I am head of thermionics at a successful British hifi company, so I am a valve designer through and through. I agree that many GZ34 designs don't have limting resistors, and some of these can get away with it on the grounds you mention, while others are either built on the cheap or simply copied for existing resistor-less designs without thought for the change in transformer. You will note that designs using other rectifier type DO have litming resistors. Note also that the GZ34 datasheet quotes limiting resistors for all cap input rectifiers, in addition to the transformer being used...kevinkr said:
My issue with the Simple SE is that it is fundamentally a DIY project, so there is no guarentee that that particular tranny will be used, and since even a 10R resistor is cheap and is unlikely to affect the amp's measured performance, it strikes me as cavalier not to include it. The is a difference between an amp which is stable, and one which cannot be unstable. I build my designs to last years, not hundreds of hours.
Incidentally, what iare the DCRs of that tranny's windings? Hammond do not seem to quote it on their site.
10R is not going to limit current much, either. It is swamped by the source resistance of PTs with secondary ratings measured in milliamps.
Merlin, your comments come across as unnecessarily negative. I built a Simple SE that did have one teething issue which was due to me shorting out one of the speaker terminals.... (George generously put in some time to help me fault find). Since then I have had over 100 hours of trouble free stable operation making great sounding music & all the more satisfying for the fact that I built it (which still amazes me). For the cost of a board if you don't have a background in electronics (like me!), I don't think you can beat the Simple SE as an intro to tube amp building. It has certainly spurred me on to have a go at other projects & try & understand in more depth what's going on. I would like to thank George for the inspiration especially with all the other stuff he has going on. I'm sure there are others who feel the same.
Mike
Mike
That was just an example; any resistance is better than nothing, and 10 ohms is a significant contribution, since the transformer will typically offer in the region of 100R. 10% is not insignificant. (Personally I'd like to see 47 ohms min.)Tweeker said:
I'm not criticising the project as a whole, it is very admirable. I simply point out that not as much thought has gone into it as should have. The power supply, is after all, the most important part of an amp, and a valve rectifier is the most fragile valve in a whole audio amp! I do not expect any design to be perfect, but these were (to quote bad police dramas) rookie mistakes.waam68 said:
I was one of the early builders of the Simple SE. For me it was a great introduction to building Valve amplifiers. The better than expected result, the ease of construction, the well presented information on the web site and Tube Lab's involvement in this site made the whole experience of building a pleasant, rewarding and enjoyable one.
I think I was also one of the first to have a problem with the power supply. I blew up a few diodes, a rectifier and a couple of fuses. I learned a little about trouble shooting. I posted my findings on this site and emailed Tubelab, who has subsequently amended the building advice on his site.
I look at the whole process (broken amp included) as a positive one. That is mainly due to the product, and support offered by Tubelab and this site.
The design allows for a very simple build, while also allowing a lot of flexibility of features. As it turns out, my combination did not quite work out. For me it was no big deal and a good learning experience.
Merlinb, in the spirit of cooperation and assistance that makes this site so much different from some of the others around, what would you suggest as some additions or changes to the implementation of this design? I am sure that builders and perhaps the designer, would welcome any constructive advice.
Cheers!
Chris 🙂
I think I was also one of the first to have a problem with the power supply. I blew up a few diodes, a rectifier and a couple of fuses. I learned a little about trouble shooting. I posted my findings on this site and emailed Tubelab, who has subsequently amended the building advice on his site.
I look at the whole process (broken amp included) as a positive one. That is mainly due to the product, and support offered by Tubelab and this site.
The design allows for a very simple build, while also allowing a lot of flexibility of features. As it turns out, my combination did not quite work out. For me it was no big deal and a good learning experience.
Merlinb, in the spirit of cooperation and assistance that makes this site so much different from some of the others around, what would you suggest as some additions or changes to the implementation of this design? I am sure that builders and perhaps the designer, would welcome any constructive advice.
Cheers!
Chris 🙂
Merlinb said:
My Simple SE is the PA in our home theater system - it is on whenever someone is home. I estimate that it has almost 1900 hours run time at this point.
I have consistently used it outside of TubeLab's published guidelines, and I have never been able to create any condition in which the Simple SE was anything other than unconditionally stable.
In response to the assertion that the design is flawed or may be conditionally unstable because of the lack of a 10 ohm resistor, the field experience seems to be otherwise.
Win W5JAG
GE 5AR4 datasheet gives 125ohms as minimum source resistance/plate for 400VAC supply with 40uF input capacitance. Amperex same, lists 60uF cap.
Merlinb said:
By what standard? The stated design goal was a simple, reliable amp, using a minimal parts count, and with cheap and readily available parts. If there is one area George, in hindsight, could have been more rigid on, it would be on insisting on a tighter specification for the power transformer. On the other hand, it seems the failure rate is pretty low, which reflects well on the design process overall.
Merlinb said:
I know that was intended as the pejorative form of rookie. The truth is that it should be high praise, as George is indeed a rookie - a rookie kit supplier to the DIY market. Thank heavens for rookie businessmen willing to provide new options to rookie builders . The inevitable "rookie mistakes" are going to include how to judge and account for the skill level of the customers. Easy to snipe from the safety of the sideline. Takes some courage to give it a go.
And George, have you seen this one: http://www.intactaudio.com/forum/viewtopic.php?t=549 A little creative application of sand from a kindred spirit.
Sheldon
Tubelab, could starting your own amp company a possible option? Kind of like Jim McShane, Decware and Vaughn Audio. After using TubelabSE amp for a while, I can see myself buying more and recommending to others.tubelab.com said:
Let us see more BIG SE-amps, and door-slammers!
(Seems that you know how to build mopars...)
Arne K
(Seems that you know how to build mopars...)
Arne K
I probably put more time, thought, simulation, breadbaording, and testing into my designs than most commercial tube amp designers do. Several hundred hours went into the Simple SE, probably a lot more, since I don't keep track. I have personally built at least a dozen. There were 3 different beta builders who built pre release amps to insure that the assembly instructions were complete. Each got to keep their amps, I know that two are still alive, I have lost track of the third. I have 2 of them. All 4 are still on their original rectifier tubes (2 Sovteks, 1 Shuguang, and 1 RCA). I have my "Industrial Amp" set up with KT88's at 100mA with 430 volts B+. All tubes are the originals.
I have been working on two (maybe more) versions of Tubelab P-P amps since last summer, yes almost a year. I am not anywhere near done with them. I am now working on an amp that uses 4 octal output tubes. If KT88's are going to fit the board must be at least 10 inches wide. Many users requested an all octal design, so I considered it. Eight octal tubes makes the PC board about 8 by 10 inches. This is a large, expensive board, that winds up being too flexible. The current version uses 9 pin miniatures for gain and phase splitter, and the rectifier tube is gone. I am laying out the first prototype currently. Hey, if there is another thoughtless rookie out there that could do a better job, let me know.
I have been called a lot of things, but rookie, that was low.
This thread is beginning to remind me why I never participated in those "other" forums. I have spent too much time participating in this "stuff" already, and I will no longer spend any more time on it.
This forum has been a good vehicle for builders to ask questions They get to hear several different opinions, while I don't need to answer the same questions over and over again. The subject of a suitable power transformer for my amps has come up here and in emails. In some cases I have actually purchased the perspective transformer and tested it (Hammond 272JX for a Tubelab SE). I obviously can not always do that. If I had known that this user was considering an 800VCT power transformer, I would have asked them to reconsider that choice, because I have tested that combination, and while it can be made to work, it is NOT for a first time builder.
Most members here understand my ethics, and my willingness to help out when something isn't right. I have received about a dozen emails today from previous customers. All were positive, and some contained some nasty words for Mr. Merlin. It is the positive comments here and in my email that have kept me in this game. Please put yourself in the first time builder's place. He spent a considerable amount of money, asks for help, and hears that the design that he just spent a lot of money on is a POS. This is a sure fire way to drive another builder away from this hobby. Why?
I don't think that I want to do that. I am finding this far less fun than it used to be, primarilly because I spend most of my time doing non tube stuff, like trying to convince someone that I am not a thoughtless rookie! I turned down a consulting job last weekend. If it is still available, I may just try that for a while
Actually, that is not even true. There have been several plug-in computer board kits for the SS-50 bus (1977 to 1980) and a few TV related devices including a build it your self C band satellite TV receiver and dish kit, all sold under the DMA Engineering name (1980 - 1990). During the 1990's I did a lot of consulting (no kits) in embedded controllers (mostly PIC based) under the G&S programming name (still an operating business).
Yes, I know how to build Mopars (and Mustangs, and Camaros) but I have never finished the Challenger. Not enough time.
tubelab.com said:
I stand happily corrected. I hope it was clear that I have nothing but admiration for your efforts.
Sheldon
this is a shame-what started as a trouble shooting thread has gone off course thanks to Mr. Merlin (who is a "troll' as far as I am concerned)
http://en.wikipedia.org/wiki/Internet_troll
didnt think I would see this at this forum
http://en.wikipedia.org/wiki/Internet_troll
didnt think I would see this at this forum
Mama Pajama! 
So if I had a big ole Edcor power transformer I'd be thinking of ways to get that to work somehow. So here what I'm thinking. Replace the first capacitor after the rectifier with something that can handle the higher voltage. Perhaps an appropriate motor run cap? Then either replace the choke with enough resistance to bring the voltage down below 500v. That or keep your current choke an slip a 5w wirewound power resistor inline with the choke. Sanity check anyone?
Definitely check out Duncan Amp's PSUD2 tool and play around with that some.
I'm just making guesses without any experience, so don't take my suggestions too seriously.
So if I had a big ole Edcor power transformer I'd be thinking of ways to get that to work somehow. So here what I'm thinking. Replace the first capacitor after the rectifier with something that can handle the higher voltage. Perhaps an appropriate motor run cap? Then either replace the choke with enough resistance to bring the voltage down below 500v. That or keep your current choke an slip a 5w wirewound power resistor inline with the choke. Sanity check anyone?
Definitely check out Duncan Amp's PSUD2 tool and play around with that some.
I'm just making guesses without any experience, so don't take my suggestions too seriously.
This thread went on for 2 pages, and no one seems interested in helping the thread starter fix his amp.
First, I must appologize for letting this whole thing get me far too irritated. I should have ignored this person, but this has been a rather ugly week. I said goodbye to just about everybody that I have worked with for the past 35 years last week, 355 engineers were laid off. I got so annoyed yesterday that I came home and cleared my desk of all the tube stuff. I even tossed the Simple P-P prototype in the trash.
Second, I want to thank everyone who responded with words of encouragement, both here and through my email. It was you guys that convinced me that my emotional response is exactly what this person wanted. So after reading my email this morning, I rescued the Simple P-P from the trash before the trash truck came. There was another surprise in my email box, 5 new board orders, about twice the usual number. Probably not the response the the poster intended either.
Third and most important, eddiemeddiem still has a broken amplifier. It is unfortunate that someone new to this hobby had to listen to all of the "stuff" that was said when all he asked for was an answer to the question "why doesn't it work?" I have studied his pictures carefully, and I don't see anything obvious.
I believe that the major issue here is that the power transformer is producing too much B+ voltage for the amp in its current configuration. Yes, it probably can be made to work, and crank out some good power to boot. Can we do it remotely considering the possibility that capacitors, tubes, and even resistors could explode at the voltage levels that could be present in this amp. I don't think so.
How do we even know what the B+ voltage is in this case? The fuse blows as soon as the rectifier warms up. If it didn't, C1 would! If you have seen these things explode, you know that it is a mess, it smells bad, and the flying fragments are hot. This is a dangerous and unknown situation.
The simplest way to solve this problem is to use a power transformer that is known to work with the Simple SE, get the amp to work, then hook up the Edcor arc welder, if desired. This means that Eddie will need another transformer. Since I feel at least partially responsible for this mess, I offer the following solution.
Several years ago I witnessed a crime being committed. I saw pallets of vintage Hewlett Packard test equipment being dumped into a scrappers truck to be crushed and melted. Armed only with a screwdriver and a pair of vice grips I rescued a hatchback full of tubes and transformers. I had about 30 transformers that are suitable for use with the Simple SE. I have 2 left. I hooked one of them up to a board, popped in some EH EL34's and let it play all afternoon. The B+ is steady at 390 volts, and it runs far cooler than a Hammond. The wires are short, but long enough to be useful, it is not pretty, but not ugly. It has a vintage 1962 date on it. Eddie, if you are still out there, let me know and I will send it to you, free of charge. It is the grey one in the picture.
I think that you should replace C1, and maybe C2 since C1 is probably toast, and if it isn't I wouldn't trust it. I do not have any spare capacitors. If everything else is OK, the amp should work. If not, at least I can duplicate your set up exactly here and talk you through the troubleshooting.
After the amp is working, we can discuss how to make the Edcor work if you want. I have an 800 VCT Antek toroid that I can use to find out what component values to try in your amp. I don't know if the EH EL34's can take that kind of voltage (I used KT88's in my previous 500 + volt tests), but I have a box full of them and I got them cheap, so I don't mind finding out.
Attachments
Eddie,
Take Tubelab up on his offer. It is an excellent and equitable solution to your problem. The corporate world should work as hard to keep their customers happy. James
Take Tubelab up on his offer. It is an excellent and equitable solution to your problem. The corporate world should work as hard to keep their customers happy. James
The British "thermionics head highfi valve through and through" guy
Curious. I've read some articles by Andy Grove and never seen that sneering tone in any of them, so I doubt you're him, Mr. Merlin. And it's unlikely Tim De Paravicini would sully his waistcoat by posting on a DIY forum, so I doubt you're him either.
My Audio Note 300B amp doesn't have the resistor you claim is essential, so I presume you don't work for AN UK. Which leads to the obvious questions: what is the name of the SE amp you designed, and where can I find a schematic so I can see how the pros do it? Surely that would help all the "rookies" here; it will also allow us to assess how much you charge for your company's implementation of what is in essence a very simple topology, and to learn from the innovations (if any) that an experienced designer like you included. (Maybe someone here will even buy one of your amps!)
Mr. Anderson, I'll shortly be buying a set of boards for both types of SE amp, in part because of the above condescension from a "real" tube designer who apparently missed the fact that this is a DIY forum. As you indicate on your website, these are fundamentally simple amplifiers, perfect for experimentation as long as you respect Mr. Electron. (Did you ever read the Hunter Thompson piece titled "Electricity"? Priceless.) AFA the "rookie" crack, I think Merlin would find that while he may know more than some people here about tube technology and engineering, t there are people here who know considerably more than he does about same. And that those people share their knowledge in this forum rather than sneering at DIY hoi polloi. We'll probably never know, though, unless he tells us what product(s) he designed. Until then, he's just another poster like me.
Curious. I've read some articles by Andy Grove and never seen that sneering tone in any of them, so I doubt you're him, Mr. Merlin. And it's unlikely Tim De Paravicini would sully his waistcoat by posting on a DIY forum, so I doubt you're him either.
My Audio Note 300B amp doesn't have the resistor you claim is essential, so I presume you don't work for AN UK. Which leads to the obvious questions: what is the name of the SE amp you designed, and where can I find a schematic so I can see how the pros do it? Surely that would help all the "rookies" here; it will also allow us to assess how much you charge for your company's implementation of what is in essence a very simple topology, and to learn from the innovations (if any) that an experienced designer like you included. (Maybe someone here will even buy one of your amps!)
Mr. Anderson, I'll shortly be buying a set of boards for both types of SE amp, in part because of the above condescension from a "real" tube designer who apparently missed the fact that this is a DIY forum. As you indicate on your website, these are fundamentally simple amplifiers, perfect for experimentation as long as you respect Mr. Electron. (Did you ever read the Hunter Thompson piece titled "Electricity"? Priceless.) AFA the "rookie" crack, I think Merlin would find that while he may know more than some people here about tube technology and engineering, t there are people here who know considerably more than he does about same. And that those people share their knowledge in this forum rather than sneering at DIY hoi polloi. We'll probably never know, though, unless he tells us what product(s) he designed. Until then, he's just another poster like me.
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