Well done vgeorge! What you do next depends on your system. If you use the LL1660 it's best to have the 5mA version because more inductance which you'll need as much of as you can get with a 26. I tried it with a Hammond 126C which is 105H and it wasn't comfortable. If you have that, then run the 26 at 5mA straight into the transformer.
If you want to keep as much gain as possible and can use short leads to a tube amp, then go for 1:1. That might usefully cut down on he stages you need for the amp.
I'm waiting to try battery bias - a 9v battery should be fine. Filament bias, which I use, is good. Rod can give you details of filament bias with his boards.
With 5ma and 9v bias you need 130v on the plate. Assuming the battery is exactly 9v. It's all in Franks data sheets.
andy
andy
If you want to keep as much gain as possible and can use short leads to a tube amp, then go for 1:1. That might usefully cut down on he stages you need for the amp.
I'm waiting to try battery bias - a 9v battery should be fine. Filament bias, which I use, is good. Rod can give you details of filament bias with his boards.
With 5ma and 9v bias you need 130v on the plate. Assuming the battery is exactly 9v. It's all in Franks data sheets.
andy
andy
Thanks for the advises Andy. I can get away with 4.5:1 and 4dB gain in my system.
However some recommended higher bias for better sound. What do you think?
Nicoh46, regarding sound, it' s early to comment, not the resolution of a fet pre, but a lot more musical and you get more the feel of the various instruments.
However some recommended higher bias for better sound. What do you think?
Nicoh46, regarding sound, it' s early to comment, not the resolution of a fet pre, but a lot more musical and you get more the feel of the various instruments.
Hi!
Use the 1660 in 4.5:1 The 26 has too high plate resistance to use in 1:1.
Also the 1660 performs way better when wired 4.5:1 than with any other of the possible rations.
I've used the 26 with the 10mA and it works fine. If you have the choice go for 5mA though.
When you use 4.5:1 take advantage of the low output impedance and convert to transformer volume control on the output
Thomas
Use the 1660 in 4.5:1 The 26 has too high plate resistance to use in 1:1.
Also the 1660 performs way better when wired 4.5:1 than with any other of the possible rations.
I've used the 26 with the 10mA and it works fine. If you have the choice go for 5mA though.
When you use 4.5:1 take advantage of the low output impedance and convert to transformer volume control on the output
Thomas
According to Lundahl spec the 1660 in 4,5:1 mode has a primary inductance of 100H.
Frequency bandwidth is specified being 11Hz - 35kHz with a 3k source impedance (I don't see if this is -1dB or -3dB).
As a 26 tube with some 5mA of plate current will have an Rp of about 8k, I am very curious how the frequency bandwidth will be with a 1660 in 4,5:1 mode, I guess not within - 1dB from 20Hz to 20kHz. Then we leave HiFi specs; I don't like this, especially not in a line stage with some more amplifying stages coming after.
When the 26 line stage is a stand alone unit I would add some kind of output buffer, and load the 26 1:1 or just a plate choke; that will give much better HF (phase behavior).
When the 26 is integrated with the power amp I would prefer a 1:1 load with short low capacitance connection to the next stage. All IMHO.
Frequency bandwidth is specified being 11Hz - 35kHz with a 3k source impedance (I don't see if this is -1dB or -3dB).
As a 26 tube with some 5mA of plate current will have an Rp of about 8k, I am very curious how the frequency bandwidth will be with a 1660 in 4,5:1 mode, I guess not within - 1dB from 20Hz to 20kHz. Then we leave HiFi specs; I don't like this, especially not in a line stage with some more amplifying stages coming after.
When the 26 line stage is a stand alone unit I would add some kind of output buffer, and load the 26 1:1 or just a plate choke; that will give much better HF (phase behavior).
When the 26 is integrated with the power amp I would prefer a 1:1 load with short low capacitance connection to the next stage. All IMHO.
Hi Thomas,
That's nice for low frequency performance.
My major concern is the treble side.
I have been experimenting quite a lot with tubes in the 7 to 8k Rp class (6SN7, 26, 76) and I am pretty convinced that these tubes are the "limit" when it comes to inductive loading.
It ends with a 1:1 interstage transformer; all other ratios, step-up or step down, will show HF loss under 20kHz. This is understandable: the source impedance is simply too high with respect to the winding capacitances of the transformer.
With the 1:1 interstage transformer actually we use the capacitance by tight coupling to make the HF better, but it sure needs to be done with tight coupling. You can use a Tango NC-14 and NC-20 both in 1:1 mode, but you will see that the NC-20 is made for 1:1; the NC-14 can also be used for phase splitting, and that requires a quite different winding technique, which makes the NC-14 a very mediocre 1:1 transformer. It's either this or that.
I realize that many are only interested in the resulting sound, so do I. However I want to keep an eye on things like bandwidth, especially in a line stage. The power amp should be the decisive factor here (tube/opt combo).
You stated in one of the threads that "headroom" is important; I certainly would share good front end specs among "headroom".
That's nice for low frequency performance.
My major concern is the treble side.
I have been experimenting quite a lot with tubes in the 7 to 8k Rp class (6SN7, 26, 76) and I am pretty convinced that these tubes are the "limit" when it comes to inductive loading.
It ends with a 1:1 interstage transformer; all other ratios, step-up or step down, will show HF loss under 20kHz. This is understandable: the source impedance is simply too high with respect to the winding capacitances of the transformer.
With the 1:1 interstage transformer actually we use the capacitance by tight coupling to make the HF better, but it sure needs to be done with tight coupling. You can use a Tango NC-14 and NC-20 both in 1:1 mode, but you will see that the NC-20 is made for 1:1; the NC-14 can also be used for phase splitting, and that requires a quite different winding technique, which makes the NC-14 a very mediocre 1:1 transformer. It's either this or that.
I realize that many are only interested in the resulting sound, so do I. However I want to keep an eye on things like bandwidth, especially in a line stage. The power amp should be the decisive factor here (tube/opt combo).
You stated in one of the threads that "headroom" is important; I certainly would share good front end specs among "headroom".
Hi Pieter,
as I mentioned in another thread, I prefer lower rp tubes for transformer coupling too. But I have tried the 26 in a linestage with 4.5:1 step down. Actually I built a universal linestage which can accept 801A, 10Y, 26, UX112 and UX201A tubes.
Adding a buffer would defeat the purpose of a DHT linestage IMHO. And I rather have low Zout possibly driving an inductive volume control than a high Zout linestage with a 26 and a 1:1 transformer.
It's a matter of personal preference and where you are willing to put the compromise. I have built it and in this case the sacrifice of ultimate treble bandwidth is where I would choose to compromise. A 26 linestage with all it's associated issues (microphonics) has nothing to do with 'HiFi specs' anyways
Best regards
Thomas
as I mentioned in another thread, I prefer lower rp tubes for transformer coupling too. But I have tried the 26 in a linestage with 4.5:1 step down. Actually I built a universal linestage which can accept 801A, 10Y, 26, UX112 and UX201A tubes.
Adding a buffer would defeat the purpose of a DHT linestage IMHO. And I rather have low Zout possibly driving an inductive volume control than a high Zout linestage with a 26 and a 1:1 transformer.
It's a matter of personal preference and where you are willing to put the compromise. I have built it and in this case the sacrifice of ultimate treble bandwidth is where I would choose to compromise. A 26 linestage with all it's associated issues (microphonics) has nothing to do with 'HiFi specs' anyways
Best regards
Thomas
Hi George,
As I wrote in other threads, I'm not too obsessed with op points. Well implemented, a change in op point will not change the overall character. In a linestage the 1660 has enough overhead that you can run it with a bit more current. Choose a point in the plate curves which gives you good overhead and equal room for positive and negative excitation of the grid.
As for TVCs, I'm using Dave Slagle's (intactaudio)
best regards
Thomas
As I wrote in other threads, I'm not too obsessed with op points. Well implemented, a change in op point will not change the overall character. In a linestage the 1660 has enough overhead that you can run it with a bit more current. Choose a point in the plate curves which gives you good overhead and equal room for positive and negative excitation of the grid.
As for TVCs, I'm using Dave Slagle's (intactaudio)
best regards
Thomas
It's a matter of personal preference and where you are willing to put the compromise. I have built it and in this case the sacrifice of ultimate treble bandwidth is where I would choose to compromise. A 26 linestage with all it's associated issues (microphonics) has nothing to do with 'HiFi specs' anyways
Agreed!
I've listed many times to 01A compared with 26 and others. The 01A is a little more dynamic - involving but not quite as smooth overall as the 26. They are close but if pushed I'd take the 26. Nevertheless we are talking two of the best tubes at any price here, so this is still way ahead of most other tubes except for 10Y and a small number of others.
As for availability, I bought loads of both when they were cheaper. The 01A has gone up in value more than the 26, so again I'd go with the 26. What the 01A does have is a thoriated filament like the 10Y so it's pretty, plus filament requirements are easier.
Andy
As for availability, I bought loads of both when they were cheaper. The 01A has gone up in value more than the 26, so again I'd go with the 26. What the 01A does have is a thoriated filament like the 10Y so it's pretty, plus filament requirements are easier.
Andy
Hi!
I have built a universal linestage which can be configured to use 26, 10Y, 801A, UX112 and UX201A. This linestage was publicly demoed at last years 'Vienna Vibes' festival. A brief report can be found under this link. The part about the linestage is around the middle of the page.
http://theaudioeagle.com/columns/vienna_vibes_2010.html
My personal favorite is the 801A for it's neutral and extremely transparent sound. The 26 is a bit creamy in comparison which sounds quite pleasant, it has a bit less resolution. The UX201A is very special. It is extremely euphonic but in a positive way. It is less transparent and shaves off some rough edges in a pleasant way. Some people call it the ideal tube for blues music. It could be very beneficial with digital sources which sound a bit harsh.
Here some more pics of that linestage:
ImageShack® - Online Photo and Video Hosting
ImageShack® - Online Photo and Video Hosting
ImageShack® - Online Photo and Video Hosting
ImageShack® - Online Photo and Video Hosting
ImageShack® - Online Photo and Video Hosting
ImageShack® - Online Photo and Video Hosting
Best regards
Thomas
I have built a universal linestage which can be configured to use 26, 10Y, 801A, UX112 and UX201A. This linestage was publicly demoed at last years 'Vienna Vibes' festival. A brief report can be found under this link. The part about the linestage is around the middle of the page.
http://theaudioeagle.com/columns/vienna_vibes_2010.html
My personal favorite is the 801A for it's neutral and extremely transparent sound. The 26 is a bit creamy in comparison which sounds quite pleasant, it has a bit less resolution. The UX201A is very special. It is extremely euphonic but in a positive way. It is less transparent and shaves off some rough edges in a pleasant way. Some people call it the ideal tube for blues music. It could be very beneficial with digital sources which sound a bit harsh.
Here some more pics of that linestage:
ImageShack® - Online Photo and Video Hosting
ImageShack® - Online Photo and Video Hosting
ImageShack® - Online Photo and Video Hosting
ImageShack® - Online Photo and Video Hosting
ImageShack® - Online Photo and Video Hosting
ImageShack® - Online Photo and Video Hosting
Best regards
Thomas
Andy & Thomas
Thank you both.
I have some 801A's; but Rod's supply has the option of 01A with jumper to allow a #26
But i love old blues - which sounds great via the UX-201A . .
Can you show the circuit of the universal linestage? I'd be VERY happy with the ability to swap creamy 26/ transparent 801A / bluesy UX201A
to switch tubes, how many parts need replacing ?
Thank you both.
I have some 801A's; but Rod's supply has the option of 01A with jumper to allow a #26
But i love old blues - which sounds great via the UX-201A . .
Can you show the circuit of the universal linestage? I'd be VERY happy with the ability to swap creamy 26/ transparent 801A / bluesy UX201A
to switch tubes, how many parts need replacing ?
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Thomas has got it exactly right with "euphonic" for the 01A. I'm not sure if I'd call the 26 creamy - though it does have a very lovely midrange. I'd say it was neutral, though with a little warmth, so I can see what THomas means.
One trick you could use is glow tubes. When I was discovering DHT small tubes I used to switch tubes by using a bench supply for the filaments. To change the operating point I had two sockets for glow tubes. By using a selection of two glow tubes I could get the following values for the HT in a couple of seconds.
75
85
90
105
150
180
195
210
225
240
255
255
300
Andy
One trick you could use is glow tubes. When I was discovering DHT small tubes I used to switch tubes by using a bench supply for the filaments. To change the operating point I had two sockets for glow tubes. By using a selection of two glow tubes I could get the following values for the HT in a couple of seconds.
75
85
90
105
150
180
195
210
225
240
255
255
300
Andy
Hi Andy,
I think we pretty much mean the same, maybe creamy was not the right word. The 26 is warmer in comparison to the 801A in the same circuit environment. A bit less transparent but very good nonetheless.
The universal linestage I built was a bit complicated to enable the usage of allt hose different tubes. I'm currently working on another DHT line which is switchable just between 26 and 801A with minimal circuit overhead.
The UX201A is quite worthwhile to try. Very special, so maybe not so well suited for general use. But it could be the right ticket in certain set ups to get a good overall balance.
Best regards
Thomas
I think we pretty much mean the same, maybe creamy was not the right word. The 26 is warmer in comparison to the 801A in the same circuit environment. A bit less transparent but very good nonetheless.
The universal linestage I built was a bit complicated to enable the usage of allt hose different tubes. I'm currently working on another DHT line which is switchable just between 26 and 801A with minimal circuit overhead.
The UX201A is quite worthwhile to try. Very special, so maybe not so well suited for general use. But it could be the right ticket in certain set ups to get a good overall balance.
Best regards
Thomas