Is a MKP an MKP is an MKP &c.
I'd like to limit my orders for this project to only 3 or 4 places. So I wanted to order the capacitors from Digikey. They have many flavors of MKP's (none of them Wima way too many to list
They also have Tantalum caps
Microtan
Supertans ST
Supertan ste etc (too many to list)
Just go with V rating and uF rating and possibly operating temp. ?
What should a poor boy do?
Thanks Paul
I'd like to limit my orders for this project to only 3 or 4 places. So I wanted to order the capacitors from Digikey. They have many flavors of MKP's (none of them Wima way too many to list
They also have Tantalum caps
Microtan
Supertans ST
Supertan ste etc (too many to list)
Just go with V rating and uF rating and possibly operating temp. ?
What should a poor boy do?
Thanks Paul
What about using a srpp 6sn7 as i/v with a resistor
check this url http://www.analogmetric.com/goods.php?id=89
Any advice ?
check this url http://www.analogmetric.com/goods.php?id=89
Any advice ?
If you use opamps, I think (I hope...) the following circuit is reversed accordingly, to avoid problems.
If you plan to bypass opamps and use transformers, or tube output, then you'll have to take care of it.
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Well the Gigaworks arrived, and no sound!
My Shigaclone is feeding it just over 1 volt (DC)
I see there is place for a switch to choose between inputs. It is labelled: OPT SB COAX.
The way it is now there is a connector between OPT and SB (The COAX metal prong in visible.
Not wanting to harm it before I listen to it even once! I'll ask here.
I should move the connector over to the SB and COAX?
Thanks,
Paul
My Shigaclone is feeding it just over 1 volt (DC)
I see there is place for a switch to choose between inputs. It is labelled: OPT SB COAX.
The way it is now there is a connector between OPT and SB (The COAX metal prong in visible.
Not wanting to harm it before I listen to it even once! I'll ask here.
I should move the connector over to the SB and COAX?
Thanks,
Paul
replacing smd caps
I wanted to replace some of the caps on the curcuit board with better caps
(a'la lampucera mods). But the larger (still very small) electrolytic caps have a plastic base and can't really get at them.
How do you get those originals out- use a hot sewing pin for a soldering iron?
I don't have a micro heat gun as I saw on the internet. Even then I'd think I'd remove several adjacent components if you used one.
Thanks,
Paul
I wanted to replace some of the caps on the curcuit board with better caps
(a'la lampucera mods). But the larger (still very small) electrolytic caps have a plastic base and can't really get at them.
How do you get those originals out- use a hot sewing pin for a soldering iron?
I don't have a micro heat gun as I saw on the internet. Even then I'd think I'd remove several adjacent components if you used one.
Thanks,
Paul
Ok, yesterday bypassed most of the small smd's with MKP's, removed most of the electrolytics and replaced with pansonic FC's. I found that holding down the plastic base for the electrolytic and shimmying the electrolytic prevented me from ruining the traces. I have this built into the base of my shigaclone. In that thread, mostly people step down the output of the shigaclone by using a resistor network from the D OUT and Grnd. I am getting just over 1.1 volts when playing -20 dB pink noise with no resistor network. I am happy with this sound now ( havent tried the other op amps yet etc.) but am wondering if this level of input is hard on the dac? Can't seem to find what the maximum level input is for this dac Thanks for your help Paul
Very happy with the sound! Still using the stock opamps.
I am getting low level hum that is still there when the shigaclone is unplugged, and only comes on when the DAC is plugged in.
Quite audible when no music is playing, barely hearable on quiet passages.
Also on my stepped vol. control (Audible illusions) there is a quiet "pop" whenever I adjust the vol.
I'm using the supplied interconnect to phono jack which I shortened to 3".
Any suggestions?
Thanks,
Paul
I am getting low level hum that is still there when the shigaclone is unplugged, and only comes on when the DAC is plugged in.
Quite audible when no music is playing, barely hearable on quiet passages.
Also on my stepped vol. control (Audible illusions) there is a quiet "pop" whenever I adjust the vol.
I'm using the supplied interconnect to phono jack which I shortened to 3".
Any suggestions?
Thanks,
Paul
Are you using the coax input or optical? If coax, see if the hum still exists when you disconnect the input. On mine, I get a very quiet buzz when the coax is connected and absolute silence when it's disconnected. I know the coax creates a ground loop in my house and i'm surprised the problem wasn't worse. With mine, I know I can fix it by using a pulse transformer on the coax input, so it hasn't bothered me. Also, I can't hear it unless the amp is turned right up and no music is playing which is rare.
On the volume control, I suspect the 'pop' is being created by your volume control unit. My DAC goes straight into one of gigawork's stepped attenuators and there is no 'pop' when I turn that.
Hi All
Excellent thread - so good that I have just this minute ordered a DAC (perhaps you should all get a cut from Gigaworks !).
Anyway, after reading (rather quickly I admit) there seems to be some talk that the standard components are not the very best. And that there may be some connections on the pcb that are questionable?, specifically there was some mention of inverted inputs to one of the op-amps ?
Has anyone considered a 'best practise' for the mods for this DAC ? perhaps it could be in two stages ?
1. The DAC using the original design.
2. More substantial mods - ie. transformer/valve o/p stages ?
Now just have to wait the few weeks (hopefully) for the kit to arrive !
Graham
Excellent thread - so good that I have just this minute ordered a DAC (perhaps you should all get a cut from Gigaworks !).
Anyway, after reading (rather quickly I admit) there seems to be some talk that the standard components are not the very best. And that there may be some connections on the pcb that are questionable?, specifically there was some mention of inverted inputs to one of the op-amps ?
Has anyone considered a 'best practise' for the mods for this DAC ? perhaps it could be in two stages ?
1. The DAC using the original design.
2. More substantial mods - ie. transformer/valve o/p stages ?
Now just have to wait the few weeks (hopefully) for the kit to arrive !
Graham
Just a little extra info.
Running coax.
The shigaclone and dac are in a wooden box mounted on granite.
Neither has any wire connected to safety ground. Not from laser sled mechanism, nor any of the boards.
I've read in threads for the shigaclone on star grounding the case (not necessary for me) but haven't read anything about grounding for the DAC.
The gigaworks DAC comes with a electrical jack that doesn't have a ground wire.
Should I be connecting something to the ground on the elecrical cord?
Wheres the best place if so?
Thanks Paul
Running coax.
The shigaclone and dac are in a wooden box mounted on granite.
Neither has any wire connected to safety ground. Not from laser sled mechanism, nor any of the boards.
I've read in threads for the shigaclone on star grounding the case (not necessary for me) but haven't read anything about grounding for the DAC.
The gigaworks DAC comes with a electrical jack that doesn't have a ground wire.
Should I be connecting something to the ground on the elecrical cord?
Wheres the best place if so?
Thanks Paul
Mine's also in a wooden box, but that doesn't stop the coax connection from causing noise in the DAC. In my case I'm pretty sure it's due to a ground loop simply because I know the loop exists - it's entirely possible the problem is some other noise on the coax cable (which is ~20m long).
I'm reasonably sure the ground in the gigawork DAC isn't connected to the ground on the outputs, but suspect there are some tracks running parallel to the coax ground in my DAC. Hence the noise would be induced from coax to my output. All suspicions of course until I put the pulse transformer in.
If you suspect a ground loop, put the DAC, shigaclone and your amp close together, then using short cables, connect the coax ground in the shigaclone, the coax ground in the DAC, the output ground in the DAC and the input ground on the amp together. Then connect it all to the ground in the same powerpoint your pre/amp share. If the noise goes away, you have a grounding problem.
I don't think there is a list of 'best practice' per say, but there seem to have been a few good ideas. It seems basically that the output stage is the weakest link, so completely swapping it for either an Xformer or tubes will probably give the greatest improvement. I was recently shown this 'universal' tube output that seems like a simple, low risk option and there are recommendations for specific (Lundorf?) transformers in this thread.
I've seen options and opinions on other mods to this DAC, but most are minor mods until you eventually attack the output stage. I'd say the 'essential' and simple mods are to replace the opamps, possibly put in better filtering in the power supply and perhaps a pulse transformer for people using coax. In general I fear the quality of most parts but at the same time I don't expect cheap parts on the input side will cause major harm.
Also, I think the talk of inverted input to the opamps was resolved. The thread's too long for me to find the answer though...
Thanks for that MellowFellow
I will just use it as supplied for a few months to get used to it's sound - and then think about modifying it.
Most likely when I have finished fitting this into a compact box (current candidate is a Sun external tape drive enclosure) I will have added a couple of analogue inputs, two more digital inputs into a Pass Labs B1 buffer with either a Gigawork stepped attenuator or ALPS pot.
With the B1 buffer board I may well be able to do without some/all of the op-amps in the output stage, I haven't yet had a chance to do any proper thinking about it.
Interesting what you say about the general quality of the components, makes you wonder just what is inside some of them. I bought a couple of Naim clone boards and the supplied o/p transistors looked fine but the pins were so brittle that I seriously doubted their authenticity - they are still working though (listening to the amp now !).
Can you explain the benefits to the pulse transformer idea for co-ax ?,and I did find the bit about inverted connections - it does indeed looks like a red herring.
Thanks
Graham
A pulse transformer simply provides electrical isolation for the coax input, stopping any possible grounding problems from being transferred over the coax cable. It's reasonably common when connecting a DAC to a PC to create a ground loop (PCs often have poor grounding) and sticking a $2 pulse transformer inline is an easy fix. A common way to source suitable parts is to rip one off an old ethernet card as most ethernet cards use pulse transformers to stop grounding problems arising via network cables. Your shiga is probably better than a PC, but when you use the word "hum" to describe a problem, I immediately think of grounding issues.
In case you're not really familiar with the problem solved by this mod... Although "ground" is supposed to be basically an infinite sink for voltage, there is often a difference in the level of the "ground" seen by different devices. This means when the two devices are connected to each other (eg, via a coax) the "ground" from one leaks into the other, generally manifesting itself as a 50/60Hz hum.
Right, got it - the transformer is primarily used to isolate the DC parts of the circuit and allow the AC signal through - as in telephone lines.
The schematic from a previous post certainly shows a transformer in circuit so it can be necessary, probably even desirable. I have looked at the DAC images and there is no obvious transformer on the board.
I haven't (yet) got a hum problem as my DAC is still en-route from China-land !
Thanks
Graham
The schematic from a previous post certainly shows a transformer in circuit so it can be necessary, probably even desirable. I have looked at the DAC images and there is no obvious transformer on the board.
I haven't (yet) got a hum problem as my DAC is still en-route from China-land !
Thanks
Graham
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You don't !!!!!!!
If you have a metal case then the mains earth connection is fixed to this using a screw/locknut/earth tag/star washer/nut.
This is a safety earth - it is not the audio ground return - keep them separate unles you want some nice earth loops !
Graham
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