Hi Stephensank, I very much appreciate your comments. With regards to the Lundahls I'd agree based on the weird zoebel and load values needed to get good sound from them. Maybe not the best engineered transformer out there. My LL1690's are very sensitive to load and work best with very short interconnects with exceptionally low parallel capacitance. On the CS4398, there is practically no dc offset to speak of. I measured a fraction of a mV. Maybe they vary from unit to unit. The point of the transformer is it functions as your reconstruction filter with the cap across the primary. Since the internal opamp is a part of that dac that you can't get rid of or work around, the idea is to add no additional opamps in the signal path to further degrade performance. I can't comment on the TDA1549. Can't recall ever hearing one. When I can find the money I'll try to get a hold of a pair of Jensen's. It would be interesting to hear the difference a better transformer could bring. Thank you for the suggestion. My cousin did extensive test on a pair of Edcor WSM series transformers and said they measured very well with his CS4397 dac. He has never had another to try so it's only a single data point. When we tested his 4397 dac against another with an opamp based filter the result was quite clear. The transformer was better in his system. It wasn't subtle. I can only imagine how it would sound with a better Cinemag or Jensen's. 
Dave
DaveWhat you need to remember is that a transformer has no more "line drive" power than what goes into it, minus the power loss determined by quality of core material & of design. So, it's absolutely no surprise that you need great cables for your dac to not sound deficient. If I were doing a transformer as i/v converter/passive-gain for a current out dac, I would positively, even with a Cinemag(which are half the price as Jensen for same or better quality), add a no-feedback buffer stage after it to drive the line. The positively largest advantage of using a transformer for a dac out is the elimination of feedback, so you don't want to screw that up by having a feedback stage after, or before, it.
Hi GLENZWORLD, I would have to agree with stephensank. The TDA1549 isn't going to be easy to directly replace with a CS4398. It sounds best (CS4398) with the Lundahl LL1690 or other good quality transformer. I didn't get good sound from the CS4398 with opamps or capacitors. Your experience may no doubt be different. My experience with the transformers I mentioned including the Edcor is that they work best in a voltage situation. My TDA1541A dac doesn't have enough current output to drive any transformer that I am aware of. That's why I use an AD844 in a Pedja I/V setup. Modified for 4X oversampling. That drives the Edcor with no problems. The Pedja is also no negative feedback and has 150 mA driving capability. Cinemag or Jensens would be an excellent choice, yes better then an Edcor. Edcor's are cheap, behave pretty well but lack shielding and are large in the 2.5 Watt version. The parallel cap is used to adjust the frequency response of the transformer. In a dac situation you want the rolloff to be lower then the transformer is designed to be. I have seen values of 4 to 7 nF used with many different transformers. The best sounding dac of the 1 bit type that I have heard to date is a CS4397 with output transformers. That one benefits from using a 1:2 transformer ratio as the CS4397 doesn't have the output of the 98. I find that the CS4397 sounds closer to a properly applied TDA then anything else I have heard. YMMV.... I have tried many output filter types. Sallen-key is bad. GIC gyrators sound interesting however are hard to build and fussy about opamps and don't always perform as you'd expect. I'm still listening to a 7th order Bessel filter on one of my dac projects. I wanted to hate the transformer approach. After trying it I was surprised in the simplicity and ease of building with it. The clarity and musicality can be outstanding. If you try the transformer approach by all means go with the better transformers. If your budget is tight give the Edcor a try. I'm putting my Edcors in a box to shield them, so far I'm happy with them. Although now I'm curious to try the Cinemags or Jensens.
yeah I won`t be fitting transformers into cdp anytime soon I was just curious how others were avoiding signal caps
Hi stephensank, I appreciate your comments. Some wisdom there. Actually my CS4398 will be in a shielded enclosure within my preamp. I have been working on a DacPrePhono solution. I can keep the cables lengths short that way. The dac will be on line 1 and will benefit from the output drive of the linestage. The preamp portion can drive headphones directly. Preamp on steroids. I see the transformer in my application as nothing more then an element in the reconstruction filter. Not really a current situation at all, 1:1 ratios. Certainly not an I/V. The way I use them so far has always been voltage mode. I will look into the Cinemags. They sound interesting, I'll need to get a price quote. Thanks again. Lots to think about and ponder. Dave GLENZWORLD, I just wanted you to be aware that there is another way. DIY is about trying things. I'm as surprised as anyone that transformers worked so well as a filter element. The quality of the caps in your cdp will be the determining factor in your ultimate sound quality. I have been there. Opamps are also a huge factor in how a cdp will sound those who tried the transformers found they tend to sound better then opamps. One suggestion: Don't get into gyrator or GIC filters. Tough to get right. Good luck on your cdp.
I see the transformer in my application as nothing more then an element in the reconstruction filter. Not really a current situation at all, 1:1 ratios. Certainly not an I/V. The way I use them so far has always been voltage mode. I will look into the Cinemags. They sound interesting, I'll need to get a price quote. Thanks again. Lots to think about and ponder. Dave GLENZWORLD, I just wanted you to be aware that there is another way. DIY is about trying things. I'm as surprised as anyone that transformers worked so well as a filter element. The quality of the caps in your cdp will be the determining factor in your ultimate sound quality. I have been there. Opamps are also a huge factor in how a cdp will sound those who tried the transformers found they tend to sound better then opamps. One suggestion: Don't get into gyrator or GIC filters. Tough to get right. Good luck on your cdp. After the input cap pair, the Acurus is all dc-coupled, so there is no cap on the output, just the chunky red film cap & resistor from output line to ground for HF stability. The gold lytic & the black film cap sitting above it are the LF corner cap, which are in series with the gain-setting resistor that goes to ground from the input-end of the feedback resistor. So, the only significant caps to upgrade are the input caps and the power supply caps.
A small heatsink-mounted transistor is almost always a dead giveaway that it's part of the bias circuit, and the pot's placement right above it clearly indicates it is the bias trimmer. The black film cap in between is across the bias network, and may or may not make a difference to upgrade that one.
I have worked on a lot of Cambridge gear, and I have never seen one piece that I would recommend to anyone. I have not yet worked on a dvd player from them, but I would be shocked if they did not make a very, very poor choice of laser/mechs, most likely using one of the cheap Hitachi or Sanyo units that have been so disastrously unreliable for Denon, Rotel & others, and I can predict with great confidence that the power supply will totally suck, both for performance & durability. Cambridge has a great talent for cutting corners in the worst possible areas.
A small heatsink-mounted transistor is almost always a dead giveaway that it's part of the bias circuit, and the pot's placement right above it clearly indicates it is the bias trimmer. The black film cap in between is across the bias network, and may or may not make a difference to upgrade that one.
I have worked on a lot of Cambridge gear, and I have never seen one piece that I would recommend to anyone. I have not yet worked on a dvd player from them, but I would be shocked if they did not make a very, very poor choice of laser/mechs, most likely using one of the cheap Hitachi or Sanyo units that have been so disastrously unreliable for Denon, Rotel & others, and I can predict with great confidence that the power supply will totally suck, both for performance & durability. Cambridge has a great talent for cutting corners in the worst possible areas.
great info and I wish I understood all of it but I think I get the jist
LF corner cap and pot are to ajust voltage to transistor input
LF is low frequency so would a larger cap here give better bass?
then bias would need adjusting too would it not?
do you recommend any books? I need to do more reading
interesting what you say about cambridge as I have heard their build is decent for price. what can play sacd dvda dvd cd cdr and bluray that is decent on the market?
it`s horse#%@* that the whole world has waited for 15 plus years for universal players and they still withhold something so they can market that next year
well you were spot on with the dac it has 2.4vdc my new agilent meter says and no dc after opamp so I soldered vishay ww 250 ohm from cap +(after removing) to rca + and left the rca pin connected to board. should I clip that?
bought some film caps from partsconnection to bypass the dac out caps
multicap was reasonable and much as I like rel 80 bucks for a cap is rape.
maybe on a nice single disk if I could find one that plays all in the grand range
also bought some nichicons and will compare with the silmics in there now
got some orange drop.22 and .022 for bypassing if multi caps don`t fit or sound right and some 220pf pp I was going to put from after resistor on opamp to -rail for ultrasonic
removing caps on opamp out was like pulling a veil away but lost some smoothness in the highs so either resistor is picking up noise (also got wrong resistor its copperweld and stainless end cap) I put teflon tube over leads but?
or the hash in hf I hear is caps need bypass and resistor (new ones coming)
needs small cap across rails for ultra sonic?
am I close?
thanks again Stephen
Glen
My dad started me off at 10 years old reading the first few chapters of an ARRL Radio Amateur's Handbook, which, I think every year, has a great primer on electronic components & basic design. It gave me a very good start. I think one from the 60's would have a likely the best coverage of both tube & ss circuits.
On the Acurus, the pot & the LF cap are unrelated. The LF corner cap simply cuts off most of the gain of the whole amp channel below usually about 10Hz, to prevent it having dc gain. There is a cap accross the bias network, but proper capacitance value is pretty much all that matters there. You should not have to adjust bias unless a channel is running quite hot or cold, but these amps are not prone to bias drift, so should be fine.
I really used to love Multicaps, but I don't think they are as good these days as they used to be, and the standard line Rel PPFA. PPT and RT's sound smoother & better to me. Only the teflon Rels should be more expensive than the multicaps, and I think a combo of PPFA + RT sounds at least as good for far cheaper than the teflon.
It's no surprise that you lost smoothness when you eliminated the final output coupling caps on the CD. You did not actually lose smoothness, you lost the upper treble rolloff of the caps, and revealed unsmooth sound that was already there. Adding film caps to the supply lytics for opamp & dac chip will give you as much smoothness as the dac is capable of. The ww resistor would not be my choice, I would just use a short jumper wire, but it should only reduce transparency very slightly, no effect on smoothness. No reason for a resistor there, though.
On the Acurus, the pot & the LF cap are unrelated. The LF corner cap simply cuts off most of the gain of the whole amp channel below usually about 10Hz, to prevent it having dc gain. There is a cap accross the bias network, but proper capacitance value is pretty much all that matters there. You should not have to adjust bias unless a channel is running quite hot or cold, but these amps are not prone to bias drift, so should be fine.
I really used to love Multicaps, but I don't think they are as good these days as they used to be, and the standard line Rel PPFA. PPT and RT's sound smoother & better to me. Only the teflon Rels should be more expensive than the multicaps, and I think a combo of PPFA + RT sounds at least as good for far cheaper than the teflon.
It's no surprise that you lost smoothness when you eliminated the final output coupling caps on the CD. You did not actually lose smoothness, you lost the upper treble rolloff of the caps, and revealed unsmooth sound that was already there. Adding film caps to the supply lytics for opamp & dac chip will give you as much smoothness as the dac is capable of. The ww resistor would not be my choice, I would just use a short jumper wire, but it should only reduce transparency very slightly, no effect on smoothness. No reason for a resistor there, though.
Forgot to answer about universal players.
I have not yet encountered a blu-ray player that can do sacd/dvd-a which I find acceptable both in performance & build quality/durability. I really like my Pioneer BDP-95FD, which has, in stock form, OPA2134PA output stage chips after it's very nice PCM1738 dac chips, and surprisingly has ALL Nichicon lytic caps on it's supply board. It's also got a very well built & reliable Pioneer drive/laser, which I haven't yet seen need more than lens cleaning in any model I've found it in. It's a player that takes an irritatingly long time to boot up, and doesn't like being left on 24/7, but it's video & audio performance are worth it for blu & dvd, and cd sound is also excellent, even as stock. For sacd/dvd-a and everything but blu-ray, my favorite unit as yet is the Pioneer DV-79avi, from which the BDP-95FD got it's dacs & output stages, but the 79's PCM1738's and OPA2134 are frontended by a superior DSD proc/digital filter chip set. I absolutely LOVE how the BDP-09FD is built, it's absolutely gorgeous inside, but the Wolfson dacs it uses are just horrible to my ears. But if you like the sound of metal scraping against glass, hey, whatever.;-)
None of the above can be made to sound quite as good as my heavily upgraded Pioneer DV-S9 or PD-S06, but these can't do dvd/cd only and cd only respectively, although the DV-S9(Japan market DV-09) can act as a 24/96 dac for external input source.
Gotta add that for super cheap, though, and I mean as little as $20 for a fully working nice unit on ebay, the DV-578A can be made into a disgustingly beautful sounding universal(exc. blu) player very easily. It's dirt cheap but strangely great PCM1742 dac chip is voltage out, and the external opamp after it is unnecessary. So, just by taking the dac's output lines straight to output jacks, via, say, a 100uf Nichicon Muse KZ + parallel 0.47-1uf metallised PP(panasonic, seacore, etc.) + 0.022 or larger polystyrene film cap, as a grouped coupling cap on each channel, plus some larger & nicer caps on the dac's power supply line, it is simply shocking how sweet and lovely this player sounds.
I have not yet encountered a blu-ray player that can do sacd/dvd-a which I find acceptable both in performance & build quality/durability. I really like my Pioneer BDP-95FD, which has, in stock form, OPA2134PA output stage chips after it's very nice PCM1738 dac chips, and surprisingly has ALL Nichicon lytic caps on it's supply board. It's also got a very well built & reliable Pioneer drive/laser, which I haven't yet seen need more than lens cleaning in any model I've found it in. It's a player that takes an irritatingly long time to boot up, and doesn't like being left on 24/7, but it's video & audio performance are worth it for blu & dvd, and cd sound is also excellent, even as stock. For sacd/dvd-a and everything but blu-ray, my favorite unit as yet is the Pioneer DV-79avi, from which the BDP-95FD got it's dacs & output stages, but the 79's PCM1738's and OPA2134 are frontended by a superior DSD proc/digital filter chip set. I absolutely LOVE how the BDP-09FD is built, it's absolutely gorgeous inside, but the Wolfson dacs it uses are just horrible to my ears. But if you like the sound of metal scraping against glass, hey, whatever.;-)
None of the above can be made to sound quite as good as my heavily upgraded Pioneer DV-S9 or PD-S06, but these can't do dvd/cd only and cd only respectively, although the DV-S9(Japan market DV-09) can act as a 24/96 dac for external input source.
Gotta add that for super cheap, though, and I mean as little as $20 for a fully working nice unit on ebay, the DV-578A can be made into a disgustingly beautful sounding universal(exc. blu) player very easily. It's dirt cheap but strangely great PCM1742 dac chip is voltage out, and the external opamp after it is unnecessary. So, just by taking the dac's output lines straight to output jacks, via, say, a 100uf Nichicon Muse KZ + parallel 0.47-1uf metallised PP(panasonic, seacore, etc.) + 0.022 or larger polystyrene film cap, as a grouped coupling cap on each channel, plus some larger & nicer caps on the dac's power supply line, it is simply shocking how sweet and lovely this player sounds.
I will see if I can find any of the 60 s radio stuff on pdf to understand some basics
so you are saying bypassing on supply caps helps as well, I was going to ask that next.
why does the stock circuit on the op amp output have 1k res in path and 220 pf to negative rail?
I heard somewhere that your receiver or pre amp wants some impedance from source and that is why I used a resistor to jump to rca. but I have also been told that decent rca s have enough resistance
hopefully when I bypass dac out lytics the highs will smooth and if not maybe I need to clip the positive rca pin (on board) to old circuit (now bypassed with jumper)
thanks again for sharing your knowledge
Glen
ps I must owe you at least a couple of beers
never been a big fan of pioneer sound but you would know build quality better than me and it would get tweeked anyway. I just wish I could find a single disk that plays all and sounds good (no space for 2 players)
I will keep an eye on ebay
that bd09 looks sweet
Glen
Always a good idea, but much larger value total of film cap is needed for big lytics to have much effect. You'd need at least 40uf on your Acurus main filters, for example. More effect can be had, though, by film capping lytics used for input/driver stage secondary filtering.
yes that makes sense and I read somewere 1/1000th of main caps is a rule of thumb
how much larger can you go on large cans like that before inrush starts popping fuses
I suspected that the low level or input driver stage would make more noticeable difference
that is the black nichicon 10 uf with film bypasses .1uf and .22uf on the acurus amp right?
turns out the .22 film (it just say 220 on them) is not even same brand L and R channel
I also want you to know that after you have taught me some of this my audio system will never really be finished. my girlfriend will curse you for time spent with a soldering iron
power to dac circuit allready has bypasses in the form of smt 100nf , I will assume these are crap and remove and bypass with poly?
thanks again you rock Stephen. I don`t care what my girl says about you lol
Glen
how much larger can you go on large cans like that before inrush starts popping fuses
I suspected that the low level or input driver stage would make more noticeable difference
that is the black nichicon 10 uf with film bypasses .1uf and .22uf on the acurus amp right?
turns out the .22 film (it just say 220 on them) is not even same brand L and R channel
I also want you to know that after you have taught me some of this my audio system will never really be finished. my girlfriend will curse you for time spent with a soldering iron
power to dac circuit allready has bypasses in the form of smt 100nf , I will assume these are crap and remove and bypass with poly?
thanks again you rock Stephen. I don`t care what my girl says about you lol
Glen
It's been a good few years since I've worked on an Acurus, and your photo did not show the whole channel board. In your photo, there are no secondary supply filter caps showing for the input/drive stages, just the input dc blocking cap & LF corner cap. It's possible that there are no secondary filter caps, but it would be a darn good idea to add them, but that's the sort of thing for which you need a schematic or my sort of knowledge to do safely & properly. Looking at the Acurus DIA-100 schem, the only Acurus schem I have, which appears to be a darn similar schem to what I see in your board photo, it does not, in fact, have secondary filtering, so yours probably doesn't either. That being the case, without altering the circuit to give the early stages some resistively-isolated secondary filtering, you should definitely add some whopping big film caps to the main supply caps. I would do 50-100uf of SCR/Axon metallised PP + as large a pair of RelCap PPFA's as can be afforded. And, of course, I would also replace the rectifier bridge/bridges with individual IXYS soft recovery diodes. As far as increasing total supply capacitance, I routinely increase by easily 50% without doing more than changing the main supply fuse to slo-blo. And I always eliminate supply rail fuses(which the DIA-100 has) when I know an amp is reliable enough to be safe with just a mains fuse, which the Acurus/Aragon amps are. Frankly, if it were physically & financially practical, I would do as much as 20% of a power amp's supply capacity in film caps.
You can leave the smd caps in place, as they have do no harm, and simply add some nice film caps for better bypassing on the dac.
You can leave the smd caps in place, as they have do no harm, and simply add some nice film caps for better bypassing on the dac.
Caps are not evil. Bad ones are. Incorrect ones are. It seems we modders get obsessed with removing one cap where we really need one and forget how many HUNDREDS of caps, some very bad, the signal has made it through before it ever made it onto our CD. Start at the mic.
I have seen the direct test reports that show higher voltage caps, all other things being equal and they are not, have lower distortion. Either Self or Cordell. Most pronounced with electrolytics. Higher voltage for the same value is physically bigger.
If you look at the distortion of a cap, it rises with decreasing frequency, so the point where it becomes a problem is lower with a larger value cap. Where a 10 Hz cutoff may take a .1uF cap, a 470 may have lower distortion. Frequency is not the only parameter. BUT, that 470 will be an electro so it will be terrible, which means that 2uF film may be the best bet.
Lower LF distortion is "better" low end in my book, so bigger is better. Simple, right?
I have seen the direct test reports that show higher voltage caps, all other things being equal and they are not, have lower distortion. Either Self or Cordell. Most pronounced with electrolytics. Higher voltage for the same value is physically bigger.
If you look at the distortion of a cap, it rises with decreasing frequency, so the point where it becomes a problem is lower with a larger value cap. Where a 10 Hz cutoff may take a .1uF cap, a 470 may have lower distortion. Frequency is not the only parameter. BUT, that 470 will be an electro so it will be terrible, which means that 2uF film may be the best bet.
Lower LF distortion is "better" low end in my book, so bigger is better. Simple, right?
thanks for the reply
I will check out those tests with Douglas Self ? and Cordell ?
I am starting to gather that a lot of different thing effect distortion in capacitors including physical size (ie larger mass resonates at lower frequencies)
and like you say it starts at the mic and most recordings for hard rock (my main music) are poorly recorded. not to mention it is mosty compressed so junior can`t smoke the boom box dad bought him.
so before that music ever gets to your system it can 20% less real or there or big or pick your own term for the loss of resolution
unfortunatly there is nothing that can be done about that side short of not buying crappy recordings (good luck)
yes I am learning bigger is better in the capacitor world but slippery wet and tight is better
tight wound dialectic, what did you think I was talking about?
Glen
thanks again Stephen
I was looking at schematic for marantz cdp and power in to dac has no smoothing caps just shunts to - rail or ground and opamp power supply is the same but no bypasses on those
should supply for those have dc go through a cap to smooth the dc and shunt to ground ?
accidentally got multi cap metalized poly so I may try orange drops for coupling bypass till I get poly and foil .22 and polystyrene? .022 ?
as for the acurus the secondary stage that is not there on that a150 is that to clean up the dc before it hits transistor on the heat sink?
I have a copy of acurus a200 schematic(vinyl engine) and will post along with more pics of amp inside, but indy labs would not give or could not find a skematic for a150
thanks to Ted Moore and rick Santiago at indy audio labs for sending out a new power switch when first ones bulb burnt and for giving schematic for rl11
I was looking at those axon for bypass on main supply and will follow your advice on that
when you say add secondary filtering do you mean a smoothing cap in dc before transistor on heatsink?
as for diodes to replace bridge to you mean you would remove the rectifier and just put diodes on power in to pcb?
I knew I should have gone bigger on those mains caps but could not find other than nos or buy 10 min
main supply fuse is a slo blow, but are you saying to jumper where fuse is on channel pcb board?
you are a wealth of info Stephan and maybe someone will read this and spend a little less time watching tv and maybe learn something
thanks much
Glen
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