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MEH Synergy

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1 hour ago, iaRIVR said:

Another thought is the ACA, also a Nelson Pass solid state design. I know it's not tubes, but you do get 8 WPC class-a and the full kit is around $350.

I just built one of those, great sounding amp.  Would love to compare a tube amp with similar specs.  

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2 hours ago, tigerwoodKhorns said:

Thanks,

 

These are my retirement plan for when I am really old and no longer want to lift heavy things.  Solder away and listen to music. 

 

 

I picked up my soldering iron almost two years ago. You're going to love it!

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3 hours ago, iaRIVR said:

But, I will say the cost of parts is still up there and chassis/housings are surprisingly expensive.  Plus your time. I just finished an Aleph J build, and even reusing a Hafler 220 chassis I got for $20 it took quite a bit of fabrication. Not trying to be discouraging, but as someone that has been trying to find high-quality DIY designs and build them cheaply it always takes way more time and money than I expected. Still fun.

 

Thank you for your response, and all valid points. George has sent me two of his boards, the TSE and the SSE, I preferred the TSE better and ended up with 45's in it but that was a birthday gift to my bass player along with a pair of Heresy's. He desperately needed a good sound system for the level musician he is. I have been building other peoples designs and my own for decades and have made some really nice things for not much scratch. I am not looking to profit from these, so cost to forum members will be parts and shipping.

 

4 hours ago, henry4841 said:

With the goal of 15 watts I assume it is going to be a push pull design. I have one PP amplifier using the EL84 tubes. Sounds really good and will not break the bank building. 

 

Not necessarily, I can do a 15w single ended amplifier, I have some 6550, KT88's here I can breadboard with, owners can swap to KT120 also.

 

57 minutes ago, Marvel said:

I wouldn't mind a 2a3 with the JJ 2A3 40. Too bad it costs so much, but you would only need two. With a 40 plate dissapation you could probably make a nice single ended 15 watts.

 

That would be a decent idea, I do not have any of those to breadboard with. I will have to crunch numbers but they may push the price limit too high and have not much tube rolling options, I know folks love to try different tubes out as part of the fun.

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29 minutes ago, captainbeefheart said:

 

Thank you for your response, and all valid points. George has sent me two of his boards, the TSE and the SSE, I preferred the TSE better and ended up with 45's in it but that was a birthday gift to my bass player along with a pair of Heresy's. He desperately needed a good sound system for the level musician he is. I have been building other peoples designs and my own for decades and have made some really nice things for not much scratch. I am not looking to profit from these, so cost to forum members will be parts and shipping.

 

 

Not necessarily, I can do a 15w single ended amplifier, I have some 6550, KT88's here I can breadboard with, owners can swap to KT120 also.

 

 

That would be a decent idea, I do not have any of those to breadboard with. I will have to crunch numbers but they may push the price limit too high and have not much tube rolling options, I know folks love to try different tubes out as part of the fun.

Very true ... I loved my 2A3 amps, but have never heard a SEP. Certainly more options for tube rolling. I did a Curcio front end on my Dynaco ST-70 about 16 yrs ago, but have it out and another board to put in but I've not populated it yet. I would like to switch from 6550s to 6L6s, but I'm not far enough along to figure out what other changes I'll need to make.

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2 hours ago, Marvel said:

, but have never heard a SEP.

 

The vast majority of tube audio amplifiers are going to be push pull, and for the single ended fans I would say the majority of them tend to go the full Monty to single ended triode amplifiers. I could be wrong of course, this is just my observation and certainly there are not a lot of SEP amplifiers offered from major commercial tube amplifier companies which strengthens the notion that not many people have heard one. The few I have heard from commercial offerings were not terrible but also not great.

 

Personally I jump back and forth between SEP and SET as my favorites, I just haven't cared for push pull amps for the past decade at least. Well not really, I am lying I have been listening to a Sherwood 700a SS push pull receiver with RB-81 mkII speakers and it sounds quite good. That system mainly plays FM radio all day for the wife, she's easy. BUT for when I get into serious listening mode it's La Scala room and tubes :D

 

I have found that one major aspect to getting a SEP amplifier to sound great is the feedback. I still have global feedback but some nested loops at the output stage ala plate to grid yields excellent results. I like variable damping and no matter how the design of this amplifier turns out I will most likely include one ala current feedback from speaker. From being a member for a little while now and reading what people are mainly running I don't think many have amps that can do this and they might have fun with an amp and a new feature to tweak the amp/speaker relationship by ear for their preferred listening pleasure.

So many circuits...........so little time

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10 hours ago, Shakeydeal said:

Aric from Aric Audio makes a nice SEP amp. I owned one for a while and it was very good indeed.

 

I was intrigued so I went and took a look, it appears his designs are ultralinear/triode which in my book is much different compared to a true pentode amplifier. I have built and listened to many UL amps and just feel pure pentode when done well is better driving real loads like speakers. Plus he is asking $4,000 for one!! Wow.

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First circuit I am drawing up is a KT88/6550 SEP amp class A2 operation.

 

Gain - 20db

 

15 watts at 1.88% THD second harmonic dominant

 

Fixed bias with external tip jacks and control to easily adjust bias.

 

With a nice looking chassis I can build this for around $400. It blows my mind to see some of these builders asking $3,000 for a simple single ended amplifier (Aric Audio) that doesn't even drive grid current A2 operation. I get there needs to be profit but there should be a healthy profit margin with a retail of $1,200-$1,500 dollars. The fact they do not even show distortion output at any given power and frequency tells me they probably don't even measure anything once completed. How are they calculating compensation networks? Do they even have them? I would like to see some square waves from these amps. I am not saying the amp sounds bad, just not much info for a pretty healthy price tag.

 

This is what is driving me to do this project. I have seen far too many amplifiers hit the market without much research and development. I see way too many guys that can solder and have a somewhat decent understanding jump into the market and start building and selling amplifiers for big money. The refinement in the product is missing on a technical measure, upgrades consist of brand name capacitors instead of putting effort into actual circuit improvements that will yield much more. For example the lack of SE smaller powered amps with no grid current drive capabilities. I truly feel that it makes a big difference with lower powered amplifiers to not run into blocking distortion bias shifting the amp until it recovers over time back to normal operation. With A2 operation the driver can push current into the grid maintaining the signal integrity with no recovery time smear. If you are going to ask a huge price tag at least put the money into something that will greatly improve performance instead of extremely minor esoteric boutique capacitors and silver wire. Those gains are diminished returns for the investment, you get FAR more bang for your buck implementing circuit changes to mitigate some of the pitfalls of the specific design. I really want people to have the opportunity to get good performance and sound for a reasonable price. I don't think the majority know enough about control networks to properly implement feedback so they stray away from it instead of fine tuning it. I use Lissajou formula to look at phase relationship input to output, mark the breakpoints of the amplifier on a Bode plot and then calculate the compensation networks to increase phase margin to where it's unconditionally stable. This is best done with the built amp and not in a simulation as stray capacitance will just change your simulation results. Once calculated and installed I do square wave tests which may lead to some empirical adjustments and fine tuning. This only needs to be done once if you continue to use the same output transformers. The majority of time is spent on the very first prototype, after that it's just rinse and repeat and I can probably knock a build out in one weekend. I hope this can come to fruition, I don't expect many here to jump in and purchase an amp so I am sure will be able to keep up with the demand if there is one. Basically once I am done with the first amplifier I will sell it, if anyone else wants one after that just let me know and I will build per order.

 

 

 

 

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3 minutes ago, Shakeydeal said:

Some want the sizzle and the steak. I’m a firm believer that better caps, resistors, wire, RCA jacks, etc. contribute to the end result. This can separate the best from the really good.

The way I understand the saying, better caps, resistor, wire, RCA jacks, etc. would actually be the steak. The sizzle doesn't really add anything. I will pay more for a prime steak, and I can taste the difference. But, I can make a choice cut of meat sizzle just like a prime cut of meat...it just won't taste the same.

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10 minutes ago, Shakeydeal said:

Some want the sizzle and the steak. I’m a firm believer that better caps, resistors, wire, RCA jacks, etc. contribute to the end result. This can separate the best from the really good.

 

That's fine, if someone asks for specific brand capacitors and I feel it will not diminish performance just pay the difference and I will build it with them.

 

My point is the actual difference between these parts are so small, probably 1% or less where actual circuit improvements gets you a 20% increase in performance/sound it's obvious which gets priority to me.

 

I choose parts by their application and how different component types will effect the total outcome. I'll most likely go paper capacitors for coupling so I don't know what anyone else prefers but if they want film types that's ok also.

 

Connections are important and I never skimp on them, it's not expensive to get good In/outs, sockets, pots etc... I usually install lots of filters on the primary side of the power transformer so it sort of has internal 'power conditioning' if you will, common mode chokes, with X and Y capacitors for common and differential mode noises. This goes both ways, filtering both AC coming into the amp but also not polluting your house power either. Yes your amplifiers are awful non-linear loads polluting your power with distortion and harmonics. The average linear power supply has a power factor of .3 which is awful compared to the ideal 1 or .8 Federal standard requirement. Hence to meet compliance you see so many switch mode power supplies going into products these days.

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19 minutes ago, CWelsh said:

The way I understand the saying, better caps, resistor, wire, RCA jacks, etc. would actually be the steak. The sizzle doesn't really add anything. I will pay more for a prime steak, and I can taste the difference. But, I can make a choice cut of meat sizzle just like a prime cut of meat...it just won't taste the same.

 

I agree, the proper component selection for best results I also consider the meat and not the sizzle. The sizzle for me is eye appeal, meters, fancy chassis, and sometimes boutique name capacitors. If I choose a paper capacitor what costs me $5 for our intensive purposes it will perform the same as a $100 Jensen paper capacitor. Same dielectric will have the same linearity and hysteresis properties, there may be a slightly different resonant frequency from the parasitic properties (series inductance) but that's true for any capacitor you purchase, a radial will have slightly different series inductance so resonant frequency will somewhere different but so far above the audio band it's moot, especially tube amps.

 

Resistors, most have no idea what to look for, name doesn't matter. Look at the datasheet and look at the coefficients, typically voltage and temperature. The lower the number, mind you this is measured in parts per millionth (10-6) the better. This means the hotter the resistor gets or the more voltage across it will change the resistance value making it slightly non-linear. Well lets look at the problem and find a better solution. For the temperature issue size the resistor appropriately so it doesn't get even warm and it will stay linear. So even a carbon composition resistor with terribly high temperature coefficient will not drift as long as it doesn't get hot, so over size it to keep it's value within tolerance. That's easy enough right? The voltage issue isn't avoidable, any resistor with a large signal swing across it you choose a type that has a low voltage coefficient that way it's linear with the large signal swings. It really takes a lot of swing to start to see the distortion increase but it is a real issue and not just 'mojo'. Carbon composition resistors will have higher voltage coefficients so using them as say plate load resistors for a phase inverter where signals are larger will most likely show an increase in distortion. Luckily the voltage coefficient also is reduced with increase in resistor size/dissipation rating so again selecting a wattage rating very conservatively improves performance. I try and follow a 10x rule where the rating of the component is 10 times what the working value is. So for a resistor that sees 100mW I'll go ahead and use a 1 watt resistor. Typically 5x is adequate but if I can go ahead with 10x for not much money or loss in physical space it takes up I will. It's simple physics, there is no magic inside these parts, knowing how the data will relate to sound it's easy to see if you want low distortion there are solutions without ever mentioning "Allen Bradley" or "Jensen paper/wax" etc..... Choose things via the data and smart engineering practices and you will achieve your goal of good performance and sound.

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I started this thread for as much feedback from people as possible. If folks want a little 'sizzle' and up the target price to say $500 that's fine with me. I am trying to figure out what people consider inexpensive. Originally this idea came from a mix of two threads, the tubecube 7 and the Crimson 275. I mean the more I look at similar offerings (quality 15 watt single ended tube stereo amp) $500 is peanuts compared to what I am seeing for commercial offerings.

 

The reason I am leaning towards SE is because I believe the majority here using tubes have push pull amps so why not make something everyone wants to try but doesn't want to spend $4,000 for 15 watts. Honestly I also am leaning that way because I prefer SE and feel it can work very well with Klipsch speakers. I have heard and owned so many amplifiers and I also have the ability to build myself anything I want to try if it isn't offered commercially so I like to think if my ears have landed on SE amps as sounding the best it's for a reason. Clearly it isn't just vanishingly low distortion as SE typically will have more vs push pull so something else is at play here. I surmise it's just more natural to how we hear in nature, sound propagates through the air in a single ended fashion. Fluid dynamic equations clearly show the peaks of the waveform travel faster than the low energy troughs making whole process non-linear and rich with even harmonics dominant with the second harmonic. Processing this type of information is natural to us, our brains say 'normal' and we relax and feel we can just listen endlessly without fatigue. Sadly if one owns an amplifier that can't be dynamic and clean enough we don't get to enjoy the benefits of the topology.

 

Wave equation that accounts for non-linearity up to the second harmonic

 

where p {\displaystyle p} p is the sound pressure, c 0 {\displaystyle c_{0}} c_{0} is the small signal sound speed, δ {\displaystyle \delta } \delta is the sound diffusivity, β {\displaystyle \beta } \beta is the nonlinearity coefficient and ρ 0 {\displaystyle \rho _{0}} \rho _{0} is the ambient density.

 

\,\nabla ^{{2}}p-{\frac  {1}{c_{{0}}^{{2}}}}{\frac  {\partial ^{{2}}p}{\partial t^{{2}}}}+{\frac  {\delta }{c_{{0}}^{{4}}}}{\frac  {\partial ^{{3}}p}{\partial t^{{3}}}}=-{\frac  {\beta }{\rho _{{0}}c_{{0}}^{{4}}}}{\frac  {\partial ^{{2}}p^{{2}}}{\partial t^{{2}}}}

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