Hi,
I have always been an electronics hobbyist but never went ahead and built a *good* vacuum tube audio amp - except for a little 6C5 triode amp that I built few years ago while reading an old book(ARRL handbook?), which was more of a self initiated school project. Nothing serious. I have a fair idea about tubes and have worked with them. Have a few vacuum tube radios lying around(including an R-390A/URR) that I love working with. Yes I am a ham .
So I've been around tubes but never really built a serious 'audio' amplifier for listening pleasure.
What I'd like to do now is learn more about designing audio amplifiers - feedback, SE, push-pull, power supplies, layouts,...all there is to it for building a good tube audio amplifier. Now come the questions -
So where do I go from here ? Books ? Links ? I am right now reading the Svetlana Tech notes and AudioXpress audio class articles. Especially books - which ones should I get ? I have in mind the Morgan Jones and the 'Valve & Transistor Amplifiers'(by Hood?)
And while I am taking everything in, I'd like to build a quick basic kit - like the ASL Wave 8 and the AES or S5 K-12. I saw AX84 also but I am not sure if their amps are more 'guitar' amps or typical audio amps for typical stereo applications - or if there is any difference?!
As you might have already guessed by now - I am on a budget - ideally $150. Max $200.
I'd like to build something more than an first step "learning" kit, something that will give me good performance also.
I am open for suggestions of kits that have scope for improvements(mods, upgrades) and will eventually perform much better. That could become a learning process too.
Your inputs, suggestions, will be of invaluable help to set me off in the right direction from where I am right now.
Looking forward to an exciting ride!
Thanks!
I have always been an electronics hobbyist but never went ahead and built a *good* vacuum tube audio amp - except for a little 6C5 triode amp that I built few years ago while reading an old book(ARRL handbook?), which was more of a self initiated school project. Nothing serious. I have a fair idea about tubes and have worked with them. Have a few vacuum tube radios lying around(including an R-390A/URR) that I love working with. Yes I am a ham .
So I've been around tubes but never really built a serious 'audio' amplifier for listening pleasure.
What I'd like to do now is learn more about designing audio amplifiers - feedback, SE, push-pull, power supplies, layouts,...all there is to it for building a good tube audio amplifier. Now come the questions -
So where do I go from here ? Books ? Links ? I am right now reading the Svetlana Tech notes and AudioXpress audio class articles. Especially books - which ones should I get ? I have in mind the Morgan Jones and the 'Valve & Transistor Amplifiers'(by Hood?)
And while I am taking everything in, I'd like to build a quick basic kit - like the ASL Wave 8 and the AES or S5 K-12. I saw AX84 also but I am not sure if their amps are more 'guitar' amps or typical audio amps for typical stereo applications - or if there is any difference?!
As you might have already guessed by now - I am on a budget - ideally $150. Max $200.
I'd like to build something more than an first step "learning" kit, something that will give me good performance also.
I am open for suggestions of kits that have scope for improvements(mods, upgrades) and will eventually perform much better. That could become a learning process too.
Your inputs, suggestions, will be of invaluable help to set me off in the right direction from where I am right now.
Looking forward to an exciting ride!
Thanks!
Last edited:
At the top of this forum is a permanent thread : "On Line Tube Learning for newbies...."
http://www.diyaudio.com/forums/showthread.php?s=&threadid=38278
It has enough reading to keep your attention for quite some time, and can lead you to other links, etc...
For your budget, you might want to start with a preamp.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=38278
It has enough reading to keep your attention for quite some time, and can lead you to other links, etc...
For your budget, you might want to start with a preamp.
the next level
I did go through that thread last night. Its a very useful thread for the absolute newbie, and definitely has some information for intermediate to advanced diyers also - like some of the Svetlana Tech Bulletins and AudioXpress audio classroom series.
Someone mentioned in that thread - there should be two threads one for people who havent seen or know what a tube is, and one for people who have some knowledge. I believe that thread should progressively extend into advanced level also or atleast above beginner/newbie level. Thats the area where I am looking for information - 'the next level'.
I did go through that thread last night. Its a very useful thread for the absolute newbie, and definitely has some information for intermediate to advanced diyers also - like some of the Svetlana Tech Bulletins and AudioXpress audio classroom series.
Someone mentioned in that thread - there should be two threads one for people who havent seen or know what a tube is, and one for people who have some knowledge. I believe that thread should progressively extend into advanced level also or atleast above beginner/newbie level. Thats the area where I am looking for information - 'the next level'.
Question about (Topologies used in) the S5 K-12 and ASL Wave 8.
Yes I did see the review and looks like its acousitc qualities are better than the measurements - and so does the reviewer asserts also.
I am trying to select between these two kits and I'd like to find out more before I make a decision.
I'd like to know what topology each one uses. Push-pull ? or SE ? What class ? Is feedback used ? how much ? what type ? Quality of power supply, output transformers etc...
I am guessing given the power output they produce(~8W) using those tubes they must be push-pull.
BTW, can I get just the PCB of either of these amps ? or do I have to buy it as a kit ?
Yes I did see the review and looks like its acousitc qualities are better than the measurements - and so does the reviewer asserts also.
I am trying to select between these two kits and I'd like to find out more before I make a decision.
I'd like to know what topology each one uses. Push-pull ? or SE ? What class ? Is feedback used ? how much ? what type ? Quality of power supply, output transformers etc...
I am guessing given the power output they produce(~8W) using those tubes they must be push-pull.
BTW, can I get just the PCB of either of these amps ? or do I have to buy it as a kit ?
I built my first tube amp earlier this year and almost bought the S5 kit. Glad I didn't, as I found I could build a better amp with the same money. I chose the 6S4A amp at www.the-planet.org. 6S4's are extremely cheap but good for a couple watts of clean power in a single-ended triode amp (no feedback or tricky adjustments). This circuit worked well at first power-up. I added a second 6S4 in parallel to get 4 watts with no problems. I spent less than 150, including chassis.
The most expensive parts is transformers. Output transformers cost about 100 or more, but the Hammond 125SE series are closer to 30 apiece and sound fine to me. I used a generic 12v ct, 3A transformer for filaments, and used a 12v, 1.5A transformer to jump back up to 120v, then a voltage doubler to get over 200 volts for plate voltage.... works great.
A decent SET amp gives great dynamics and depth to acoustical music, I love it. If you prefer rock or modern processed music, you might consider a pentode push-pull design instead. The Svetlana 6AS7 SET amp design looks pretty good too, and more power than the 6S4. If you use low cost transformers, you could build that for your price range. You could always upgrade the transformers later!
The most expensive parts is transformers. Output transformers cost about 100 or more, but the Hammond 125SE series are closer to 30 apiece and sound fine to me. I used a generic 12v ct, 3A transformer for filaments, and used a 12v, 1.5A transformer to jump back up to 120v, then a voltage doubler to get over 200 volts for plate voltage.... works great.
A decent SET amp gives great dynamics and depth to acoustical music, I love it. If you prefer rock or modern processed music, you might consider a pentode push-pull design instead. The Svetlana 6AS7 SET amp design looks pretty good too, and more power than the 6S4. If you use low cost transformers, you could build that for your price range. You could always upgrade the transformers later!
As far as I know, the ASL Wave 8 is a commercial product, not a kit. It was manufactured by Antique Sound Labs a couple years ago but (if I'm not mistaken) has since been discontinued. You can still probably find them used easily enough.
The S5 K-12 uses a PP pentode output stage. You can convert it to triode mode very easily, but power drops to 2-3 watts. Converting it to SE is not very realistic; it would be better to start with something else if you plan to go that route. There is global feedback. Quality of the power supply and output transformers is poor in absolute terms (this is why distortion increases so significantly in the bass) but excellent for the price and appropriate for the kit. As far as I know the PCB is not available separately. Just in case you're not aware of it there is a related kit based on the same circuit, just in monoblock form, available from Antique Electronic Supply.
If you're looking for a raw PCB, the closest project easily accessible to beginners is DIYtube's Dynaco ST-35 clone. That whole project can come in around $300 (you'll probably end up spending as much just on transformers as the whole SE K-12 kit price, but good iron is expensive).
The S5 K-12 uses a PP pentode output stage. You can convert it to triode mode very easily, but power drops to 2-3 watts. Converting it to SE is not very realistic; it would be better to start with something else if you plan to go that route. There is global feedback. Quality of the power supply and output transformers is poor in absolute terms (this is why distortion increases so significantly in the bass) but excellent for the price and appropriate for the kit. As far as I know the PCB is not available separately. Just in case you're not aware of it there is a related kit based on the same circuit, just in monoblock form, available from Antique Electronic Supply.
If you're looking for a raw PCB, the closest project easily accessible to beginners is DIYtube's Dynaco ST-35 clone. That whole project can come in around $300 (you'll probably end up spending as much just on transformers as the whole SE K-12 kit price, but good iron is expensive).
How good are the OPTs of the S5 and AES kit as compared to Hammond's 125 series (universal PP) in terms of quality/performance ? Is it night and day ? or not much ?
(Although the frequency response of the transformers is not below 100hz. The cool thing I like about the universals is that noobs like me can experiment with the impedance matching. Saw them going for ~$25 on Angela). Anyway back to the original topic -
If there is not much difference then it would not make sense to upgrade or even build this kit. I'd rather drop the idea of the kit, pick a *good* design and spend my time and money on the iron and parts there. Although I did a quick price check list for the ST-35 idea, it comes out around ~$350 or maybe even a little more. I am looking at something to complete around $200-$250 max until I can afford better.
But if there is considerable difference then maybe I can apply upgrades to the kit like better transformers, power supply etc.., learn on the way, enjoy it for some time while I plan a *real* project.
Makes sense ??
(Although the frequency response of the transformers is not below 100hz. The cool thing I like about the universals is that noobs like me can experiment with the impedance matching. Saw them going for ~$25 on Angela). Anyway back to the original topic -
If there is not much difference then it would not make sense to upgrade or even build this kit. I'd rather drop the idea of the kit, pick a *good* design and spend my time and money on the iron and parts there. Although I did a quick price check list for the ST-35 idea, it comes out around ~$350 or maybe even a little more. I am looking at something to complete around $200-$250 max until I can afford better.
But if there is considerable difference then maybe I can apply upgrades to the kit like better transformers, power supply etc.., learn on the way, enjoy it for some time while I plan a *real* project.
Makes sense ??
I don't have any experience with Hammond's 125 series, so I can't comment on that question.
$200-$250 is a challenging price point for a tube integrated amp. Your criteria (good design, good iron, low cost) are at least partly mutually exclusive at this level. You can definitely build something decent for this price, but you're white knuckling it. I still think you could build an ST-35 for just over $300, given that there's a guy who sells a kit version of that project for $400 (if I recall correctly), and there's got to be a profit in it for him somewhere.
Have you thought about picking up a dead Dynaco on eBay? The iron is better than virtually all iron of modern manufacture (measurements are available on DIYtube's forum), and it could knock off $150 off the total cost of the ST-35, putting it squarely in your price range, with very good iron to boot.
Another good alternative would be to build a tube preamp as your first project. You could put together a 12B4A (one tube per channel) for around $125, possibly under $100. Combine it with an older solid state power amp off eBay and you'd have a very decent system to start with until you save enough for a bigger project.
$200-$250 is a challenging price point for a tube integrated amp. Your criteria (good design, good iron, low cost) are at least partly mutually exclusive at this level. You can definitely build something decent for this price, but you're white knuckling it. I still think you could build an ST-35 for just over $300, given that there's a guy who sells a kit version of that project for $400 (if I recall correctly), and there's got to be a profit in it for him somewhere.
Have you thought about picking up a dead Dynaco on eBay? The iron is better than virtually all iron of modern manufacture (measurements are available on DIYtube's forum), and it could knock off $150 off the total cost of the ST-35, putting it squarely in your price range, with very good iron to boot.
Another good alternative would be to build a tube preamp as your first project. You could put together a 12B4A (one tube per channel) for around $125, possibly under $100. Combine it with an older solid state power amp off eBay and you'd have a very decent system to start with until you save enough for a bigger project.
I would second the suggestion of picking up an old stereo parts unit and restoring that. It will be a lot of fun, I have hunted down several old tube stereos at junk shops near me, ususally for very cheap. Old stereo consoles can be raided for their amps and the rest binned. There are several threads and web pages about people who have built nice chassis for console amps.
With new coupling capacitors, they can sound very good indeed.
I would recommend against the hammond 125E series, they are ok but a bit limited in the bass, and vintage iron definitely sounds better...
One thing, don't worry too much about power, 5W is quite loud for most listening!
With new coupling capacitors, they can sound very good indeed.
I would recommend against the hammond 125E series, they are ok but a bit limited in the bass, and vintage iron definitely sounds better...
One thing, don't worry too much about power, 5W is quite loud for most listening!
The only things I looked for on Ebay was the Dynaco ST-35 and ST-70. And mostly I have seen that people sell it in working or 'upgraded' condition (aka with their profits) so the ending prices go way above my budget. And I have rarely seen a ST-35 come along.
I have to either just keep looking (for a dead one) or I need to know which other models (Eico?, Marantz?, ??, etc..) are worth considering even though dead.
For the preamplifer - I will eventually need it(phono) but currently I dont have any application for it. So even if I build it I feel I wont be able to enjoy it (or even find out if I built it good or not) because the only sources I have right now are a Dynaco FM-3 tuner or maybe the CD/SACD/DVD-A player and I believe either one of them wont need a preamp(?)
. So thats why I was thinking about a power amp for now.
Or maybe I guess I can start the ST-35 project now - it will just be a little longer before I complete it - as and when I am able to route more funds towards that project, from my other speaker project
.
By the way is the ST-35 PCB a clone of the original design or has any mods in it ? Are there any known mods to the ST-35 anyway ?
I have to either just keep looking (for a dead one) or I need to know which other models (Eico?, Marantz?, ??, etc..) are worth considering even though dead.
For the preamplifer - I will eventually need it(phono) but currently I dont have any application for it. So even if I build it I feel I wont be able to enjoy it (or even find out if I built it good or not) because the only sources I have right now are a Dynaco FM-3 tuner or maybe the CD/SACD/DVD-A player and I believe either one of them wont need a preamp(?)
. So thats why I was thinking about a power amp for now.Or maybe I guess I can start the ST-35 project now - it will just be a little longer before I complete it - as and when I am able to route more funds towards that project, from my other speaker project
.By the way is the ST-35 PCB a clone of the original design or has any mods in it ? Are there any known mods to the ST-35 anyway ?
SHiFTY said:
Don't bin the speakers... they are usually worth something... i started buying consoles for the amps, and have ended up making a significant portion of my living selling the speakers out of them (and ending up with enuff console chassis to keep me in amp parts for a Loonnnggg time. Mostly SE EL84s, which can make a pretty decent amp -- the Decware Zen is the one to clone, but there are at least a 100 design variations floating around -- including a recent thread here with an opamp as driver.
Careful shopping for a console and you can end up with a dertified frugal-phile (tm) Pheonix* amp
* as in risen from the ashes.
This
Also, I believe that the budget kits - or like Shifty suggested picking up an old unit dead or alive - will provide for many learning opportunities - to improve or mess around with the design and thereby learn.
The ST-35 as is, is a time tested and proven design, hence I guess it has limited scope for improvement or messing around with the design. It will denfinitely offer a great listening pleasure and a building experience as well, but not much of a 'learning' experience, I feel.
The ST-35 as is, is a time tested and proven design, hence I guess it has limited scope for improvement or messing around with the design. It will denfinitely offer a great listening pleasure and a building experience as well, but not much of a 'learning' experience, I feel.
percy said:
Not true...
An externally hosted image should be here but it was not working when we last tested it.
Vacuum State
And after i have that working (i'm starting with SCA35), superreg PS then the CCS trick on the bottom of the output cathodes ... should be a real killer 4W amp.
dave
I have built the Vacuum State design above, and it is a very outstanding circuit. I would say it would be way out way from what the original poster was asking for, however. BTW, I've actually done two versions, one with EL34s and one with 300Bs. Both were excellent!
To the original question, I would agree that getting a used piece of equipment and tinkering would be a great start. A fun project I did about 6 months ago was to buy an old Heathkit AA-151 integrated amp from ebay and restore it. First off, the 151 uses 6BQ5 outputs and the iron is very nice. So you've got an excellent foundation. Second, it lends itself to some refinements due to good chassis room and easy parts layout. But finding one in really nice shape might be hard to do.
Here's where my fun began. Remember those days of putting together old Heath's? Well I decided why not? So I took the thing apart. I mean completely apart. Right down to every last screw. I took that opportunity to clean the chassis, repaint the transfomer end bells, and so on.
Then I got an original assembly manual and went through it, step by step. What a blast! In the process I installed all new hardware and mostly new parts. I saved a couple of old carbon resistors to help preserve some of the original sonic character. And since I'd taken care to reform the two major electorlytics, I saved them, too. Now what I have is a beautiful amp, that works very well, and a lot of fun too! By the way, the amp includes a phono stage, so if you ever want to venture away from CDs, you're all set.
Modifications? Sure! How about bypassing tone controls? Or putting in a better phono circuit? Anything based on 2x 12ax7's can be fitted in there. For those who want to learn about tube amps, the Heath manuals also include a nice theory section, voltage charts, and so on. And the best part? Some of these old Heathkit amps can be snagged for a nice price. I think about $120 or so is what I paid.
Best of luck!
Steve
To the original question, I would agree that getting a used piece of equipment and tinkering would be a great start. A fun project I did about 6 months ago was to buy an old Heathkit AA-151 integrated amp from ebay and restore it. First off, the 151 uses 6BQ5 outputs and the iron is very nice. So you've got an excellent foundation. Second, it lends itself to some refinements due to good chassis room and easy parts layout. But finding one in really nice shape might be hard to do.
Here's where my fun began. Remember those days of putting together old Heath's? Well I decided why not? So I took the thing apart. I mean completely apart. Right down to every last screw. I took that opportunity to clean the chassis, repaint the transfomer end bells, and so on.
Then I got an original assembly manual and went through it, step by step. What a blast! In the process I installed all new hardware and mostly new parts. I saved a couple of old carbon resistors to help preserve some of the original sonic character. And since I'd taken care to reform the two major electorlytics, I saved them, too. Now what I have is a beautiful amp, that works very well, and a lot of fun too! By the way, the amp includes a phono stage, so if you ever want to venture away from CDs, you're all set.
Modifications? Sure! How about bypassing tone controls? Or putting in a better phono circuit? Anything based on 2x 12ax7's can be fitted in there. For those who want to learn about tube amps, the Heath manuals also include a nice theory section, voltage charts, and so on. And the best part? Some of these old Heathkit amps can be snagged for a nice price. I think about $120 or so is what I paid.
Best of luck!
Steve
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