I did look it up, I think it is older than the 4398. It has Vout at only 1.33v p-p which is about 0.45v RMS. They are probably not abundant so they command a higher price. I'm sure someone has tried it, maybe we will hear from them.
Impedance into a transformer is a complex business. There are actually two impedance's, one the load line or reflected impedance presented to the chip through the primary, but developed by the secondary load and winding and modified by the turns ratio involved. The second is the amount of inductance required, in the primary without respect to any secondary loading, to provide a load that will allow the chip to produce a 20Hz, or lower, signal across the primary winding.
If the transformer is required to provide a 600 ohm load, and the app notes for the 4398 show a 560 ohm resistor as the load without a transformer involved (page 20, Analog output and filtering), then a minus -3 db output into a 600 ohm inductance load at 20 Hz, requires 4.8 henry. To attain -0.5 db at 20 Hz 13 .2 Henry are required. This is across the entire chip output, from plus to ground, and, incidentally provides 150 ohms per half, of inductive loading.
If you are going to step up the output, by addressing it in the transformer attached to the DAC, you must be sure that the DAC can drive the secondary load and winding LCR multiplied by the square of the turns ratio. A 1:1 turns ratio just provides the secondary load, plus the LCR of the transformer secondary, as the reflected load. The only way to mitigate this is by using a physically larger transformer, to drop the LCR load of the secondary.
And all of this without asking you why you would want to step up the output of the DAC chip in the first place.
Bud
Thank you Bud for your reply, I'm new to this transformer bussiness so that's why I asked judging by what I saw in cs4398 datasheet as output impedance and as for the step up part, as I heard a while ago that people "complain" that with 1:1 transformer attached the signal level from the dac chip is lower than the opamp solution (opamp used as buffer not to amplify);
But judging by your answer I think I'll go on the 1:1 (600 ohm:600 ohm) trafo way and I'll give it a try on 3 different dac chips, CS4397,4398 and AKM4396 to see on which one do I get the best result (for my tastes and ears 🙂 )
Thanks
But judging by your answer I think I'll go on the 1:1 (600 ohm:600 ohm) trafo way and I'll give it a try on 3 different dac chips, CS4397,4398 and AKM4396 to see on which one do I get the best result (for my tastes and ears 🙂 )
Thanks
You will want to investigate Edcor, for lowest prices and quite good performance, Jensen for technically perfect performance, Lundahl for very dynamic, tonally accurate sound and very low distortion, Cinemag for excellent tonal quality and O-Netics for their typical fire hose of information approach.
I have heard that Partridge have also begun providing suitable transformers, but have no further information.
Bud
I have heard that Partridge have also begun providing suitable transformers, but have no further information.
Bud
I received my transformers RE 11-FL bought on eBay. These Jensens transformers are small but I think that they are really high quality transformers. I injected 20 khz and 100 khz square waves in them and They are the best i've seen from any transformer manufacturer. In the bass they should be ok but are perhaps easy to saturate. I'll try thenm during this weekend. I have in hand the UTC HA-101, Lundahl LL1690, Studer bought from Franz, Ramsa 600-600.
Look at the square waves. Transformers loaded or unloaded doesn't do any difference.
Look at the square waves. Transformers loaded or unloaded doesn't do any difference.
Attachments
Here is something about Jensen transformers and Re transformers that were on eBay
Hello,
The RE series of transformers were made by another company attempting
to copy our designs. They are not Jensen transformers. However, the basic
function and application of these two part numbers will be the same. You
will probably find that they will not be close enough in performance to use
for a well matched stereo pair. The company that made the RE series has been
out of business for several years. We can't say much more on this subject for
legal reasons.
Please let us know if you need further assistance.
Best Regards
Larry Hathaway
Jensen Transformers, Inc
Hello,
The RE series of transformers were made by another company attempting
to copy our designs. They are not Jensen transformers. However, the basic
function and application of these two part numbers will be the same. You
will probably find that they will not be close enough in performance to use
for a well matched stereo pair. The company that made the RE series has been
out of business for several years. We can't say much more on this subject for
legal reasons.
Please let us know if you need further assistance.
Best Regards
Larry Hathaway
Jensen Transformers, Inc
That's very interesting. I wonder why he wouldn't mention the company. Still, I am very happy with mine, I do not agree with Mr Hathaway's conclusion. The imaging is excellent, as is the balance, and they are definately nickel cores.
After further thought I remembered a little fact about the trafos I received. One was marked RE 11-DM, and the other was marked JE 11-DM. They test, measure, look, and sound identical. They even have the same fabrication stamp on the frame sheetmetal.
There is an old addage that is fitting. If it walks, quacks, looks and acts like a duck, it's probably a duck. I believe someone is in error.
There is an old addage that is fitting. If it walks, quacks, looks and acts like a duck, it's probably a duck. I believe someone is in error.
Response from Mr Hathaway seems strange and suspicious. Why all this mystery ?😱
As there's still only one RE 11-DM transformer left on eBay, I was asking him if I could mate the RE 11-DM with a Jensen JE 11-DM.
I strongly think that the RE 11-DM and JE 11-DM are exactly the same transformers.
As there's still only one RE 11-DM transformer left on eBay, I was asking him if I could mate the RE 11-DM with a Jensen JE 11-DM.
I strongly think that the RE 11-DM and JE 11-DM are exactly the same transformers.
Anyone made any more or new experienses with the PCM1798,is it worth upgrading with chip and new trafos?
Hi all. I've joined the fray. I received my 2010 Big Dac almost a week ago. I am using two Antek toroid transformers. So far all I have done is bypassed the 2nd opamp, just by jumpering pins on the empty socket, now that I'm looking at the schematic I might still be going through a pair of 2.2uF caps, which might be good if there is any DC. (Well, that and adjusting the analog voltage regulators to a solid +/- 15v and popping in an OPA2132 I had lying around). The analog stage is fairly significantly modified out of the box from the older ones on the earlier posts, but I haven't actually traced it out completely to see if they followed the modifications to the filter in earlier threads. There are several resistors and caps removed and jumpered, especially in the 2nd opamp.
Anyway, I am taking things one step at a time, but I have ordered two Edcor XSM 10K/10K's, and just today I picked up a pair of Tamura GA80080's on ebay for $50/pair, not too bad. I didn't want at this point to spend more on the output transformers than the DAC itself 😛
I'm using it exclusively for headphones, with a "Millett Hybrid almost a max" and a Cavalli/Bijou tube amp. The whole rig is essentially my play rig, usually one or both of the amps and now the DAC will be in a constant state of "mods".
I could tell the improvements I've made so far, and as you already know, it's a pretty fine sounding DAC for the money. My only other DAC's have been a PCI EMU0404 soundcard and a little USB Aliendac kit I built (which really sounds pretty nice considering). This is already on another level from those. Can't wait to try the transformers!
Anyway, I am taking things one step at a time, but I have ordered two Edcor XSM 10K/10K's, and just today I picked up a pair of Tamura GA80080's on ebay for $50/pair, not too bad. I didn't want at this point to spend more on the output transformers than the DAC itself 😛
I'm using it exclusively for headphones, with a "Millett Hybrid almost a max" and a Cavalli/Bijou tube amp. The whole rig is essentially my play rig, usually one or both of the amps and now the DAC will be in a constant state of "mods".
I could tell the improvements I've made so far, and as you already know, it's a pretty fine sounding DAC for the money. My only other DAC's have been a PCI EMU0404 soundcard and a little USB Aliendac kit I built (which really sounds pretty nice considering). This is already on another level from those. Can't wait to try the transformers!
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Thanks. I've got the schematic from the Wiki that hoverdonkey used. Of all things I can't seem to find any 1 nf caps, so for now I'm going to try some 500pf silver dipped mica and I have enough to parallel them. I've been on that ebay again and should have a nice selection of the Russian PIO caps soon. They use these a lot in headphone amps. They aren't the Russian Teflon ones, there doesn't seem to be any 1 nf in those at the moment. There are some styroflex ones 🙂 Come to think of it I need to look in another drawer, I used to have some polypropylene (I think) ones that look a lot like those styroflex ones 🙂
I'm using 500pf micas and 500ohm Rs on the primaries now, and .001uf and 1k R on the secondaries. They are far enough away from the audio signal you'll never hear them.
I believe the Edcors will need a load resistor on the secondaries, around 10-15k. I may be wrong about that though, I don't know much about them and their datasheet sucks.
I believe the Edcors will need a load resistor on the secondaries, around 10-15k. I may be wrong about that though, I don't know much about them and their datasheet sucks.
I've got the Tams hooked up in a VERY temporary fashion 🙂
They sound wonderful.
I soldered direct to the relatively large solder pads on the edge of the DAC board, and I'm using "regular" resistors (metal film) and mica caps. I did parallel the 470 pf's to get close to 1 nf on the primaries. Other than that I followed your recommendations to the letter, the only diff between them and hoverdonkey's were smaller capacitance on the
primary (dac side).
Things are really opening up, and not noticing any deficiencies in freq. response, either on the upper or lower end. Of course using the computer source with Foobar 2K and the convolver plugin I may not have exactly a "flat" signal going in.
Anyway, thanks for all the help and this great thread. I am probably not going to do much but mount all this a little better (mount everything actually) until my "audiophile" resistors and caps come in from Canada (partsconnexion) and Bulgaria (ebay) 🙂
Oh, I guess I've got an extra 15v-0-15v toroid now and some opamps 🙂
They sound wonderful.
I soldered direct to the relatively large solder pads on the edge of the DAC board, and I'm using "regular" resistors (metal film) and mica caps. I did parallel the 470 pf's to get close to 1 nf on the primaries. Other than that I followed your recommendations to the letter, the only diff between them and hoverdonkey's were smaller capacitance on the
primary (dac side).
Things are really opening up, and not noticing any deficiencies in freq. response, either on the upper or lower end. Of course using the computer source with Foobar 2K and the convolver plugin I may not have exactly a "flat" signal going in.
Anyway, thanks for all the help and this great thread. I am probably not going to do much but mount all this a little better (mount everything actually) until my "audiophile" resistors and caps come in from Canada (partsconnexion) and Bulgaria (ebay) 🙂
Oh, I guess I've got an extra 15v-0-15v toroid now and some opamps 🙂
Changing the primary resistors to carbon or what ever you think might change the sound depending on the resolution of the rest of your system, but I would be surprised if you would hear a difference with any other changes. The filters operate at very high frequencies, 150khz or so.
Sounds like you are a convert, have fun.
Sounds like you are a convert, have fun.
Since the beginning I have also been using 2x510R with 0.001uF. Somebody told me he thought this was too high. Based on calculations made with this tool I arrive at 156Khz. I was told by the same person the ideal cutoff would be around 50Khz which would require 2x510R with 0.003uF.
I'm by no means questioning what was said by anybody here or elsewhere - I'm just trying to understand what effect a higher or lower cutoff would have on the (audible) end result .
I'm by no means questioning what was said by anybody here or elsewhere - I'm just trying to understand what effect a higher or lower cutoff would have on the (audible) end result .
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