Hi!
Thomas
Va max is from plate to cathode. Since the tube is cathode biased in your schem the 45 only sees a Va of 50V. If you want the full power from the 45, go to the suggested 300V B+
26 or 10Y are much better choices for the driver in an all DHT amp. Of the two I prefer the 10Y
Thomas
Hi!
Some more remarks:
You don't really need DC on a 45 output I use AC there, with the 2.5V and a center tapped fil transformer or with a hum pot, you'll get it very quiet. DC fils are needed on the driver
Yes, or go ultrapath (see my single ended amplifier concept series on my blog)
Best regards ... Thomas
Some more remarks:
You don't really need DC on a 45 output I use AC there, with the 2.5V and a center tapped fil transformer or with a hum pot, you'll get it very quiet. DC fils are needed on the driver
Yes, or go ultrapath (see my single ended amplifier concept series on my blog)
Best regards ... Thomas
Well, the 26 and 10Y are great sounding (we are talking the Holy Grail of tubes here) - when properly implemented probably superior but I wouldn't say much better. I happen to like the tone of the 46 on acoustic instruments, piano, voice etc. Crucially it has lower plate resistance while still having useful gain, so the implementation really counts here. I found the 46 into a 100H interstage like 126C or LL1692A sounded really good. Better, into the same interstage, than a 10Y when they both had cathode bias. I might have to re-check that because I didn't try the 10Y with battery grid bias, which is where the 46 really shone.
When you write 5K:5K for an interstage this really only says it's 1:1. What is the inductance of the primary in Henries? 100H is good for a 46, a bit more for a 10y and 200H or over for a 26. So the interstage is really going to determine your driver. You can't just slap these things together - they work together to give you the sound you are seeking. I've been through several combinations here, as Thomas has, and it was quite time consuming!
Also in my schematic I chose 174v to give me 10mA with -24v grid bias. If you put 24v on the cathode your plate to cathode voltage is 150v.
Andy
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Hi Andy
the 46 has to little gain for a driver in my taste.
Sound differences between set ups with such different tubes cannot be attributed just to the tubes themselves. The differences are valid in the given set up.
with a 26 or 10Y a 1:4 step up would be sufficient to get a sensitivity of about 1V for full power output. The 46 would probably require a 1:8 or even higher step up ration which can impose other problems (more difficult to drive)
Anyhow you would need to make up for the lack of gain somewhere in the system.
In my switchable amp with 26 or 10Y driver for the 45, the 10Y is really great! It combines very well with the 45
Best regards ... Thomas
the 46 has to little gain for a driver in my taste.
Sound differences between set ups with such different tubes cannot be attributed just to the tubes themselves. The differences are valid in the given set up.
with a 26 or 10Y a 1:4 step up would be sufficient to get a sensitivity of about 1V for full power output. The 46 would probably require a 1:8 or even higher step up ration which can impose other problems (more difficult to drive)
Anyhow you would need to make up for the lack of gain somewhere in the system.
In my switchable amp with 26 or 10Y driver for the 45, the 10Y is really great! It combines very well with the 45
Best regards ... Thomas
Hi Thomas
pardon my ignorant. i am really not sure. is it a typo or do you mean that on the schematic, the 45 only sees a Va of 200v? (250v-50v). i am just want to be sure. so with B= 310v, hence 300v-50v, the #45 only sees Va of 250v?
thanks Erwin
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Hi Andy
same here i am puzzle. so if i put 24v on the cathode, hence my B+ is around 210v?
i got question: if i follow you schematic, would the bias volt of -24v post problem for input transformer? while in your case you have the capacitor that block it to the previous stage (#26)? am i getting it right?
thanks,
Erwin
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Hi Thomas
may i know which interstage you use for the switchable amp? however 10y is really scarce now
regards,
Erwin
Depends on your goals and priorities. I assign greater emphasis on low output impedance on my drivers rather than gain. Then again, I run three stage amps. With more iron than I can carry. And one amp consists of three chasses.
I still question the choice using the 26 when using interstage transformers. The 26 does not appear on paper to be a very suitable driver. Highish plate resistance and low plate current in my mind has an uphill battle in driving a power triode grid, especially at the high frequencies. If anyone has a frequency response measurement and THD vs. freq. measurement of this setup, I would be interested to see it. 10Y seems like it would do nicely- what is the plate resistance?
I wouldn't argue that the setup doesn't give a lot of pleasant sounding even harmonic. So to claim that it sounds good is somewhat irrelevant; an equalizer or expander may sound good, too, but I don't think that's the purpose of an amplifier.
I'm with zigzagflux here - the three stage solution. I'm also a bit in the dark as to what interstage you'd use with a 26 driver. I did actually try it as a driver into the 300b using a LL1660/5mA interstage but it didn't sound as good as I thought it might and I went back to the 46. I love the 26 and I'd use it at the drop of a hat, but this whole macro business of putting an amp together depends on combinations - how the DHTs work into the iron. I was surprised in this amp to prefer the 46 to the 10Y but like I say, it's all about combinations.
Erwin - I have some 10Y if you are interested, but choose the circuit first!!
Andy
Erwin - I have some 10Y if you are interested, but choose the circuit first!!
Andy
Hi!
I generally agree that a low impedance driver has advantages. But a 45 is really easy on the driver and the 7k of the 26 are more than adequate to drive a 45.
There are interstages which work well with the 26, for example the Tango NC20 gives a very good bandwidth with it, Lundahl 1660 also works well.
I tried both in multiple amps with tubes even with higher plate resistances with these transformers
Yet as I wrote I still prefer the 10Y over the 26.
10Ys are not really that scarce and stille asy to source.
On large tubes like 211 I sure prefer low impedance drivers, but the 45 is really easy to drive, which is one of it's advantages.
As for voltages: The voltage which the tube sees is that from plate to cathod (filament in case of the 45) So in case of a cathode biased stage, B+ is the voltage across the tube plus the bias voltage.
Best regards
Thomas
I generally agree that a low impedance driver has advantages. But a 45 is really easy on the driver and the 7k of the 26 are more than adequate to drive a 45.
There are interstages which work well with the 26, for example the Tango NC20 gives a very good bandwidth with it, Lundahl 1660 also works well.
I tried both in multiple amps with tubes even with higher plate resistances with these transformers
Yet as I wrote I still prefer the 10Y over the 26.
10Ys are not really that scarce and stille asy to source.
On large tubes like 211 I sure prefer low impedance drivers, but the 45 is really easy to drive, which is one of it's advantages.
As for voltages: The voltage which the tube sees is that from plate to cathod (filament in case of the 45) So in case of a cathode biased stage, B+ is the voltage across the tube plus the bias voltage.
Best regards
Thomas
Hi!
What makes you think that the proposed line input transformer would add pleasant distortion? It is one of the best performing input transformers available. It is actually designed for studio equipment. Probably many of the recordings you listen to have been recorded with equipment with this exact transformer or similar ones in the signal path.
Best regards ... Thomas
What makes you think that the proposed line input transformer would add pleasant distortion? It is one of the best performing input transformers available. It is actually designed for studio equipment. Probably many of the recordings you listen to have been recorded with equipment with this exact transformer or similar ones in the signal path.
Best regards ... Thomas
Actually, I wasn't talking about input transformers, I was referring to interstage transformers. Specifically, between the 26 and the 45. I would expect high distortion, and if one liked the sound, I would predict mostly even. Hence my interest in seeing graphs if anyone had measurements.
I am certainly not one opposed to transformers! Currently, I have them on the output of my D/A, at the output of the preamp, the input of the power amp, followed by two stages of IT's, followed by the OPT. That's six transformers in the chain - probably more iron than 99% of the users on this forum would use, and at overall low measured distortion.
However, it took a deal of work and many mistakes to realize that iron likes low impedance drivers (or at least within a very specific range). Tack on the grid capacitance of a triode and things get ugly quick. The math is pretty easy to do- a few mA cannot drive many pF at 20 kHz.
Anyone know the plate resistance of the 10Y? $60 a tube isn't exactly cheap.
I am certainly not one opposed to transformers! Currently, I have them on the output of my D/A, at the output of the preamp, the input of the power amp, followed by two stages of IT's, followed by the OPT. That's six transformers in the chain - probably more iron than 99% of the users on this forum would use, and at overall low measured distortion.
However, it took a deal of work and many mistakes to realize that iron likes low impedance drivers (or at least within a very specific range). Tack on the grid capacitance of a triode and things get ugly quick. The math is pretty easy to do- a few mA cannot drive many pF at 20 kHz.
Anyone know the plate resistance of the 10Y? $60 a tube isn't exactly cheap.
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hi zigzagflux
i read that 801a and 10y share the same characteristic. hence i assume plate resistance is 5K.
http://www.diyaudio.com/forums/tubes-valves/116291-need-tube-data-10y.html
i havent found 10y datasheet that has plate resistance stated myself
would you kindly share your finding or personal opinion on how the plate resistance relate to the interstage transformer use?
i have limited use of transformer. i am using 10k:600 for my #26. though it sounds good but i feel that low frequency suffer abit. not sure its the Line output transformer impedance or capacitor bypass at cathode resistor of MKP 22uf i am using.
thanks in advance
erwin
i read that 801a and 10y share the same characteristic. hence i assume plate resistance is 5K.
http://www.diyaudio.com/forums/tubes-valves/116291-need-tube-data-10y.html
i havent found 10y datasheet that has plate resistance stated myself
would you kindly share your finding or personal opinion on how the plate resistance relate to the interstage transformer use?
i have limited use of transformer. i am using 10k:600 for my #26. though it sounds good but i feel that low frequency suffer abit. not sure its the Line output transformer impedance or capacitor bypass at cathode resistor of MKP 22uf i am using.
thanks in advance
erwin
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Hi
So why do you think in the case of the 26 / 45 it would create distortion? Apparently you use them yourself and like it???
Of course the interstage transformer has to match to the driver tube, it's plate resistance and current. The 26 would run at around 5-7mA that is plenty to drive the miller capacitance of a 45. The 10Y would run at may 15 or more. The mentioned interstage transformers are trusted and tried in this application and work well.
rp is 4.6k. I'd say $60 for a directly heater power triode with thoriated tungsten filaments, the linearity and sound of a 10Y is very reasonable.
Best regards ... Thomas
So why do you think in the case of the 26 / 45 it would create distortion? Apparently you use them yourself and like it???
Of course the interstage transformer has to match to the driver tube, it's plate resistance and current. The 26 would run at around 5-7mA that is plenty to drive the miller capacitance of a 45. The 10Y would run at may 15 or more. The mentioned interstage transformers are trusted and tried in this application and work well.
rp is 4.6k. I'd say $60 for a directly heater power triode with thoriated tungsten filaments, the linearity and sound of a 10Y is very reasonable.
Best regards ... Thomas
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Hi!
What are the specs of your transformer? 10k:600Ohms only tells the winding ratio. What is the primary inductance? What is it's DC current rating?
You'd want a primary inductance well above 100Hy for the 26
22uF seems low. What is the value of the cathode resistor?
Thomas
What are the specs of your transformer? 10k:600Ohms only tells the winding ratio. What is the primary inductance? What is it's DC current rating?
You'd want a primary inductance well above 100Hy for the 26
22uF seems low. What is the value of the cathode resistor?
Thomas
Hi Thomas
sorry of topic guys:
i am using james transformer. Primary inductance is 58H. DCR 1K. current is 20mA. kinda low for 26 which i just found out recently. learning curve
the Rk is 1K8 running at B+ 170v. Vg= 12-13v. yes i calculate that 22UF is abit low but its what i get at the moment for mkp type. might change to bigger one latter. maybe 47uf?
btw i am thinking of trying 112a. which has Rp=5k. is this good move? any impression from on this tube?
Back to topic:
how bout using 112a to drive 45? mu is 8.5. rp=5k
anyone has datasheet of 10y that has the curve? thanks
regards,
Erwin
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Hi!
For tubes with an rp in that range it is of course important to use a high quality interstage transformer which is designed to work with such driving impedances. It is important to choose a transformer which is up to the task.
58Hy is very low for such tubes. The Lundahl LL1660/10mA for example has
145Hy if wired 4.5:1 The 1660/PP (which can handle 5mA DC) has double the primary inductance.
Yes you can use the 112A too. But if you are willing to choose the right transformer rp of 5k or 7k will not be such a huge difference.
In my 45 with IDHT driver, I use the 6N7 with interstage coupling and that has a rp of 11k. Admittedly this is borderline but still measures and sounds excellent with Lundahl 1660
datasheet of the 10 / 10Y :
http://frank.pocnet.net/sheets/021/1/10.pdf
Thomas
For tubes with an rp in that range it is of course important to use a high quality interstage transformer which is designed to work with such driving impedances. It is important to choose a transformer which is up to the task.
58Hy is very low for such tubes. The Lundahl LL1660/10mA for example has
145Hy if wired 4.5:1 The 1660/PP (which can handle 5mA DC) has double the primary inductance.
Yes you can use the 112A too. But if you are willing to choose the right transformer rp of 5k or 7k will not be such a huge difference.
In my 45 with IDHT driver, I use the 6N7 with interstage coupling and that has a rp of 11k. Admittedly this is borderline but still measures and sounds excellent with Lundahl 1660
datasheet of the 10 / 10Y :
http://frank.pocnet.net/sheets/021/1/10.pdf
Thomas
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As for voltages: The voltage which the tube sees is that from plate to cathod (filament in case of the 45) So in case of a cathode biased stage, B+ is the voltage across the tube plus the bias voltage.>>
Thanks for bringing this up. I just want to be clear on this:
For operating point 174v anode, -24v, 10mA
Grid bias: 174v anode, -24v grid, 10mA as above. This would be as in the datasheet and in the supplied curves. Anode to cathode is 174v since cathode is at zero.
Cathode bias: 174v anode, 0v grid, 24v cathode ?mA. The anode cathode voltage is now 150v.
So how do you read the curves on the datasheet with cathode bias? Do you read the curves in exactly the same way as with grid bias, or do you assume the anode voltage is now 150v because it's the anode-cathode voltage, and read the curves for an anode voltage of 150v?
Andy
Thanks for bringing this up. I just want to be clear on this:
For operating point 174v anode, -24v, 10mA
Grid bias: 174v anode, -24v grid, 10mA as above. This would be as in the datasheet and in the supplied curves. Anode to cathode is 174v since cathode is at zero.
Cathode bias: 174v anode, 0v grid, 24v cathode ?mA. The anode cathode voltage is now 150v.
So how do you read the curves on the datasheet with cathode bias? Do you read the curves in exactly the same way as with grid bias, or do you assume the anode voltage is now 150v because it's the anode-cathode voltage, and read the curves for an anode voltage of 150v?
Andy
Erwin - to my ears the LL1692a sounds better than the LL1660. That's if you want to pay money. If you want to experiment and see what driver sounds best to you, then try the Hammond 126C with a few DHTs. You want 1:1 here
I've tried several drivers with all three of these, and the sound I liked was the 46. It isn't a case of "lower plate resistance will give you better sound". I tried the 71a and liked that less than the 46. I'll persevere with trying the 10y and 26 as drivers, because these are the best tubes out there, but right now I'm Ok with the 46. The 12A (112A) never fired up my enthusiasm much. It looks useful on paper but I found the sound uninteresting, like the 49 which I also tried. The 31 was nice, but not as good as the 46. Better than the 71A in that particular application which surprised me a bit. You don't really know how a tube is going to sound into an interstage until you try it and use your ears. Well - that's what I do.
andy
I've tried several drivers with all three of these, and the sound I liked was the 46. It isn't a case of "lower plate resistance will give you better sound". I tried the 71a and liked that less than the 46. I'll persevere with trying the 10y and 26 as drivers, because these are the best tubes out there, but right now I'm Ok with the 46. The 12A (112A) never fired up my enthusiasm much. It looks useful on paper but I found the sound uninteresting, like the 49 which I also tried. The 31 was nice, but not as good as the 46. Better than the 71A in that particular application which surprised me a bit. You don't really know how a tube is going to sound into an interstage until you try it and use your ears. Well - that's what I do.
andy
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