Experience with this DIY DAC ?

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legarem

legarem

Member
Joined 2005
legarem said:


Why asking for a bigger core ?
Click to expand...


I repeat

The Lundahl don't lack any bass. This is due to breaking time

I bought 5 pairs of LL1690 and compared new ones with old ones that had breaking time.

The sound is REALLY NOT the same. I have two dacs side by side so the swich was easy and fast.

Never talk to me that this psycoacoustic related difference when you can do right comparaison.

Ask to Per Lundahl about Breaking time and he will tell you that amorphous core take a long tome to be settled correctly.
 
Franz Gysi

Franz Gysi

Member
Joined 2007
Disregarding my Lundahls are just 48h burned in (pink noise at 0 dB and Music), I continued to experiment with it (I had to postpone the comparison session, planned for today).

I attached the input filter like showed in posting #299 by legarem.

And it filters to much for my taste. It is like a curtain between the music and me.

My ears are 53 years old and they have a natural roll off over 13kHz.

Maybe, thats why I dont need additional filtering? Why I prefer phase accuracy?

The output filter is O.K. for me.

Now, I have the answer, why bigger cores are theoretically better for the bass (the Digitecs are still better in this regards):

Must be lower distortion.

Franz
 
johnm

johnm

Member
Joined 2003
Is it worth putting 50k load on the outputs of each Digitec? I am currently using them with no load/filter at all, and I have to say they sound fantastic... the best qualification I can give is that I am not missing my turntable at all... The dynamics on good recordings are astounding through this DAC/Digitecs - I have actually jumped several times it sounds so realistic. This has NEVER happened before :)

I am using a KingRex Pre, and unfortunately cannot find what the input impedence is on the internet:

http://www.kingrex.co.uk/preamp.html

Am I OK using these digitecs without a load resister into this pre-amp?

- John
 
legarem

legarem

Member
Joined 2005
johnm said:
Is it worth putting 50k load on the outputs of each Digitec? I am currently using them with no load/filter at all, and I have to say they sound fantastic... the best qualification I can give is that I am not missing my turntable at all... The dynamics on good recordings are astounding through this DAC/Digitecs - I have actually jumped several times it sounds so realistic. This has NEVER happened before :)

I am using a KingRex Pre, and unfortunately cannot find what the input impedence is on the internet:

http://www.kingrex.co.uk/preamp.html

Am I OK using these digitecs without a load resister into this pre-amp?

- John
Click to expand...

There is a load at the input of your preamplifier. You can check it with an ohmeter.

To load correctly the transformers, I use a signal generator that feed the transformer primary. I connect a scope on the secondary and look at the square wave at 20 khz. I load the secondary to get the best square wave.

Many transformers when not enough loaded shows ringing at 20 khz.
 
legarem

legarem

Member
Joined 2005
johnm said:
Thanks for your reply.

I don't have a signal generator, only a digital multimeter. How would I go about measuring the input impendence then?

Many thanks.
Click to expand...

Turn off your preamplifier. Place the selector swich in a position (ex: cd)

Measure the resistance at the input selected. (RCA jack center pin and outer pin) on one channel.

I suspect that it is low on this kind of preamplifier (10-25 K)
 
johnm

johnm

Member
Joined 2003
hmmm I'm not getting any resistance reading at all :eek:

I know the pre-amp has two inputs, and either one is selected automatically via a relay, when there is a signal present at either set of inputs. I suspect with nothing plugged in the input is switched off? Tried both pairs of phonos and 0-ohms each.

Any tricks I can try to get a reading?

Many thanks,

- John
 
Franz Gysi

Franz Gysi

Member
Joined 2007
John

Why do you want to know the input imp of your pre amp?

Because you want to know, if some additional loading of the trannie is an advantage.

So, why don't you just attach a 10k resistor in parallel with the secondaries and listen, if you hear a difference?

Just try, no risk at all!

BTW: it is not very friendly from your preamp producer, not to publish the input impedance. Did you ask the supplier?

Imho an essential parameter for a pre amp, input and also output impedance should be documented.

Regards
Franz
 
S

surfstu

Member
Joined 2008
which 'big' dac?

hi, I am newbie round here but a brief read of this thread has convinced me that this is the dac for me.... I was hoping for some wisdom as there appears to be several similar 'big' dacs on ebay. I have posted links to the two I'm watching as was hoping someone could shed some light on them as neither dac seems to be exactly the same as the pic at the beginning of this thread...


http://cgi.ebay.co.uk/NEW-BIG-24bit...hash=item140314682026&_trksid=p3286.m63.l1177

this dac has 4 large capacitors which i assume are part of the psu?

this dac has the dir9001 included? what does this do?


http://cgi.ebay.co.uk/NEW-BIG-24bit...3286.c0.m14&_trkparms=66:2|65:1|39:1|240:1318

this dac has 5 large capacitors and fewer small capacitors

this dac seems to come with an optional extra of a dir9001? do i need it?

also.... any advice on transformers? should i buy the kit with the toroidal included or will it be cheaper/ better for me to make that purchase seperatley here in the UK?

thanks in advance for any tips...

stuart
 
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