audio-kraut said:
Well that's good news. I haven't had any noise issues either, but I never run the power amps wide open. (Might have to try, just for a test). My set up is unbalanced, Pin 2 hot - Pin 3 tied to ground via 15K ohms.
Lots of other users around the Internet complain about noise, tho. The common thread seems to be that they run power amps with no attenuation. Is your Bryston using a balanced input?
Sorry not to really answer your question, Col. AUD$350-500 seems a bit steep. But what can you do?
Hi - I use mixed inputs - the 4b for sub runs rca (converted from xlr out, just cold on mass of the RCA), the mid/high via xlr.
If there is noise - it is a fault in the output board of the dcx, and is/was a common problem - frying egg sound. There are some remedies.
I supply the deq/dcx with a maximum signal from the src input converter - all analog signals go at peak to the red indicator. Between the src/deq/dcx every connection is via aes cable.
I attenuate with six gang pot between the dcx and the brystons.
This one however is giving me grief right now - channel outage, crackling from then pot when turning. Encapsuled, cannot clean properly.
If there is noise - it is a fault in the output board of the dcx, and is/was a common problem - frying egg sound. There are some remedies.
I supply the deq/dcx with a maximum signal from the src input converter - all analog signals go at peak to the red indicator. Between the src/deq/dcx every connection is via aes cable.
I attenuate with six gang pot between the dcx and the brystons.
This one however is giving me grief right now - channel outage, crackling from then pot when turning. Encapsuled, cannot clean properly.
brucemck2 said:
Pilgham Audio (www.pilghamaudio.com) sells kits for the DCX but also do complete mods for my remote 6-channel level/offset control, my linear replacement power supply and Frank Oettle's digital input and regulator mods. They also mod your unit for you or even get the DCX2496 for you at competitive pricing and then mod it for you. Ask them for what you would want.
Jan Didden
panomaniac, I'm having a go at one of these: http://www.diyaudio.com/forums/showthread.php?s=&threadid=123409
Picked it up off Ebay for a very reasonable $85 and I just bought $45 worth of op-amps for it
VT67 said:
I got them from local AKM rep in San Francisco. I originally wanted to buy them, but it turned to be such a hassle. First I contacted AKM directly, and than they transfered me to a local rep. After a few months of waiting and checking with them if it was sent or not, they decided to send me samples since I needed only few. It was exception to the rule so your situation could be quite different, but nothing stops you of trying.
Good luck
AR2
A bit of the same story here. Contacted AKM directly but got no reply. Few weeks later I got a phone call from the Belgian distributor asking me the purpose of the chips and how many I would be buying. Honest as I am I told here that it was for hobby reasons and I only needed three. The lady said she would look if these particular chips where in a sample program and would let me know. Haven't heard nothing from here ever since. The thing is that I rather change everything in one go than to take the DCX apart several times.
Regards
Regards
Yeah, I know - same story. I was able to place the order through the rep, but after I checked several times on status and they realized that they forgot on me they gave me samples. It seems like they were short on them as well. I wanted to buy 10 and they were hunting them, so finally after they offered samples I agreed on 6. Regarding opening of DCX I suggest you start practicing now, because you will be opening it more than once.VT67 said:
AR2 said:
Hi AR2,
I have just read through the whole DCX-thread as I wanted to find if someone else had used transformers in and out. Found out that you did the right thing!
The AKM4393 is a voltage-out DAC but the LL1674 seems to be connected for some kind of current-out. With the primary center grounded, each side of the balanced out will see 33ohms DC load parallelled with the AC-load from the secondary!
I have read Kevins (K&K) explanation at their forum but I do not buy it as we are talking DC here. With +2,6VDC at the both of the DAC outputs and a current capability of 3,5mA there shouldn´t be much left in terms of AC-output level. The data sheet says min 1k DC connected. Ground-connecting shouldn´t anyway be needed as I see it. Without it both sides is at same potential and no DC current will flow. Have you tried with the ground lifted?
The AKM gives 4,8Vptp balanced out (if I understand it right) so a 1:1 (without CT to ground
) should be able to deliver 1,7Vrms into any typical power amp input-load. Transformer should be the obvious choice when modding the DCX even if it also is the most costly. I have ordered LL1544A for mid+treble and LL1690 for low output. Will also use a 4+4:1+1 connected LL1674 (but for the input) that also serves as parafeed transformer for the presceding tube preamp. The tube pre is needed as the sensitivity at the transformer input will be just below 7Vrms.
You are right that you must treat current output and voltage output DAC differently.
The DAC chip in RAKK DAC is a current out and the K&K passive output board works flawlessly for it.
I found a schematic for a voltage DAC and I believe a 10K + 100 uF were connected from center tap to ground, with the secondaries either unloaded or 100k across the secondary.
I will try to find it for you tonight.
HTH
Doug
The DAC chip in RAKK DAC is a current out and the K&K passive output board works flawlessly for it.
I found a schematic for a voltage DAC and I believe a 10K + 100 uF were connected from center tap to ground, with the secondaries either unloaded or 100k across the secondary.
I will try to find it for you tonight.
HTH
Doug
revintage said:
Hi AR2,
I have just read through the whole DCX-thread as I wanted to find if someone else had used transformers in and out. Found out that you did the right thing!
The AKM4393 is a voltage-out DAC but the LL1674 seems to be connected for some kind of current-out. With the primary center grounded, each side of the balanced out will see 33ohms DC load parallelled with the AC-load from the secondary!
I have read Kevins (K&K) explanation at their forum but I do not buy it as we are talking DC here. With +2,6VDC at the both of the DAC outputs and a current capability of 3,5mA there shouldn´t be much left in terms of AC-output level. The data sheet says min 1k DC connected. Ground-connecting shouldn´t anyway be needed as I see it. Without it both sides is at same potential and no DC current will flow. Have you tried with the ground lifted?
The AKM gives 4,8Vptp balanced out (if I understand it right) so a 1:1 (without CT to ground
Transformer should be the obvious choice when modding the DCX even if it also is the most costly. I have ordered LL1544A for mid+treble and LL1690 for low output. Will also use a 4+4:1+1 connected LL1674 (but for the input) that also serves as parafeed transformer for the presceding tube preamp. The tube pre is needed as the sensitivity at the transformer input will be just below 7Vrms.
It didn't work without ground. Ground has to be connected. I also remember that I had to monkey around with the ground as it didn't work exactly as it was on schematics, but do not take me by the word since it was long time ago. The fact is - there is O V DC at the output.
Depending of your amp - speaker situation after the Lundahls, you might be able to drive it without any line or pre amp. When you do it, it is such a great sound. I use that as a reference to compare anything else to. Typically my amps are without any caps in the line of signal. So it is as clean, straight and short as it is possible. I have tested various opamps, discrete caps and resistors after the DAC and nothing compares to Lundahls. Simple and works great.
There are several benefits in using transformers:
1. Removes DC
2. Unobstructed and clean AC out
3. Provides galvanic insulation
4. AC rolls off starts at 50 KHz, so there is automatic HF filtering, that normally would need to be done with additional electronics.
Here is the measurement done on stock DCX without any modifications - bottom and measurement on modded Lundahls output DCX - top graph. It is remarkably obvious difference.
AR2,
Great to have your immediate response. Totally agree with you of the benefits. Have already done a tube/transformer out mod on my Sony CDXP3000E so I know digital+transformer is a win/win concept. Used Slagle bifilars for that and it works well. Thought of Slagle for the DCX outputs too, but the cost and size of his irons made me choose Lundahl.
Will come back with an update as soon as I have tried the grounding variations. Still believe it shouldn´t be centergrounded
. Will have to be convinced by testing.....
This is for Crystal/Jensen but should be the same for AKM/Lundahl:
http://www.jensen-transformers.com/as/as093.pdf
The offset trim is interesting!
PS AR2, Saw your rig on the Burningamp site, truly impressing!DS
Great to have your immediate response. Totally agree with you of the benefits. Have already done a tube/transformer out mod on my Sony CDXP3000E so I know digital+transformer is a win/win concept. Used Slagle bifilars for that and it works well. Thought of Slagle for the DCX outputs too, but the cost and size of his irons made me choose Lundahl.
Will come back with an update as soon as I have tried the grounding variations. Still believe it shouldn´t be centergrounded
. Will have to be convinced by testing.....This is for Crystal/Jensen but should be the same for AKM/Lundahl:
http://www.jensen-transformers.com/as/as093.pdf
The offset trim is interesting!
PS AR2, Saw your rig on the Burningamp site, truly impressing!DS
