ES9038PRo or 9018S have ~2VRMS (do not remember exactly now) at 2kOhm in the secondary. It is about 5.6Vpp. Well to be under 3Vpp it is needed to use 1k or less. Indeed your 500r (+/-) 🙂
Anyway kindly ask you to comment if it is good sound now after "right" resistor choised?
Anyway kindly ask you to comment if it is good sound now after "right" resistor choised?
Yes, much better. At 2k it was also good and maybe having higher gain than before could sound better for DAC chip (or transformer could respond better?). With lower gain the lossless digital volume control has more resolution, that is the main benefit.
Im noticing there is a low ground loop noise, the DAC and amp ground are isolated and amp is silent with shorted inputs, so it must be from cable to transformer. There was no noise with old output stage and same cable so its confusing, the cable is around 1M twisted pair RCA.
Did you connect the (-) wire of the secondary and shield to the ground of your DAC as shown in the first post of this thread? If we talking about 50/60 Hz from the mains, then of course you should avoid any loops of the ground.
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no, I hadnt. thats fixed it and it sounds even better too.
I thought it was possible to seperate DAC and amp ground, but I guess that is only possible with balanced connection, which will give full galvanic isolation between devices.
I thought it was possible to seperate DAC and amp ground, but I guess that is only possible with balanced connection, which will give full galvanic isolation between devices.
Personally in my practice full galvanic isolation doesn't "open the third eye", may be because all the people including musicians doomed to live grounded... I don't know...
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I believe that the sound is alreay "formed" inside transformer. But to be honest I don't have such recommendations because I do not hear any significant changes. Very subtle differences - sounds excellent with any type for my ears 🙂
So far I tried a couple small resistor tweaks.
500r 1/4W replaced with 500r 1W (2 x 1k 1/2w in parallel), this seemed to improve sound a bit.
But going even lower to 120R sounded much better!
The DAC volume still has a lot of headroom so I will try to go even lower if it means better SQ, these trafos have already met my expectations so anymore improvement is a bonus.
I read going too low can cause ringing , something I will watch out for.
500r 1/4W replaced with 500r 1W (2 x 1k 1/2w in parallel), this seemed to improve sound a bit.
But going even lower to 120R sounded much better!
The DAC volume still has a lot of headroom so I will try to go even lower if it means better SQ, these trafos have already met my expectations so anymore improvement is a bonus.
I read going too low can cause ringing , something I will watch out for.
Seems that your head amplifier has a GOOD voltage amplification to signal. Is it some of amplifier from market and there are specs of it somewhere in the net? Because with 120 Ohm of load you are not far from loading transformers directly onto your headphones 
Seems that your head amplifier has a GOOD voltage amplification to signal. Is it some of amplifier from market and there are specs of it somewhere in the net? Because with 120 Ohm of load you are not far from loading transformers directly onto your headphones
with 300 ohm headphones I think that means I already am? 😱
This is the amp, designed by fellow diyaudio member:
xrk971 Desktop Class A (DCA) Headphone Amp
Driving the headphones directly from trafo works very well, amazing to have just one passive component between DAC and drivers.
9018S or 9038PRO are strong enough sources to drive high impedanced headphones directly. But do not connect your phones directly to (+)/(-) because after playing musical signal, there can be constant high DC-offset. Be careful, across capacitors or transformers only!
very interesting,
I remember someone mentioned that for trafos which are sensitive to DC the Sabre offset is not a problem, the DC for each differential output is equal (+1.65V) so the headphone/transformer will see 0V.
I remember someone mentioned that for trafos which are sensitive to DC the Sabre offset is not a problem, the DC for each differential output is equal (+1.65V) so the headphone/transformer will see 0V.
You are right, sorry. I confused ES with AK. ES have no DC-offset between (+) and (-). Well, you can try your headphones directly, but my DT-880 (250Ohm) sounds very poor from the raw output of ES9018S (one channel or two speakers in parallel - no mater). Additional amplifier is needed, right.
yes, wasnt a very good sound.
The trafo alone sounds nice and pure with high sensitivity headphone, but otherwise there is no substitute for the amp.
I received a second pair of transformers a while ago - they are used in the same CD player but apparently wound with a differnt wire - I undesrand it is something vintage - anyway, I did not have any expectation - after all - just a differnt wire - but the same transformer for the same DAC chip.
But when I connected those I immediately noticed a change - even more smooth sound (though the previous model already sounded smooth and - like written above - so much more musical than any opamp I had tried) and even greater clarity. So I certainly do not regret ordering another set of transformers - now if only I used less DACs regularly....lol.
But when I connected those I immediately noticed a change - even more smooth sound (though the previous model already sounded smooth and - like written above - so much more musical than any opamp I had tried) and even greater clarity. So I certainly do not regret ordering another set of transformers - now if only I used less DACs regularly....lol.
I am working on two different dac projects.
One is using a PCM1794 in dual mono mode
Other is the IanCanada ES9038Q2M dac, also in dual mono.
I think the PCM1794 will output 15.6 ma peak to peak, and the ES9038 about 1/2 of that, 7.7 ma p2p.
Wondering if I would be able to use the same iv transformer for both DACs, changing the resistor to get the appropriate output levels?
Looking at your first post, seems like it should be fine.
Would this approach make any compromises, vs a transformer just designed for one of these dacs? (or do you have one design that covers all current out dacs?)
Randy
One is using a PCM1794 in dual mono mode
Other is the IanCanada ES9038Q2M dac, also in dual mono.
I think the PCM1794 will output 15.6 ma peak to peak, and the ES9038 about 1/2 of that, 7.7 ma p2p.
Wondering if I would be able to use the same iv transformer for both DACs, changing the resistor to get the appropriate output levels?
Looking at your first post, seems like it should be fine.
Would this approach make any compromises, vs a transformer just designed for one of these dacs? (or do you have one design that covers all current out dacs?)
Randy
Hi Randy,
Yes it is possible to use the same transformer for both of your DACs. And yes it is possible to cover many of current DACs by one 0.5+0.5:2+2 version. Except of TDA1541 (if there is no anti-DC-bias circuit).
Regarding PCM1794. I have sound card Asus Essence STX on 1792:
Yes it is possible to use the same transformer for both of your DACs. And yes it is possible to cover many of current DACs by one 0.5+0.5:2+2 version. Except of TDA1541 (if there is no anti-DC-bias circuit).
Regarding PCM1794. I have sound card Asus Essence STX on 1792:
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