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While I was listening to the 813 amp burn in this morning I was looking back through my notebooks for a candidate for my next breadboard project.I ran across a hard copy of one called "Sakuma style single ended EL84 drive el84". I had printed a copy out a while back intending to do a breadboard and got busy with other things. It's a very simple amp so I put one channel together this afternoon and was amazed at how good it sounds. Went on the web to try and find the article to share with everyone, but it appears the site no longer exists. All I have is the one hard copy. If anyone has an electronic copy could you please post it? It is a great little amp with a very low parts count. The el84 has always been one of my favorite tubes, but about all you ever see are pp designs. This one has the sonic signature of an el84 and the sound of an se amp, and that is a great combination. If no one has an electronic copy of the original article, I guess I could post a photo of the schem for one channel. I can not believe the sound you get with so few parts, and I am a firm believer in the KISS principal.
Follow Ups:
Got my psu up and running again. It had a bad small solen 1uf cap that was being used as a trimmer to adjust the voltage out of the rectifier and it must have been shorting out. Still have a small buzz, but will worry about it later.
I was finally able to get both channels up and running, and then I did the right channel as triode connected and the left channel as pentode connected and did some comparisons between them using a mono cd and switching back and forth between the channels with the volume knobs. The most obvious difference was the expected much lower gain with the triode channel. Very noticeable indeed. The other thing that was most apparent to me and somewhat of a surprise was that pentode channel seemed to sound more lively, the triode side sounding a tad dull by comparison. Now there may be more at work here than just the different modes, but that is the only difference I am aware of at the moment. I must say the little bugger is pretty impressive with both channels in pentode mode. I think I am going to have to play with it a while and see just how far I can go with it. It is such a simple little amp, and it sounds so good. Only complaint so far is a bit of shrillness on the high end and I do not know for sure what is causing that. Will have to do some AB testing against my other two amps as I tweak it to see what I hear.
Anyway, if you want a great little SE amp that is not too expensive and easy to build, you might want to give it a try.
Edits: 06/05/17 06/05/17 06/05/17 06/05/17
It's interesting vinnie... I was once surprised when I heard similar differences between triode and pentode modes on a Primaluna (I think) PP amp some decade or so ago. I put the differences down to (lack of) level matching, imperfect implementation for triode mode, system suitability, but I'm really not sure what was going on.
So, I would not be surprised now, but I was when I first heard it.
Cheers,
91.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
Yes, that is the problem. Knowing exactly what is causing the difference may take some study. Once I get everything running right and my amp switching system going I might just try to figure it out. It was not what I expected.
Betcha you'd forgotten about this one! ;-)
Edits: 06/05/17
Sure as heck I did! Lots of helpful info there. Thanks a bunch!
Glad to have been of help. I found this old thread while searching for the schematic hoping to find it somewhere on the net, but no luck so far. I remember first coming upon that site at least 6-7 years ago, then again about a couple of years back and it did pique my interest. Too bad the wayback machine can't access it.
I was looking at the schem I posted trying to figure out what would have to be changed on the output tube to make it triode connected instead of pentode connected and realized I did not know what had to be done. Can someone please explain it? I don't see very much difference in the way the driver and output are connected in the schem.
Edits: 06/04/17
Simply tie the screen to the plate with a resistor like the first stage for triode connection.
The screen is tied to B+ per your schematic right now
"The screen is tied to B+ per your schematic right now"
I thought G2 in a pentode was run at a fixed voltage lower than what's on the plate?
Maybe there's some parts missing in that schematic?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
G2 only needs to be a fixed positive voltage, with no signal on it, in order to create pentode operation. It can be at the same voltage as the B+, although usually not more than that.
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Buy Chinese. Bury freedom.
Wasn't it the Sakuma goal to preserve and reinforce the sonic integrity of a specific tube by using the same type as both driver and output? I don't see how that could take place with one tube in triode and the other in pentode. The two configurations don't respond the same electrically, and as anyone who has switched a 6BQ5 output stage between triode and pentode can attest, they don't sound the same. Are we certain the schematic you posted is the original Sakuma? In any event, it will be interesting to hear your opinion on the difference when both stages are either pentode or triode. :)
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Buy Chinese. Bury freedom.
Not sure who you are responding to, me or deaf. I am going to compare the two modes once I get the original working right. I think your first sentence is the most important part of this though; the idea is not to duplicate a sakuma design entirely but to check on his idea that using the same tube as driver and output will give you a better idea of the true sound of that tube. If what deaf says is correct, it sure isn't going to take much to change the output tube from pentode to triode. I still have a few issue to sort out with my psu, but I am hoping that within a few days I can answer that question, because I really want to know too.
Edits: 06/04/17 06/04/17
Sakuma just rolled over and went digital in his grave.
No one is trying to duplicate his design, we are just investigating his premise that only by using the same tube as a driver can you hear the true sound of a tube. I don't think an interstage tranny is necessary for that. Also, I think Sakuma would have approved as he encouraged experimentation.
"Also, I think Sakuma would have approved..."
Highly unlikely. I read Sakuma's philosophies on audio years ago, and he considered interstage transformers to be absolutely necessary. For that and other reasons, labeling the schematic presented here as having anything in common with Sakuma designs is simply wrong. He would almost certainly consider it an insult.
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Buy Chinese. Bury freedom.
Sorry TK, but I just can't agree with that at all. Anyone truly into audio experimenting is not going to be upset by someone else doing a riff on their design as long as they are not trying to steal it or profit from it. I am not doing either one, I'm just trying to give the man the credit he is due for the concept.To quote from the "direct heating" website"
Sakuma says "I opened the reference books every day. And then, that old interstage transformer asked me:
'Sakuma, who do you build this amplifier for?
Do you make the amplifier to get praise from electronics teachers?'
Since that day, I have made amplifiers for my own pleasure as an amateur".Sounds good to me.
Edits: 06/06/17 06/06/17 06/06/17 06/06/17
"...as long as they are not trying to steal it or profit from it."
The individual who first posted the schematic with the "Sakuma" label next to it did exactly that - he stole the Sakuma name by pasting it on something that doesn't meet the fundamental requirements. You're now doing the same thing by attributing the design to Sakuma's concepts, and you're excusing this practice by pretending to know his mind. Really, the man's dead. Have some respect.
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Buy Chinese. Bury freedom.
Really, lighten up TK. The amp is called Sakuma STYLE, not Sakuma amp. What part of that is getting past you? No one is claiming it is a Sakuma amp, just that it is following his concept of like tube driving like tube, as I have said 3 or 4 times now. Did you read the quote from the direct heating web site? No mind reading, just quotes.
Edits: 06/06/17 06/06/17 06/06/17 06/06/17
"...following his concept of like tube driving like tube,"
That's only one of many concepts Sakuma explored and implemented in his designs. Ironically, the "Sakuma Style" amplifier schematic you posted doesn't even do that . One tube in pentode, the other in triode is not the concept of interest. This is simply a case of a hanger-on attempting to affiliate sketchy and unrelated work with that of a master. As for what you're doing, it might be accurate to say you're experimenting with one of Sakuma's concepts, but even that's questionable. Unless you're planning to replace the 6BQ5s with DHTs, it's overtly dishonest to refer to the work you're proposing as having any relation to that of Susumu Sakuma. Argue all you want, but that's the long and short of it.
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Buy Chinese. Bury freedom.
must be nice to run through things so black and white. Further, if your assessment is anything resembling reality, his memory does not need any attention at all.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
The long and short of it is we have different opinions on this and neither of us is going to get the other to change their mind. Find something else to grouse about TK.
k
No it is not, it is giving credit where it is due.
That's the only difference? Well this will really be interesting to see if it makes a difference I can hear. thanks!
Just had to go back through the schematic and plus up the breadboard in a few places. Turns out my breadboard psu is just fine for running both channels. Ended up with a B+ of 360 vdc and a B+2 of 275 vdc. Lots of gain, nice clean sound, even on my small jbl test speakers. Time to hook it up to my Altec Granadas and see if I can tweak it a bit. Also want to try one channel with the output tube in triode mode instead of pentode as it is now. Here is a pic of one channel and the psu, I am also using my test bench filaments supply for the 6bq5 filaments. Don't let all the wires fool you. If you look at the schem I posted below you will see that each channel is just a handful of parts. It's a great candidate for a poster child for the KISS principle.
Edits: 06/04/17 06/04/17
http://home.comcast.net/~jafix/SakumaEL84.html
However, when I try to access it through the web.archive.org site it will not come up, while displaying the following message:
Page cannot be displayed due to robots.txt.
Anyone know why this might be?
Apparently the site was set up so robots could not search it. Not sure why. How did you find the old url?
A search lead me to an old diyaudio thread that contained the url. In post #7 of that thread, someone build the circuit but uses a somewhat different OP for the driver tube as compared to the one that you posted here.
Can you post the schematic here, so people who aren't members of that crappy site can see it?
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Buy Chinese. Bury freedom.
I would have, but unfortunately that poster did not provide a schematic and only mentions the component values that he used for the driver.
I run EL-84s in pentode with my KT120 amp. (in a differential pair as drive/phase splitter)
Douglas would be best to comment- but I run 8k plate load, 15-20mA per tube. Screen is bypassed to cathode with 4uf cap.
Plate voltage roughly 150v, screen 100v.
It sounds great.
You are on your own for the psu. Correction on the schematic... I actually used a 100 uf cap rather than the 47 uf as noted on the schem.
Edits: 06/05/17
Just FYI, I suspect that arrangement won't provide enough gain for some systems. Most people would probably use a 12AX7 or EF86 (pentode mode) to drive the 6BQ5. That's an unusual treatment of the suppressor grid. Wonder why he did that?
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Buy Chinese. Bury freedom.
Actually it has gain up the wazoo using it with even my test speakers which have an efficiency of only about 85. I was surprised by how loud it plays.
Again, this is an application of the Sakuma principle which calls for driving a tube with a like tube.
"That's an unusual treatment of the suppressor grid"
I think vinnie just left out the cathodes. G3 connects to the cathode.
Also I'm guessing the G2 of the output tube connects to the plate.
While I'm at it, using a 47uf cathode bypass cap instead of a 470uf cathode bypass cap was probably ill advised if the amp was being used full range.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Why do you say ill advised? I used it because that was what I had on hand, but it sounds just fine. What are you expecting to have happen?
Yes, each G3 should also have a k by it.
Edits: 06/04/17 06/04/17
"What are you expecting to have happen?"A loss of amplifier bass response and a loss of damping factor.
When the cathode is not bypassed to the lowest frequency of interest it allows current feedback to happen at the low frequencies (amplifier bass response loss).
That current feedback will increase the plate resistance of the output tube and that will lower the damping factor (and, depending on the speaker being used, cause the speaker's bass output to increase).
The two in combination can cause bloated, slow sounding bass on most true full range speakers.
On the other hand, some speakers need just that kind of thing to produce low bass.
On the third hand, if the speakers have no output at the lowest of frequencies then the effect might not be heard at all.
I was just saying that technically cathodes should be bypassed all the way down to the lowest frequency that the amplifier is meant to be used at.
For instance, (speaking of just the filter created by the total cathode impedance and the cap) if the -3db point was calculated at 4Hz with a 470uf cap in place (leaving 40Hz completely un-attenuated and phase shift free) then a 47uf cap would give a -3db point of 40Hz (meaning that the amplitude would be down at least some all the way up to 400Hz and the phase would be shifted all the way up to 400Hz)
If it sounded "good" to you, I can't/won't argue with that. But it's just not technically correct.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 06/04/17 06/04/17
Well, just for the hell of it I will have to try it with a 470 uf cap (if I can find one in my parts bins somewhere) just to see what it sounds like by comparison.
In addition to speaker response, whatever it might be, I'm pretty sure Vinnie isn't using full range OPTs.
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Buy Chinese. Bury freedom.
There are many factors that can play into this.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Isn't the 125ese considered a full range opt?
From the data sheet,"Designed for general purpose or replacement use (not Hi-Fi) in single ended tube output circuits.
Frequency response: 100 Hz. - 15 Khz (+/- 1db max. ref. 1 Khz).""For full frequency response (20 Hz. to 20 Khz.) single ended output transformers - see our 1627-1642 Series"
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 06/04/17
Yes, I know what the blurb says, but many people have been very impressed with the performance of them, myself included. Don Garber also offered them as a cost saving option in his 2A3 amp and said he was impressed with the bang for the buck you get with them.
Besides, how many of us are really running opts that go 20 to 20? Not very many I will bet, considering the extra cost. It's that last 5% again that can cost you big bucks.
Very few gapped SE transformers will go flat to 20Hz because it's hard to get the necessary inductance without introducing a lot of capacitance that causes losses of the high frequencies.
Having said that, the "big buck" transformers get very close to 20Hz and extend well beyond 20kHz.
There are a lot of things that factor into what a system ultimately sounds like but I have always believed that the best output transformers, together with circuits that are built as broad band and distortion free as possible results in really good sound.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Can't argue with that, but it leaves one thing out. How close to perfect do you want to get, and how much are willing to spend to get there?
I suppose for some people money is no object, but for the rest of us there will always be trade offs. Each of us has to determine for themselves what those will be.
It's not a philosophical issue. The Hammond transformers you're using fall short of hi-fi performance. Reasonable cost alternatives are available from Hammond, Edcor and Triode Electronics. Used transformers by HK, Scott and Fisher also show up occasionally on eBay. Full range OPTs will make a significant contribution to the sound of your amps.
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Buy Chinese. Bury freedom.
It is a philosophical issue in that we all have our own opinion of what "reasonable" is and what sounds good to us and how much we want to spend.
There is no such thing as perfection with audio electronics.
Even with the best parts it's always a series of compromises, as is life.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
It's hard to screw up the sound of a 6BQ5. You can drive it with a number of tubes, and it will sound amazing. Don't care for the 'AX7 in this situation, but the EF86 and other pentodes do a terrific job. The 6V6 is very close, perhaps not quite as dynamic, but a little more natural to my ears. Difficult to beat the cost of the Russian 6BQ5 these days. :)
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Buy Chinese. Bury freedom.
I think the whole idea is using a like tube to drive a like tube as Sakuma swore that it was the only way to hear the true sound of that particular tube. I did notice in the article that the first tube is triode connected while the second is pentode connected though. If I ever get two channels working I will have to try one channel each way and compare them with a mono source.
I have not tried the russkie 6bq5 yet, perhaps it's about time too.
Edits: 06/04/17
If you have the URL for the original website please post it. There's a chance it can still be found using the Wayback Machine linked below.
If not, please do post the schematic and any other relevant info.
No luck so far finding an electronic copy. I will draw up a schem for one channel in a couple days and list his recommended operating conditions. I used my own psu, so I will leave that up to everyone to use their own as well. Still having some issues getting both channels working at once. I am beginning to think my psu can't handle both channels. I think I had better run it through psud2.
Edits: 06/03/17
n
"Grandpa's basement"
Jeremy Fixx
Former aerospace engineer, and pretty good writer {he made me laugh}... he may have passed as all trace of him has disappeared.
Try the memory hole.
The Mind has No Firewall~ U.S. Army War College.
All those terms are new to me, "grandpa's basement, Jeremy Fixx and memory hole"? Never heard of any of them. You sure we are talking about the same amp? He didn't sound that old in the article.
Edits: 06/03/17
He never sounded old to me but @ 55 the phrase is starting to sound bizarre. Still, Jeremy did craft a Sakuma San amp with that topology
The memory hole is archived information (no longer found on the web) ergo the wayback machine... Tennessee Tuxedo cartoon daze.
The Mind has No Firewall~ U.S. Army War College.
Edits: 06/03/17
I think you are right... up in one corner of the paper copy I have I found J. fix 10/5/09 very lightly. Bad copy I think. Too bad none of his stuff has survived, I would have liked to see what else he may have done. Too bad he didn't post it on AA.
Edits: 06/04/17 06/04/17
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