Hi, I'm having a hard time deciding which is better. The LL1660 by Lundahl or the Sowter 9050. I am using it for a 6sn7 balanced (push-pull) line out. Will try parafeed or dc coupled.
I've heard about people using torroid (power) transformers as a parafeed tranny. Does anyone have any experience with this technique? Does it SOUND good? Could it sound as good as a Sowter or Lundahl?
Thanks for any info!!!!
- Matt
I've heard about people using torroid (power) transformers as a parafeed tranny. Does anyone have any experience with this technique? Does it SOUND good? Could it sound as good as a Sowter or Lundahl?
Thanks for any info!!!!
- Matt
Matt,
Sowter 9050 or LL1660PP: It depends what you want to achieve.
For the 6SN7 (R_p= 7k) the Sowter 8650 or 9050 certainly is better suited as the tube should face a load of atleast 15k.
With the 8650 you get 185R (+ secondary DCR) as output resistance, with the 9050 417R plus sec.DCR.
I am not sure if the 6SN7 is the right choice if you want to use the LL1660; it only has a stepdown turns ratio of 2.25 in PP to line out mode. You end up at about 3k output resistance then. Better use a 5687 or a juicy 12B4A to drive the LL1660.
Sonics: i haven't heard either in my system, but i heard the LL1660 in Thomas Mayers system and liked it very much; Thomas even recommended the thing for single-ended mode.
Sowter makes any custom job you want, Lundahl does not. But in general the sonic reputation of Lundahl is considerably better (exceptions exist).
I have decided to use the LL1660 PP for my preamp project; i will use a 12B4 to drive it and i guess the Lundahl driven by the right tube will be dramatically better than the Sowter. Moreover, it has way higher safety margins concerning isolation voltages. The only Sowter i considered was the 9111 but this baby has to be used in parafeed mode which i want to avoid: parafeed needs a cap to block the CD; this is a coupling cap. I strive to avoid coupling caps in my system.
Sowter 9050 or LL1660PP: It depends what you want to achieve.
For the 6SN7 (R_p= 7k) the Sowter 8650 or 9050 certainly is better suited as the tube should face a load of atleast 15k.
With the 8650 you get 185R (+ secondary DCR) as output resistance, with the 9050 417R plus sec.DCR.
I am not sure if the 6SN7 is the right choice if you want to use the LL1660; it only has a stepdown turns ratio of 2.25 in PP to line out mode. You end up at about 3k output resistance then. Better use a 5687 or a juicy 12B4A to drive the LL1660.
Sonics: i haven't heard either in my system, but i heard the LL1660 in Thomas Mayers system and liked it very much; Thomas even recommended the thing for single-ended mode.
Sowter makes any custom job you want, Lundahl does not. But in general the sonic reputation of Lundahl is considerably better (exceptions exist).
I have decided to use the LL1660 PP for my preamp project; i will use a 12B4 to drive it and i guess the Lundahl driven by the right tube will be dramatically better than the Sowter. Moreover, it has way higher safety margins concerning isolation voltages. The only Sowter i considered was the 9111 but this baby has to be used in parafeed mode which i want to avoid: parafeed needs a cap to block the CD; this is a coupling cap. I strive to avoid coupling caps in my system.
6H30pi for LL1660pp?
OK, thanks for the info. I have decided to go with the LL1660PP and got 4 of them! Hopefully I do this right and don't waste any money in the process.
Now, I'm just trying to figure out which output tubes to use with this transformer. I want to use dual triodes. Originally like I said, I wanted to use 6sN7gt's, but not sure about that now after reading your response.
What does anyone know about the Sovtek 6H30pi? Is this a good tube to use as a push-pull with the LL1600PP? I was thinking the 12b4 but it's a single section, and i'm hoping to get away from having too many tubes on my 4 channel preamp (mic and line/instrument).
I guess what I'm asking is can some of you give me the names of tubes that would work well with a LL1660PP besides the 12b4?
Also, a more general question...
If your grid voltage is -10 volts with respect to the cathode, does that mean that you can't have an input siganl greater than 10 volts? The preamp that will be driving the output stage will have sometimes a voltage of 30-40 volts ac, so just wondering if i need that kind of bias?
thanks a lot for any help!
- matt mitchell
OK, thanks for the info. I have decided to go with the LL1660PP and got 4 of them! Hopefully I do this right and don't waste any money in the process.
Now, I'm just trying to figure out which output tubes to use with this transformer. I want to use dual triodes. Originally like I said, I wanted to use 6sN7gt's, but not sure about that now after reading your response.
What does anyone know about the Sovtek 6H30pi? Is this a good tube to use as a push-pull with the LL1600PP? I was thinking the 12b4 but it's a single section, and i'm hoping to get away from having too many tubes on my 4 channel preamp (mic and line/instrument).
I guess what I'm asking is can some of you give me the names of tubes that would work well with a LL1660PP besides the 12b4?
Also, a more general question...
If your grid voltage is -10 volts with respect to the cathode, does that mean that you can't have an input siganl greater than 10 volts? The preamp that will be driving the output stage will have sometimes a voltage of 30-40 volts ac, so just wondering if i need that kind of bias?
thanks a lot for any help!
- matt mitchell
Matt,
no knowledge of the 6H30.
It is an advantage to have a singel section tube: for PP use you can match the tubes, with a dual-system envelope you have to like with what you got. Or seek for internally matched ones, have fun!
Better go fot he 12B4.
Bias: if bias is -10V, then indeed you are well advised to keep your input signal below a peak voltage of 10V (p2p of 20 Volt). Make that 9V/p2p 18V, as the tube starts to pull grid current between 0 and -1 V at the grid. One exception: the driving stage is designed to deliver enough current to drive the grid..
no knowledge of the 6H30.
It is an advantage to have a singel section tube: for PP use you can match the tubes, with a dual-system envelope you have to like with what you got. Or seek for internally matched ones, have fun!
Better go fot he 12B4.
Bias: if bias is -10V, then indeed you are well advised to keep your input signal below a peak voltage of 10V (p2p of 20 Volt). Make that 9V/p2p 18V, as the tube starts to pull grid current between 0 and -1 V at the grid. One exception: the driving stage is designed to deliver enough current to drive the grid..
Matt,
The 6H30 will be fine in your pre, PP driving an LL1660. Set the Vp to 200V (B+ ~210V), Ia to 20mA/triode and Vg will be about -7.5V. I would put a constant current sink in the tail of each triode pair to ensure that the two tubes remain as close to each other in performance as possible. Whilst the LL1660PP has a small gap to allow for imbalances betwen the tube pairs, if you exceed what the gap allows, the performance of the transformer will degrade significantly.
Other options would be the ECC99 or 6N1P, but both have more gain and a higher Rp, and Zout. Use the 6H30, nice tube, tough as nails, and <b>very</b> linear.
<b>If your grid voltage is -10 volts with respect to the cathode, does that mean that you can't have an input siganl greater than 10 volts? The preamp that will be driving the output stage will have sometimes a voltage of 30-40 volts ac, so just wondering if i need that kind of bias?</b>
Why are you building another stage with a gain of around 15, when you already have 30Vac+? All you'll be doing is attenuating the signal down to get the next stage not to clip. Too much gain means noise and headroom problems. What you want is just enough gain, and lots of headroom. You're bass ackwards here.
To answer the question, with a Vg of -10V, if you apply a signal to the grid that is greater than 10V, you'll cause the grid to go positive, grid current to flow, and the stage to "clip" and distort radically. You can't just up the bias on a stage (that much), because all the tube's parameters and external loads are interdependent, and doing so might cause lots of distortion or the tube to switch off.
Cheers
The 6H30 will be fine in your pre, PP driving an LL1660. Set the Vp to 200V (B+ ~210V), Ia to 20mA/triode and Vg will be about -7.5V. I would put a constant current sink in the tail of each triode pair to ensure that the two tubes remain as close to each other in performance as possible. Whilst the LL1660PP has a small gap to allow for imbalances betwen the tube pairs, if you exceed what the gap allows, the performance of the transformer will degrade significantly.
Other options would be the ECC99 or 6N1P, but both have more gain and a higher Rp, and Zout. Use the 6H30, nice tube, tough as nails, and <b>very</b> linear.
<b>If your grid voltage is -10 volts with respect to the cathode, does that mean that you can't have an input siganl greater than 10 volts? The preamp that will be driving the output stage will have sometimes a voltage of 30-40 volts ac, so just wondering if i need that kind of bias?</b>
Why are you building another stage with a gain of around 15, when you already have 30Vac+? All you'll be doing is attenuating the signal down to get the next stage not to clip. Too much gain means noise and headroom problems. What you want is just enough gain, and lots of headroom. You're bass ackwards here.
To answer the question, with a Vg of -10V, if you apply a signal to the grid that is greater than 10V, you'll cause the grid to go positive, grid current to flow, and the stage to "clip" and distort radically. You can't just up the bias on a stage (that much), because all the tube's parameters and external loads are interdependent, and doing so might cause lots of distortion or the tube to switch off.
Cheers
12B4
Folks,
Other than the fact that I'm happy to see the 12B4 is still around. In the long run I'd certainly opt for a currently manufactured tube.
Nobody can predict pricing on either one of them but logic tells me the latter stand a better chance for maintaining prices in the long run.
Rgds,
Folks,
Other than the fact that I'm happy to see the 12B4 is still around. In the long run I'd certainly opt for a currently manufactured tube.
Nobody can predict pricing on either one of them but logic tells me the latter stand a better chance for maintaining prices in the long run.
Rgds,
OK, thanks everyone for your very valuable help.
I'm wondering about the gain issue. If a tube has a mu of 15, BUT going into a step-down transformer, what REALLY is the gain of the tube (plus the transformer)? I mean, if my desired output impedance is to be somwhere around 600 or less, what kind of ac voltage do I really need? what if i want it to interface with +4dB inputs? what voltage would i need to be outputing?
a million thanks again to you all!
matt
I'm wondering about the gain issue. If a tube has a mu of 15, BUT going into a step-down transformer, what REALLY is the gain of the tube (plus the transformer)? I mean, if my desired output impedance is to be somwhere around 600 or less, what kind of ac voltage do I really need? what if i want it to interface with +4dB inputs? what voltage would i need to be outputing?
a million thanks again to you all!
matt
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