Hi-Fi amp question.

[ratgon]

Hey all. I realize that this is probably not the exact forum room to ask this and if it needs to be moved I understand but I'll start it out here.

Having all but finished my last build I'm looking for a new project. Just getting ready to put a PPIMV in Sluckeys AC-15 design and build a cab and then it's time to move on. Honestly, I'm much more a singer songwriter than a guitar player so, I have an awful lot of amps stacking up around here. I'd like to make something else. So...hi-fi.

I've built a Dynaco kit and it turned out great but I've developed a new obsession:

Do any of you guys have any experience or interest in SET (single ended triode) amps? I'd really like to build one if I can decide on a particular design or starting point.

So...SETs. 

[shooter]

So...SETs.

I've done 4 hifish builds, none triode though.  I believe if you get a clean class A build, the difference is probably at the cork-sniff range.  Quality parts, attention to detail, start with a sound proven design and you have good quality audio from tubes.

[Tony Bones]

Talk about rabbit holes...

But yeah, I've know a few SET's. I still play a lot of music through 2A3 's into a pair of Altec 755C in open baffles, which is the hi-fi worlds version of open back cabs.

The first thing to accept is that you're going to be working with just a few watts of output power. Maybe even a fraction of one watt. So, you'll need some very sensitive speakers. I think full range drivers and SET's are natural allies. No, you can't have my 755C's.

[DummyLoad]

voice of the theater  + 811/845 SET in class A2.     


--pete

[ratgon]

Hey thanks! Yeah, I can sense the rabbit hole but I mean, that's why we do this right? I'm always looking for a pointless?obsessive/passionate hole to jump into.

The super low watt aspect of the SET's are kinda what appeal to me. But the speaker situation is for sure an issue. I certainly have nothing efficient enough at the moment. I'd like to go down that rabbit hole as well. Building speakers.

Anyway, I'm just at the beginning research angle of this so I'm looking, but I'm excited to get learning.

Oh, and Pete - Nice work and nice website! I hadn't seen your work before. Those designs and builds are beautiful!

-Mike

[DummyLoad]

Hey thanks! Yeah, I can sense the rabbit hole but I mean, that's why we do this right? I'm always looking for a pointless?obsessive/passionate hole to jump into.

Oh, and Pete - Nice work and nice website! I hadn't seen your work before. Those designs and builds are beautiful!

-Mike

thanks mike! 


--pete

[SoundmasterG]

I've got a Dynaco Stereo 70 and a Scott 299B to rebuild, and a Dynaco PAS to pair with them, but haven't really been able to get into them very much yet as getting my BSEE got in the way the last few years. My brohter inherited a McIntosh MC240, a Sargent Rayment, a Fisher 400C, some big corner speakers, etc., and he'll need me to get them working, so I will likely get into some of this stuff soon, but no single ended triode stuff in the bunch yet. I've heard they sound really good and I read the Vacuum Tube Valley mags about them. If you haven't you might want to read up on those and search out Glass Audio also. A lot of interesting articles over the years in those. You can get all 20 VTV issues for free but the Glass Audio you need to pay for.



Greg

[shooter]

I have the Voice of the theater cab if you want it, using it as a skeet launcher
now the speaker......  one of the best 15" I've had.

my best 'fi-ish build was a QuadSE EL84, 6SN7 driver into a pair of Audio Nirvana 8" mounted in my custom cabs, Iron from EDCOR

saving my change to get a JBL 2035 pro series re-coned, slowly carving a cone for the 18lb tweeter mate

[DummyLoad]

hi-fi, lo-fi... a pair of VTL 185 monoblocks would be nice. or a pair of ARC reference 300 monoblocks even sweeter.    i'm driving magnepans... 


 https://www.youtube.com/watch?v=faxBtVkyIuY


--pete

[jjasilli]

Be aware of matching speaker requirements.  It's not just the amp, but the amp-speaker combination.  When Dummyload refers to Voice of the Theater, he's not kidding.  Those speakers are each the size of a washing machine.  Today's typical hi-fi speakers are pretty small.  To get loud room-size volume level powerful amps are needed to drive small boxes.  Back in the day AR Speakers were the first successful, smallish design, maybe driven by a 35W per channel Dynaco amp.  But when you're below 10W, large speaker enclosures are needed. 


Mathematically, a Voice of the Theater might have an SPL of 110dB or more!  Today's small boxes, probably in the high 80's dB, or less.  Every 3dB requires a doubling of amp power in Watts.  And to avoid clipping, this must include transient spikes which might be 12dB higher than the average listening level. 


This is Hoffman's Iron Law (not our Doug).

[HotBluePlates]

... I still play a lot of music through 2A3 's into a pair of Altec 755C in open baffles ...

The first thing to accept is that you're going to be working with just a few watts of output power. Maybe even a fraction of one watt. So, you'll need some very sensitive speakers. ...

My one experience with SET was listening to someone else's homebrew 2A3 amp, with a whopping 3w of available power power per side (yeah, I know the 2A3 should be able to do more, but that's what he told me).

He was playing the amps through Klipschorns; I don't recall the model.  Volume control half-up was just shy of blowing me out of the room.

[jjasilli]

Klipschorns are fabulous speakers!  And they're humongous:  https://www.google.com/search?q=Klipschorns&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjQgOOGzZ3UAhXGLyYKHc8fC4MQ_AUICygC&biw=1680&bih=920

They're also highly efficient: 105 dB 1W / 1M.  http://www.klipsch.com/products/klipschorn-floorstanding-speaker

Some math: I use Infinity Qa's from the '80's (custom rebuilt crossovers).  89 dB 1W / 1M.  The loudest music I like in my listening room is 80dB. (I don't know how some people like 90dB!?!) My transient spikes hit 92dB.  My listening spot is 4M from the speakers.  That doubles the standard measuring distance (1M) 2X:  1M doubled = 2M doubled again = 4M.  Every time you double the distance you drop 6dB in SPL:  at 4M from the speakers I drop 12db.  So, 1W into the Infinity Qa's produces 89dB at 1M which drops to 77dB at my 4M listening position.  I need to increase that by 3dB; so I need to double 1W to 2W.  Now to keep transient spikes clean up to 92 dB.  That's 12dB more than the average of 80dB.  12dB is 4 increments of 3dB each; and each 3dB increment requires a doubling of amp power in Watts.  So, 2 (80dB) > 4 (83dB) > 8 (86dB) >16 (89db) > 32 (92 dB). 


You can see why 30 - 35W amps -- Eico or Dynaco ST-70's, e.g. -- became popular with the advent (no pun intended) of smallish AR speakers, and competitors.  But this maxes out the amp; no headroom.  For a lousy extra 3dB of headroom I need 64W.  Hence, the  Harmon Cardon Citation II @ 60W per channel; Dynaco Mark III's, e.g.

****
Now, let's compare the Klipschorns.  1W into the Klipschorns produces 105dB at 1M; minus 12dB at my listening position = 93dB.  Yes a 1W amp into the Klipschorns would blow me out of my room.  But the Klipschorns don't physically fit well in my listening space.

Big speakers move lots of air (SPL) with little excursion, so they can be driven with little power.  I.e., they are highly efficient.  Small speakers need lots of excursion working against the impedance of the air trapped in the box. This requires lots of power; and power requirements increase logarythmically. 
***

Hoffman’s Iron Law of Speaker Building (from the 60's):  1) sound quality; 2) Efficiency; 3) Small Enclosure.  You can't have all 3; only 2 out of 3. So if you want a reasonably sized enclosure with good sound quality; you can't have efficiency.  There was a time when a 20W tube amp was exotically powerful.  Today watts are cheap & plentiful, and few people have the space for horn speakers.

[Tony Bones]

My one experience with SET was listening to someone else's homebrew 2A3 amp, with a whopping 3w of available power power per side (yeah, I know the 2A3 should be able to do more, but that's what he told me).

He was playing the amps through Klipschorns; I don't recall the model.  Volume control half-up was just shy of blowing me out of the room.

The standard datasheet operating conditions for SE 2A3 is 3.5W. I measured the output of my system playing music at my typical listening level and it was about 0.5W. (Typical listening level for me above normal conversation, but not enough to make conversation difficult.)

Horns are king. I have a friend that builds giant horn systems for a living. They are magical. But SET can be done without heroics. In fact, I think that's where some of the real fun is; building a modest system that is rewarding to listen to. All it takes is 100dB/W or so. Once upon a time many speakers were that sensitive. It's still pretty common with guitar speakers, but hi-fi has gone hi-power. It's like all the new software needs a quad core processor, all the new speakers need three digit power.

I haven't tried it, but I bet a simple 2W SET would sound OK through a pair of vintage smooth cone P10R's in open back cabs. Anybody have two 5E3 deluxes they want to try as stereo speakers? It would be a very different listening experience to what you're used to, but if you can put aside you're usual yardstick for measuring stereos and just listen to the music, I bet it would be enjoyable.

[jjasilli]

It depends on what you're listening to and how loud you want it to be.  Open back is efficient.  But bass vanishes at 100Hz & below.  Also, hi-fi drivers would be better than guitar speakers. For human voice and/or acoustic guitar reproduction, e.g., open back works great. A full orchestra, rock & roll or Motown would be disappointing.


At conversational volume, SET will probably work into bookshelf speakers. 

[ratgon]

Man. I really have pulled the lid off the rabbit hole. I really appreciate all you guys input. So much of it is well, well beyond my experience but it's a place to start learning.

The thing is that these SETs obviously exist and they can't all be driving massive horns in every dudes living room. So what the middle ground? The Iron Law makes a lot of sense but I suspect there must be some compromise in there.

There's another law as well. Maybe it's just my law but one thing that has always served me well is screwed up hearing after years of playing extremely loud music for a living. I can't tell the difference between capacitors and I suspect I can't tell the real difference between matched or unmatched SET/HES systems. Not that I don't think the difference exist, I just know I can't hear them.

A big part of the appeal of SET is their simplicity and construction elegance. They just look cool! So does any tube amp in my opinion but incredible sound coming out of a single output tube seems magical.

Now, what exactly makes a Champ so different from a hi-if SET? Seriously, I know only enough to wonder

Mike

[Ed_Chambley]

Now, what exactly makes a Champ so different from a hi-if SET? Seriously, I know only enough to wonder

Mike

About 5 hundred dollars. 


I have a pair of 2a3. They are Servicemaster international in the boxes. They have been auditioned and sound really nice. I have built mono blocks. The output transformer is a lot different from a Champ. I would think you know this tho.


If you decide on a 2a3, and want to make me an offer for them send me a PM.


Running through a lot of different amps, I have found I simply prefer Push Pull KT88 for the exact reason already mentioned. Speaker size. However, I do think if one has the room for the large enclosure it is the best I my opinion. I do have a few GEC KT88 around that I use for what is basically a reved up Dynaco running 2 pairs stereo.


Take a look at Pete Millet site for some ideas.

[jjasilli]

The thing is that these SETs obviously exist and they can't all be driving massive horns in every dudes living room. So what the middle ground? The Iron Law makes a lot of sense but I suspect there must be some compromise in there.
There is no more compromise to Hoffman's Iron Law than there is to Ohm's Law, or Newton's Laws of Physics.  Actually, it's a restatement of Newton's Laws applied to speaker enclosures.  A Law of physics is not a Law because it "makes sense".  It's a Law because it corresponds, uncompromisingly, to objective reality. 

But compromises can be made elsewhere, in a number of ways, such as: 

* Forego volume. Conversational volume is about 65 Hz.  1W into an 80dB bookshelf speaker yields 74dB at 6' from the speaker.  That  exceeds conversational volume.  It would be like having Joni Mitchel with her guitar performing personally in your room.  This is where SET shines in low volume systems.  It sounds fabulous and very intimate with the right musical genres.
*  Have a complete other sound system for Led Zeppelin at rock & roll volume & window rattling bass.  This is a common solution for SET devotees.
*  Forego bass response below 100Hz
* Build a music room large enough to properly house horn speakers
* Squeeze horn speakers into your existing room and lose your wife



The experience of music feels magical. But the circuits and devices that produce, or reproduce it are creatures of cold, hard science; even if we subjectively love the technology. 

[ratgon]

But compromises can be made elsewhere, in a number of ways, such as: 



Yes. That's what I was trying to get at. The Iron Law "makes sense" to me because, yes, it's a law but it speaks to absolutes of each design goal so adjusting the imperfection of each goal can lead to possible solutions. Just how big of a cabinet can I, and yes, more importantly my girlfriend, live with and how much bass extension and volume will that buy me? And so forth. The truth is that for all my tinkering and amp building my space is pretty limited and there are already rumblings of "how many amps do you need??"

But this all helps so thanks. I suppose I just need to find a set of speakers that handle Pink Floyd, Velvet Underground and the Dead equally well. And, speakers that don't break the Law of the Wallet.

Ed- I did know that the OT is obviously a huge factor but I am curious to see where the basic circuits cross paths and diverge, which is easy enough to do. I mean, just how close is an inexspesive Champ build to a $1000 + SET, OTs notwithstanding?

I know, I know..who's this rookie guy with all these rookie ideas? Ha! But this is how I'll learn so thanks for indulging me.

Oh and ED...let me do some more research into this deal and if it leads me to 2A3s I'll for sure get back to you. Thanks

Mike

[Tony Bones]

I recommend joining diyaudio.com and audioasylum.com to see what other people are doing.

If you want to build you own speakers, take a look at BIB's. It's an inexpensive, simple to make back loaded horn that takes up very little floor space and can have a good wife acceptance factor. There's a lot of discussion about them in the speaker forum on diyaudio.com, including a massive 500+ page thread.

[ratgon]

Thanks Tony. Yeah, I've been snooping around there a lot. Appreciate it!

[jjasilli]

Some thoughts on SE Triode vs. SE Tetrode or Pentode:


http://theartofsound.net/forum/showthread.php?5987-Single-Ended-Triode-vs-Pentode
http://www.audiocircle.com/index.php?topic=109098.0
http://www.diyaudio.com/forums/tubes-valves/117158-triode-versus-pentode.html


Recurring points:  Power triodes are very linear, so feedback circuits are not needed to force the amplified signal wave into "alignment" with its shape at input.  Power triodes have good speaker damping factor due to low plate resistance.  This is good for open back, or large speaker cabs with little to no back pressure in the cab to physically damp speaker drivers.  This eliminates another need for NFB. The result is pure & natural sound (at least to the ears of power triode devotees).  By contrast the Champ does use NFB, even though it drives a stiff, relatively inefficient guitar speaker.


Speaker damping is needed: (i) to keep from damaging the driver due to over excursion; and (ii) to eliminate back EMF by the driver's generating signal back into the amp at the driver's (or system's) resonant frequency, thereby skewing linearity.  Power triodes do this automatically, but at the cost of output power.

[PRR]

> what exactly makes a Champ so different from a hi-if SET?

Tonestack and tweed/tolex.

OK, there's several different "Champs". The AA-Champ with light NFB would be a lovely hi-fi amp, with 1st stage and tonestack amputated. Maybe a WE 350 instead of 6V6 (same tube). The light NFB makes it similar to a triode. But it has to be dressed-up in chrome and plexiglass, with $30 speaker terminals and a $800 power cord.

[DummyLoad]

> what exactly makes a Champ so different from a hi-if SET?

Tonestack and tweed/tolex.

OK, there's several different "Champs". The AA-Champ with light NFB would be a lovely hi-fi amp, with 1st stage and tonestack amputated. Maybe a WE 350 instead of 6V6 (same tube). The light NFB makes it similar to a triode. But it has to be dressed-up in chrome and plexiglass, with $30 speaker terminals and a $800 power cord.

....and $10/ft silver hookup wire with gold plated sockets. and we haven't even budgeted for interconnects yet, have we?


--pete

[DummyLoad]

i'll just stick with my (s)adcom 5302 and MG1.6. life's less complicated with no tube faults to chase...


--pete

[jjasilli]

   SS, for shame!  My Stromberg Carlsons sound much better than my Adcom GFA-54511. Heck, even my wife can tell the difference.  They're also ugly as sin and ain't got no silver or gold. 

[DummyLoad]

  SS, for shame!  My Stromberg Carlsons sound much better than my Adcom GFA-54511. Heck, even my wife can tell the difference.  They're also ugly as sin and ain't got no silver or gold. 

you own a GFA 545 Mk2? i'm sorry...truly i am. that is a pathetic excuse of an amp riding on the coattails of the GFA555 Mk2 which is actually a decent sounding amp. the 555 mk2 was designed by walter jung: Mr. op-amp god. i should have kept my ARC D400 Mk2 - money was tight so it found a new home.


and... FYI, i ran a pair of CJ premier 5's for some time. glorious sounding but unreliable with east yurop glass. bought that SS ARC D400 and haven't looked back at tubes since.


--pete

[ratgon]

Now we're cookin!

[shooter]

Now we're cookin!

I can smell the cork

[jjasilli]

That's no cork.  It's the smell of the blown channel in my Adcom. 

[DummyLoad]

That's no cork.  It's the smell of the blown channel in my Adcom. 

hence why i call them a (s)adcom.    Mg3.5's ate a GFA-5802 i had. neg rail blew on the right channel blowing a hole in the PCB and lunching every output device. it was just over 2 months out of warranty, but because i bought it as "B" stock new, they wouldn't warranty it. after tripping over it in my storage room for a few years, it ended up at the goodwill as a tax deduction; so not fond of sadcom to say the least... i wouldn't mind having another ARC D400 Mk2.


--pete

[DummyLoad]

That's no cork.  It's the smell of the blown channel in my Adcom. 

sure it's not that grommes? 


--pete

[HotBluePlates]

... Just how big of a cabinet can I, and yes, more importantly my girlfriend, live with and how much bass extension and volume will that buy me? ... I suppose I just need to find a set of speakers that handle Pink Floyd, Velvet Underground and the Dead equally well. And, speakers that don't break the Law of the Wallet. ...

I live in an apartment.  I have a 6 year old.  I have a pair of McIntosh MC-30's.

But living room shape isn't ideal for speaker placement & listening position.  6 Year old will likely destroy anything of value within his reach, or within range of a thrown toy.  I'm unsure how well the walls keep my good sound out of the neighbor's apartment.

So I made the choice 4 years ago to let the MC-30's sleep in a safe place, get a great pair of headphones, listen to music that can't bother neighbors and is out of reach of the Tiny Tornado.  Maybe I could have a better headphone amp than the one I've got, but that can wait until I win the lottery.    It's sounding plenty-good for me now.

[kagliostro]

...... is out of reach of the Tiny Tornado

Was a long timr ago, but I know the problem 

! No longer available

Franco

[jjasilli]

For SS info:  http://education.lenardaudio.com/en/13_guitar_amps_3.html  Also, click the Subject tab top right. 


By the power vested in me by the Solid State, I hereby declare:      



 

[shooter]

Overdrive management

This should be avoided in HI-FI
seems like way to much thinking to make a SS amp sound like my tube amp already sounds

[jjasilli]

But your tube sounds the way it does because of overdrive management.  If you don't want overdrive you need to manage tube amps for that; e.g., Fender Twin.  If you do want overdrive, then you manage for the type you want.  E.g., smoothe Class A overdrive in the power tubes, with even order harmonics.  Hi preamp gain for a metal sound, with odd order harmonics. 

[shooter]

For HIFI OD doesn't exist, or shouldn't, and the article you referenced seem to suggest with lots of work n thinking you can make SS sound like tubes, my point was, I already have that from tubes, why make it more complex.

[jjasilli]

I don't necessarily agree with Lenard, or his compatriot Tod Elliot.  But they know a lot about tubes & SS, and do build & sell tube equipment.  That article states that to understand it (the article) you first need to read the prior articles on the site.  That site contains tons of info which took me years to learn elsewhere.  But it's concise & dense, so it's difficult to read.


That was one small section on guitar amps, which is not really pertinent to this thread, or to Lenard's entire site.  BTW, Lenard has little regard for SET, and is with Ed Chambley on the merits of KT-88's in PP.


It is not clear that SS is more complex than tubes.  I, like you, got used to tubes.  So tubes seem less complex to me.  But in the beginning, tube circuits seemed complex.  Back in 2004, before I joined, I read this Forum for 4 months before I could make any sense of it.

[shooter]

Back in 2004, before I joined, I read this Forum for 4 months before I could make any sense of it.

Yup, I came from 30+yrs in hi-tech sand, when I got here I just smiled, and started askin ?'s

the merits of KT-88's in PP.

I have enough yard, and house for that, but I like using the 88 as SE  for audio as long a s you keep it clean

[DummyLoad]

i also did/do favor 6550/KT88/EL34 in PP over SE for HiFi.  around 2-3 years ago i was going to draw up a plan for a monoblock running 6 x 6CD6GA/7867 that was to push about 190W, but never followed through with it as i don't listen to my hifi much anymore. i've lost most of my hearing so listening to music with headphones is the norm for me now. 

--pete

[DummyLoad]

oh, and...


https://www.youtube.com/watch?v=BZhfFXEMMI4


--pete