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The long awaited "Little Sweetie" mono SETs


tube fanatic

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My Edcor transformers were shipped today for the "Little Sweetie" and they were ordered on 11/01/15. Good service and great price. I ordered this little gizmo on Ebay after some good reviews from other hobbyist. By no means quality equipment but for a hobbyist it should do just fine. I checked it with some components I have and it will surely tell you what you need to know when building an amp or other piece of equipment and it is best to check every resistor and capacitor before building. It will save a lot of trouble from installing a 1k resistor instead of 100k and the same thing with capacitors. 

 

http://www.ebay.com/itm/New-12864-LCD-Mega328-ESR-Meter-Transistor-Tester-Diode-Triode-Capacitance/321866908829?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D34226%26meid%3Db23d813289854037a8e39111b5870570%26pid%3D100005%26rk%3D3%26rkt%3D6%26sd%3D171285924831

 

I am going to check it with my other equipment later but if will get the job done for most builders. Designers and testers need better for sure. 

"it is best to check every resistor and capacitor before building"

My Dad was buying me simple heathkits, i think i was on my third one before he ask "How are the others working sport"?

As i recall my 10 year old response was "They Dont" :unsure2:

Dad proceeded to instruct me on the proper reading of the color code....... :o

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Hello Mike, I am fairly certain William built Thomas Mayer's amp; http://vinylsavor.blogspot.de/2011/01/single-ended-amplifier-concept-part-4.html

 

When the screen is tied to the plate as in the schematic the 6CB5A's curves look like a triode and not a pentode, so in theory the second harmonic should dominate just like 6EM7 amp.  

Edited by xxJPMxx
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Because the output stage uses "triodes" doesn't mean they will sound the same. The power supply, driver stage, output transformer, operation point, device linearity, etc......   The amp as a whole makes the sound. 

 

 

My honest opinion is since you don't require much power for your listening preference the 6EM7 is being run closer to it's max output than the 6CB5 amp so there will be a higher percentage of distortion overall; i.e. The 6CB5A has more headroom.  

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It could be but by my measurements I am not using even a watt.

 

Measuring music is tough because of transients. Those transients have much more headroom in the 6CB5A amp. This is why I think I like a good low impedance driver so much, it doesn't fart out on transients when the impedance of the grid on the output tube suddenly falls like a brick @ 0V. 

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Hi Maynard, you mentioned at the beginning of this threat that you were going to audition this amp with the guy down the road with Cornwalls. Have you already done so and if you have what was the result?

It would be easier to catch the wind than to try to pin him down to get together!  He's the hardest working guy I know between his f/t job as a middle school music teacher, giving lessons, working with his wife at her dance studio, and doing gigs with some buddies.  He says he'll be around the week between Christmas and New Years, so that's what we're planning on. 

 

Maynard

 

Edit- my wife just reminded me that he also is the director of the marching band at the local HS!!!

Edited by tube fanatic
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  • 3 weeks later...

I won't be building this amp, but I did want to chime in and throw some accolades in Maynard's direction. I have one of his dual mono SEP amplifiers and absolutely love it. It powered Cornwalls with ease and I just spent all of this past weekend cranking tunes through my KP-201's. There's nothing fancy about these builds.. but his products are cleanly designed and implemented with excellent quality. My amp provides good clean sound, the tubes used are robust and inexpensive, and his post-purchase customer support is superb. well worth the time and money to either grab one of his amps when he puts them up for sale, or to build one of his designs freely given here on the forum.

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  • 11 months later...
  • 9 months later...

I'm getting real interested in building this. I have a pair of Hammond 1615 5Kct to 4,8,16ohm 15watt transformers from a Glass Audio Single 45 Amp I made back in the 90s. The power transformer opened up once, and after replacing it a few years later it developed a hum. I'm done with it and want to make something new. I was looking at the Moondog 2A3 monoblock schematic but the tube price turns me off. Being able to reuse some of the parts from the 45 amp is a plus here.

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  • 6 months later...
Guest wdecho

The stereo version of the "sweetie" was one of my favorite SET amplifiers I have built but it was 2nd or 3rd tube build for me and it was built on a cake pan not knowing if only a watt or so would be worth keeping and to keep the cost down. I would like to think my tube building skills have improved over the years so I decided to rebuild it using a better looking chassis and some different, better parts. Below is a couple of pictures of my redo stereo 'Sweetie" designed by Maynard (tube fanatic as he is known on this forum). My testing and measurements of this new build were really good. I measured a touch more than 1 watt of power and the distortion number I came up with on the Arta software was less than 1% at 1/2 watt. The figure of 1/2 watt is where the amplifier is operating at with my LaScala's where conversation is not possible without shouting. In fact I will say the power is less than 1/2 watt and more like 1/3 watt. Peaks do go higher at around the 1 watt high end of the amplifier but clipping just on peaks are not really detectable with the soft clipping nature of a SET amplifier. In other words 1 watt is all that I really need and use in my setup. I have built some 1 watt amplifiers since I first built the sweetie that just did not have the omph this amplifiers does. A lot can depend on the design of the amplifier whether 1 watt will be enough. I certainly am not giving up anything in the power department with this amplifier in my setup. From the harmonic distortion graph one can see that the distortion figure of 1% at 1/2 watt is 2nd harmonic dominated which in my world is a good thing. Square waves at 1kz are respectable with no ringing present. The amplifiers has really good bass that does go really low and the high end reaches out with a slight reduction, I am guessing a few dbs down at 18Kz judging from the sine waves on my scope. This is an very easy build for someone wanting to get into diy tube building especially when built as a stereo build and cheap as well. I used a toroid transformer which is mounted underneath the chassis. The amplifier is extremely quiet with nothing from the high and mid horn with your ear against the horns and nothing from the bass a foot away from the speaker. I am very happy with the result of this build and it still remains one of my favorites. 

P1030780.JPG

Screenshot (22).png

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That's a really nice implementation of the Sweetie design William!  Those who accuse SETs of having extremely high distortion should take a good look at the FFT that you posted.  That says all that one needs to know, and explains why flea power SETs are capable of sound quality which is so good that nothing can compare.  When one looks at how little such an amp costs, it's very surprising that more guys don't give them a try.  And the best part is that the tubes are not only inexpensive and abundant, but should last almost "forever."

 

Maynard

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I once had a pair of the highly touted Wright Monos (2a3), and thought they were the most anemic, flat sounding amps I'd ever heard.  I couldn't get rid of them fast enough. After that experience, I was pretty much done with the low power thing. No, I'm not trolling you guys -- I just don't get it.

 

I later tried some Welborne Apollos, and liked them very much. I never should have sold those.

 

https://positive-feedback.com/ambackissues/WelborneApollo.htm

 

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40 minutes ago, Deang said:

I once had a pair of the highly touted Wright Monos (2a3), and thought they were the most anemic, flat sounding amps I'd ever heard.  I couldn't get rid of them fast enough. After that experience, I was pretty much done with the low power thing. No, I'm not trolling you guys -- I just don't get it.

 

I later tried some Welborne Apollos, and liked them very much. I never should have sold those.

 

https://positive-feedback.com/ambackissues/WelborneApollo.htm

 

 

That's really weird. Possible system cohesiveness? The pair I owned, now with another Forum member,  were paired with a Wright preamp and played with Jubes, KHorns and LS. I was always amazed at how clean and detailed with amazing bass, relative to 3.5 watt output. Another member heard them on Jubes and commented how they equalled if not surpassed, another highly touted Forum amp. Sonics, not power of course. No doubt they run out of steam when going concert level but for everyday listening they were great sounding. This particular pair had Sowter transformers which were reputed to bring them to another level but that I can't verify. I really enjoyed them but have slowly pulled away from tubes hence the sale. To my ears I've found the right solid state designs can equal and surpass many tube amps particularly most PP designs and now really closing in on single ended which I really favor. 

Enjoyed your opinion, no trolling sensed --- 

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Guest wdecho
4 hours ago, Deang said:

I once had a pair of the highly touted Wright Monos (2a3), and thought they were the most anemic, flat sounding amps I'd ever heard.  I couldn't get rid of them fast enough. After that experience, I was pretty much done with the low power thing. No, I'm not trolling you guys -- I just don't get it.

 

I later tried some Welborne Apollos, and liked them very much. I never should have sold those.

 

https://positive-feedback.com/ambackissues/WelborneApollo.htm

 

In the text of the "Sweetie" review.

 

" I have built some 1 watt amplifiers since I first built the sweeties that just did not have the oomph this amplifier does. A lot can depend on the design of the amplifier whether 1 watt will be enough."

 

I have built a number of around 1 watt amplifiers, and some closing in on 2 watts, that just did not have the power I really like for my taste. This one and my SET 45 tube amplifier are 2 that really are great designs using just 1 watt of power. There is a noted international reviewer that participates on this forum that owns K-horns who reviewed a 1 watt SET on his K-horns claiming it was the best sounding amplifier he had ever heard on his K-horns. His name alludes me right now. The only way to know for sure is to build it. I was skeptical myself before building but wanting a new project gave it a try of which I am glad I did. 

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