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Amps and Sound SE-84


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Amps and Sound SE-84

I enjoy my weekly call from Dave Harris since it always

provides an opportunity for a good rant. This is cheap

entertainment for Dave, and I'm pretty sure it's the main

reason he calls. Sometimes we're forced to talk business,

since we often share customers, and other times we actually

talk about the things that make music sound better.

"So, I've got this amp over here."

"What is it?"

"A tube amp."

"I'm sick of tube amps."

"You might like this one."

"I like all tube amps, but I'm still sick of them."

"This one's different."

"They all say that."

"No, this one really is."

"Okay, so what is it?"

"Single Ended Pentode."

"I'm sorry you ended up with it."

"Uh, no, it sounds really good."

"No it doesn't."

"I think you need to hear this thing."

"What kind of output tube?"


"Didn't they use that for clock radios?"

"I didn't think it would sound good either."

"Who built it?"

"Justin Webber, from the forum."

"I don't have a preamp."

"You don't need one, it has a volume control."

"How much power?"

"3 watts."

"I really don't have time for this."

"It has a headphone jack."

"Okay, send it."

The days of emptying out the checking account on big

speakers and expensive gear are over, and have been for a

long time. Watching my house fall apart around me and

putting a kid through college probably had something to do

with that, and then of course there was that other thing.

Also, working during the day and running a small business

leaves very little time to pursue other endeavors, even

something as simple as sitting down to listen, which is one

of the reasons I adopted IEMs. It's a win-win, they sound

great, block out distractions, don't disrupt others, and I

don't have to put down the soldering iron. To be honest, I

really haven't missed 2-channel listening in the

conventional sense since getting into IEMs and headphones.

Now, before I talk about Justin's amp, I want to talk a

little bit about what I've be using to listen to it.

My source is the Oppo BDP-93, which has an admirable analog

output stage. There is certainly better, but there's also

far worse. I believe the unit ran me around $550.00. I have

no complaints, and considered it a major step up from the

Denon transport I was using (in conjunction with the DACs in

the Denon 3808ci receiver).

The loudspeakers are my home-brew monitors using Radian

5208C coaxials mounted in 1 cu. ft. ported cabinets.

Sensitivity is 95dB/2.83v, they go down to 50Hz, and

can handle 200wpc. The crossovers are Radian designed

(12dB octave/12dB octave), and I built them using Jantzen

Supremes and Mills resistors.

I built these for quasi-near field listening in a small

space, using a sub, preferably two, which is how they're

currently set up. Since the set up is primarily for HT and I

have a center channel, the speakers are about 12 feet apart

and just off the corners, which is good, because since I

won't be able to use the subs -- I'm going to need the


The box shows up on one of the coldest days of the year.

It's been sitting on the porch most of the day. I bring it

into the house and put it in a safe place. Okay, this is my

house -- there is no safe place. I ask everyone to try and

not kick the box as they make their way to the bathroom.

Don't ask.

It's been a few days. I want to play, but I can't. I've been

completely buried since October, and I'm working on my last

set of crossovers. Finally caught up, I decide it's safe to

open the box. To be honest, I'm mostly interested in the

performance of the output jack for headphone use. The amp

only has three watts, so it's of no real use to me as a

long term solution.

I go to Justin's website to see what I really have. I notice

it's $900.00, and start thinking that's pretty expensive for

a headphone amp. Well, not really, but it's still $900.00

for a guy that's perfectly happy with his FiiO E-17.

Dave did a nice packing job, it took me about about an hour

to find the amp.

The amp is about the size of one of those big family Bibles.

Compact and dense - heavier than I expected. Nicely finished

all the way around. The output and power supply iron is

small, but sporting a high quality painted finish. IOWs, it

doesn't look like some guy did it in his shed with a can of

Rustoleum. Same with the top plate, gorgeous. The wood

finish is as good as I've seen, and I've seen a lot. There's

nothing to down-rate cosmetically speaking -- A1, very nice.

Time to dig out some cables. Really, do I even care about

this? What's wrong with what I have up here? Hmm, let's see

... Some nice Monster from the Denon to the speakers, and

then all HDMI. Okay, that won't work. I go down to the

workroom and find my bag. This is the bag with all of my

retired "audiophile" cables. I feel a tinge of guilt and


I see my Cardas 300B Mircotwin interconnects -- yes, those,

grab the short ones, .5 meter will do nicely. Litz wire with

a teflon/cotton dielectric, probably still one of the best

deals in cable. I grab my spool of Supra 1.6 Classic and

decide to go with bare wire terminations between the amp and

the speakers. Hardcore.

What else? Uh, let's see. Well, I guess that's it. Wow, this

2-channel stuff is pretty simple. I wire everything up and

hit the power switch.

I suppose I should let the thing warm up a little. Man, what

a hassle. I start looking for a CD, which is a challenge

since they're all downstairs in the basement with the other

system. I find a little stack over by the movies and don't

recognize any of them. I turn to Deb,

"What are these?"


"Where did they come from?"

"I bought them."

"What for?"

"So I could listen to them."


At the top of the stack is "The Very Best of Cream".

I really don't feel like listening to Cream, but the

basement is really far away. I open the case and on the

inside jacket it says,

"Remastered from the original master tapes utilizing Apogee

Electronics' AD1000 Reference Standard 20 Bit Analog to

Digital Converter and UV22 Super CD Encoding."

Impressive. I have no idea what any of that means. I

decide I'm going to just put it in and hope that it

doesn't sound terrible like most of my other stuff.

I notice that the tubes are lit up, and that's warmed up

enough for me. In goes UV22 Super Encoded Cream.

The first song is called "Wrapping Paper". I've never heard

it before. I'm not sure if I like the song or not, and the

mix is typical of the time period - some instruments coming

out of the left speaker and the rest coming out of the

right. It sounds nice though. I got lucky, it's a good

recording. I get up to go sit in the chair, and before I do,

I turn it up just a little. UV22 Super Encoded Cream is

sounding pretty good.

Deb wants me to tell her about the amp. I tell her I don't

know anything about the amp. She wants to know why I don't

know anything about the amp. I tell her that I'm a speaker

guy and that I'm not supposed to know anything about the amp.

She asks me why my speakers sound different. I ask her if

she'd like to know something about the amp. She asks me if I

plan on buying the amp. I remind her that we have to buy

Colter's LaScalas first. I tell her that one good recording

isn't enough to go on. She says that maybe we should think

about buying the amp. Yeesh woman, seriously?

You guys know how this works. It's new, it's different, it

puts a different spin on everything in your collection, and

it's fun. We listened for several hours before shutting down

for the evening. Deb never once asked to watch TV, and in 25

years of marriage, this was the first time she ever spent an

entire evening listening with me.

I'm having a terrible time critically evaluating this amp,

since in effect, the music keeps getting in the way. It's

been since Saturday, and I'm sill waiting to get used to the

sound so I can honestly approach it. Single Ended anything

is not my thing. I've only had two experiences with it, once

with the Wrights, which I thought produced some of the most

wretched sound I'd ever heard, and the Welborne Apollos,

still on my short list as producing some of the most amazing

sound I'd ever heard. What a contrast between those two

sets of monoblocks, having nothing in common whatsoever

except for the Single Ended designation. So where does

this thing fall?

This particular amplifier is Single Ended Pentode -- and I

always thought pentode was a "dirty" word of sorts. However,

after four days of non-stop listening, and the flashing of

the television screen reduced to about zero, it's obvious

we've stumbled onto something special. I can see why Dave

felt compelled to send it to me.

This amplifier's strength lies in its ability to spread

things out and pull the layers apart a bit. Everything is

laid bare, and it's done in a wonderfully rich and non-

fatiguing way. The sound is textured and vivid. We found

ourselves watching a lot less television and listening to

a lot more music. Notice I keep saying "we" and not "me",

and this is because the whole family has been enjoying it.

Ian and me played Yugioh for three hours on Sunday night,

completely forgetting about the movie we had planned to watch.

Ian is 10, and really digs Elton John -- so we did a lot

of Elton John that night. I was trying really hard to

listen to the amp, but it was impossible because of Ian's

singing. I instead found myself wondering why he was so

engaged. Ian is not shy by any stretch, but he's not the

the type to burst out into song either.

This small amp is a music machine. I never once thought

about the fact that I only had three watts at my disposal. I

think one of the bigger surprises is how balanced it sounds.

I was really expecting the sound to be somewhat tipped up,

but that's not how it sounds at all. It has all of those

things that good tube amps are supposed to have, and then


I'm glad I no longer feel the need for the higher SPLs, as

it affords me the ability to get back into tube audio

without the sizable investment. I also never felt the need

for a preamp, which can only mean that I was dialing right

into the sweet spot. I've been hovering between 7 and 9

o'clock on the attenuator for the majority of the time, and

apparently, this is the place to be with this speaker/amp


There is a "rightness" to the sound that makes you want to

keep on listening, and the imaging is phenomenal. Regardless

of cost, I think the sound is scary good, and this amp

should be given strong consideration.


Edited by DeanG
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They also sound pretty amazing with zero feedback. I have a single-ended EL84 (with 12aX7 driver -- the usual companion for this topology) that was among the first amps I used with La Scalas and then Klipschorns about 12 years ago. I am now listening to Lowther PM5A drivers on an open baffle with La Scala bass bins. This little amp is, as mentioned above, a very, very good performer.

I also own a single-ended 6V6 stereo amplifier that is as nice, if a bit more bit more powerful.

Have fun, these little amps are a blast! Amazing with my Grado headphones, too.

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Guest David H

I though you would like that little guy. I was also incredibly pleased with its sound.

I hope it is just as pleasing to listen to with your Lascala's.


Edited by GotHover
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Yup I do.

thank you for the kindness.

I actually just finished Brads amp simply wonderful results from the bench... Did a bit of tweaking on my parts list.

The P-P EL84 is getting 18watts 20-20khz and peaks of 40.5 watts when I was testing in the mid band. Ill do a separate post tomorrow... long story short... was super happy with the test bench results... I took the extra time out and went into the NOS bins and tested what Im shipping... I think he will approve.

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Little ben I believe rolls off around 6db after 20hz and prob about the same on the top. The Amp is pretty darn flat 20-20khz. Its a fine line between how flat you want a response curve and how much feedback you're willing to use. The nice thing is the better the output, every ofter, the less feed back which is needed.

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Nice job, Justin! I really like the layout of the that little guy! Like several guys here, I have an assortment of homemade single-ended amps configured around the big triodes, but the little 6BQ5, either single-ended or push-pull, gives the 300Bs, 2a3s, and 45s a serious run for their money (qualifier: in my experience).

I LOVED the Wright 2a3 monoblocks. I once worked on a pair where the user adjustable output transformer secondaries were not only connected out-of-phase, but were on mis-matched impedances. They also sounded just plain wrong, totally out of balance, until I looked more closely to try to find out what was going on.

I still look for Welborne Apollos.....neat amps. I may build a pair; schematics for all those amps are on their website, however, the aesthetic aspect of factory Welborne amps are, IMO, hard to beat.

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Little ben I believe rolls off around 6db after 20hz and prob about the same on the top. The Amp is pretty darn flat 20-20khz. Its a fine line between how flat you want a response curve and how much feedback you're willing to use. The nice thing is the better the output, every ofter, the less feed back which is needed.

It is always useful to specify the conditions under which you make frequency response measurements. Saying that it is pretty darn flat doesn't really say much in and of itself. In the "old days" we measured at 3 db and 10 db below maximum ouput (referenced to a given frequency- often 1 kHz), with the latter defined as either clipping, or distortion above a certain amount. In addition, the load impedance into which you are feeding the output when measuring should be specified, as well as the amount of neg. fb used. Many amp manufacturers have gotten themselves into a pickle by stating specs which, in reality, didn't exist. Hope this helps!


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Let me be more specific... Im not here to advertise my equipment and make others who build or sell or klipsch in general angry. (I like that others dig what Ive done). I was tryign to be coy about specs. I know full well what each amp does and share specifics via phone. I believe publishing specs lends its self to bench racing which is not my aim. My site doesnt include that info on purpose. That said.The SE-84 is not nearly as linear as my larger amps... biger iron and biger caps will do that, but it does many things really well.

After each build, the amp is placed on the bench and measured using 2 volt meters, my ociloscope and a signal generator. Its not fancy but tell alot of what the amp is capible of doing. Listening is done on my 2 way cornscalas. When thats done they are ready to ship.

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I wasn't referring to the circuit. I tend to believe the limiting factor of a circuit is the implementation not the circuit as much. Small power supplies of output transformers that are not idea are limiting. Larger/better output transformer would allow the SE84 to go deep (frq response) without distortion but there is no room :-). I generally use bigger iron for that reason but opted for a more balanced approach this time. The SE84 is meant as a great all around solution/ office amp.

So general rules for me... Output iron with largest cores possible (less prone to saturation, etc.) and largest power supply possible... Ive seen difference robust power supplies make. The SE-84 limitation was not price but size. As it is... it required me to use tools to hold thing in place during the final assembly as my hands were getting cut.

If I were not trying to build based on repeatable results/ ability to scale up if needed. The RH84 circuit is wonderful. There is a gentleman here who built an example with truly awesome attention to detail using turrets.

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I agree on the issue regarding output transformer construction, the importance of adequate air gapping, etc. However, this is a multi-faceted equation. I have built single ended amps with OPTs of reasonable to even smaller dimensions that performed better at frequency extremes than some amps I've made using very large and heavy output transformers. I also agree that a power supply that provides "well- behaved", thoroughly filtered B+ is important.

I have to say that my SE EL 84 amp with Klipschorns or Lowther horns had applications well beyond the confines of a smaller bedroom or workroom, but I totally agree they can work quite satisfactorily in a smaller space too. As you put it, a great all around amp. Absolutely.

I like your construction very much! Nicely done!

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