Little Sweetie Forum amplifier project

[CWelsh]

Little Sweetie Parts List - final version

 

I've attached what I think will be the final version of the Little Sweetie parts list for a stereo version. I've included a few parts that will be different if someone decides to build a mono version and have highlighted them to try to keep the list from being confusing.

 

Some suggested including current prices for the parts so I've done that. The price columns include an "as of" date.

 

 

Little Sweetie Parts List.pdf

[henry4841]

1 hour ago, CWelsh said:

Little Sweetie Parts List - final version

 

I've attached what I think will be the final version of the Little Sweetie parts list for a stereo version. I've included a few parts that will be different if someone decides to build a mono version and have highlighted them to try to keep the list from being confusing.

 

Some suggested including current prices for the parts so I've done that. The price columns include an "as of" date.

 

 

Little Sweetie Parts List.pdf 579.11 kB · 4 downloads

Good work CWelsh. Those considering now or in the future when they run across this thread will appreciate all the work you did if they decide to take on this project and will be rewarded with a darn good SET tube amplifier at a good price using quality parts. You are to be commended. 

[jjptkd]

2 hours ago, CWelsh said:

Little Sweetie Parts List - final version

 

 So looks like $300 not including the chassis? How much is the premium version for comparison? 

[henry4841]

This is the final cost of the low cost Sweetie $369. +100 labor putting all the parts together, + $100 for the wood case total $569 was what I was paid plus shipping and paypal fee. I added $35 to parts list being I used my supplies like wire, solder, standoffs, nuts, screws. etc. I believe it actually was slightly more than $35. The listed prices include tax and the high price shipping cost getting everything to my house. 

 

Chassis 44.20

Hammond 131.00

PS tran 50.50

Tubedepot 65.22

Mouser 42.69

Miss 35.00

 

Total $369.

 

The Premium build is rising pretty fast. My estimate is going to be $500 or really close to it just for the parts. 

[Curious_George]

31 minutes ago, henry4841 said:

This is the final cost of the low cost Sweetie $369. +100 labor putting all the parts together, + $100 for the wood case total $569 was what I was paid plus shipping and paypal fee. I added $35 to parts list being I used my supplies like wire, solder, standoffs, nuts, screws. etc. I believe it actually was slightly more than $35. The listed prices include tax and the high price shipping cost getting everything to my house. 

 

Chassis 44.20

Hammond 131.00

PS tran 50.50

Tubedepot 65.22

Mouser 42.69

Miss 35.00

 

Total $369.

 

The Premium build is rising pretty fast. My estimate is going to be $500 or really close to it just for the parts. 

To save some money of the Premium Sweetie, but still keep it "dual mono" for all intents and purposes, you can use the same power transformer and split off each channel using a separate rectifier & filter for each channel. A shared power transformer does no harm and still has excellent performance for both channels. Something to think about when wanting to build the premium version and maybe want to save a few dollars. 

[henry4841]

30 minutes ago, Curious_George said:

To save some money of the Premium Sweetie, but still keep it "dual mono" for all intents and purposes, you can use the same power transformer and split off each channel using a separate rectifier & filter for each channel. A shared power transformer does no harm and still has excellent performance for both channels. Something to think about when wanting to build the premium version and maybe want to save a few dollars. 

I have done that myself a few times but I could not find a correct PS transformer at Mouser so I went with two PS transformers. Judging by some prices at say Edcor for a adequate PS transformer for stereo the price is about the same as buying 2 Hammond PS transformers. That and I have never built mono amplifiers. I put everything in one chassis being I think this way is more practical. Something new for me. Just trying to have some fun doing something I really enjoy doing. 

[henry4841]

12 hours ago, henry4841 said:

This is the final cost of the low cost Sweetie $369. +100 labor putting all the parts together, + $100 for the wood case total $569 was what I was paid plus shipping and paypal fee. I added $35 to parts list being I used my supplies like wire, solder, standoffs, nuts, screws. etc. I believe it actually was slightly more than $35. The listed prices include tax and the high price shipping cost getting everything to my house. 

 

Chassis 44.20

Hammond 131.00

PS tran 50.50

Tubedepot 65.22

Mouser 42.69

Miss 35.00

 

Total $369.

 

The Premium build is rising pretty fast. My estimate is going to be $500 or really close to it just for the parts. 

I forgot to add that included in the miss fee were the RCA input jacks, IEC connector, fuse holder, switch and speaker out jacks. All I had in stock and was not about to go searching for what all that cost again. Just added miss $35 to the low cost build. I tried to be honest as I could on that last build. The selling price for the amp was $100 over the parts which was $469 then after some back and forth with Area51 he decided he liked the idea of a cherry wood stand for the amp to sit in. I told him I would build one for $100 for him raising the cost to $569. The stand did raise the look a lot. That project came about with the talk on this forum of the cost of building a good low cost amplifier and I wanted to see what I could build one for using good parts and not the lowest cost parts that could be found. 

 

I have given some thought about the Premium build and right now my thoughts are it is not going to be for sale after I finish building it. At least for awhile, months, years down the road. I have just got too attached to that amplifier and it is the first mono build for me along with using some of the best parts, within reason, I have ever used to build an amp. The price of the iron alone was close to the $300 price George mentioned about the low cost build. I had thoughts of asking $900 plus shipping and my paypal fee which is going to total right at $100. $1000. total. I feel like I would be leaving money on the table at that price. I honestly think an amplifier built the way I am building this one would be closer to being actually worth $1500. Since I have decided to keep the Premium I think it will alright to say my thoughts on pricing when I was considering selling it. The other two pretty wood builds of mine are built with what are called box joints that are made with a jig on a table saw. Not hand cut dovetails as this one and they were built with walnut and maple I believe. This one is built using solid cherry. This chassis starts out about as basic as you can get. Pieces of solid wood and heavy gauge sheet metal then cut and machined and put together with hand cut dovetails. Lots of myself put into this build. I need to hang on to this amplifier and enjoy it for a while and not sell it. I am enjoying it now just looking at it. I could use extra money for sure but I do not actually need any. I am getting by better than many with my SS. 

[Area 51]

3 minutes ago, henry4841 said:

Lots of myself put into this build. I need to hang on to this amplifier and enjoy it for a while and not sell it.

Good for you, Henry. Enjoy!

[henry4841]

3 minutes ago, Area 51 said:

Good for you, Henry. Enjoy!

I added some more info on your build on the above post you may want to read again. I believe you are very satisfied with the price you paid for what you got. At least I hope so. 

[henry4841]

On the previous page I posted the distortion profile of my two signal generators I am now using with the Arta distortion software. For those that do not know a really good new distortion analyzer gets into the thousands of dollars and I have watched videos of those that have an expensive distortion analyzer say that software like Arta is plenty good enough and the best thing is it is a free download. Look at the two pictures of the images and you can see the primary signal, 1Khz from both generators, looks much better with the $100 Chinese generator. Not unexpected since the BK 4003a I just bought is rated at 2% distortion new. For repair work on the bench the BK is more what a repairman wants for $350 though. Signal plenty good enough for audio work with a scope and the BK is much simpler and easier to use. Does what it is supposed to do and built to last and serve someone who makes a living working with electronics. The Chinese $100 one is aimed more for the hobbyist with price a determining factor on quality. Neither one of them are built for distortion analyzing of an audio signal. Both have too much distortion on the signal for serious analysis of an audio amplifier. I still need to shop around for a better generator for distortion analyzing. That is if I want to do any more looking at distortion profiles again. Aimed more for designers than what I like doing with electronics. Fun playing with something that cost practically nothing though for audio enthusiast. 

[Area 51]

On 9/10/2022 at 1:32 AM, henry4841 said:

very satisfied

Indeed! I'm a happy guy, thank you.

[henry4841]

5 minutes ago, Area 51 said:

Indeed! I'm a happy guy, thank you.

Thanks Area. I do honestly think you have a well built amplifier, that is what I would like to think, with really good decent parts that should last a lifetime or at least a few decades before needing a freshening up. NOS tubes as well. And it sounds really good to boot. 

[Area 51]

1 minute ago, henry4841 said:

should last a lifetime or at least a few decades

Sweetie looks like she's bulletproof. She'll probably outlive me. (She's certainly in better shape).

[henry4841]

This is long overdue and something I should have posted at the beginning of this project. Maynard's original presenting of his design of this amplifier in 2015 to the Klipsch community. 

 

Jason ("thesloth") originally proposed developing a number of low power diy tube amplifiers for the new forum section with two goals in mind: 1) easy to construct by those with enough experience to work with high, potentially lethal, voltages in a safe manner, and 2) to provide a level of sound quality, when used with Klipsch speakers, which rivals that of very costly amps.  I thought it was an excellent idea.  Of course, neither of us expected William ("wdecho") to bag the first entry award!!!  And now he is getting ready for yet another amp project!

In thinking about what I wanted to offer, a number of goals came to mind:

1) use of inexpensive, readily available, tubes which were originally designed for radio service, and which offer extreme long-term reliability.

2) a design which offers no compromises (to me, that means at least 1 watt/channel, which is more than enough for 90% of the users of both Heritage and Reference Series speakers with whom I'm acquainted), and very low distortion.

3) crosstalk limited to that of the source device to allow the speakers, which are capable of breathtaking imaging and a huge soundstage, to deliver the goods.

4) built like a tank with very cool operation, allowing use all day every day if desired.

5) low parts cost to be comparable with the imported offerings seen on Amazon and elsewhere.

6) ability to shape the high frequency response to suit individual taste and room characteristics.

The first two goals are easily met by more tubes than you can imagine.  I've always believed that the finest sounding audio tubes were developed for use in radio service.  So, it was a matter of choosing a driver and output tube which provide very low distortion.  The 6Y6, which was originally registered by Raytheon in July, 1937 is a very tough "battleship" of a tube with a 12.5 watt plate dissipation based on the extremely conservative design-center criteria.  It also happens to be very linear when used as a triode (since SETS are unsurpassed for creating an enormous soundstage and pinpoint imaging, there was no decision to be made about using that mode of operation).  It's only limitation is requiring a lot of drive to achieve full output (approx. 21 volts rms in this design), so a pentode driver was needed to effortlessly provide the tube with what it needs.  The latter function is filled by the 6SJ7, which can drive the output stage fully with only about 200 millivolts of input signal, while its distortion stays very low (approx. 1% thd per published specs).  In this design, 2nd harmonic distortion of the 6Y6 is only 2% at full output into the calculated 5k plate load (corresponding to a speaker impedance of 8 ohms when connected to the amp's 8 ohm tap).  When the plate load drops to 2.5k, which corresponds with the typical minimum impedance of most Klipsch speakers of 3.5-4 ohms, the distortion rises to only 5%!  Remember that the latter figure represents 1/400 of the total output power- quite insignificant.  Speaker impedances greater than 8 ohms will reduce the distortion to well below 2%.  Power output is approx. 1.3 watts at the onset of clipping into an 8 ohm resistive load.  I know many of you are laughing at this figure.  Well, don't!  Unless you have experienced just how loudly and cleanly even half that amount of power can drive the speakers in a majority of installations you will remain skeptical.  To eliminate soundstage reducing crosstalk issues (typically encountered when both channels share a common high voltage supply), these are constructed as individual mono amps.  That can be done on a single chassis, if desired.  Cool operation is no problem at all.  The specified power xfmr is used well below its rating, and only gets mildly warm after extended use.  Little heat is developed under the chassis as well.   Longevity of the 6Y6 should not be an issue at all since the quiescent plate dissipation is about 10 watts, a very comfortable margin of safety for the tube.  In addition, as noted on the schematic, filament voltage is going to be set not to exceed 6.3 under typical operating conditions.  Excessive filament voltage is a common cause of premature tube failure.  The 6SJ7 is unlikely to ever need replacement.  Parts cost for the amps, as constructed, is in the low $300 range depending on the source you choose.  Hammond output xfmrs tend to be a bit on the expensive side- going with Edcor can save some money.  I have never heard the latter; however William, and others, has reported that they sound wonderful.  Lastly, the amp incorporates the variable low pass filter which has become a standard feature in all of my designs.  R1, the 10k pot on the schematic, allows the user to shape the high frequency characteristics of the amps to individual taste.  I install it as an under-the-chassis control which is set once and then forgotten (until the amps are used with different speakers, or in a different room, etc.).  You can just as easily panel mount the control if you plan on using it regularly, or simply eliminate it along with C1 if you don't want that capability.  Lastly, the parts ratings are, in some cases, much higher than needed for this circuit.  Since the higher rated parts are often only a few cents more than those with a lower rating, there's no reason not to over-build.  Capacitors, in particular, last much longer if run well below their rated operating voltage and internal temperature.

The amps are totally silent with an ear at the front of the speaker.  The sound is silky smooth, definition (tested with vocal and choral music) is as real as if the performers were in the room, and bass output is very potent and approaches that of a well constructed SEP amp.  I can't understand why some claim that SETs provide anemic, mushy bass.  It isn't true.  As expected, the imaging is precise and the soundstage is positively huge with my RF-15s.  The amps will be tested with CWs as soon as I can get hold of  "the guy down the road" (a professional musician and music teacher who auditions all of my creations with very critical ears!).  From past experience we have found that when voiced for my speakers, we rarely have to change anything when used with CWs.  The same voicing usually applies to K-horns and LSs as well, based on my own experiences.

I've attached pics which should be useful for anyone who wants to use a similar format.  Most importantly, star grounding (bringing all grounds to a single chassis point), and keeping all AC wiring as far from the driver as possible is critical for keeping the amps hum free.  If you use a different layout, I suggest cutting a sheet of paper to the size of the chassis you will use and placing out the xfmrs, sockets, and so on to get the arrangement you desire.  Then, mark up the chassis and re-check the component placement a couple of times before drilling.

So, who's going to build a pair of these?  If you do, you are likely to question why you ever spent a large sum on an amplifier!  These could easily be the last amps you will want to own!  

If anyone notices something in the schematic which doesn't seem correct, please let me know asap!

 

DO NOT ATTEMPT TO CONSTRUCT THESE AMPS IF YOU ARE NOT SKILLED IN WORKING WITH POTENTIALLY LETHAL VOLTAGES! 

[henry4841]

I like single ended amplifiers whether tube or SS. My preference for best sound is a tube single ended triode amplifier. For the technical minded below is an old article by Nelson Pass regarding single ended amplifiers. Lot of mentions of SET tube amplifiers in the article. 

https://firstwatt.com/pdf/art_se_classa.pdf

[henry4841]

After posting the original introduction Maynard presented of this amplifier I do not know much more I can add about the great sound of this design. Good place for me to fade into the sunset. The place for anyone building a Sweetie to post your build and results though. Not much I can say that Maynard did not say in the above post for me to say more. I will be posting results of my new build, the Premium Sweetie on another thread. See everyone there. 

[LongPlay]

This thread is very interesting to me. I would like to try building a Little Sweetie. But nowhere do I see the schematic. Can someone help me out?

[tube fanatic]

Here’s the original thread.  The schematic is a pdf between the pictures in the first post.  
 

https://community.klipsch.com/index.php?/topic/159805-the-long-awaited-little-sweetie-mono-sets/

 

Maynard

 

 

[Area 51]

Hello Klipsch heads (and especially my friend, Henry4841). The Little Sweetie amplifier built in this thread is alive and well living happily with the Heresies in my shop. As I wrote almost two years ago, the Little One will probably outlive me.

 

Thanks,

geo

[CWelsh]

On 6/30/2024 at 9:31 PM, LongPlay said:

This thread is very interesting to me. I would like to try building a Little Sweetie. But nowhere do I see the schematic. Can someone help me out?

Also note that there is a parts list in one of the posts near the top of this page.