Thanks Thomas, also can I use the same output LL1660 to drive my headphones Senns HD600 or but can do to use it?
Felipe
Hi Felipe,
this depends on what your headphones need. What is their impedance and the voltage they need? If they are 600 Ohm, a 9:1 transformer would be better, like LL1689 but then the linestage would have a gain of less than 1.
Porbably a separate headphone amp would be better in this case.
Thomas
this depends on what your headphones need. What is their impedance and the voltage they need? If they are 600 Ohm, a 9:1 transformer would be better, like LL1689 but then the linestage would have a gain of less than 1.
Porbably a separate headphone amp would be better in this case.
Thomas
Hi!
That's quite low impedance.
That won't really fit for the 26. Either go for a different concept, or make a separate headphone driver
Thomas
That's quite low impedance.
That won't really fit for the 26. Either go for a different concept, or make a separate headphone driver
Thomas
Member
Joined 2006
Nice looking amp Andy!! And that's clever 😉
Someday I would like to try out 10Y, heard a lot of good things about it...🙂
Currently both this amp and the preamp are on cathode bias, battery bias is something I want next...
26 tube with 8:1 transformer; that means 2 VRMS in for about 2 VRMS out.
2 VRMS with a load of 300 ohms is about 13 mW.
Should be plenty enough to drive a HD600.
2 VRMS with a load of 300 ohms is about 13 mW.
Should be plenty enough to drive a HD600.
Currently both this amp and the preamp are on cathode bias, battery bias is something I want next...>>>
If you try filament bias, Rod's boards will be substantially the same as for cathode bias but you should check with him on that. The difference will be that you will need a higher voltage transformer, caps and maybe a larger heatsink. Worth thinking about!
Andy
If you try filament bias, Rod's boards will be substantially the same as for cathode bias but you should check with him on that. The difference will be that you will need a higher voltage transformer, caps and maybe a larger heatsink. Worth thinking about!
Andy
350 ohms would agree reasoably well with hi-impedance headphones. Does a pair of 26's have enough grunt to run 600-ohm cans like the old style AKG k240's?
Thx!
Hi Pieter,
You would loose some gain since the output impedance would be somewhat above 100 Ohm. Loaded with 300 Ohm you will loose some signal. Also that would mean to load the tube with less than 3 times it's rp.
But the intention was to use it for both linestage with some gain and headphone amp.
What could be done is to provide some switching at the output between 9:1 for headphone and 4.5:1 for linestage
Best regards
Thomas
You would loose some gain since the output impedance would be somewhat above 100 Ohm. Loaded with 300 Ohm you will loose some signal. Also that would mean to load the tube with less than 3 times it's rp.
But the intention was to use it for both linestage with some gain and headphone amp.
What could be done is to provide some switching at the output between 9:1 for headphone and 4.5:1 for linestage
Best regards
Thomas
Hi!
Not optimal. That would load the tube too much. The point of transformer coupling (among others) is to give the tube a high impedance load to achieve a load line close to horizontal. I like to load a tube with 5 times it's rp or more.
In your case that would be less than 2 times the rp
better would be a 9:1 output trans like Lundahl LL1689
Thomas
Not optimal. That would load the tube too much. The point of transformer coupling (among others) is to give the tube a high impedance load to achieve a load line close to horizontal. I like to load a tube with 5 times it's rp or more.
In your case that would be less than 2 times the rp
better would be a 9:1 output trans like Lundahl LL1689
Thomas
Very doable; actually I made some line output transformers for this application with very good results. Even 1 VRMS into the 300 ohms HD600 will be very very loud. Nice tricks can also be done to make the transformer as a volume control as well (very good for load and noise!).
At some point it becomes an idea to use two stages in the preamp - a 26 direct coupled to a low Rp tube like a 6B4G, 2a3 or 71A. Makes the output transformer a hell of a lot easier to manage.
Andy
Andy
If the preamp is merely for line level it's being a separate unit is already questionable, adding another tube to get more drive would be a nice example of over-engineering IMHO.
Way more sense would make to drive an integrated line level input amplifier with an inductive volume control. These controls are very well able to drive long interconnects; something like this www.tribute-audio.nl/products/signal/inductive volume control.htm
Way more sense would make to drive an integrated line level input amplifier with an inductive volume control. These controls are very well able to drive long interconnects; something like this www.tribute-audio.nl/products/signal/inductive volume control.htm
Hi Pieter,
but how do you ensure that the inductive volume control is adequately driven? I found inductive volukme controls to sound best when driven from a low impedance source. Preferably a transformer coupled one.
This is the reason why a stand alone linestage makes sense IMHO to provide a high impedance to all possible sources and to act as a buffer to drive an inductive volume control nicely
Thomas
but how do you ensure that the inductive volume control is adequately driven? I found inductive volukme controls to sound best when driven from a low impedance source. Preferably a transformer coupled one.
This is the reason why a stand alone linestage makes sense IMHO to provide a high impedance to all possible sources and to act as a buffer to drive an inductive volume control nicely
Thomas
Hi Thomas,
In the meantime a bit OT..., but when I developed my autoformer volume control, I tested it with source impedances up to 3k, which is pretty "safe" I think. That asks for quite some inductance. My autoformer has an inductance of about 150H, that is an AC impedance at 20 Hz of almost 20k, going up with frequency of course. At the same time, using advanced core material, coil DC resistance could be kept very low at some 30 Hz. Bandwidth depends on volume position but with a 2k source impedance it nevers falls under 200 kHz. Already some 8 years ago I visited Dave Slagle and we did some comparisons, showing that the quality was very much on par, using pretty different materials. In the meantime there have been some improvements, and Dave's will not be the same now I guess, but these autoformers are excellent options for volume control.
In the meantime a bit OT..., but when I developed my autoformer volume control, I tested it with source impedances up to 3k, which is pretty "safe" I think. That asks for quite some inductance. My autoformer has an inductance of about 150H, that is an AC impedance at 20 Hz of almost 20k, going up with frequency of course. At the same time, using advanced core material, coil DC resistance could be kept very low at some 30 Hz. Bandwidth depends on volume position but with a 2k source impedance it nevers falls under 200 kHz. Already some 8 years ago I visited Dave Slagle and we did some comparisons, showing that the quality was very much on par, using pretty different materials. In the meantime there have been some improvements, and Dave's will not be the same now I guess, but these autoformers are excellent options for volume control.
Hi Pieter,
I have not heard yours yet, but I heard other TVCs which claimed to work well with highish output impedances. I never liked them.
As you read in this thread some DIYers don't really care a lot for low Zout even linestages with 7k Zout are not uncommon. I've seen Phonostages with even more.
To be universally usable a linestage should have very high input impedance and low Zout. That's what I'm doing with my commercial linestages since I don't know what customers use them with.
Different with my own stuff where I have everything under control.
Thomas
I have not heard yours yet, but I heard other TVCs which claimed to work well with highish output impedances. I never liked them.
As you read in this thread some DIYers don't really care a lot for low Zout even linestages with 7k Zout are not uncommon. I've seen Phonostages with even more.
To be universally usable a linestage should have very high input impedance and low Zout. That's what I'm doing with my commercial linestages since I don't know what customers use them with.
Different with my own stuff where I have everything under control.
Thomas
Hi Thomas,
There is a difference between transformer volume controls (TVC's) and autoformer volume controls.
Feedback from listeners always confirm the autoformer type to be more transparent and dynamic.
I do care very much for correct impedances between elements of a chain. When output impedances are (too) high I always find the sound stage to suffer; with correct impedances the sound stage is broad and deep. Therefore I wound for a high inductance with the autoformer; interface with normal source equipment seems OK, but yes not everything can be controlled. When something is wrong it points to something weird with the source.
There is a difference between transformer volume controls (TVC's) and autoformer volume controls.
Feedback from listeners always confirm the autoformer type to be more transparent and dynamic.
I do care very much for correct impedances between elements of a chain. When output impedances are (too) high I always find the sound stage to suffer; with correct impedances the sound stage is broad and deep. Therefore I wound for a high inductance with the autoformer; interface with normal source equipment seems OK, but yes not everything can be controlled. When something is wrong it points to something weird with the source.
Are we talking here of using the same 9:1 Lundahl OT, with headphone and line out hooked up differently at the seconday?
IIRC, the 1669 is wired something like 9 : 9 / 1 : 1 : 1 : 1, tho I don't really know what that means.