Be aware that Zout will be a tad on the high side when using only a 1:1 transformer out.
If we take Legarems circuit as example Zout will be 118(dacout)+1k(ser.res)+1k(ser.res)+150+150(primdcr)+150+150(secdcr)//40k(resload)=2.7kohm
Without series resistors(we can probably do that as the LL1690 should be ca 1k at 2Hz and the datasheet says min 1k AC-load), Zout is just above 700ohms.
To get a lower Zout with seriesresistors one could go for 2:1 and this gives us just above .9kohms with 1k and .5kohms with 220ohm series-resistors. If we skip the resistors we are down to ca 400ohms. The output will still be above 1Vrms.
Another, but far more complicated, way to do it, is to feed the DAC signal without caps to a differential tube(ex. 6H30) stage loaded with a 1689/PP Lundahl connected 9 or 18:1. This way Zout will be extremely low. It will probably also sound much better than using a cathode-follower. And it is completely capacitor-free.............
If we take Legarems circuit as example Zout will be 118(dacout)+1k(ser.res)+1k(ser.res)+150+150(primdcr)+150+150(secdcr)//40k(resload)=2.7kohm
Without series resistors(we can probably do that as the LL1690 should be ca 1k at 2Hz and the datasheet says min 1k AC-load), Zout is just above 700ohms.
To get a lower Zout with seriesresistors one could go for 2:1 and this gives us just above .9kohms with 1k and .5kohms with 220ohm series-resistors. If we skip the resistors we are down to ca 400ohms. The output will still be above 1Vrms.
Another, but far more complicated, way to do it, is to feed the DAC signal without caps to a differential tube(ex. 6H30) stage loaded with a 1689/PP Lundahl connected 9 or 18:1. This way Zout will be extremely low. It will probably also sound much better than using a cathode-follower. And it is completely capacitor-free.............
Something like this. Output will be in the ballpark of 0dBU. By connecting the LL1689 9:1, output will be 6dB higher. R4 to be choosen for optimal loading of the chip. R2 shows Zout and should be of a lot higher value or omitted.
An externally hosted image should be here but it was not working when we last tested it.
These UTC A-43 transformers might be worth a try:
Ebay New UTC A-43 transformers (x16) $49!!!!!
The max level is +15dB which isn't ideal, but they are very cheap so probably worth a play.
I ordered a batch
Ebay New UTC A-43 transformers (x16) $49!!!!!
The max level is +15dB which isn't ideal, but they are very cheap so probably worth a play.
I ordered a batch
suggestion?
Hi. I'm new in this group. Someone I know bought a pair of Digitec transfos and told me about this thread. Since I was looking a good DAC kit or something to improve the "digital side" of my audio stuff, I read with interest several posts here...
So I began to look for LOT and found some...Jensen are too expensive (so are the new Tamura) and others are very big to fit in a "regular" space like Tamura GA80080, UTC HA-108 or old Triad.
Lundhal is interesting and also Sowter:
http://www.sowter.co.uk/specs/5069.htm
and also:
http://www.sowter.co.uk/pdf/3603.pdf
with the OCC wire option:
http://www.sowter.co.uk/occ.php
But someone knows about that one?
http://www.altrancorp.com/audio_transformers.asp?id=45
Hi. I'm new in this group. Someone I know bought a pair of Digitec transfos and told me about this thread. Since I was looking a good DAC kit or something to improve the "digital side" of my audio stuff, I read with interest several posts here...
So I began to look for LOT and found some...Jensen are too expensive (so are the new Tamura) and others are very big to fit in a "regular" space like Tamura GA80080, UTC HA-108 or old Triad.
Lundhal is interesting and also Sowter:
http://www.sowter.co.uk/specs/5069.htm
and also:
http://www.sowter.co.uk/pdf/3603.pdf
with the OCC wire option:
http://www.sowter.co.uk/occ.php
But someone knows about that one?
http://www.altrancorp.com/audio_transformers.asp?id=45
The LL1690 has an open impedance of ca 10k and should be a good candidate.
I talked to Per Lundahl and he recommended to always use his transformers with seriesconnected primaries.
It could then be used with its primary windings in series w/o series resistors and will then have a Zout of a rather high 718 ohms when connected 1:1.
If a lower Zout is needed one could connect it 2:1 to get a Zout of 405 ohms.
I talked to Per Lundahl and he recommended to always use his transformers with seriesconnected primaries.
It could then be used with its primary windings in series w/o series resistors and will then have a Zout of a rather high 718 ohms when connected 1:1.
If a lower Zout is needed one could connect it 2:1 to get a Zout of 405 ohms.
Solved! Just mounted the digitec transformers and... I can make an hand shake with Peter Gabriel at my home!!
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Piero
Did you have a look at post #306 how to connect the trannies in correct phase?
And I really recommend for safety reasons to insert two 10 to 33 Ohm resistors in series with the primaries.
Remember, the Digitec's have very low DC resistance and we don't know, if the CS4398 does like this over time.
With this resistors, you have a higher DC resistance for the price of a very little bit lower level.
Franz
Did you have a look at post #306 how to connect the trannies in correct phase?
And I really recommend for safety reasons to insert two 10 to 33 Ohm resistors in series with the primaries.
Remember, the Digitec's have very low DC resistance and we don't know, if the CS4398 does like this over time.
With this resistors, you have a higher DC resistance for the price of a very little bit lower level.
Franz
Franz Gysi said:
I'll add the two resistors soon, I was just testing it.
Franz, I did not noticed it, but why the left channel has the input inverted and the right not?
Note: I have the digitec trannies not the studer,
An externally hosted image should be here but it was not working when we last tested it.
