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Old 22nd July 2012, 07:53 PM   #21
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Location: Prior Lake, MN
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
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Old 23rd July 2012, 02:49 AM   #22
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What 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.
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Old 23rd July 2012, 02:56 PM   #23
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Quote:
Originally Posted by DF96 View Post
No, spectrum analyser.
you could probably do that though pc no?
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Old 23rd July 2012, 03:01 PM   #24
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Originally Posted by Torchwood421 View Post
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. A warning on the Lundahls.... The zoebel in the datsheet is not optional. They can sound very hard edged without that resistor capacitor across the secondary. With the zoebel they work well. A little exotic with the permalloy.... Not to mention the price is in the painful zone. Ouchhhhh! Dave
yeah I won`t be fitting transformers into cdp anytime soon I was just curious how others were avoiding signal caps
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Old 23rd July 2012, 03:43 PM   #25
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Originally Posted by stephensank View Post
I would frankly replace your RL11 and RXV1000 with a stock Nakamichi CA-5(the first, NOT the CA-5II, nor the truly awful CA-7). It's typically $250-350 on ebay or canuckaudiomart, and it's a very, very neutral and considerably transparent sounding preamp, both for line & esp. nice phono, and it's built so well that there's nothing to upgrade except the rectifier diodes. I think it's the best SS preamp out there for under a few grand. And frankly, I would also replace the amp entirely with a mod'd Nak PA-5 stasis amp(or any of the four Nak stasis amps), although it should darn well beat the Acurus even stock.

while the nakamichi is nice stuff and I may look at that down the road, I am not looking to change all my gear

Unless dynaudio used electrolytic caps, you'll make the biggest improvement by using foil inductors. It's a not at all subtle improvement versus ANY other coils.

thanks I will look into that when I do a rewire and dampening

Although I have three Fluke meters, I have had just as accurate results with "house brand" meters from MCM Electronics and such. Nowadays, a DMM is a DMM, and Fluke has very little advantage.

looking at bk and extech

Exactly right on pulling the Acurus boards. The sink compound will have a lot of stick, so you just need to pop each xstor loose before yanking on the board. And, yes, I would keep it cap input, with mainly just a better film cap/caps than that cheap black one. The other lytic/film cap combo nearby would be the low frequency corner cap from the feedback loop, and needs to stay there to prevent amp from having DC gain, and what's there is about as good as will make an audible difference. Any other lytics on the board will be supply line secondary filtering for the drive/input stages, and can increased in value liberally with potentially excellent effect, and film capping is good there, too.

very good info and I appreciate your experience

when you say LF corner cap you mean the gold 220uf one?

below the black nichicon looks like a rectifier circuit in the center is a potentiometer is that for bias?

when you say keep it cap input do you mean I can remove any output caps?

Wouldn't touch Cambridge with a ten foot pole. If you want great dvd video & excellent sacd sound, along with the BEST reliability, get a Pioneer DV-79avi or DV-59avi for hdmi, or the DV-47ai or DV-45a if hdmi is not needed. These are all really cheap now, having been replaced by Pioneers quite excellent & reliable blu-ray(no sacd) players and by successor DV models that have garbage mechs(i.e., stay away from DV-58avi, 46av, etc.). I've been running a DV-59avi literally 24/7 at my shop for over a year with perfect performance, which replaced, for the sake of hdmi out for led monitor, a DV-45a that was still perfect after 2 years or more of 24/7 play. Of course, if you get a DV-79avi, which comes stock with great Burr-Brown OPA2134 opamps after the PCM1738 dac, it might make you want to abandon the Marantz player upgrades.

why so down on the cambridge?

many say it sounds better than the pioneer.

Judging by opinions of one or two that I trust, the TDA1549 in your player is pretty certainly better than a CS4398(which I consider quite etched sounding), and there is no easy way to replace one with the other, without designing an adaptor board. There are very few dac chips that match pin for pin with any other, even from same maker.

heard it was not bad

It would be very complicated and expensive to try to use transformers for decoupling in that unit, and I would sure as heck not choose a Llundahl or, yecch, Edcor. I would choose an appropriate Cinemag(started by the designer of all of Jensen's transf) if I was going to do that sort of thing, but I would not even try it on a voltage out dac like yours, as there would not be any expectation of benefit, versus what could be more easily and cheaply achieved with caps as I suggested. Transformers only make sense on current output dacs, IMO.
no room for that, I was just curious.

thanks for all your time and help
Glen
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Old 23rd July 2012, 03:49 PM   #26
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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.
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Old 25th July 2012, 02:59 AM   #27
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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.
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Old 31st July 2012, 01:57 AM   #28
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Torchwood

I appreciate the input no pun intended

I am just learning so ALL info is good

Glen
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Old 31st July 2012, 02:49 AM   #29
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Quote:
Originally Posted by stephensank View Post
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.
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
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Old 31st July 2012, 05:07 AM   #30
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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.
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