Amp Design ?, (especially SE-84 that Justin Builds)

[joessportster]

Which part of an amps circuit / design makes it so revealing ??

It is a general thought that tubes are warm, and Sennheiser HD-650 Headphones are dark and veiled. The SE-84 cuts those

notions to pieces,

If something is warm and on the dark side, wouldn't it be less revealing making everything more listenable ??

I like revealing (as everyone who owns Klipsch does, Horns are revealing) Garbage in =Garbage out, But I don't think I never really understood how much music was poorly recorded until now

One more question, Does revealing = neutral ?? To me the answer would be yes, an amp so revealing would point out shortfalls in design, if it had a Hot highend, or bloated bass, recessed mids etc...

We always talk about amps as they should be neutral so they can reveal exactly what was recorded as the artist intended, I guess i finally found an amp that accomplishes that at a high level, and its a tube amp no less

[Schu]

have you heard it yourself or are you basing those ideas off what others have said?

I to am understandably curious about his builds... and the iron he uses.

[Ski Bum]

There are a few main factors at play. I'm not personally familiar with Justin's work, but most single ended amps have relatively high output impedance, which results in non-linearity into a speaker load. Also, they generally have high distortion but in a low order, monotonic (even and odd), rapidly decaying pattern, and this has ramifications for musical tone coloration. Digging deeper, when over driven their electrical output levels off, but the low order harmonics continue to increase, preserving subjective loudness, making them act almost like an ideal compressor (at least up to a point). Very neat trick, that last one.

There is other stuff in play too, such as a very low parts count in the signal path, absolutely zero crossover distortion (and thus require no circuit complications to combat it) that may help account for their charms. And I find them rather charming. Almost like a narcotic, highly habit forming.

So I personally wouldn't call them "neutral". That being said, if they are truly revealing or simply distorting, they sure seem revealing and honest in their presentation. Almost everyone who hears my tube rig has the same extemporaneous response, along the lines of "Wow, it's so clear!"

Edited March 9, 2014 by Ski Bum

[joessportster]

have you heard it yourself or are you basing those ideas off what others have said?

I to am understandably curious about his builds... and the iron he uses.

I own the amp, listening to it for about a month now. Overall very happy with it

Thanks for the responses, I was just curious about this subject because i have had several SET Amps in the past that cost 10X what the SE84 did and I dont recall the detail, and clarity being at this high a level

[rbrown0678]

neutral aught to be the ability of any system to reproduce sound to the hearer as one would speak to

another person ,as a group of people might speak their invidual voices would be reconise by all others

in the room, plus should one be a distance away, that distension would also be revealed.

but since we dont all hear the same,there are aids that we use to bring us to that place of acceptance.all the other adjective are used to describe how far we are away from our point of satisfaction.

are they then establish norms, presented to qualify the differences.

[Ski Bum]

I was just curious about this subject because i have had several SET Amps in the past that cost 10X what the SE84 did and I dont recall the detail, and clarity being at this high a level

Who knows. They may have used horribly expensive and exotic yet poor performing caps and other foofy parts, bad iron, and/or a less well thought out circuit. And don't forget the fancy case work. And the marketing costs, if the amps you had were the sort to appear in the glossy mags. What were they? I'm sure Justin wouldn't mind a mention of which multi-kilobuck amps couldn't beat his most inexpensive offering.

Justin's little amp sure appears to be a nice value proposition. Sensible parts employed in a sensible manner for a sensible price, with sublime results per at least two reputable posters here.

[jcmusic]

have you heard it yourself or are you basing those ideas off what others have said?

I to am understandably curious about his builds... and the iron he uses.

I own the amp, listening to it for about a month now. Overall very happy with it

Thanks for the responses, I was just curious about this subject because i have had several SET Amps in the past that cost 10X what the SE84 did and I dont recall the detail, and clarity being at this high a level

Joe,

Have you only listened to this amp through headphones???

[joessportster]

I have used a single driver bookshelf speaker as well and it performed very well (my hearing is not the greatest and I am able to discern differences MUCH better with headphones) 30 years in the labor / construction / maintenance fields has taken it's toll, Back when I started working no one discussed hearing loss.

Ski Bum, a couple of the fore mentioned high dollar amps would be Joule Electra marquis otl monos, Sun 45 SET monos, Deja Vu 45 PP monos, Coincident 300b monos, and there were more , Now all theses amps (except the coincident, These were so poorly made, I could not wait to sell them, Also the Builder was a complete A$$) were / are very good amps that i used with High effecient horns, (edgar, Klipsch, Altec, Oris) In those systems I could hear some detail, clarity etc... But Honestly nothing like I can hear now. I am sure headphones play a part in what I am able to hear, However I know the amp is a big part of it as well because i Have used 3 or 4 other headphone amps / receivers that were not near as revealing

[mark1101]

_{The EL-84 amp that Justin posted is a kit.........I thought.........with the exception of the transformers, and the wood.}

[joessportster]

No its not a KIT, You receive the amp built and ready to play I should say you receive the amp OVERBUILT and ready to play

name any other builder that builds the amp in a full metal enclosure and then installs that enclosure inside a full wood enclosure. I don't personally Know of any

[jcmusic]

I have used a single driver bookshelf speaker as well and it performed very well (my hearing is not the greatest and I am able to discern differences MUCH better with headphones) 30 years in the labor / construction / maintenance fields has taken it's toll, Back when I started working no one discussed hearing loss.

Joe,

That is why I asked I too listen to music through headphones at work, and I can hear alot more detail there then through my big horn speakers.. Just trying to gauge the amps quality on a level playing field.

[justinsweber]

Kit... depends on how you consider it... I do buy my PCBs from shannon... I we also have alot of discussion with Shannon, my tech and myself re: changes to the circuit and different parts used.

DIYtube makes amazing PCBS which hare well thought-out.

That said, building them and getting the performance desired has taken many revisions.

The SE-84 is based on Shannon's top-plat and PCB. Specific changes include cathode biasing, feedback value changes and output transformers with different specs... though sources from edcor on this model.

Re: mental enclosure inside the wood... I originally was picking up noise. and so tried this simple suggestion and its worked... Ive now moved onto spraying the inside of the wood plinths with RF shielding which has accomplished the same goals.

KITS or not... an amp should measure well and try to employ the best build practices… I am not Shindo or Audionote… god I wish I were… I don’t make my own caps or wind my own iron… don’t forage my own chassis.

We do buy our own wood, mill it down; finish it to mate to its top-plate. Though I own some of my PCB gerbers outright… I don’t own them all and source from OE supplies who want my business and want to see their ideas get executed well. I ask for the design expertise to aid in building something which is different/improved from their original concept and pay for the advise.

I’ve said repeatedly… if anyone wants advise or would like more intimate details of what I use/ how I do it… call me. I have only received 3 such calls which covered cornscala configurations, sourcing for good iron and how to get a similar wood plinth. I don’t think its fair to ask me to place schematics, build of materials and grounding schemes for public consumption… Happy to share to an individual who wants to build for themselves and takes it upon themselves to ask.

With each of the amps I sell… they start with someone else’s good idea and good implementation of that idea… I try to then put my spin on it… not just solder it together but chose parts and values which make sense for me, and very often are not what are spec’d. In the end, each amp is bench tested, burned in for a several hours and then listened to. I’m not the most handy with a scope… My tech is… but my Cornscala’s sure as shit are revealing of problems… generally I fight noise floor battles… I want vanishingly low noise, good bass extension, neutral presentation and mid HF that floats… If I can hear it then there is a problem.

Re: the orig post… My exp has been circuit, output iron, passive components and grounding to make the largest share of differences on performance. Crapy circuits are real performance killers, but generally will exceed the ability of the iron. Passive components and their inability to remain stable over time or provide reliable/repeatable values has been a historic problem which has gotten considerably better over time. I think there was another post re: building practices… there is own books on this… building practices matter because the physics are non-negotiable and should be respected.

Lastly... if asked... I think Petter Millet and Shannon sparks create truely amazing designs worth exploring and builing.

[Schu]

You may have only recieved three calls... but beleive me, people are thinking about it my friend. The right people are giving great reviews, we're listening and you are using the right parts.

Times are a bit tough, but maybe slowly we'll come out of it someday.

[justinsweber]

You may have only recieved three calls... but beleive me, people are thinking about it my friend. The right people are giving great reviews, we're listening and you are using the right parts.

Times are a bit tough, but maybe slowly we'll come out of it someday.

Schu

Kind of you. I do think things are hard for many. I heard this interview on PBS... basically concluded that in the 90s to 2000s the middle class leveraged the income of both heads of family to send their children off to college or buy a home.

The reality of 2010s forward has been both heads of house work and that the husband typically has 2 jobs to provide the $ to maintain the middle class dream.

Id consider myself a bit more ambitious than many people I know... but I too work too much. (Trying to learn better ways to make the same $ but work less.)

About the transformers... If you didn’t own Klipsch Id say Edcor transformers are great...They are cheap by comparison, Their. GXSEs have great power handling and HF extention… but only go to 40hz. The SE-84 uses these outputs with a custom primary impedance and a lot of work with the feedback network. My Tech has those stacked cap and stacked resistor networks that helps to dial in such things.

If you want iron that does what it should and can handle big power… Hammond 1600 serious iron is wonderful without being pretentious. They are BIG… will require a braced chassis…. Problem with bracing is it Fs with how you route wires almost always. That said, Great power headroom, goes low, goes high.

Transcendar iron is generally my iron of choice. US made, natural midrange, great primary inductance, goes low, goes really high… not big. I always go for lower distortion over power when choosing primary impedances and bias tubes really conservatively.

With each of iron I use now… Ive gone to custom impedances to match the BOM of the circuits… just one more way to get a bit more out of it.

[mark1101]

http://store.triodestore.com/diy35kit.html

This is what I was referring to. I had been looking at these myself and I recognized it right away when you posted pictures of it. I assume this is your EL-84 push pull amp........but with the different transformers and a few other goodies.

I have been getting gradually more interested in putting one of these together for the heck of it. Mostly to learn and then of course enjoy.

[justinsweber]

The PCB is Shannons... but greatly changed... I’ve prob spent the most time reworking the design of this amp. I consider myself a purist... not a fan of pots on amps... Simpler the better. I’ve had to service too many amps in which no one did the requisite adjustments. Though I think the world of Chicago magnetics... I’ve moved away from their use is some cases... Having built alot of kits sourced from Triode of the years... like many... their kits (metal work is great). And the ST-35 offers the most support. I would strongly sugest you order your own parts.

Here is a bit of what we have been up to the last 2 weeks.

Edited March 10, 2014 by justinsweber

[Schu]

Omg... great stuff. I wish I was that talented

[mungkiman]

Beautiful speakers, too.

[justinsweber]

Thanks guys. The wood work is the efforts of partner.

I tried to embed the pics... didnt seem to work... can anyone help?

Edited March 10, 2014 by justinsweber

[Deang]

Justin, Is there any difference between what I'm using and what Joe has? Are there any differences between what Dave sent me and your current production version? Thanks.