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Post by Deleted on Mar 6, 2010 10:52:27 GMT
Leo Feel free to comment. There are plenty of things that we may not have thought of. Alex
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Post by leo on Mar 6, 2010 11:08:48 GMT
Even cheap op-amps could be used for the error amp in the crickets so it wouldn't be expensive to make quite a few of them Leo So when are you going to make some ? ;D The big 10uF could also be scaled down to 4.7uF if hard to obtain. The main thing slowing me down from making more is that I am having trouble getting more DP50 +VE Developer sachets. Alex If I get one of these dacs I'd build a few crickets on vero at the same time, one would be used for comparing error amps mainly to see how cheap it can go before performance takes a hit. The problem with threads like these is that they tend to get big, very big and often any updates for mods etc usually get lost, I'd personally start a new thread for the mods and edit the first post adding any extra worthwhile things on there so its easy to find especially for us lazy buggers who can't be bothered reading through all the posts
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Post by leo on Mar 6, 2010 11:13:53 GMT
Obviously little etched pcbs look far nicer but at least they are easy to build p2p on vero
Regarding the 10uf, I'll dig the datasheets out but I'm wondering if the larger 10uf is rolled film and the lower 4.7uf is stacked? if so I'd prefer the stacked for decoupling, should be lower inductance
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Post by Deleted on Mar 6, 2010 11:23:19 GMT
Leo In our defence, I would say that everybody who is making an SC DAC in RG, is kept up to date with all the latest results and changes via email, including info on the PCB artwork etc. Perhaps when we get to an agreed performance point, we should post a block diagram including the additions? Don't forget too, that Alfred and Jeff are further advanced with their mods than I am. Alex
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Post by leo on Mar 6, 2010 11:43:19 GMT
Just an observation is all, as we know some are quicker than others at trying things, some may take weeks longer even months, by then you've had a lot more emails , posts added etc Anyway it was just a thought
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Post by Spirit on Mar 6, 2010 14:26:47 GMT
A good thought Leo... - the SCHA mods thread was very useful indeed when building mine.
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Post by Deleted on Mar 6, 2010 20:58:49 GMT
A good thought Leo... - the SCHA mods thread was very useful indeed when building mine. Do we have something like that in the RG "ESS Saber DAC" thread ?
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Post by Spirit on Mar 6, 2010 21:36:29 GMT
Nope.... the list goes: 1. Get PH regs 2. Do Leo's AVCC mod There are admittedly a few others in there, but you do seem to like mentioning PH stuff Alex ;D
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Post by Deleted on Mar 6, 2010 21:52:41 GMT
Nope.... the list goes: 1. Get PH regs 2. Do Leo's AVCC mod There are admittedly a few others in there, but you do seem to like mentioning PH stuff Alex ;D Phil This time I was not mentioning PH stuff,or even inferring that. There was a lot of other stuff about Salas regulators IIRC. It's somewhat premature to post a concrete list of mods until all the results are in, and confirmed by at least several other members. Like with the SC DAC, there hasn't yet been adequate confirmation by more than a few members, and also bearing in mind that in both cases, the designers aren't in agreement with many of the modifications either. That could of course come down to pure commercialism or stubborn pride. With the Jaycar kit modifications, there was also a lot of collaboration, both in posts and behind the scenes, with at least 3 members involved. The Tweaks thread represented these confirmed tweaks. Leo and CJ in particular, were involved in a large amount of consultation,and extended listening sessions, and the posted results reflected this consultation.Dave also passed around screen shots of the SC HAs square wave performance. Regarding the SC DAC, I also have a degree of concern that some of the modifications could end up "oversaucing the egg" if not careful. Alex
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Post by leo on Mar 6, 2010 22:25:01 GMT
A good thought Leo... - the SCHA mods thread was very useful indeed when building mine. Do we have something like that in the RG "ESS Saber DAC" thread ? I knew from the start far less would be trying the Sabre dacs and especially the PH regulation, I simply posted a few impressions and pics, if I felt more would be interested or had requests like on another forum I'd have done a full list of mods on here. I'd have thought far more would be interested in this cheaper kit. Infact in all honesty I wish I'd never posted about the Buffalo or PH regs over on here
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Post by Deleted on Mar 6, 2010 22:31:21 GMT
Do we have something like that in the RG "ESS Saber DAC" thread ? I knew from the start far less would be trying the Sabre dacs and especially the PH regulation, I simply posted a few impressions and pics, if I felt more would be interested or had requests like on another forum I'd have done a full list of mods on here. I'd have thought far more would be interested in this cheaper kit. Leo Unfortunately, it is still early days with the SC DAC, with Will,and Chris yet to start, and Adrian not even up to the point of a JLH yet. With the Sabre DACs, I think that Will may have posted many experiments with shunt regulators, and the Salas was judged to be the best of the cheaper shunt regs.Are any of these other shunt regs still in use ? Alex
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Post by leo on Mar 6, 2010 22:46:56 GMT
I knew from the start far less would be trying the Sabre dacs and especially the PH regulation, I simply posted a few impressions and pics, if I felt more would be interested or had requests like on another forum I'd have done a full list of mods on here. I'd have thought far more would be interested in this cheaper kit. Leo Unfortunately, it is still early days with the SC DAC, with Will,and Chris yet to start, and Adrian not even up to the point of a JLH yet. With the Sabre DACs, I think that Will may have posted many experiments with shunt regulators, and the Salas was judged to be the best of the cheaper shunt regs.Are any of these other shunt regs still in use ? Alex Alex, Probably why I'm trying to hold off getting the SC kit for now because I'd probably have it built in a day and be fiddling later that evening A good shunt reg is hard to diy and keep stable imo so I didn't personally experiment with many types, the Burson ones was pretty decent but they are ready built. I think Will still does use the Salas in some locations. Leo
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Post by jeffc on Mar 6, 2010 23:27:32 GMT
Alex, I've had a +V JLH PSRR in this position from the outset. The DAC chip is still supplied direct from the onboard Reg5 supplied by the +15V JLH. I was thinking I might be able to remove this JLH now a Cricket is supplying the DIR9001 IC, but seems it might best be left in, if those SPDIF receiver ICs are possibly benefiting from it. ;D My 2 cents, I think a dedicated and concise "SC-DAC mods" thread will be a good idea too..... in a little while....., particularly as a few more are built and modded with favourable outcomes and others then get interested. It is a fantastic value DAC and easy to mod. Agreed also that it would be best if mods recommended in such a thread are the consensus of more than 1 or 2 sets of ears. That said, there are a few now that could be recommended unreservedly as good things. Alfred…. Thanks for the comment I didn’t quite get… but your lead with mods on this DAC and reports emailed by Alex were a big part of my decision to have a play with it.. and so far all mods you’ve suggested have been very beneficial to my ears…. cheers for that. Seeing my soldering station has just died and I’m off O/S next week and need to get organised for that, you guys have plenty to time to catch up and overtake me with Cricket mods.. and looking forward to whether you get similar outcomes in improved SQ. cheers.. jeffc
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Post by leo on Mar 7, 2010 0:46:29 GMT
Better see what single op-amps I have ;D
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Post by Deleted on Mar 7, 2010 1:19:14 GMT
Better see what single op-amps I have ;D Leo I hope that you checked the forward voltage of the Zener at around 5mA before inserting ? The BZX55C3V3/5V1 are the best to use, as the 1N746 etc require much higher current. With the BZX55C3V3, 2K4 is often better than 2K2 ,as we want to keep the Zener voltage just below 3.3V Alex P.S. We are using 2 ferrite beads. One on each side of the small loop is easy to do. The X-DAC V3 uses several special encapsulated devices, which appear to be 2 FBs done this way. I would suggest 2 beads for the oscillator module, but the normal PSU is unlikely to be critical.
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Post by leo on Mar 7, 2010 8:47:08 GMT
Alex,
Ok ta, The zener values was wrong anyway, I just fitted one I had to allow easy testing (to make sure it works) into a light load. May call in maplins today later on to see if they have any 3v3's
Leo
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Post by leo on Mar 7, 2010 8:51:22 GMT
Better see what single op-amps I have ;D P.S. We are using 2 ferrite beads. One on each side of the small loop is easy to do. The X-DAC V3 uses several special encapsulated devices, which appear to be 2 FBs done this way. I would suggest 2 beads for the oscillator module, but the normal PSU is unlikely to be critical. Ok ta, thats easy enough to do, regarding the caps in the X-dac I presume the ones you mean are ceramic T-networks?
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Post by Deleted on Mar 7, 2010 8:52:35 GMT
Alex, Ok ta, The zener values was wrong anyway, I just fitted one I had to allow easy testing (to make sure it works) into a light load. May call in maplins today later on to see if they have any 3v3's Leo Leo Just remember that if you need to use the 1N746 that you will need a series resistor somewhere around 680R Alex
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Post by leo on Mar 7, 2010 8:55:59 GMT
Alex, Ok ta, The zener values was wrong anyway, I just fitted one I had to allow easy testing (to make sure it works) into a light load. May call in maplins today later on to see if they have any 3v3's Leo Leo Just remember that if you need to use the 1N746 that you will need a series resistor somewhere around 680R Alex I'd imagine they'll be the common BZX55C types from Maplin, I'll see what they have when I'm there I was thinking of trying other things too apart from a zener to get the desired voltages ;D
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Post by Deleted on Mar 7, 2010 8:57:44 GMT
? ? ? Leo I was referring to what appears to be quite a bit of use of 2 ferrite beads in an encapsulation in the X-DAC V3. They are zero resistance, as measured Alex.
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Post by leo on Mar 7, 2010 15:59:37 GMT
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Post by Deleted on Mar 7, 2010 20:20:05 GMT
Leo I will send you a photo, so that you can work it out. Alex [/quote]
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Post by leo on Mar 7, 2010 21:41:23 GMT
This is how I think they work, could be wrong Anyway see if the middle leg goes to ground, if so I'd imagine its like in the drawing
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Post by Deleted on Mar 7, 2010 21:54:25 GMT
The FBCs used in the X-DAC V3 are just 2 ferrite beads on a wire, with the centre of the 2 beads connected to earth via a capacitor. The DSS9 from Jameco has a 47pf to earth.
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Post by Deleted on Mar 11, 2010 4:26:31 GMT
DUAL "Cricket" PCB (This one is 2 x 3.3V) 2.7K dropping resistors were used with the BZX55C3V3 Zener Diodes to keep the Output Voltage just over 3.2V
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