B, R11C, R11D, R11E, and R11F on the PCB.
I have tested this amp bridged. It put out some serious power, but I was only using one bridged channel and it really stressed out the power supply. Don't expect a full doubling of power using two bridged channels unless you plan on getting a new transformer.
Using an external inverter to bridge is fine, but if you don't want the added components in the signal path it is possible to just use a SPDT switch to go from stereo to bridged using the method described in the data sheet. I would try to explain exactly how to do it, but it would probably be easier for you to just figure it out on your own.
Also, correct grounding is very important with this board. If your grounding scheme is wrong the amp won't fully turn on. I'll hold off on a drawing on how to do it until someone asks; too much work for me at the moment.
Member
Joined 2003
I don't think I'll ever need the extra power that bridge mode will provide, I just don't have any use at the moment for more than 2 channels, so I figured I might as well get the most out of what I have. Maybe in the future I will be ambitious enough to build a pair of speakers that is driven from an active crossover.
No need to draw any diagrams for me, as I am quite capable of sorting out circuits on my own 😉. I've graduated from an electronics diploma program last year (Electronics Technologist), and am currently working in the RF communications field.
No need to draw any diagrams for me, as I am quite capable of sorting out circuits on my own 😉. I've graduated from an electronics diploma program last year (Electronics Technologist), and am currently working in the RF communications field.
DcibeL said:
Sorry, I didn't mean to imply that you couldn't do it on your own. I meant that I would draw a diagram for anyone else, when and if they need it.
I need to correct my last post, as it was made after a long night at work.
.....When you bridge the amp it will effectively quadruple the output into an 8 ohm load. BUT, there is no way the supply can produce 400 watts per channel into 8 ohm's, so bridging this amp with the stock supply is a no go as it's not worth the higher THD and noise floor.
Anonymous1 - I may need a bit of direction once I get re-started on my next unit - the Toroid had a 2 pin connection to mains power but no mains earth. It was a Centertapped 40V - 0V - 40V trannie (Im remembering this from a few months ago - I may have this a bit wrong)
The Tranny connected to the Power Supply board thru three headers. From the PS board there were two headers that supplied power to the Amp board. At the signal input header on the Amp board, there were Signal and grds for 5 channels, and there were three pins that needed 5V to enable or "power on" the board. Now there was a spare header that had a 5V - GRD pins went to the Preamp section (me thinks)... I could this use to supply the 5V to the three power on pins ...
Now the power - chassis ground - where does it need to connect on the power supply board? I don't remember there being a power ground - does it float?
I just checked to power plug on teh DCP and there is no ground pin...should take care of that question...
Also the signal ground and speaker out grounds - connect all to a star ground to chassis also? I remember these Tripaths being kinda goofy on signal grounds and speaker out grounds - on the TA2024, they all need to be separate and floating (becasue they are already bridged?)....while the Gainclones speaker out gnd and input grn are all connected through a star ground, and eventually connected to power ground...maybe I will read up on the TA3020 pdf soon...
Forgive the lame, neophytic (?) questions...It's been 20 years since my EE courses...If anyone needs some help designing and building a Diesel Hydrotreater, come see me...
Can't spell GEEK without EE!!! (ouch - sorry)
The Tranny connected to the Power Supply board thru three headers. From the PS board there were two headers that supplied power to the Amp board. At the signal input header on the Amp board, there were Signal and grds for 5 channels, and there were three pins that needed 5V to enable or "power on" the board. Now there was a spare header that had a 5V - GRD pins went to the Preamp section (me thinks)... I could this use to supply the 5V to the three power on pins ...
Now the power - chassis ground - where does it need to connect on the power supply board? I don't remember there being a power ground - does it float?
I just checked to power plug on teh DCP and there is no ground pin...should take care of that question...
Also the signal ground and speaker out grounds - connect all to a star ground to chassis also? I remember these Tripaths being kinda goofy on signal grounds and speaker out grounds - on the TA2024, they all need to be separate and floating (becasue they are already bridged?)....while the Gainclones speaker out gnd and input grn are all connected through a star ground, and eventually connected to power ground...maybe I will read up on the TA3020 pdf soon...
Forgive the lame, neophytic (?) questions...It's been 20 years since my EE courses...If anyone needs some help designing and building a Diesel Hydrotreater, come see me...
Can't spell GEEK without EE!!! (ouch - sorry)
Member
Joined 2003
theAnonymous1 said:
Hmm...I have always understood that bridge mode will only double the power output at the very maximum. Since you are doubling the voltage present at the speaker terminals I don't see how this can translate into a power quadrupling.
Maybe I will just stick to a non-bridged amp and just hook up 2 speakers, or 4 speakers for parties. All the possibilities! 😀
john65b said:
When I spoke about proper grounding I wasn't referring to the AC mains ground. The AC mains ground has no relevance in getting the board working.
I personally don't connect the mains ground to any of my equipments power supply grounds for noise reasons. I will sometimes connect the mains ground to the chassis, but that is only if everything else is isolated from it.
The 5v wire on the other end of the supply is NOT referenced to the amplifier supply section. You will either need to tie both sides of the supplies ground planes together, or just use the 5v going into the amp. Also, all of the input grounds have to be referenced to the supply/analog ground or the board will not turn on.
This is not a bridged amp, so the speaker grounds(-) are referenced to the supply/analog ground.
john65b said:
Don't worry about it, my educational background is embarrassing to say the least. I'm learning as I go along and just share the things that I have already proved to work for me. I try my best not to stray off into territory I don't know anything about as to not look like a complete buffoon.
DcibeL said:
Here is a bit of a modified quote from someone better at explaining things than I am...
Member
Joined 2003
So the power supply ground/chassis ground is not an issue...good deal.
As far as the 5V - I know there is a 5v connection to the amp board. Just splice another wire from this 5V and connect to the those 3 pins? Easy enough.
The grounding technique you describe is a star ground, right? Our terms are a bit diferent - Supply/Analog Ground - Supply Ground is Power Supply Ground (duh) and Analog Ground is Speaker Out Ground?
Connect all input signal grounds and speaker output grounds and connect them to a grd pin on the PS board or Amp board (or does it matter?)?
As far as the 5V - I know there is a 5v connection to the amp board. Just splice another wire from this 5V and connect to the those 3 pins? Easy enough.
The grounding technique you describe is a star ground, right? Our terms are a bit diferent - Supply/Analog Ground - Supply Ground is Power Supply Ground (duh) and Analog Ground is Speaker Out Ground?
Connect all input signal grounds and speaker output grounds and connect them to a grd pin on the PS board or Amp board (or does it matter?)?
john65b said:
Basically if you use the 5v line thats going to the board, all the grounds are already connected together. All you have to worry about then is the 5 input grounds. You can connect these to the braided wire with the ring terminal over on the corner. Here is an example of what I mean, although it can be done a little better....
http://i14.tinypic.com/30lykn7.jpg
When all the parts were inside the unit the chassis tied all these different ground points together.
Here's a pic of some extra heatsinks I plan on adding....
http://i13.tinypic.com/2n6i14p.jpg
john65b said:
Thats up to you. Its not necessary, but might be a good idea if you have any noise issues.