Rosendorfer:
WhEn you ran Legato to your transformers were the caps in the circuit?
I built a second Legato w/o caps. I jumpered the C5-C8 positions and then went to my Onetics for balanced to SE. Volume with greatly reduced and sound was muffled.
On my first board with caps in place everything sounds fantastic with the Onetics.
Thanks
Bob
WhEn you ran Legato to your transformers were the caps in the circuit?
I built a second Legato w/o caps. I jumpered the C5-C8 positions and then went to my Onetics for balanced to SE. Volume with greatly reduced and sound was muffled.
On my first board with caps in place everything sounds fantastic with the Onetics.
Thanks
Bob
Hi
I am no expert on transformers and transformer coupling, but my understanding is that transformers do not like to see a lot of DC, as this saturates their cores and causes problems. The Legato has a lot of DC from + to G and - to G, and it may be that this makes transformer coupling alone impractical. Perhaps a real transformer expert might be able to comment on this?
I am no expert on transformers and transformer coupling, but my understanding is that transformers do not like to see a lot of DC, as this saturates their cores and causes problems. The Legato has a lot of DC from + to G and - to G, and it may be that this makes transformer coupling alone impractical. Perhaps a real transformer expert might be able to comment on this?
I am
running Mundorf zNs Film/Foils, mounted vertically on small boards, the output of the zNs goes straight to the XLR jacks, and I mounted the drain resistors on the XLRs. Sound is great, but I never tried the OE electrolytics. I just assumed a good film/foil cap would be more transparent.
Right now I am playing with power supplies a little for the Legato. Tried using a single Placid just as a regulator with a separate rectifier/filter board (CRCRC, R47/3300uF, with Qspeed soft recovery diodes) but there was too much volatge drop for my transformer. Going to try ON MSR860 diodes next, and get a 18/18 volt transformer as well. Sound is so good, I keep thinking I can eek a little more performance out of it!
running Mundorf zNs Film/Foils, mounted vertically on small boards, the output of the zNs goes straight to the XLR jacks, and I mounted the drain resistors on the XLRs. Sound is great, but I never tried the OE electrolytics. I just assumed a good film/foil cap would be more transparent.
Right now I am playing with power supplies a little for the Legato. Tried using a single Placid just as a regulator with a separate rectifier/filter board (CRCRC, R47/3300uF, with Qspeed soft recovery diodes) but there was too much volatge drop for my transformer. Going to try ON MSR860 diodes next, and get a 18/18 volt transformer as well. Sound is so good, I keep thinking I can eek a little more performance out of it!
Dear Bob
I'm at other side of Atlantic .... so good morning...
..
Regrading Your question...
I do run my Legato with Buffers and to LL1517 without Caps.
I did measure the DC before caps and it was in milivolts 5-20mV so I decidet that it is OK to put trafo directly, as well as my HD650..to listen for caps influence...
Please measure DC before Caps..
There can't be too much DC, at my Legato it is just region of 5-20mV. If there is much more, trafo without caps will made DC short and definetely this is not gooing to work OK as barrows is explaining..
Did You made adjustments of Legato as per manuall..?? This is important for low DC ..
Russ is saying "do not sweet too much about it " and If You use Caps this is not so important but with trafo conected directly this could made diference.
There is also question about right trafo parameters for this application but here some imput from Russ would be great...
I hope this helps...
Best Regards
Rosendorfer
I'm at other side of Atlantic .... so good morning...
..Regrading Your question...
I do run my Legato with Buffers and to LL1517 without Caps.
I did measure the DC before caps and it was in milivolts 5-20mV so I decidet that it is OK to put trafo directly, as well as my HD650..to listen for caps influence...
Please measure DC before Caps..
There can't be too much DC, at my Legato it is just region of 5-20mV. If there is much more, trafo without caps will made DC short and definetely this is not gooing to work OK as barrows is explaining..
Did You made adjustments of Legato as per manuall..?? This is important for low DC ..
Russ is saying "do not sweet too much about it " and If You use Caps this is not so important but with trafo conected directly this could made diference.
There is also question about right trafo parameters for this application but here some imput from Russ would be great...
I hope this helps...
Best Regards
Rosendorfer
Rosendorfer...
Thanks for clearing that up, not knowing anything about coupling with transformers, I was not sure whether DC from +/- to ground was a concern. Now you have me interested in perhaps trying some Lundahls in place of the coupling caps... I would be going Balanced to Balanced, as I have no need for single ended output.
Do you think the extra current drive of the bufffers is needed with the transformers for any reason? I am going into 22K per phase (preamp) so I would not think so.
Thanks for clearing that up, not knowing anything about coupling with transformers, I was not sure whether DC from +/- to ground was a concern. Now you have me interested in perhaps trying some Lundahls in place of the coupling caps... I would be going Balanced to Balanced, as I have no need for single ended output.
Do you think the extra current drive of the bufffers is needed with the transformers for any reason? I am going into 22K per phase (preamp) so I would not think so.
Thanks to everybody for your comments.
I am using the Onetics to do balanced to SE conversion. I also have a pair of Lundahl 1674s I could try.I am probably a month or two away from a balanced system.
I did set up according to the Legato manual.
I will measure the differential DC voltage.
As I mentioned my first Legato board with caps and the Onetics give a very nice sound. The second board is with no caps. Once I confirm it is working I will try some experiments.
barrows - What value Mundorfs are you using? I have some Russian PIOs I could try but they are approximately 3-5microF.
Again thanks Rosendorfer, barrows, chipzahoy.
I am using the Onetics to do balanced to SE conversion. I also have a pair of Lundahl 1674s I could try.I am probably a month or two away from a balanced system.
I did set up according to the Legato manual.
I will measure the differential DC voltage.
As I mentioned my first Legato board with caps and the Onetics give a very nice sound. The second board is with no caps. Once I confirm it is working I will try some experiments.
barrows - What value Mundorfs are you using? I have some Russian PIOs I could try but they are approximately 3-5microF.
Again thanks Rosendorfer, barrows, chipzahoy.
Barrows
Sorry but I'm not sure if I understand what You mean with "extra current drive of the bufffers" ??. Could You explain bit more..
Best Regards
Rosendorfer
Transformers like to be driven from a low impedance, the lower the better. With the buffers the transformers will give lower distortion, particularly in the bass region. See some of the Jensen data-sheets for more info.
Theo...
I hate math, so I do it the easy way with this online calculator:
Guitar Pedals: R-C Filter Calculator
The formula is really easy though, just do not remember it since I got lazy.
Spartacus, thanks for that, answers my question perfectly.
Russ, what will be the output impedance of the Legato 2 with the paralleled MOSFETs?
I hate math, so I do it the easy way with this online calculator:
Guitar Pedals: R-C Filter Calculator
The formula is really easy though, just do not remember it since I got lazy.
Spartacus, thanks for that, answers my question perfectly.
Russ, what will be the output impedance of the Legato 2 with the paralleled MOSFETs?
Nice calculator for the rolloff
I believe the formula is f= 1/(2*pi*R*C)
Thanks again all for your help.
I did have a small amount of DC between + and - outputs. For experimenting I put some old Blackgate 47μF Electrolytics in ( I know, I know). Everything working fine and sounding pretty good.
I believe the formula is f= 1/(2*pi*R*C)
Thanks again all for your help.
I did have a small amount of DC between + and - outputs. For experimenting I put some old Blackgate 47μF Electrolytics in ( I know, I know). Everything working fine and sounding pretty good.
The reason is because Russ cannot possibly predict which preamp/amp you are going to use your Legato with to drive. Input impedances on amps/preamps can vary depending on manufacturer and design. I've seen some as low as 1000 ohms and as high as 200,0000 ohms.
So with a 100uf capacitor, he gets a corner frequency of 0.2Hz, with an input impedance of 10,000 ohms. If it is an input impedance of 1,000 ohms the same capacitor value, gives a corner frequency of 1.6Hz.
But you can change it to the value you think is appropriate in your system.
Anand.
Thanks for that additional detail. Makes even more sense now. In a fully balanced system, the Ballsie stage can be completely eliminated. One can use the cap value/quality of choice as long as the restrictions of a 5-10Hz corner frequency and the input impedance of the following stage or preamp or amp are taken into consideration. My preamp has a balanced shunt (or U) attenuator at the input and as such, has a set 10K input impedance per phase, therefore a cap value of about 2.5 to 3 uf is just fine.
Anand.
What about placing the capacitor at the output of the BAL/SE section? That will allow you to use smaller film caps direct to high impedance power amplifiers.