data said:Hay, Bill...
I measured the transformers like you suggested, and I got a reading of 2.5Mohms in one direction and .47Mohms in the other direction
Oooh, that cant be right. You mean one winding reads 2.5 megohms and the other reads .47 megohms? I can't even imagine how much wire that would take to wind on a core. Check your meter by measuring some known resistances, then check your connections and try again.
I cant think of any other explanation that would make sense, unless you dont have the right pair of wires for each winding.
Bill
Sumlink ST-DV709 Digtal Audio isolation transformer
The new board does not have the Sumlink ST-DV709 Digtal Audio isolation transformer, is that going to be an issue I read way back in the thread that it basically renders the S/PDIF inputs weak, I have contacted the seller and she will supply one for $30!! but I can pick them up for under $10 delivered.
what does it do ? will I need it and if so how and where does it go on the new board.
And is there better ones.
Thanks
The new board does not have the Sumlink ST-DV709 Digtal Audio isolation transformer, is that going to be an issue I read way back in the thread that it basically renders the S/PDIF inputs weak, I have contacted the seller and she will supply one for $30!! but I can pick them up for under $10 delivered.
what does it do ? will I need it and if so how and where does it go on the new board.
And is there better ones.
Thanks
data said:Checked all the connections on these and they are unsuitable for this application, looks like I need some transformers again
Did anybody try the EDCOR transformers? how are they?
I'm looking at these trannies as well, I contacted the company and its $13.50 shipping or two XSM's to Australia via USPS Flat Rate, not sure if they are any good though.
crazyfrog said:
I don't have any A20s, but if they are 500 or 600 ohm 1/1 trafos suitable for output use, then there really is no "right" secondary setup in that they do not need a load to work properly, contrary to some people's belief. I have read up on the subject since starting my experimentations by going to various manufacturer's websites.
Incidentally, the primary filter arrangement is for the chip output and really has no influence on trafo operation.
Feel free to use your ears for the sole judgement.
Best, Bill
utc a-20
Yes Bill, they're output transformers 1/1 and can be set at 500-333-200-125-50 / idem for sec. Since I can "play" with these values that's what I'm going to do. And you're probably right about the need for stuff at the secondary. But even I'm no expert I heard the "ringing effect" ( if it's significant) can be improved.
Thanks
Yes Bill, they're output transformers 1/1 and can be set at 500-333-200-125-50 / idem for sec. Since I can "play" with these values that's what I'm going to do. And you're probably right about the need for stuff at the secondary. But even I'm no expert I heard the "ringing effect" ( if it's significant) can be improved.
Thanks
Does it list a max dbm or dbv number for them. They are apparently the "swiss army knife" of the older broadcast equipment, I've seen them used on both ends of equipment.
Don't get stuck on the impedance numbers, the real impedance is related directly to the load they see. In a 1/1 setup the load on the secondary is reflected through the core to the primary. The rating, be it 150 or 600 is the max load that the transformer will operate into with the rated distortion numbers. An easier load such as 10k gives it a lot more headroom.
Don't get stuck on the impedance numbers, the real impedance is related directly to the load they see. In a 1/1 setup the load on the secondary is reflected through the core to the primary. The rating, be it 150 or 600 is the max load that the transformer will operate into with the rated distortion numbers. An easier load such as 10k gives it a lot more headroom.
Re: utc a-20
I have a pair of UTC HA-108 which have the same specs as A-20. After many tryings, I use the 500 ohms primary and secondary taps. With a scope, I looked at the square waves and can tell you that the UTC I have don't ring a lot so I tried many secondary loads. The best square waves I got were near 680 ohms at the secondary.
With that setup, the sound is simply marvelous. Authority with unagressive sound. The battle with the best transformers is between the Lundahl LL1690 and the UTC HA-108. HA-108 are beefy and are terrific in the bass. As I have to decide which one is the best I could say that the Lundahl are champion for unagressive detailed sound but the UTC HA-108 wins in the bass region and with a huge soundstage. I will surely keep both UTC and Lundahls. The Tamura is still one of the best for the price.
crazyfrog said:
I have a pair of UTC HA-108 which have the same specs as A-20. After many tryings, I use the 500 ohms primary and secondary taps. With a scope, I looked at the square waves and can tell you that the UTC I have don't ring a lot so I tried many secondary loads. The best square waves I got were near 680 ohms at the secondary.
With that setup, the sound is simply marvelous. Authority with unagressive sound. The battle with the best transformers is between the Lundahl LL1690 and the UTC HA-108. HA-108 are beefy and are terrific in the bass. As I have to decide which one is the best I could say that the Lundahl are champion for unagressive detailed sound but the UTC HA-108 wins in the bass region and with a huge soundstage. I will surely keep both UTC and Lundahls. The Tamura is still one of the best for the price.
brianco said:
That's around 4V RMS into a 500 ohm load so you have tons of headroom.
The A22s I bought were Real NOS so I'm running them in for a while, but they lack nothing except half of the bottom octave. Maybe they'll get better, maybe not, time will tell. They didn't ring much either. They immediately kicked the cheap Jensen JT-123s butts in every respect.
Many thanks for advice.
My UTCs have reached Scotland - I have had to pay about $30 import charges!!
There are probably many kicking around here neglected and not likely to be used again - but it is the finding of them!!!! That is where the great on line auctioneer is indispensable!!
What is interesting is that the UTC a-20 Txs on my factory specs, starts to roll off at at around 30+K with -1Db at 100K. THat is pretty good! Some others such as the A-10 start downward as low as 7K with -2Db at 20K.
I will scan these and post the graphs and the specs later today - they may help in choice making for those in search of such things.
My UTCs have reached Scotland - I have had to pay about $30 import charges!!
There are probably many kicking around here neglected and not likely to be used again - but it is the finding of them!!!! That is where the great on line auctioneer is indispensable!!
What is interesting is that the UTC a-20 Txs on my factory specs, starts to roll off at at around 30+K with -1Db at 100K. THat is pretty good! Some others such as the A-10 start downward as low as 7K with -2Db at 20K.
I will scan these and post the graphs and the specs later today - they may help in choice making for those in search of such things.
low pass filter
I'm a little puzzled...When Bill write:
"You can try doubling the primary Rs to around 500 and halving the cap to around 1000pf. Some, including me, found slightly fuller bass"
That makes a 159 kHz filter.
But Legarem uses a different setup:
"On the transformer primary, I just use 220 ohms Allen Bradley carbon composition resistors (old stuff) The cap I use is 7 nF (7000 pF)
This gives a low pass filter of 51.68 khz at -3 db"
We're talking about the same DAC here...
I'm a little puzzled...When Bill write:
"You can try doubling the primary Rs to around 500 and halving the cap to around 1000pf. Some, including me, found slightly fuller bass"
That makes a 159 kHz filter.
But Legarem uses a different setup:
"On the transformer primary, I just use 220 ohms Allen Bradley carbon composition resistors (old stuff) The cap I use is 7 nF (7000 pF)
This gives a low pass filter of 51.68 khz at -3 db"
We're talking about the same DAC here...