[PatOMalley]

That would be the case if that resistor was really 75ohms but in reality on ourt machines it is a 100ohm resistor.

It seems Michael is mistaken about what is really on his board. That can happen.

Also there are no caps between my transformer and my RCAs. The caps are on the other side of the transformer.

It goes like this..

stock
75ohm cable => RCA => switch => .01uF cap => 100ohm resistor => IC

Mine
75ohm cable => RCA => 75||110 transformer => switch => 100ohm resistor => IC

I am going to at least remove the switch from the path and run some line from the 110 tap to the trace right before the 100ohm resistor. Possibly connect a 10ohm resistor to bring the load up to ~110.

that picture looks to be an example of how to implement not 'what is".

In any event a 75/75 trans is not a match, a 110/110trans is not a match. A 75/110 trans is a very close match.

but maybe the small impedance mismatch is meaningless and a 75/75 or 110/110 is just fine. but the stuff I have been reading says that matching the resistance allows for a better transmission line and if our attempt with all this is to reduce jitter then that matching is part of the playbook. - only my opinion.

"In order to let it work correctly with a transformer a 75R resistor needs to be added between pin 1 and 2 of th" ... not if you use a 75 to 110 ohm transformer. when you say "won't work", I think that is incorrect. It will work in several load configurations, just not optimally. I mean, mine is working great!

I know I am starting to get strident on the issue but I just wanted to plead the case for load matching and why the LL1574 might be a good thing. Anyway I am done being a nut over the issue with this post.

Quote:

Originally Posted by rhodes54 /img/forum/go_quote.gif Pat, I had contact with Michael today and he gave us the answer on our questions regarding the transformer on the coaxial input by sending me one simple picture: There's only one question not answered after looking at this picture, which Michael gave us: The 100R resistor is used to let the 26C32 work. This means that the coaxial input is not terminated in the current design. In order to let it work correctly with a transformer a 75R resistor needs to be added between pin 1 and 2 of the 26C32 (see picture). Or in other words: between pin 3 and 4 of the transformer. Thanks again Michael @ Teradak for your help!

 

[PatOMalley]

rhodes,

there are two sets of holes you can use for the caps. I went right back into the ones the caps were originally in but there is another set hardby. If you remove the caps and use that second inner set then the circuit is left open by the empty hole..

In this picture you can see the jumpers gout out to the outer holes. You can also see the inner holes under the jumper. You gotta use those outer holes.

Quote:

Originally Posted by rhodes54 /img/forum/go_quote.gif I removed the Russian 0.01uF filmcaps tonight and changed them for Vishay (ERO) MKP 1837's of the same value. From what I heard so far (it's on for an hour or so) is that the sound is 'cleaner' than before. Less grainy highs and the bass seems less boomy and even a bit tighter. So far it seems another nice $1,- upgrade but I will listen to it for a few days first, then switch back to the russian filmcaps to see if I was really right. If you have them at hand, just try them. I'm curious if other people experience the same. b.t.w. I tried to bypass them completely like you did but that didn't work in my DAC: It didn't lock anymore and the sound was gone on both inputs.

 

[primetecpromo]

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[PatOMalley]

I removed the jumpers and tried to go straight from the transformer to the trace before the 100ohm resistor but lost both channels like you did. I mocked it up in several ways but best I could et at a certain point was a flashing green, in and out on locking.

Apparently I had lost a pad. Finally, after all the heat in repairing it all I lost the smd resistor so I replaced it with a NOS ~1970 Dale[?] Vishay, jumpers back in place. The only difference is from the previous is the resistor change.

By a freak that timbre has taken small shift to the meaty side of things, a lucky benefit of a comedy of errors.

In part of this I tried to add a 10ohm resistor to bring the load up to 110 but it would not lock under that condition. Circuit must be temperamental to having a 100ohms. So if you tap a 75ohm in the path and loose locking maybe taking it out will restore it.

I will post pictures of how I sat the standard resistor later.


Quote:

Originally Posted by rhodes54 /img/forum/go_quote.gif I removed the Russian 0.01uF filmcaps tonight and changed them for Vishay (ERO) MKP 1837's of the same value. From what I heard so far (it's on for an hour or so) is that the sound is 'cleaner' than before. Less grainy highs and the bass seems less boomy and even a bit tighter. So far it seems another nice $1,- upgrade but I will listen to it for a few days first, then switch back to the russian filmcaps to see if I was really right. If you have them at hand, just try them. I'm curious if other people experience the same. b.t.w. I tried to bypass them completely like you did but that didn't work in my DAC: It didn't lock anymore and the sound was gone on both inputs.

 

[PatOMalley]

Here is a picture of the Vishay taking the place of the SMD 100ohm resistor

This board is a real battleground.

If you want to know, the Vishay sound better.

And the Lunadhl transformer wired direct to the 100ohm resistor which takes the coax/optical switch and traces out of play.

 

[r8833]

Rhodes54,

I just replaced the russian .01uf input caps to the Vishay MKP1837's and I am hearing a clearer sound too. ..more snap and faster sound ..the russian caps are sluggish compared to the MKP's.

Rich

 

[tubes]

Thanks to Pat, I just installed a PE-65612 Pulse Transformer in my Teradak, I used some thin solid core what appears to be silver wire to connect it to the board. The only other change I've made to this particular dac is to bypass the coupling caps with the .22 Obligotos. To be brief, the improvements were not small in my system, rather than describe the improvements let me just say it sounds like a new dac, more transparant, more detail, more dynamic, more of everything. The only downside I hear so far with this transformer is a slight hardness and a little bloating in the bass but not enough of a problem to prevent me from enjoying what I hear.

I've only had this transformer in my dac for a day but unless things go downhill with break in I don't think I'll change my opinion of the improvements that I hear. From what I understand this transformer is bettered by the Lundahl Pat is using, if you are sitting on the fence trying to decide if you want to try a transformer all I can say is that in my system it's a no brainer. I've seen these on Ebay for $1.99 shipped, so give it a go, not much to lose. Again, thanks to Pat for jumping into this transformer thing head-first, the Lundahl will be up next.

 

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[r8833]

tubes,


another transformer to try is the scientific conversions sc944-05..highly recommended at 16.00 each..they will sell samples

Scientific Conversion, Inc. - Transformers and Inductors


Rich

 

[PatOMalley]

I have the original PE-65612 Pulse Transformer that I pulled from the DAC when I installed the Luindahl

Let me know who wants it. They are cheap to get but you can have this one for free shipping on me.

Of all the mods I've done this one is way way up there.

 

[awkwardbydesign]

A sideways question; has anyone tried Valab's solid core digital cable? The one Kevin sells for $80. I can't afford to keep buying lots of different cables, the DC-30, the Lundahl, and various caps have nearly cleaned me out.
Richard.

 

[PatOMalley]

I am going to get that cable.
I know that switching to a DIY mostly threaded silver on copper cable made a difference. Solid core should be better.


Quote:

Originally Posted by awkwardbydesign /img/forum/go_quote.gif A sideways question; has anyone tried Valab's solid core digital cable? The one Kevin sells for $80. I can't afford to keep buying lots of different cables, the DC-30, the Lundahl, and various caps have nearly cleaned me out. Richard.

 

[Bill Allen]

Guys-

Make your own Coax digital cable using the best wire on the planet. Buy it by the foot from VH Audio, all there stuff is top of the line, I use their silver wire exclusively.

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[r8833]

on the low end of the scale I made a digital cable using a sata cable. just cut the ends off and solder some rca's . Not too bad for $5.00

 

[dannie01]

Sorry, deleted.