Little Sweetie Forum amplifier project

[henry4841]

Those heavy air coil inductors look impressive but guys that really understand electronics know that as long as an inductor does not saturate at the chosen point of power by the designer it is going to work just as good as one that is more expensive. If it works great how are you going to make it better by spending more. The engineers at Klipsch, that have had electronic training, have decided that the inductor they use, iron core inductor most likely, will get the job done excellently without spending a lot more for eye candy. They know this, not by trial and error like novices, but by the specifications on the specification sheet of that part. They find an inductor at an electronic house that meets the specifications they are looking for and if they are really smart and have the lab they will test that inductor to be sure it meets what is specified in the spec sheet from the manufacturer. If so they are ready to proceed building their crossover design. Not many have the talent and means to do what a large company like Klipsch does designing a crossover period. Many of those youtube experts are just after your money. And succeed. 

 

If you have bought into the guy on youtube and purchased the kit it may sound good after doing the changes. But most certainly you will not hear what the audio the engineers at Klipsch decided sound best to them. You will be hearing what the guy, with dubious credentials, decided sounded good to him. Bet he does not have the equipment and testing facilities a large audio company like Klipsch has. What you think?
 

[Shakeydeal]

6 hours ago, Area 51 said:

I once read, "The best pre amp is no pre amp". I guess it's safe to assume you would agree with that, Henry. I hope I'll be able to experiment and play with some A-B comparisons so I can contribute from experience.

That’s certainly been my experience. I’ve owned many well regarded preamps from the likes of Audible Illusions, Audio Research,  Cary, CJ, BAT and many more. A well designed passive has beaten them all. With high efficiency speakers and tube amps there really is no reason not to give one a try. One might be pleasantly shocked.

[henry4841]

3 minutes ago, Shakeydeal said:

That’s certainly been my experience. I’ve owned many well regarded preamps from the likes of Audible Illusions, Audio Research,  Cary, CJ, BAT and many more. A well designed passive has beaten them all. With high efficiency speakers and tube amps there really is no reason not to give one a try. One might be pleasantly shocked.

No two people hear the same or have the same taste. Find what pleases you and the heck what others think. 

[tube fanatic]

1 hour ago, Shakeydeal said:

That’s certainly been my experience. I’ve owned many well regarded preamps from the likes of Audible Illusions, Audio Research,  Cary, CJ, BAT and many more. A well designed passive has beaten them all. With high efficiency speakers and tube amps there really is no reason not to give one a try. One might be pleasantly shocked.

No question that the least number of powered devices in the signal path, the better.  Even more revealing is directly driving the power amplifier stage with the source.  Only one amplifying device in the path between the source and speaker produces some amazing results.  This has been confirmed by folks who built a Little Millie or Little Sweet Potato (the LSP has been updated since the original was posted).

 

Maynard

[Travis In Austin]

4 hours ago, tube fanatic said:

No question that the least number of powered devices in the signal path, the better.  Even more revealing is directly driving the power amplifier stage with the source.  Only one amplifying device in the path between the source and speaker produces some amazing results.  This has been confirmed by folks who built a Little Millie or Little Sweet Potato (the LSP has been updated since the original was posted).

 

Maynard

I agree with that premise 100%, but I don't know why. Can you help a neophyte understand why this is true? Does it add distortion?

 

Is this the same premise for the no tone controls debate on preamps? (Which was a marketing thing started by Mark Levinson when he ran the company with his name. He removed tone controls from all of his designs. When he lost his company, and his name, and started Cello, he went back to "you have to have a good equalizer" and developed the Pallet). 

 

There was a person on here for a time who was preaching that only a "direct coupled" amp was the way to go (eliminating a capacitor making all the difference in the world).

 

Why is the least number of powered devices in the signal path the better? Distortion. Or does each one impart a change to the sound signature? Or is it just plain common sense, the less things in the middle, the less change at the end? Does this axiom apply equally to SS at Tube amplification?

 

Thanks,

 

Travis

 

 

[Edgar]

24 minutes ago, Travis In Austin said:

I agree with that premise 100%, but I don't know why. Can you help a neophyte understand why this is true?

Every device in the signal path alters the signal in some way. The change may be small or it may be large. It may be a change in frequency or phase response, or the addition of distortion or noise, or all of the above. A large change will be obvious, and such a device will probably be noticed immediately and rejected. A small number of small changes won't matter much, but a large number of small changes adds-up to a big change. This is the theory behind placing as few devices in the signal path as possible.

 

This applies to all devices, passive or active.

[captainbeefheart]

6 hours ago, henry4841 said:

Those heavy air coil inductors look impressive but guys that really understand electronics know that as long as an inductor does not saturate at the chosen point of power by the designer it is going to work just as good as one that is more expensive. If it works great how are you going to make it better by spending more. The engineers at Klipsch, that have had electronic training, have decided that the inductor they use, iron core inductor most likely, will get the job done excellently without spending a lot more for eye candy. They know this, not by trial and error like novices, but by the specifications on the specification sheet of that part. They find an inductor at an electronic house that meets the specifications they are looking for and if they are really smart and have the lab they will test that inductor to be sure it meets what is specified in the spec sheet from the manufacturer. If so they are ready to proceed building their crossover design. Not many have the talent and means to do what a large company like Klipsch does designing a crossover period. Many of those youtube experts are just after your money. And succeed. 

 

If you have bought into the guy on youtube and purchased the kit it may sound good after doing the changes. But most certainly you will not hear what the audio the engineers at Klipsch decided sound best to them. You will be hearing what the guy, with dubious credentials, decided sounded good to him. Bet he does not have the equipment and testing facilities a large audio company like Klipsch has. What you think?
 

 

The issue with air core is you don't have a core helping you increase inductance, but you also don't have it's saturation curve characteristics. Since you need a lot of copper with an air core it will given the same inductance have higher DC resistance unless it's absolutely massive and not fit inside the speaker enclosure. The thing with cored inductors is as long as you are on the right side of the saturation curves; i.e. no saturation then the core should have minimal to no effect on the signal. I'd prefer to use very high permeability core material and less copper to keep DC resistance low and size it so no saturation occurs at maximum signal level. It will be less expensive, have a smaller footprint and function the same or better.

 

I mean most of us use very low power since our speakers are so efficient so I highly doubt the core is effecting the sound in any audible way.

[Racer X]

1 hour ago, Travis In Austin said:

I agree with that premise 100%, but I don't know why. Can you help a neophyte understand why this is true? Does it add distortion?

 

Is this the same premise for the no tone controls debate on preamps? (Which was a marketing thing started by Mark Levinson when he ran the company with his name. He removed tone controls from all of his designs. When he lost his company, and his name, and started Cello, he went back to "you have to have a good equalizer" and developed the Pallet). 

 

Boy, for a moderator, you sure do ask a lot of questions.

 

Believe your answer is in your excellent Mark Levinson example:  In Audio, one likes to have it both ways, sometimes at the same time.

 

One would think there are examples of components with few active devices in the signal path with more distortion than others with more....

[henry4841]

1 hour ago, Travis In Austin said:

I agree with that premise 100%, but I don't know why. Can you help a neophyte understand why this is true? Does it add distortion?

 

Is this the same premise for the no tone controls debate on preamps? (Which was a marketing thing started by Mark Levinson when he ran the company with his name. He removed tone controls from all of his designs. When he lost his company, and his name, and started Cello, he went back to "you have to have a good equalizer" and developed the Pallet). 

 

There was a person on here for a time who was preaching that only a "direct coupled" amp was the way to go (eliminating a capacitor making all the difference in the world).

 

Why is the least number of powered devices in the signal path the better? Distortion. Or does each one impart a change to the sound signature? Or is it just plain common sense, the less things in the middle, the less change at the end? Does this axiom apply equally to SS at Tube amplification?

 

Thanks,

 

Travis

 

 

Not so much distortion but each circuit can and often does put it's own flavor to the sound. Naturally if one of your pieces of equipment has a little bit of distortion you are going to amplify it on the next stage.

 

You will not find any tone controls on any Passlabs or Firstwatt product. The thought is to keep the audio signal alone and keep it as pure as it went in.  That is what single ended class A is all about. Keeping the audio signal as pure and original as possible. That is the reason class A is considered the purist form of amplification. No way do you want to put tone controls manipulating the audio signal after paying a premium price for a class A single ended Passlabs product. This is just one thought. Many like tone controls with treble and bass knobs. Nothing wrong with that after all this is entertainment. You do have to have your room and speakers dialed in together to accomplish this successfully. Using class A without boosting or reducing bass or treble with tone controls. All SET tube amplifiers are class A. My favorite form of amplification. That being said I still like the class A/B sound as well where the audio signal is split in half during amplification. That and class A PP. The guys that design upper end class A/B amplifiers put the signal back together after spitting do it really well with the advantage of more power and stronger bass. In SS amplifiers or tube amplifiers you can have class A action if the active devices, tube or transistor, is biased up high enough where they stay full on called class A push pull amplification. That is at a safe bias figure. Then the signal is split and put back together but the transistors or tubes are set to a specific number and not reduced and increased as in a push pull A/B amplifier. I hope I have not made this too confusing. Just different ways to achieve the same result. Pleasing sound and music. 

[henry4841]

Got the tubes from Tubedepot for the Premium Sweetie just now. Tubedepot sells the tubes for this build as various brands not specifying what you will get. I see it as so cool opening the box to see what you get this time. They sent RCA 6SJ7's and Sylvania 6Y6GA's. Look at those old 80 to 90 year old tube boxes the 6Y6's came in. Really cool for me to see them after being in storage for so long. The tubes themselves cost a total of $35.80. It is worth the price to hoard and have a pair in my little world. So cool. 

[henry4841]

Just noticed on the picture above it says on the 6Y6 tube box, date packed 10-66. Does not mean when the tube was made. When a big company made a run of a specific tube they made a surplus of them with no label put on the tube for sale to another company wanting the tube to put their label on. Unless you know code numbers, if the tube has code numbers, no way to tell who actually made the tube. Let's just say old. All the big companies had making tubes down to a science. The old guys knew what they were doing. You have to remember that is all they had for amplification way back then, for decades. Tubes

[tube fanatic]

18 hours ago, Travis In Austin said:

I agree with that premise 100%, but I don't know why. Can you help a neophyte understand why this is true? Does it add distortion?

 

Is this the same premise for the no tone controls debate on preamps? (Which was a marketing thing started by Mark Levinson when he ran the company with his name. He removed tone controls from all of his designs. When he lost his company, and his name, and started Cello, he went back to "you have to have a good equalizer" and developed the Pallet). 

 

There was a person on here for a time who was preaching that only a "direct coupled" amp was the way to go (eliminating a capacitor making all the difference in the world).

 

Why is the least number of powered devices in the signal path the better? Distortion. Or does each one impart a change to the sound signature? Or is it just plain common sense, the less things in the middle, the less change at the end? Does this axiom apply equally to SS at Tube amplification?

 

Thanks,

 

Travis

 

 

This can turn into a very long, detailed, thread so Henry can decide if it should be separated from this one.

 

Some of the points have been made already, so I will add some more:

 

1) thermal agitation- the irregular, random, motion of free electrons can produce minute currents which are greatly amplified by the driver stage (which, depending on the design, can amplify by a factor of even 100 or more).  This will pass through and can be heard at the speaker.  The higher the temperature, the more noise which is quite relevant considering the hot cathode of a tube.  And, the electron flow through solder joints, volume controls, and components may, if at the input of the driver stage, be amplified and become audible.  

 

2) shot effect- small irregularities in plate current due to individual electrons striking the plate is often encountered in high gain stages (I.e. the driver) and may be audible at the speaker.

 

3) microphonics- caused by mechanical vibration of tube elements causing variations in audio currents.  Tubes are notorious for this, but it can be noted from capacitors as well.  
 

4) hum- often attributable to AC operated filaments is often a problem in driver stages.  Proper cathode bypassing and filament lead dress can minimize, but may not eliminate, this issue.  If the B+ supply to the driver has too much ripple (AC component), it will be passed through and will be audible.  
 

5) stray electromagnetic fields from other devices, routers, lamp dimmers, etc. may find their way into high gain driver stages and become audible.

 

So, you can appreciate that elimination of the driver stage of an amp and going directly into the output stage, which has vastly lower gain, will result in a much cleaner sound.

 

I need to get back to work, so others can discuss the coupling cap (or lack of) situation.  As far as the SS ramifications, I guess that should be a topic in that section as opposed to here.

 

Maynard

 

 

[henry4841]

Glad to have you join in the conversation Maynard. After all this amplifier is your creation. Great find that 6Y6 tube. For years I have been telling you how much I like the sound of that tube. 

[henry4841]

Many may have noticed how often I mention Nelson Pass. No doubt he is a genius in his field. When he walks into a room of electronic engineers and geeks he does not try and show how much smarter he is, he knows he is the smartest one in the room. But the main reason I follow everything I can about him is he shares some of his knowledge for the hobbyist and electronic geeks all over the world. Special individual. About the discussion Travis mentioned, Nelson tries really hard to remove just one resistor in one of his designs if he thinks he can do without it. The feeling being less parts, better sound. My following his philosophy is probably why I like a simple amplifier like this Sweetie. Just two circuits in the audio part of the amplifier. A well designed SS push pull amplifier will have 8 or 10 circuits for each channel instead of just 2 circuits like in most SET tube amplifiers. 

[henry4841]

5 hours ago, tube fanatic said:

This can turn into a very long, detailed, thread so Henry can decide if it should be separated from this one.

 

Some of the points have been made already, so I will add some more:

 

1) thermal agitation- the irregular, random, motion of free electrons can produce minute currents which are greatly amplified by the driver stage (which, depending on the design, can amplify by a factor of even 100 or more).  This will pass through and can be heard at the speaker.  The higher the temperature, the more noise which is quite relevant considering the hot cathode of a tube.  And, the electron flow through solder joints, volume controls, and components may, if at the input of the driver stage, be amplified and become audible.  

 

2) shot effect- small irregularities in plate current due to individual electrons striking the plate is often encountered in high gain stages (I.e. the driver) and may be audible at the speaker.

 

3) microphonics- caused by mechanical vibration of tube elements causing variations in audio currents.  Tubes are notorious for this, but it can be noted from capacitors as well.  
 

4) hum- often attributable to AC operated filaments is often a problem in driver stages.  Proper cathode biasing and filament lead dress can minimize, but may not eliminate, this issue.  If the B+ supply to the driver has too much ripple (AC component), it will be passed through and will be audible.  
 

5) stray electromagnetic fields from other devices, routers, lamp dimmers, etc. may find their way into high gain driver stages and become audible.

 

So, you can appreciate that elimination of the driver stage of an amp and going directly into the output stage, which has vastly lower gain, will result in a much cleaner sound.

 

I need to get back to work, so others can discuss the coupling cap (or lack of) situation.  As far as the SS ramifications, I guess that should be a topic in that section as opposed to here.

 

Maynard

 

 

What Maynard just described is why I have never attempted to build a tube phono amplifier. A few transistor ones yes but never a tube one. Everything becomes critical when you are dealing with such a tiny signal coming from a phono cartridge. 

[henry4841]

Morning guys. We are up to 8.8K views on this thread and it is not even a month old. There seems to be an interest in the country boy way of looking at things. I think Maynard and I make a good pair. I try and give the country boy way of looking at electronics and Maynard gives the technical side. I am pretty sure if Maynard and I were neighbors we could sit on the front porch in the evening watching the sun set in our rocking chairs without having to say very much. 

 

First thing this morning we all need to congratulate Dean for becoming an authorized builder of Klipsch crossovers. I am sure it can be a long and happy relationship as long as Dean builds the Klipsch sound. That is what buyers of Klipsch speakers are looking for when they buy a pair of Klipsch speakers. The Klipsch sound. When people buy a Pass Labs amplifier they expect to hear the Pass Lab sound and yes they have their own signature sound. Nelson has stated this on some of his videos. Buy a Pass Lab amplifier and you are going to get a dependable well built amplifier with the Pass Lab sound, consistently. Same goes for Klipsch. Your old Heritage speakers may have not came with the capacitors that the sound guys of yesteryear liked but the sound guys at Klipsch now have determined that the parts chosen for their crossovers is the sound they want reproduced in their speakers. Their personal sound signature. If one wants to hear what the Klipsch sound engineers have determined sounds best in old Klipsch speakers you will want to get the capacitors they recommend. And if you do not want to do it yourself Dean is now the guy to see and not some of those other after market sellers of crossovers. 

[henry4841]

I would like Maynard's thoughts on increasing the power of the 6Y6 tube. Ultra-linear or pentode operation is a couple of ways to achieve it. Me personally, I have always clung to triode operation even with it's lower power figure. IMHO perfect for Klipsch speakers. The one watt the Sweetie, as it is now designed, will make a sound level in your room 3 ft. away 95db or better with Klipsch speakers before clipping. Guys 95db is loud. Too loud for extended listening. That is for sensible people. With my LaScala's one watt equals 103db.  From the net.  

 

"Is 80 dB too loud?

80 decibels is considered potentially harmful to your hearing. Especially if exposure exceeds 8-10 hours/day. The maximum noise level you can be exposed to without having to worry about hearing damage or potential hearing loss is 70 decibels over a 24-hour period."

 

I see power as what old audio folks talked about in their youth among other audiophiles, if I can use that word for me and my friends. My amplifier has 150 watts so it must sound better than your measly 100 watt amplifier, in a nice way of course without offending your friend. Just some BS from sellers of amplifiers that they want you to believe to promote their product. More has to be better, right?

 

Anyways getting back to increasing power from the 6Y6 tube, for me using another way of operation just does not set right. It is in my head from what little I know of amplification. I kinda turn my nose up on other ways of using a tube.  It is all about the curves in the data sheet of any active device whether tube or transistor. Pentode curves go horizonal and triode curves go vertical in the data sheets. Two distinctly different sounds. Most all transistors have curves like a pentode tube. There is only one transistor that I have heard about that has curves like a triode tube, static induction transistors. Nelson has been playing with them for the last 10 years coaxing the triode sound from a SS transistor. I cannot make an ultra-linear amplifier from the 6Y6 tube with the OPT's I now have. But I think it is possible to make the Premium Sweetie build into a pentode amplifier with just some minor changes in the 6Y6 circuit giving this tube possible a couple more watts. Not that I think it is needed but it seems most like to talk numbers on this forum. My ears like the pentode sound it is my limited electronic knowledge that leads me in the direction of the triode tube sound. 

 

Perhaps Maynard will post his thoughts of doing this and what would be involved in his design. 

[tube fanatic]

Although I have designed many well accepted single ended pentode amps, I still favor SET operation if having the choice.  While you can certainly get a great deal more power from the 6Y6 in pentode mode, it is not outstanding in my experience.  Other tubes sound better to me.  As for ultralinear operation, I have never liked the way it sounds having tried it with a few different tubes.
 

I haven’t encountered many situations in which increasing the power from around 1 watt to 3+ watts was worthwhile.  As you know, I have been involved with flea power amps for quite some time and, with Klipsch speakers, power output in the tens of milliwatts is often more than enough.

 

It has always been fun to let someone hear an amp without telling them its power output capability.  They often don’t believe me when I reveal it!
 

Maynard

[henry4841]

Well, there you go. SET for the 6Y6 it is.

 

I like the tone of the 6Y6. Tone is what the 6Y6 brings to the table that is absent from the modern day production tubes. At least the ones I have played with. My Gold Lion 300b amplifier has a little tone in the sound signature but nothing like the 6Y6. Possible an EL34 amplifier I have with some of those old Russian 6L6 audio tubes as well but less so. I have a pair of Gold Lion KT77 tubes I can use in the EL-34 amplifier but it has no what I would call tone. Clean and clear and really good sounding but no tone. Many will prefer that kind of sound and I can appreciate it myself. I am just trying to describe what I am hearing between some different tubes. Being 73 years old I grew up in the 50's and perhaps the 6Y6 just pleases my self conscience from an old radio my mother played in our house when I was growing up. Tone is what you get with those old audio tubes. Kinda like those old tube juke boxes in bars when I was in my early 20's sound.  

 

This is one thing that is nice with most SET EL-34 amplifiers. One can swap many different tubes in and out of it hearing a completely different sound character quite easily. The EL-34 family of tubes is quite large. Never heard my EL-34 with some USA made NOS tubes but I bet you money it will take an EL-34 amplifier to another level in pleasure. 

[captainbeefheart]

I too don't prefer ultra linear, especially in single ended amps. Some push pull amps in UL can sound good, but still not my preferred method.

 

When talking about pentode vs triode curves that's with the device on a curve tracer alone with no help from that dirty little word; feedback.

 

Feedback is what gives a triode it's curves, although it's not an external connection, it's internal, but nonetheless still feedback.

 

From the RH84 amp which is a real popular amplifier is an EL84 in pentode operation but it has plate to grid feedback also sometimes called "Schade" feedback. You get the power of Pentode but the feedback transforms the curves into more triode looking curves and greatly reduces distortion.

 

I like both methods of feedback, Schade and typical output to input. I have kinda settled on building with global feedback, output to input because it incorporates the entire circuit into the loop and gives better overall circuit results.

 

If you do try a more powerful Sweetie design I'd start with something like the RH84 "Schade" feedback scheme because it already has a pentode driver which works very well with that type of feedback due to the high plate impedance of the 6SJ7. You may need to play with the plate to grid resistor value, start at 1Meg and reduce it down until you find the sweet spot, you'll most likely end up with a final value between 220k-560k.