[raindownthunda]

No I don't plan to, I was more trying to illustrate why cutting those corners isn't worth doing! The design is final at this point.

The market has enough “someone has done it cheaper” options for people wanting to dip their toes. I would hazard a guess that a good number of us obsessed with pushing the boundaries of performance in our systems would much rather spend a good bit more for that extra 10-20% performance. I love the idea of maxing out performance with a kit that comes with the DIY labor price savings, removing the cost and time constraints of working with a custom builder. There is a satisfaction knowing this is as good as it gets, and I was able to build it while saving a good chunk of change. Are you thinking of charging a fee to purchase the plans?

 

[Monsterzero]

@L0rdGwyn

Do you happen to know what the output impedance is on the Airmid with the various power tubes is?

For example, what is it when 6AS7G in place vs. 6080 vs 5998/421a vs. 7236 vs. 7802?

 

[L0rdGwyn]

The market has enough “someone has done it cheaper” options for people wanting to dip their toes. I would hazard a guess that a good number of us obsessed with pushing the boundaries of performance in our systems would much rather spend a good bit more for that extra 10-20% performance. I love the idea of maxing out performance with a kit that comes with the DIY labor price savings, removing the cost and time constraints of working with a custom builder. There is a satisfaction knowing this is as good as it gets, and I was able to build it while saving a good chunk of change. Are you thinking of charging a fee to purchase the plans?

Nope, not planning to charge anything, it will be posted publicly. If I end up providing any parts myself, shipping PCBs for example, I may have to charge a small fee just to cover my time and shipping costs.

@L0rdGwyn

Do you happen to know what the output impedance is on the Airmid with the various power tubes is?

For example, what is it when 6AS7G in place vs. 6080 vs 5998/421a vs. 7236 vs. 7802?

Output Z with 6AS7G / 6080 is 50ohms, with 5998 / 421A is 30ohms

 

[bcowen]

You can always go with a confusing, albeit meaningless, alphabet soup name, ala ChiFi.
Then a couple months down the road, make a small change and re-release it as the "Pro" model

All of this naming stuff gets so confusing and bewildering. Just call it Bob.

 

[Monsterzero]

Nope, not planning to charge anything, it will be posted publicly. If I end up providing any parts myself, shipping PCBs for example, I may have to charge a small fee just to cover my time and shipping costs.



Output Z with 6AS7G / 6080 is 50ohms, with 5998 / 421A is 30ohms

With the WE 421A, the Airmid actually is pretty damn good with the Caldera. Not a tremendous amount of slam, but it's crystal clear, with no grain and sounds quite good.

Your prototype is being shipped out to me tomorrow.

Stay tuned

 

[L0rdGwyn]

With the WE 421A, the Airmid actually is pretty damn good with the Caldera. Not a tremendous amount of slam, but it's crystal clear, with no grain and sounds quite good.

Your prototype is being shipped out to me tomorrow.

Stay tuned

Nice. Yeah with around 2:1 damping and those big output caps, should work reasonably well.

Looking forward to seeing what you think. I think one of the output transformers sorta go bent out of alignment on the way to LA, so if it is crooked when it arrives, just ignore that lol should be a simple fix, I assume the screws anchoring it to the chassis where bent and need to be replaced.

 

[Mr Trev]

All of this naming stuff gets so confusing and bewildering. Just call it Bob.

Indeed. Why does everything have to have a mega/epic sounding name, why not Bob? Or even better, Lucius…

 

[gibosi]

Output Z with 6AS7G / 6080 is 50ohms, with 5998 / 421A is 30ohms

Are these calculated values or are you able to measure them?

 

[L0rdGwyn]

Thanks! Informative as always. I've been using all my headphones from 32-300 ohms on a 32 ohm tap, similar to how I think some of Glenn's SET amps are implemented. Interesting that you found the parallel resistors sounded better. I would have thought that a higher secondary load (and resulting higher primary load) would sound better due to the decreased distortion. I'll have to try out some parallel resistors on the 8 ohm tap and see how that sounds!

Besides loss of power, I wonder if there's a major difference between using parallel resistors with a higher turns transformer and using a lower turns transformer with a higher ohm secondary. I suppose that wraps around to the 3:1 vs 8:1 damping ratios mentioned earlier.

Well hey, give it a try yourself and see what you think, maybe you'll come to a different conclusion. Yes, Glenn ran the headphones right off the speaker tap, and I thought the same thing on the distortion. As I recall, I measured the frequency response at the output at that time as well and there was no significant difference between the three, distortion followed the expected pattern with it being highest with the 8ohm parallel resistor and lowest with the headphones right off the 8ohm tap. Despite that, the 8ohm parallel sounded best. This was a while back, I swear I posted about it but I can't find it.

 

[L0rdGwyn]

Are these calculated values or are you able to measure them?

They are measured. Well I should say they are calculated by taking some simple measurements and plugging them into a formula.

 

[whirlwind]

So there you have it. I'll get into more detail about the specifics of the schematic when I put together instructional materials. The one part of the circuit that has me a little concerned for inexperienced builders is the output switch, it's kind of a b**** to solder, but I think I'll be able to explain the method. I've thought about making an instructional video specifically for that task, which I think would help.

It's going to take some time, probably a few months, for me to put together all of the materials needed for an official DIY project release. I will be making some minor changes to the PCB for ease of DIY reasons (e.g., including test points). I will then have to build another one and take very deliberate photos along the way and compile them into a instructional PDF.

I know $1.5Kish ain't cheap, and this would be a big commitment to gather all the parts and build, but I really think people would be getting that custom / boutique amplifier sound for what I think is a pretty reasonable price. It's really very easy to build if you have all of the right parts / equipment. I would be very proud if people build and and love the sound, so hopefully that will be the case.

This DIY build is a great idea IMO.

Great project with great results can get more people hooked to build stuff, great for everyone.

 

[Xcalibur255]

No I don't plan to, I was more trying to illustrate why cutting those corners isn't worth doing! The design is final at this point.

There's a weird sort of obsession on sites like diyaudio with making these projects as cheap as possible that I personally have never understood. I can see why it would be fun to try and make something sound subjectively good for as little money as possible as a challenge, but not with every single build. The penny-pinching seems to be a broadly shared mindset with that group to the point where it almost seems to be overriding the musical priorities. I see it more the way you seem to: rather than look for a way to get a cheaper end product it's a chance to get something at a price similar to common retail offerings that offers greatly improved performance.

Ultimately there's plenty of room for both approaches in the hobby of course.

 

[L0rdGwyn]

This DIY build is a great idea IMO.

Great project with great results can get more people hooked to build stuff, great for everyone.

Yeah I hope so! Who knows, maybe it will inspire someone to start working on their own designs.

There's a weird sort of obsession on sites like diyaudio with making these projects as cheap as possible that I personally have never understood. I can see why it would be fun to try and make something sound subjectively good for as little money as possible as a challenge, but not with every single build. The penny-pinching seems to be a broadly shared mindset with that group to the point where it almost seems to be overriding the musical priorities. I see it more the way you seem to: rather than look for a way to get a cheaper end product it's a chance to get something at a price similar to common retail offerings that offers greatly improved performance.

Ultimately there's plenty of room for both approaches in the hobby of course.

Agreed, there are different camps, certainly there is a group that is very bang-for-the-buck oriented, but I don't think they need to disparage those who want to spend more for quality. We'll see how it is received on diyAudio, probably there will be a mixed response.

 

[Mr Trev]

Yeah I hope so! Who knows, maybe it will inspire someone to start working on their own designs.



Agreed, there are different camps, certainly there is a group that is very bang-for-the-buck oriented, but I don't think they need to disparage those who want to spend more for quality. We'll see how it is received on diyAudio, probably there will be a mixed response.

Isn't there some kind of saying along the lines of "you know you're on the right track when everybody's PO'd about it"

 

[Zachik]

We'll see how it is received on diyAudio, probably there will be a mixed response.

As opposed to Head-Fi, where we ALL always agree on everything!