Little Sweetie Forum amplifier project

[Curious_George]

16 hours ago, tube fanatic said:

Henry asked for my opinion about sharing a cathode resistor between the two output channels.  Well, I have never tried it!  I imagine it would result in a little crosstalk between the channels which, depending on the result one is looking for, may not be bad in that it could provide a tighter center image than dual mono would provide.  It may be similar to using a shared B+ rail to feed both output xfmrs ( there was a big discussion about this on DIY audio maybe 8-9 years ago which I will try to find).
 

Another consideration is what would happen if one tube gets weak or craps out.  Remember, the value of the shared cathode resistor is half of that for a single channel.  So, if the current through it decreases significantly, the bias will be off.  For the minimal difference in cost, I don’t see the point of not using separate resistors and caps.

 

Regarding AC vs. DC input coupling, I have always favored the former after encountering devices with leaky output coupling caps spilling DC.  Also, my preferred driver is a grid leak biased triode which, of course, requires AC coupling.  The 6SJ7 can be biased that way as well although I have not yet tried it that way.

 

If anyone wants to build but finds chassis prep to be more than they want to tackle,  the Spudkit may be a nice alternative.  Spud amps have the advantage of only using a single amplifying device per channel.  I have done a lot of work with pentode and triode spuds and elimination of a driver tube can result in some amazing sound, especially if speaker impedance variations are controlled in the pentode units (a 27 ohm resistor across the speaker terminals is all that is needed).

 

https://spudkit.com/

 

Enough rambling for today (my wife thanks Henry for convincing me to spend a few minutes on here- she thinks I don’t have enough to do 😬

 

Maynard

 

In the old Mullard publication, Tubes Circuits for Audio Amplifiers, they briefly discuss shared cathode resistors... they claim at low power, it is OK, but at higher power levels, better performance is acheived by using separate resistors/caps for each channel. This was noted on a push-pull design, not single-ended. 

[Curious_George]

Maynard, did you see the link I posted about the THD book?

[82 Cornwalls]

18 minutes ago, Curious_George said:

 

In the old Mullard publication, Tubes Circuits for Audio Amplifiers, they briefly discuss shared cathode resistors... they claim at low power, it is OK, but at higher power levels, better performance is acheived by using separate resistors/caps for each channel. This was noted on a push-pull design, not single-ended. 

 

Mr. Had does this with his single ended Inspire amplifiers (or at least he used to).

[tube fanatic]

57 minutes ago, Curious_George said:

Maynard, did you see the link I posted about the THD book?

No, I did not see it before.  Profuse thanks!  I will totally enjoy the cartoons while having lunch today!!!

 

Maynard

[henry4841]

Again I want to thank all the guys that contributed to this thread.

 

I am seriously considering building another Sweetie but this time a pretty one and mono in a single chassis. What can I say, I enjoyed building another tube amplifier. This one will use better name parts and different better looking PS transformers. The OPT's will be mounted underneath and not be seen. This is just fun for me so I plan to document the build much as I did with the previous Sweetie. This one is going to be inline with the price of the Decware Zen but better looking and sounding in my humble opinion. That is the way a standard Zen is shipped with those Russian made for something else tubes. Looking something like this build of mine. 

[Area 51]

3 minutes ago, henry4841 said:

Looking something like this

That's a good looking amp!

[henry4841]

Hey guys. I started on another Sweetie yesterday. I am going to call it a premium Little Sweetie using better known name brand parts and making it as pretty as I can for the buyers that appreciate beauty as well as function. At least what I think is pretty. The last Sweetie was made like a tool for the cheapest cost using good parts. That was the talk on the forum at the time, building a low cost but good tube amplifier. Here is a picture of what I got done yesterday. Does not look like much having been done but there is more to getting wood at the proper dimensions and making a layout for the cuts. That and I am old and slow. This amplifier is going to use the wood case as the chassis whereas the previous build was a wooden stand for the Bud chassis to sit in. The wood is solid cherry. 

[henry4841]

Little bit more done today. Busy cooking this morning taking away from my pleasure time. I am not going to talk so much from now on but let pictures tell the story. I like pictures on projects posted on the net better anyways. 

[henry4841]

My little shop. There is a radial saw not seen. One of those old Sears type. About to forget, Sears bandsaw  in another room also a wood lathe. Not very good at using the lathe. Takes practice and I have not spent much time on it.

[mike stehr]

I did hardwood flooring installs for a friend years ago, and I remember a couple we did with natural Cherry. The shade of natural Cherry darkens quickly...you would sand an area, walk away for 5 minutes, and it already went dark upon return. Looks nice, but a bit soft for flooring to me.

Not good if one has a dog.

[Area 51]

12 hours ago, henry4841 said:

Hey guys. I started on another Sweetie yesterday.

Something to look forward to ...

[henry4841]

Maynard found an excellent looking kit for diyer's to start with. The kind I started with way back when, 50 years ago or more. https://community.klipsch.com/index.php?/topic/211191-tube-amp-kits-for-the-beginner/

 

I would highly recommend a beginning builder to consider one of them to be your first choice. Cost a good bit more than the way I do it now as I have described on this thread but probably worth the extra cost for it's ease of building. Learn to make good solder joints, which is actually real easy to do with some practice, and know how to follow directions and one should have no problem putting one of those kit togethers. I looked at the schematic on the website and it is similar to the Decware Zen and this Sweetie. Simple with few parts design that sounds so good to my ears. When finished you will have as good a sounding amplifier as the Decware or Sweetie. I meant almost as good as the Sweetie. 🙂  As you can see I am partial the  design of Maynard's built around that excellent sounding 6Y6 tube. I have a Zen I built from a previous schematic by Deckert. The kit above is very much like the Zen schematic and there are few things in the kit design I like better than the new Zen schematic posted on the Decware site now. Throw in a pair of Klipsch speakers and a sub and one will have as good a system as a country boy could want. You will have to spend much more to equal or best the sound. That is if you like the single ended sound. Not everyone does. Others prefer the sound of a push pull amplifier or one of those chip amps, class D, that is becoming so popular of late. Class D amplifiers are built around a chip much like your smart phone is built around a chip. Tube amplifiers and SS A or A/B amplifiers are built around a tube or transistor. 

[henry4841]

Moved to Premium Sweetie. 

[Curious_George]

1 hour ago, henry4841 said:

Morning guys. This thread is for those that might like to hear about an old man slowly building a tube amplifier. An old guy trying real hard to just be himself on a social media site. I do not do Facebook or Twitter and only use sites like this one and some other technical forums for entertainment.

 

I ordered the parts for this project from Mouser yesterday. I am going to use better name components in this Sweetie. Will it make any difference in sound compared to the last one, probably not but some like like better and others like best. The last Sweetie is the good. This is going to be the better. The best is those amplifiers in the 5 figure range. It is going to have all Hammond iron. Two Hammond power transformers and one grade better Hammond output transformers from the previous Sweetie. Two completely separate amplifiers in one case. In other words mono's in one chassis instead of two. I chose Nichicon Audio grade electrolytic 105C caps in the two signal circuits and Nichicon 105C electrolytic caps for the power supply circuit. For the 1/2 watt resistors I am going to use Vishay resistors. Both these name parts are respected in the electronic industry. For the power resistors I am using one grade higher wattage ones than what Maynard recommends in his design. Might say overbuilding. I also ordered another aluminum plate off of Ebay to add to the one I have in stock left over years ago from another build. More work building an amplifier like this compared to the last one built on a Bud chassis. More chassis work has to be done. Time consuming but I like to make it fun. 

 

This morning I am planning on cutting the slots for those tails in the boards I made yesterday. I forget the correct name woodworkers use making dovetails. Like electronics woodworkers have their own language you need to know to understand what they are talking about. I enjoyed building the last tube amplifier after having not built one in two or more years. I forgot how much fun it can be. I have always my entire life liked working with my hands. I have also enjoyed sharing an old mans day on this forum with you guys that have an interest in hearing about me. Thanks for the support guys. 

Good morning Henry - Sounds like this amp will be one for the books, no doubt. You'll be getting multiple offers for this one, I bet. 

 

Are you still going to use Orange Drop coupling caps in this build? Dayton (Parts Express) makes some film & foil coupling caps... they are super inexpensive, but seem to be high quality, about half the price of Orange Drops.

 

Just FYI if you want to try some oneday. I've used them and I am happy with them. 

[henry4841]

Thanks for posting. I have also used some Audyn Q4 from Parts Express before in some builds as coupling caps. I use to be picky about coupling caps but not so much anymore. I use to think, when I was experimenting some with coupling caps, that I could hear some difference in caps but not so sure anymore. Back then I thought orange drops sounded better. I now think some Parts Express caps will sound perfectly fine in a tube build. As good as any. That being said I will probably just use orange drops. I am sure they are just as good as any out there and not too expensive and helps fill an order at Tubedepot. At least equal to most. I just do not buy into spending huge amounts of money on such a simple component. Most technicians I know, technicians is a college grad word for repairman, use whatever film cap they have in stock doing repairs and do not fall into the cap foolery on audiophile forums. 

[henry4841]

Forgot to be specific to your question of using Dayton caps. Yes I have a sack full of Dayton film caps for repair work and projects in the past. My understanding, at least years ago, that they are made by Bennic. Good caps.

[Curious_George]

8 minutes ago, henry4841 said:

Forgot to be specific to your question of using Dayton caps. Yes I have a sack full of Dayton film caps for repair work and projects in the past. My understanding, at least years ago, that they are made by Bennic. Good caps.

Bennic, yes. Good quality caps.

[henry4841]

And those Orange Drops are pretty too. 🙂

 

Here is a picture of one sack of film caps I have played with in the past. Most used in crossover experiments. 

[henry4841]

57 minutes ago, Curious_George said:

Bennic, yes. Good quality caps.

One thing about Orange Drops is you get a spec sheet with them that most of the specialized film caps builders do not provide. Places like Mouser carries Cornell Dubilier orange drop caps as well. I just like to assume places like the big electronic supply houses, such as Mouser, requires a part to be tested by an independent lab proving the part meets it's specification sheet before selling it in their company. They have too much to lose selling an inferior part. Engineers depend on the specification sheet to be accurate. 

[henry4841]

Morning guys, I just yesterday for the first time saw we have had 8 thousand 100 views on this thread. I could not believe it and it was started less than a month ago.  I want to thank each and every one of ya'll who have taken the time to visit this thread. Maynard's Little Sweetie that I built found it's new home yesterday. At least I hope it is it's new home. Area51 bought the sound I like and there is no way for me to know for sure if he is going to like the sound the amplifier makes as much as myself. He may think "what's wrong with this guy, I do not like this kind of sound at all." We all hear differently and have a different taste in sound. That is the reason there is not one amplifier for all. I did hear from him that he is using it but have not heard from him what he thinks about the sound. Time will tell. 

 

I started a new thread on the new Sweetie I am building. I am just going to post the work an old man has done for the day there and keep the discussion of the Sweetie here on this thread. 

 

There is talk right now happening about capacitors on this forum of which I am not going to touch with a ten foot pole. This website belongs to Klipsch and now they are marketing Klipsch approved capacitors to the public for those that feel they have a need to replace the capacitors in their crossover networks. This old country boy is smart enough to know not to insult the school trained electronic boys working at Klipsch thinking I know more about capacitors than they do. You have to understand a little of how school trained electronic guys think. You show them one of those high priced after market capacitors and the first thing they are going to say is show me the data sheet. They have been trained to understand the properties of a cap just by reading all the things in that data sheet. I can understand a little of how they think myself having the time the last 10 years to take a couple of online electronic classes. The first one I took is on Udemy recommended by Xraytony on youtube. He is an older guy with an electronic degree who says he uses the course for refreshing himself on the basics of electronics when waiting for a plane at the airport and other times. Let's face it even an engineer needs to refresh his memory on any subject they took 20, 30 or more years ago. Before retiring it had been many many years since I took any electronic lessons so I learned again a lot of the basics of electronics from taking the course. Enough to learn a little how an electronic engineer thinks. A little bit that is. Chief Bonehead, an employee of Klipsch got a little frustrated recently about all the capacitor talk on this forum and rightly so. It is insulting to Klipsch engineers to hear mostly lay people talking on a forum about a subject they have not been trained to fully understand. This is after all a Klipsch owned website. They have determined that the capacitors they have picked will do the job that a capacitor is supposed to do best at a reasonable price for the sound they have determined to sound best for their speakers. The job of a capacitor is to stop DC signals and let AC through. That and the values chosen will effect the frequency they designed for their speakers to cross over to another driver at a certain  order such as 1st order, 2nd order, etc,  period. They do not listen to all the flowery city boy salesman talk of aftermarket sellers of capacitors but look for the specification sheet of the capacitor which most of them do not provide. 

My thinking, which has no basis , about some of the aftermarket capacitors  is that they roll off the high frequencies somewhat.. Maynard actually does this electronically in the Sweetie using the R1, C1 circuit. He must enjoy the sound more with a touch of roll off at the higher frequency range. Absolutely nothing wrong with that if that is the sound one enjoys. He designed this amplifier to please himself and not what may be said on the net about what he should like. He uses a good polyester Mouser capacitor for the coupling cap and rolls the highs off some with the R1,C1 circuit. I have not actually tried it his way. Maybe it is something I should try with my personal Sweetie. I use the orange drops in my builds. They also are sold by Mouser with data sheets. Made by Cornell Dubilier. Here is a link to the data sheet for orange drops. https://www.mouser.com/datasheet/2/88/CDUBS02321_1-2540007.pdf

There are things on that data sheet that I do not understand but those college boys at Klipsch do. Such as Corona, Dissipation Factor Specifications, dV/dt Specifications, RMS Voltage vs. Frequency @ +85°C, Typical Impedance vs. Frequency. I think one can get the idea of what I am talking about. 

 

Anyways enough rambling from an old man this morning.