I have a couple of the Altecs as well.Would you mind sharing the values you settled on for making the modification? If you could include a photo or two, that would be great.
Thanks in advance,
Steve
Hey Steve,
The current hook up I am using with the Altec 15356A's are 500ohm resistors in series on the four leads going to the input side; and a 1kohm resistor in series with a .0001uf film cap wired across the secondary (output) leads of each transformer.
My set up is no different than what the others have posted, so you can refer to their pictures if you need to verify what it looks like.
The wiring diagram should be posted on your transformers so that makes it easy to follow.
By the way, I have one of the first edition boards that used the CS4397 chip, not the current 8416, so if you have the latter, your filter values may be different.
Bill Fuss is one of the main guys offering up great advice here, so hopefully one of them will address any of your concerns.
Good Luck.
I'm using the same setup(Bill's) with UTC A-20s and on another set of non-descript trafos with excellent results also. Only difference is a 0.0001uF oil cap across primaries.
I'll have to check but think my unit has the 4397 chip. Thanks for providing the values. I think it's time to warm up the soldering iron.
Steve
Hey Steve,
Bill also noted that if the DAC has the CD4397 chip, then the output will be a little less than then the CS4398, so you may want to try wiring up the Altecs using the 150ohm primary to get more gain.
I have not tried this, as the gain with the Altecs at 600/600 is great for my application.
The values on the filters will change a bit if you decide to use the 150ohm input, so search the thread for suggested values.
Cheers
For me, the whole idea of using trafos instead of active devices is getting as close as possible to a wide open window to the source material. There will be minor colorations depending on the trafos used, but any filtering schemes should be well out of the audio band, such as the secondary RC filter of 1kohms/.001 cap. It has an f3 of around 150khz and should be completely inaudible, and is not strictly needed except in the case of a trafo with a prominent resonance (ringing). It also protects your downstream equipment from ultrasonics so there is no good reason for omitting it.
The 500ohms in series with the chip outputs is a compromise value that is dependent on the trafo inductance which varies from model to model. Feel free to do the research to find the optimum values, keeping in mind the chip doesn't want to see a heavy load, it is voltage output. Hearing the difference between slightly different values is an exercise in futility unless your system has really great definition, or you have an active imagination.
You can also use a small cap(.001) across the primaries to eliminate any ultrasonic artifacts from the chips but many do not, the trafos provide a degree of filtering themselves.
There's a lot more to it that I don't fully grasp yet, but this is what I am comfortable talking about at this stage.
Best, Bill
After being very enthousiastic about this Dac I am not happy anymore.
The DAC is the big one with 4398 and Monacor trafo's.
When I listen to my vinyl I hear a full bodied, warm Van Morrisson or Cat Stevens.
With the DAC the body of the voice has gone. I tried some settings, coax and spdif but no real improvement.
Is this a signature of this Dac or can I change something?
I use 220 Ohm at primary and 1.1k at secondary with caps.
Preamp with 6N1P and 300B poweramps into modified TDL's.
Vinyl vdH frog, PT Anniversary, SME V and phonoclone.
Any Ideas?
Gerard.
The DAC is the big one with 4398 and Monacor trafo's.
When I listen to my vinyl I hear a full bodied, warm Van Morrisson or Cat Stevens.
With the DAC the body of the voice has gone. I tried some settings, coax and spdif but no real improvement.
Is this a signature of this Dac or can I change something?
I use 220 Ohm at primary and 1.1k at secondary with caps.
Preamp with 6N1P and 300B poweramps into modified TDL's.
Vinyl vdH frog, PT Anniversary, SME V and phonoclone.
Any Ideas?
Gerard.
Hi Gerard,
You will have to supply a drawing of your wiring to us to be able to comment on your findings. I cannot comment on the Monacors as I've not heard them. The A-20s have the best midrange I have heard so far. Your source and cabling is also a contributing factor, just as the components in your vinyl playback are contributing factors to its sound.
Best, Bill
Hi Bill,
I've been comparing today between PC optical/CD-coax through DAC and CD-direct and DAC through Trafo and through opamps.
I think CD-opamps (LM4562) sounds most neutral but a little boring in the end. DAC-opamps give more detail but sound to much alive or how you call this in english, not relaxing... With trafo's mid and high are perfect, clean detailed and not tiring. But the bass lacks a little, but just to much.
Difference between CD as source or PC is not really much.
Conclusion for me is the trafo's are bassshy.
I use 2 R's of 220R between plus and trafo and between minus and trafo and a cap at the primary of 7 muF. At the secondary a R of 1.1k and C of 2muF.
I wonder what changing the 220R to a higher value will bring, I expect less bass or..?
Also I still have the opamps connected in parallel with the trafo's. They have inputresistors of 2 times 22k so I imagine they don't trouble the trafo's?
@Piero7 Did you compare the utc-a20 to smaller trafo's?
And maybe what are the numbers/properties of a trafo to look for especially in combination with the CS4398?
Thanks,
Gerard.
I've been comparing today between PC optical/CD-coax through DAC and CD-direct and DAC through Trafo and through opamps.
I think CD-opamps (LM4562) sounds most neutral but a little boring in the end. DAC-opamps give more detail but sound to much alive or how you call this in english, not relaxing... With trafo's mid and high are perfect, clean detailed and not tiring. But the bass lacks a little, but just to much.
Difference between CD as source or PC is not really much.
Conclusion for me is the trafo's are bassshy.
I use 2 R's of 220R between plus and trafo and between minus and trafo and a cap at the primary of 7 muF. At the secondary a R of 1.1k and C of 2muF.
I wonder what changing the 220R to a higher value will bring, I expect less bass or..?
Also I still have the opamps connected in parallel with the trafo's. They have inputresistors of 2 times 22k so I imagine they don't trouble the trafo's?
@Piero7 Did you compare the utc-a20 to smaller trafo's?
And maybe what are the numbers/properties of a trafo to look for especially in combination with the CS4398?
Thanks,
Gerard.
I would agree with your conclusion, the Monacors are bass shy. I would try changing the 220Rs to 500Rs, that did seem to make a small improvement in the bass of mine.
The A-20s would be a very good choice for you, they are not bass shy by any measure.
In general, look for a trafo response graph that is flat down to 20hz. Stay away from trafos that are DC tolerant, ie, any with core air gaps. The air gaps compromise bass performance.
The A-20s would be a very good choice for you, they are not bass shy by any measure.
In general, look for a trafo response graph that is flat down to 20hz. Stay away from trafos that are DC tolerant, ie, any with core air gaps. The air gaps compromise bass performance.
OK
Somebody please tell me that the sound can be much better than stock out-of box!!
I am currently using the stock dac board with a Shigaclone transport- and LM4562's. The dac output is feeding a Pass B1 buffer preamp.
My speakers are Fostex FE-166E's in sealed enclosures coupled with push-pull transmission line subwoofers. Filtering is done by a pair of Fourth-order active crossover's- and it's all powered by six UCD-180HG Class-D amplifier modules.
This DAC sounds like crap!!
Compared to the Adcom GCD-750 I was using, this thing sounds muffled, muddy, and boring!
I haven't lost the faith however; I have since ordered a pair of UTC A-20's- and I'll report back with my findings.......
Somebody please tell me that the sound can be much better than stock out-of box!!
I am currently using the stock dac board with a Shigaclone transport- and LM4562's. The dac output is feeding a Pass B1 buffer preamp.
My speakers are Fostex FE-166E's in sealed enclosures coupled with push-pull transmission line subwoofers. Filtering is done by a pair of Fourth-order active crossover's- and it's all powered by six UCD-180HG Class-D amplifier modules.
This DAC sounds like crap!!
Compared to the Adcom GCD-750 I was using, this thing sounds muffled, muddy, and boring!
I haven't lost the faith however; I have since ordered a pair of UTC A-20's- and I'll report back with my findings.......
When I bought mine I didn't even consider trying the stock output circuitry. I have a sincere hatred for opamps, havent had one in my entire system for yrs. If your system is capable, you should hear a staggering difference when you switch to good trafos.
Keep us informed about your results.
Best, Bill
Keep us informed about your results.
Best, Bill
When I bought mine I didn't even consider trying the stock output circuitry. I have a sincere hatred for opamps, havent had one in my entire system for yrs. If your system is capable, you should hear a staggering difference when you switch to good trafos.
Keep us informed about your results.
Best, Bill
Keep us informed about your results.
Best, Bill
Does the non-descript trafo sound as good as the UTC? If so tell us the make/model/price as the UTC is said to be one of the best!
Just thought I'd report on my Sescom MI-97 trafos a pair of which I bought on ebay for $50. Great value, great sound - still to be tweaked http://www.diyaudio.com/forums/digi...c-ouput-using-transformer-10.html#post1972721
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Thanks Bill,
I'll try the 500's tomorrow. I guess the SC4398 can give more bass with an easier load. The monacors on the other hand like a low source resistance of about 50 Ohm. There is a graph included that shows a -3dB at 20 Hz for a source resisantce of 600 Ohm. Since the CS4398 is already 110 Ohm there will be bass loss because of that.
But after trying out the different options I'm back to the trafo's. There is no way back anymore!
Gerard.
BTW, there are a lot of connectionoptions: primary 2 times 75 Ohm connected by a centertap. Secondary 2 times 90 Ohm connected by centertap, and a 60 ohm connection without centertap.
Is there a way to improve the situation by connecting differently?
I'll try the 500's tomorrow. I guess the SC4398 can give more bass with an easier load. The monacors on the other hand like a low source resistance of about 50 Ohm. There is a graph included that shows a -3dB at 20 Hz for a source resisantce of 600 Ohm. Since the CS4398 is already 110 Ohm there will be bass loss because of that.
But after trying out the different options I'm back to the trafo's. There is no way back anymore!
Gerard.
BTW, there are a lot of connectionoptions: primary 2 times 75 Ohm connected by a centertap. Secondary 2 times 90 Ohm connected by centertap, and a 60 ohm connection without centertap.
Is there a way to improve the situation by connecting differently?
Ditto, I did however first buy the smaller board and did try that with the opamps. Pretty harsh and non-musical. Very artificial.
I then bought the larger DAC. This I immediately fitted out with A-20 transformers and with resistor/capacitors. I simply use it as it is: it answers my needs and fulfills expectations!.
However I am interested in any other mods which will improve the sound. These will come I guess in the PS side of things and also in component substitution. Any advice on such mods? Love to hear from those who have gone down this route.
Thanks.
Yes tested on this dac: Digitec, Lundhal 1540 and UTC-A20.
UTC forever!!! Do yourself a favour, buy them!
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About power supply mods......
There is a simple list of parts that I've used with every digital power supply I've ever had- and it never fails to take the sound to another level. I have had no luck with exotic clock boards, $8 resistors, $50 coupling caps, RFI shielding on individual IC's, etc.
The list is:
HFA04TB60 Diodes
Panasonic capacitors (fresh stock from Digikey)
Sorbothane blobs underneath the pcb
The list of players are:
Tandberg 3015A (Diodes, caps, dampers replaced) I absolutely loved the sound of this player after this (that is, until the laser died.)
Rotel RCD-990 (Stereophile class B) (replaced PSU 3300uf Muse caps with 10000uf Panasonic TSUP's- and also added the diodes) WOW, what an improvement!!
Adcom GCD-750 (Sorbothane isolators were placed directly under the PCB-mount trafo's, the diodes were replaced, and Panasonic FC PSU caps replaced the generic ones. Suffice it to say- that all the wonderful audiophile adjectives apply to this piece. Some players excel here or there, but I can confidently say that this player does EVERYTHING right.
Hopefully, my Shigaclone/modded Gigawork DAC combo will be a significant step up.
When I get my A-20's- I'll let everybody know whether or not it is.
There is a simple list of parts that I've used with every digital power supply I've ever had- and it never fails to take the sound to another level. I have had no luck with exotic clock boards, $8 resistors, $50 coupling caps, RFI shielding on individual IC's, etc.
The list is:
HFA04TB60 Diodes
Panasonic capacitors (fresh stock from Digikey)
Sorbothane blobs underneath the pcb
The list of players are:
Tandberg 3015A (Diodes, caps, dampers replaced) I absolutely loved the sound of this player after this (that is, until the laser died.)
Rotel RCD-990 (Stereophile class B) (replaced PSU 3300uf Muse caps with 10000uf Panasonic TSUP's- and also added the diodes) WOW, what an improvement!!
Adcom GCD-750 (Sorbothane isolators were placed directly under the PCB-mount trafo's, the diodes were replaced, and Panasonic FC PSU caps replaced the generic ones. Suffice it to say- that all the wonderful audiophile adjectives apply to this piece. Some players excel here or there, but I can confidently say that this player does EVERYTHING right.
Hopefully, my Shigaclone/modded Gigawork DAC combo will be a significant step up.
When I get my A-20's- I'll let everybody know whether or not it is.
