This is actually my next project 
I have a pair of Lundahl LL1660S/10mA that I'll use in SE input to SE output configuration. I've heard this IT in my previous project (6SN7 > IT > EL34 PP) and I wanted to use it in SE to drive a 300B (or maybe a 45).
I plan to use any of the following driver tubes-
10, 2C51, WE404A in triode
Sorry, I did not answer your question
I have a pair of Lundahl LL1660S/10mA that I'll use in SE input to SE output configuration. I've heard this IT in my previous project (6SN7 > IT > EL34 PP) and I wanted to use it in SE to drive a 300B (or maybe a 45).
I plan to use any of the following driver tubes-
10, 2C51, WE404A in triode
Sorry, I did not answer your question
I do not think that there is a concensus about using transformer as interstage. Some believe that Transformers are bad because of their unlinearity and some believe that they are good - for various reasons.
Basically there are two most often used interstage concepts: transformer and capacitor. During transients, this capacitor discharges, which is not a big problem. The problem is that re-charging can take 5 times longer. And that means distorsion. If the transients are frequent (for example when you listen Metallica very loud), then this interstage can be a source of permanent distorsion. Transformer does not have that effect, if it is designed well. And these Lundahls are. The problem with interstage transformers is that they are rather expencive.
This is actually very old subject. Recommended reading about this particular subject:
http://www.audioxpress.com/resource/audioclass/ga400ac.pdf
This is an article about PP but the statements about interstage are valid also for SE.
Another interesting reading is also:
http://www.tubelab.com/powerdrive.htm
This guy developed a completely new approach to this subject. He addresses also a very well known fact that some of the best amps (Kondo, Audio Note,...) are using capacitors as interstage. These amps are so expencieve that the cost of transformer doesn't play any role.
Andrea did a great job by adapting in reality Sakuma design and making it even more simple. About Sakuma you can read here:
http://www10.big.or.jp/~dh/index.html070810
Just go for it ...
Basically there are two most often used interstage concepts: transformer and capacitor. During transients, this capacitor discharges, which is not a big problem. The problem is that re-charging can take 5 times longer. And that means distorsion. If the transients are frequent (for example when you listen Metallica very loud), then this interstage can be a source of permanent distorsion. Transformer does not have that effect, if it is designed well. And these Lundahls are. The problem with interstage transformers is that they are rather expencive.
This is actually very old subject. Recommended reading about this particular subject:
http://www.audioxpress.com/resource/audioclass/ga400ac.pdf
This is an article about PP but the statements about interstage are valid also for SE.
Another interesting reading is also:
http://www.tubelab.com/powerdrive.htm
This guy developed a completely new approach to this subject. He addresses also a very well known fact that some of the best amps (Kondo, Audio Note,...) are using capacitors as interstage. These amps are so expencieve that the cost of transformer doesn't play any role.
Andrea did a great job by adapting in reality Sakuma design and making it even more simple. About Sakuma you can read here:
http://www10.big.or.jp/~dh/index.html070810
Just go for it ...
Its a very tough job for a driver to push both an interstage transformer and a 300B combined. If you are using it in PP then the current availble to each grid is halved (so using the LL1660 10mA, each grid only gets at best 5mA of drive). Most people tend to like to drive the 300B with a bit more than that. Also, even the best interstage transformer has capacitive loses which compound the 300B miller capacitance. Forget about stepup arrangements in the real world.
I would not like to put you off but there are other options;
1-parafeed the interstage. The transformers performance should dramatically improve and you can easily push 20-40mA of current through your driver tube. The question is does the improvement in transformer performance outweigh the penalty of the parafeed cap.
2-use an input transformer phase splitter, followed by a meaty driver, pushing a PP interstage transformer driving the 300B grids. (ala Raven amp).
Again I think the extra effort is well worth it. My current amp uses 6080's in PP with parallelled 5687 pushing a parafeed interstage transformer at 40mA. It sounds wonderful and wasn't as expensive to implement as might be expected. The 300B project would have similar drive requirements. Even in SE all of the above consideration apply.
Also remember that you are restricted to a none gNFB approach if you use an interstage transformer, so if you find that the top end is rolling off unacceptably, your only option is to push more current through your IT - which may not be an option.
Hope that helps.
Shoog
I would not like to put you off but there are other options;
1-parafeed the interstage. The transformers performance should dramatically improve and you can easily push 20-40mA of current through your driver tube. The question is does the improvement in transformer performance outweigh the penalty of the parafeed cap.
2-use an input transformer phase splitter, followed by a meaty driver, pushing a PP interstage transformer driving the 300B grids. (ala Raven amp).
Again I think the extra effort is well worth it. My current amp uses 6080's in PP with parallelled 5687 pushing a parafeed interstage transformer at 40mA. It sounds wonderful and wasn't as expensive to implement as might be expected. The 300B project would have similar drive requirements. Even in SE all of the above consideration apply.
Also remember that you are restricted to a none gNFB approach if you use an interstage transformer, so if you find that the top end is rolling off unacceptably, your only option is to push more current through your IT - which may not be an option.
Hope that helps.
Shoog
I got some homework
Hi everyone
I want to use the 300b;s in parallel set mode.. for reasons obvious and mysterious, I have my heart set on paralell single end.
SHoog in pse is there enough current to drive the 300b's?
Thanks
Ps the 417A seems a bit thin on the ground.. what octal alternatives can be used.. ?
ps number 2. Can say a 6sn7 in srpp be used (I believe that srpp can provide the swing necessary to drive the 300b)?
Thanks
Nick
Hi everyone
I want to use the 300b;s in parallel set mode.. for reasons obvious and mysterious, I have my heart set on paralell single end.
SHoog in pse is there enough current to drive the 300b's?
Thanks
Ps the 417A seems a bit thin on the ground.. what octal alternatives can be used.. ?
ps number 2. Can say a 6sn7 in srpp be used (I believe that srpp can provide the swing necessary to drive the 300b)?
Thanks
Nick
I don't know enough specifically about the 300B to pass comment really. Using two in parallel doubles your problems though.
Take a look at some respected 300B designs and see what they are pushing through their drivers, then add a little to account for the loses through the IT. This should tell you whether 20mA of drive will be enough. I have a hunch you might struggle. If I was doing it I would build the Karna instead.
Another option would be to consider direct coupling, with possibly an interstage transformer between an initial preamp and a driver.
Shoog
Take a look at some respected 300B designs and see what they are pushing through their drivers, then add a little to account for the loses through the IT. This should tell you whether 20mA of drive will be enough. I have a hunch you might struggle. If I was doing it I would build the Karna instead.
Another option would be to consider direct coupling, with possibly an interstage transformer between an initial preamp and a driver.
Shoog
Hi Shoog, what are those respected designs you mentioned? I know the works of Lynn Olson, and I don't think I can afford it 
I've seen the designs of Andrea, Andy Grove, and they do drive the 300B with an interstage. Some use 5842 - IT - 300 and the Audio Note used Pentode (triode strapped) - IT - 300B...
Thanks for your insights, keep 'em coming
I've seen the designs of Andrea, Andy Grove, and they do drive the 300B with an interstage. Some use 5842 - IT - 300 and the Audio Note used Pentode (triode strapped) - IT - 300B...
Thanks for your insights, keep 'em coming
This design was made for the KR-Audio’s T100 triode but it plays well together with 300B/842VHD etc. The IS transformer is 1:1 bifilar wound from Sowter (bw greater than 250kHz). With 300B and B+ about 500V the requirement for voltage swing from the driver is ~60Vrms (~85Vp).
With a triode like 300B you might like an OPT with 2.5-3.5k primary..
Jan E Veiset
With a triode like 300B you might like an OPT with 2.5-3.5k primary..
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Jan E Veiset
more questions
Thanks to all.
Jane how hard would it be to drive pse 300b?
Can the el84 be subsituted by another tube? I have a friend In albury who designs and builds set amps with the el84 as a driver but i find it unpleasant. I have heard one with a 6ca7 driver and it sounds much smoother.
Whilst I am on it, I have just finished building a Aikido 6sn7 as an experiment and i must say I am very impressed.. man the lack of noise is stunning.. I slapped this together in like 30 minutes, hooked it up to Doede Durmas 6sn7 phono stage.. very small amount of heater noise from the elvated heaters but not a lot.
So is the aikido topology amenable to driving the 300b? With or without IT?
Looks like I have a new preamp to build after having tried the Aikido topology.. the detail is spectacular (excuse me whilst i wipe the froth from my mouth)
Hope everyone is well
Nick
Thanks to all.
Jane how hard would it be to drive pse 300b?
Can the el84 be subsituted by another tube? I have a friend In albury who designs and builds set amps with the el84 as a driver but i find it unpleasant. I have heard one with a 6ca7 driver and it sounds much smoother.
Whilst I am on it, I have just finished building a Aikido 6sn7 as an experiment and i must say I am very impressed.. man the lack of noise is stunning.. I slapped this together in like 30 minutes, hooked it up to Doede Durmas 6sn7 phono stage.. very small amount of heater noise from the elvated heaters but not a lot.
So is the aikido topology amenable to driving the 300b? With or without IT?
Looks like I have a new preamp to build after having tried the Aikido topology.. the detail is spectacular (excuse me whilst i wipe the froth from my mouth)
Hope everyone is well
Nick
Re: I got some homework
Well, the reasons are not so misterious: parallel 300B's sound extremly good (if everything is done well). The last 300B PSE I have heard was True Sound: 300B PSE. The loudspeakers were Avantgarde Duo - exceptional sound !
It is though a bit more expencive to implement....
duderduderini said:
Well, the reasons are not so misterious: parallel 300B's sound extremly good (if everything is done well). The last 300B PSE I have heard was True Sound: 300B PSE. The loudspeakers were Avantgarde Duo - exceptional sound !
It is though a bit more expencive to implement....
A friend of mine has built paralleled 300B's with 417 drivers and transformer coupling throughout. (Input, interstage and of course output) Each monoblock has a total of 7 transformers (Including power and heater supplies) The sound is absolutely stunning! There is a catch though. You can't buy these transformers out of a catalogue or off a website. He learned how to design them and then had them all wound to his specs. There is absolutely no bass or treble rolloff. He has offered to share his knowhow with me and help me build some for myself, but I can't afford it (not even with capacitor coupling)
hihopes said:
>100% support Hihipos. I actually built mono blocks with the attached schematic using IT LL1660 and an WE input transformer 20k:80 of -19db. Warm and sweet, extended bandwith, clarity, no roll-off and, last of all, natural. I totally satisfied with 6C45Pi from Russian mil. but shall search for WE 347/317 for a comparison. This is very simple to build, no hum or noise. If anyone need tips or more info, just give me a note.
Attachments
Would be another joke. You can heat the tube with solar power.
Anyway, for simplicity, just wire the 5v AC with center tap grounded. A little hum but will give lively sound. For a tighter control, let's do a regulated DC with a 100-Ohm hum pot and get the pot's center grounded. Enjoy your tricks.
Anyway, for simplicity, just wire the 5v AC with center tap grounded. A little hum but will give lively sound. For a tighter control, let's do a regulated DC with a 100-Ohm hum pot and get the pot's center grounded. Enjoy your tricks.
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