So I am wondering if you kind folks will help me select a first, total DIY project. I want to build my first tube amp from scratch. Now, I am kind of poor compared to most so I can’t afford to make mistakes or to buy something only to decide I should have gone a different way and have to buy something else. So I’ll probably be asking quite a lot of questions calling for opinions or characteristics so I can make an educated decision on what to build and component selection for it. I want to be able to build a good sounding amp for as little money as possible but I don’t want to cheap out and end up with something completely substandard.
First thing I want to ask is characteristics of SE versus PP. Some generalizations I think I have heard is that a SE amp will reveal more of the micro details in music. And that a PP amp has more bass slam and dynamic power. In these themes I’d say micro details are good but I’d weigh more towards the more powerful sound of a PP amp. I’m wondering if these “stereotypes” (hahaha, pun intended) are somewhat accurate or if there are others I need to take into consideration. I’m also wondering on what sort of scale these apply. Such as if I have a SE amp and a PP amp maybe the level of micro detail on the SE amp is a 9 out of 10 and the dynamics are a 6 compared to the level of detail on a PP design being 8.25 and the dynamics being a 9. So in comparison I’d be loosing a very small amount of detail to gain a good bit of punch. So I am asking you guys if you’d take your vast experience and make some generalizations like these to help me decide which direction to take. Sort of a list of pro’s and con’s but also with a level of trade off.
Right now since I am leaning towards a PP design but I still want some style or class so to speak I am thinking of making a PP 2A3 amp. I like the idea of the groovy shape of the 2A3 along with the triode mystique in combination with the additional power delivery and dynamics of a PP design. I don’t find myself listening to music at top volumes all that often so I am not looking for megawatts of power but most of the speakers I have wouldn’t be considered super high efficiency so I am not interested in a flea power amp either.
Thanks in advance for your input.
Bryan
First thing I want to ask is characteristics of SE versus PP. Some generalizations I think I have heard is that a SE amp will reveal more of the micro details in music. And that a PP amp has more bass slam and dynamic power. In these themes I’d say micro details are good but I’d weigh more towards the more powerful sound of a PP amp. I’m wondering if these “stereotypes” (hahaha, pun intended) are somewhat accurate or if there are others I need to take into consideration. I’m also wondering on what sort of scale these apply. Such as if I have a SE amp and a PP amp maybe the level of micro detail on the SE amp is a 9 out of 10 and the dynamics are a 6 compared to the level of detail on a PP design being 8.25 and the dynamics being a 9. So in comparison I’d be loosing a very small amount of detail to gain a good bit of punch. So I am asking you guys if you’d take your vast experience and make some generalizations like these to help me decide which direction to take. Sort of a list of pro’s and con’s but also with a level of trade off.
Right now since I am leaning towards a PP design but I still want some style or class so to speak I am thinking of making a PP 2A3 amp. I like the idea of the groovy shape of the 2A3 along with the triode mystique in combination with the additional power delivery and dynamics of a PP design. I don’t find myself listening to music at top volumes all that often so I am not looking for megawatts of power but most of the speakers I have wouldn’t be considered super high efficiency so I am not interested in a flea power amp either.
Thanks in advance for your input.
Bryan
Just remember that the transformers make the amp. I would buy the best transformers you can afford and build around them. Vintage transformers can be got quite cheaply.
Design or use a circuit with very little open loop distortion. What distortion there is should be mainly 2nd and 3rd harmonics. Above that gets objectionable to the ear.
The traits of PP vs SE is a whole debate in itself. A good amp is a good amp, you can get very detailed PP and very punchy SE.
I like the idea of a PP 2A3, your 2A3s generate mainly 2nd harmonic distortion, which is mostly cancelled in a PP design. So its inherenly low distortion!
Design or use a circuit with very little open loop distortion. What distortion there is should be mainly 2nd and 3rd harmonics. Above that gets objectionable to the ear.
The traits of PP vs SE is a whole debate in itself. A good amp is a good amp, you can get very detailed PP and very punchy SE.
I like the idea of a PP 2A3, your 2A3s generate mainly 2nd harmonic distortion, which is mostly cancelled in a PP design. So its inherenly low distortion!
Basic rules:
1. Ignore 99% of what "people say."
2. Decide if you want the amp to be neutral or to have a sound.
3. Base your design decisions on the answer to #2.
4. Get a good, reliable book on design and absorb it thoroughly before proceeding. (Morgan Jones's book has been highly recommended by many people)
5. Make sure you have the minimum complement of tools needed. That includes a good multimeter, an oscilloscope, and a signal generator, besides the usual construction equipment.
1. Ignore 99% of what "people say."
2. Decide if you want the amp to be neutral or to have a sound.
3. Base your design decisions on the answer to #2.
4. Get a good, reliable book on design and absorb it thoroughly before proceeding. (Morgan Jones's book has been highly recommended by many people)
5. Make sure you have the minimum complement of tools needed. That includes a good multimeter, an oscilloscope, and a signal generator, besides the usual construction equipment.
For 100$ you can make a good headphone amp with tubes. But a little more and you can make an excellent little amp. As for sound quality SE usually outperforms PP, including bass respons and certainly dynamics. But given the same tubes, a PP amp will give more power than SE amp, so it will seem more bass capable and maybe even more dynamic, simply because it has more power. But a 10W SE amp will be more dynamic than a 10W PP amp.
As for cheap tubes the 6AS7 is a great triode. It is supposedly based on the 2A3 but is indirectly heated and has two smaller triode halfs in each bulb. The bulb is that nice looking coke bottle shape as well, except for the 6AS7GA version which is straight bottled. Many people think cheap tubes are bad for audio. Cheap is bad for sound right? Well it happens to be that prices of tubes is set by demand and what is on stock. The fabricators couldnt care less how a tube sounds, so they price them simply after demand and how many are in stock. The 6AS7 is plentyful, and not in such demand as 300B or 2A3s etc, so its cheap.
Admittedly a DHT is probably the best, but the 6AS7 is still a great sonicly tube, teh most under rated power triode if you ask me.
Do a search for 6AS7 based amps and ull find many SE and PP designs. A single tube will give you 10-12W in PP, and 6-8W in SE. It has low plate impedance and can be used in output transformer less amps if a couple of them are paralleled. Four of these tubes will set you back less than a decent 10W SE tranny will.
As for cheap tubes the 6AS7 is a great triode. It is supposedly based on the 2A3 but is indirectly heated and has two smaller triode halfs in each bulb. The bulb is that nice looking coke bottle shape as well, except for the 6AS7GA version which is straight bottled. Many people think cheap tubes are bad for audio. Cheap is bad for sound right? Well it happens to be that prices of tubes is set by demand and what is on stock. The fabricators couldnt care less how a tube sounds, so they price them simply after demand and how many are in stock. The 6AS7 is plentyful, and not in such demand as 300B or 2A3s etc, so its cheap.
Admittedly a DHT is probably the best, but the 6AS7 is still a great sonicly tube, teh most under rated power triode if you ask me.
Do a search for 6AS7 based amps and ull find many SE and PP designs. A single tube will give you 10-12W in PP, and 6-8W in SE. It has low plate impedance and can be used in output transformer less amps if a couple of them are paralleled. Four of these tubes will set you back less than a decent 10W SE tranny will.
Other than the power issue (P-P is much more efficient and will produce more power), all of this is quite arguable.
It is not arguable that the output transformer is the heart and soul of any tube amp, and that $100 will get you a decent output transformer- but not all the rest of the parts, the power tranny, the tubes, the electrolytics, the chassis, the case... Honestly, I'd be challenged to even get a tube-based headphone amp together for less that $100 without investing serious time, patience, and diligence in tracking down surplus.
SEMPER BIASED...
Hi,
Bass response? Dynamics? Hmmm...One would think SE amps are at a disadvantage in those departments.
Needless to say, I think there are all sorts of both kinds, SE and PP.
Oh, let's not forget you'd better have some easy going speakers for that SE amp. preferably in the 90dB/m + effeciency too.
As for the 6AS7, I love those and yes they're based around the 2A3 but:
They have only a mu of 2...O.K., 2.5 when you drop to very low plate voltages, so they're going to need some driving.
Secondly, they are DUAL triodes not TWIN triodes so you'd better think of something to adjust bias (read the datasheet about this) or select from a ton of them, especially when thinking PP or shared PS SE.
Maybe the 6AS7G from Svetlana are better matched, dunno.
If you're willing to pay a little more there's the 7236 which is a twin triode according to the datasheet and it sports a little higher mu.
No SY, I won't mention that other one...
You can still make an excellent little amp with a 6AS7 and say a 6922, for little money. But 100 peanuts? Fuggedaboudit.
Cheers,
Hi,
Bass response? Dynamics? Hmmm...One would think SE amps are at a disadvantage in those departments.
Needless to say, I think there are all sorts of both kinds, SE and PP.
Oh, let's not forget you'd better have some easy going speakers for that SE amp. preferably in the 90dB/m + effeciency too.
As for the 6AS7, I love those and yes they're based around the 2A3 but:
They have only a mu of 2...O.K., 2.5 when you drop to very low plate voltages, so they're going to need some driving.
Secondly, they are DUAL triodes not TWIN triodes so you'd better think of something to adjust bias (read the datasheet about this) or select from a ton of them, especially when thinking PP or shared PS SE.
Maybe the 6AS7G from Svetlana are better matched, dunno.
If you're willing to pay a little more there's the 7236 which is a twin triode according to the datasheet and it sports a little higher mu.
No SY, I won't mention that other one...
You can still make an excellent little amp with a 6AS7 and say a 6922, for little money. But 100 peanuts? Fuggedaboudit.
Cheers,
SE output will give a more detailed acurate sound because there is no cancelation of the waveforms hapening.
we all know that PP gives less hum than SE as we get a cancelation of the inverted waves... but we also get a bit of cancelation of our audio waves too. so yes, SE is more detailed.
As for more bass response, i'd also say this is arguable, and i say it will come down to the quality of the OT used. how good a tranny is isn't just it's high frequency response, but also it's low frequency response. you need maximum bandwidth, not just maximum frequency.
we all know that PP gives less hum than SE as we get a cancelation of the inverted waves... but we also get a bit of cancelation of our audio waves too. so yes, SE is more detailed.
As for more bass response, i'd also say this is arguable, and i say it will come down to the quality of the OT used. how good a tranny is isn't just it's high frequency response, but also it's low frequency response. you need maximum bandwidth, not just maximum frequency.
Time for a little Saturday morning fun.
Should "Ignore 99% of what people say" be ignored?
How do you define "neutral sound"? Here's my working definition derived from my experience: the sound of live music is neutral sound, "neutral," here, defined by reference to a given context (a particular concert hall, an outdoor venue, k d lang singing in my living room, etc); the sound of reproduced music, to the extent it deviates at all from the sound of live music, is not neutral sound. The sound of every form of reproduced music I have heard has not been neutral. I deduce that every means of reproduction creating the reproduced music I've heard is the source of the loss of neutrality. Proposition: non-neutrality therefore inheres in reproduction equipment (amps, tts, cds, sacds ...).
We're going in circles.
SY said:
Should "Ignore 99% of what people say" be ignored?
How do you define "neutral sound"? Here's my working definition derived from my experience: the sound of live music is neutral sound, "neutral," here, defined by reference to a given context (a particular concert hall, an outdoor venue, k d lang singing in my living room, etc); the sound of reproduced music, to the extent it deviates at all from the sound of live music, is not neutral sound. The sound of every form of reproduced music I have heard has not been neutral. I deduce that every means of reproduction creating the reproduced music I've heard is the source of the loss of neutrality. Proposition: non-neutrality therefore inheres in reproduction equipment (amps, tts, cds, sacds ...).
We're going in circles.
EACH!!! $100 EACH OPT!!! not the whole amp.
It was the middle of the night but I though I had said it clearly enough, post subject of OPT recomendations or some such and then "budget $100 each so less would be good and more would be pretty much impossible". I agree that the OPT is probalby one of the most influencial parts of the amp so what I am after is a recomendation for a "good" PP OPT for a 2A3 (or 2A3 style(6AS7))amp. I'm not looking for the best as I know it's probalby very possible / easy to spend more than $100 each on an OPT, just a good one for this design so I have a goal to save up for. What I am saying is that I am really terrible at saving money and that at some time I may have$150 - $200 burning a hole in my pocket and be able to say "OK lets get me some iron" but the odds of me being able to say to myself "OK that pair of OPT is going to cost me $275. I need to set this $25 aside and then I can get them" are pretty slim.
Thanks for reading along.
TIA,
Bryan
It was the middle of the night but I though I had said it clearly enough, post subject of OPT recomendations or some such and then "budget $100 each so less would be good and more would be pretty much impossible". I agree that the OPT is probalby one of the most influencial parts of the amp so what I am after is a recomendation for a "good" PP OPT for a 2A3 (or 2A3 style(6AS7))amp. I'm not looking for the best as I know it's probalby very possible / easy to spend more than $100 each on an OPT, just a good one for this design so I have a goal to save up for. What I am saying is that I am really terrible at saving money and that at some time I may have$150 - $200 burning a hole in my pocket and be able to say "OK lets get me some iron" but the odds of me being able to say to myself "OK that pair of OPT is going to cost me $275. I need to set this $25 aside and then I can get them" are pretty slim.
Thanks for reading along.
TIA,
Bryan
I think this was pretty stupid of me to say. I know I'm right but who am I to tell others what I know is right?
Back to the issue of finding a good but not so expencive amp for our buddy new tube amp builder.
I've built a similar SE amp to that on Svetlana's site, only I used a 12AX7 with a CCS load as gain stage. A single 12AX7 and two 6AS7s for a stereo amp. Now I only used parts I had laying around since this was to be my shop amp, and kinda built it more for fun than sound. It turned out to sound great tho. As for OPT I used some I got from an old college, probably used in PP breadboard circuits with EL84s. The turns ratio was way off for my tubes, so max power was about 3-4W. But at least the bass respons was good. I had full power to 10Hz into 4ohms. These are probably similar to the small PP trannies found at Sowter and are cheap. I also only had 200V rails, since I was using what I had laying around, and this was the closest I got. Even so, this amp could boogie! For chassis I stole the largest kettle from the kitchen. It's one of those large aluminum types. The wife didn't like it, but I still got to sleep in my bed so it wasn't that bad. A class-A amp like this doesn't need a hefty power tranny, 100VA will do fine. So all in all I think it's possible to build a decent tube amp that doesnt cost an arm and a leg as long as you don't need a lot of power. I almost never cranked the volume to clip levels, and found as usual that 2-3 watts go a longer way than most people believe.
Another option is this little SE amp using EL84s I found here:
www.lh-electric.4t.com/bin/ef80_el84.gif
As for the 6AS7s two triodes, they are not well matched, at least I have not seen any that are, but still I find them sounding great, even paralleled.
Hi Bryan,
For output transformers try the hammond 125 line like the 125ese. This particular model has several taps so you can run several different types of tubes. There are also cheaper models in the 125 line which will work, it all depends on the output tube you decide on.
These are for single end amps.
Since you do not have much money to work with you may decide to work with a triode connected pentode such as an EL34 or similar tube or maybe as someone suggested a el84, a great tube imo. If you wish to use a true triode then a Sovtek 2a3 or 6b4g would work. Use standard generic parts and do not worry about the boutique parts like fancy coupling caps or fancy input jacks or binding posts, those things do not make an amp, they only make an amp expensive. You need to make a budget and figure out how much power your speakers need and the volume you will listen at. I would (am) suggesting a single end amp since it will be cheaper for you because it uses less parts.
$100.00 is not going to get you very far unless you get stuff used or for free. Of course you could always buy the parts as you can afford them, build one channel first and listen in mono. I think all here would be willing to help you with your questions although I am sure many of us have different opinions
My opinion is that you should build a pp amp, something like this
http://www.worldaudiodesign.com/wadproducts/kecl82.html
click on the schematic link on the right for a pdf of the circuit
Whatever you decide have fun.
Andrew
For output transformers try the hammond 125 line like the 125ese. This particular model has several taps so you can run several different types of tubes. There are also cheaper models in the 125 line which will work, it all depends on the output tube you decide on.
These are for single end amps.
Since you do not have much money to work with you may decide to work with a triode connected pentode such as an EL34 or similar tube or maybe as someone suggested a el84, a great tube imo. If you wish to use a true triode then a Sovtek 2a3 or 6b4g would work. Use standard generic parts and do not worry about the boutique parts like fancy coupling caps or fancy input jacks or binding posts, those things do not make an amp, they only make an amp expensive. You need to make a budget and figure out how much power your speakers need and the volume you will listen at. I would (am) suggesting a single end amp since it will be cheaper for you because it uses less parts.
$100.00 is not going to get you very far unless you get stuff used or for free. Of course you could always buy the parts as you can afford them, build one channel first and listen in mono. I think all here would be willing to help you with your questions although I am sure many of us have different opinions
My opinion is that you should build a pp amp, something like this
http://www.worldaudiodesign.com/wadproducts/kecl82.html
click on the schematic link on the right for a pdf of the circuit
Whatever you decide have fun.
Andrew
You are right in a way regarding bass response, SE amplifiers at least those without feedback have so high output impedance that they give maybe 3dB higher power at the speaker resonance, many people experiences this as stronger bass but actually it is only eveidence of an uneven frequency response. SE amps can be nice to listen to for a while but as time goes by you realise that some things are missing, sounds that are masked by the high distorsion in most SE amps.
Regarding your claim that SE amps have better dynamics, how can you claim that an amplifier that has higher distorsion would have better dynamics, actually the opposite is obviously true.
Regards Hans
Here is an inexpencive PP ampSvetlana Tech note
The output transformers are Hammond 1620 @ $46 ea at Parts Connection. The amp should cost less than $200, depending on parts cost. Will better iron sound better? Absolutely. Will this sound good? I think so. YMMV
Something Similar could be done with EL84 or SV83 and a Hammond 1608. Should cost about the same. 10 to 15 W PP AB1 amp. What you build depends on speaker efficency more than anything.
The small pentodes are easy to drive, inexpencive and make a fun amp.
I would search the forum for power amps, both PP and SE and read what was discussed. Lots of great information on this forum.
Good Luck;
Doug
The output transformers are Hammond 1620 @ $46 ea at Parts Connection. The amp should cost less than $200, depending on parts cost. Will better iron sound better? Absolutely. Will this sound good? I think so. YMMV
Something Similar could be done with EL84 or SV83 and a Hammond 1608. Should cost about the same. 10 to 15 W PP AB1 amp. What you build depends on speaker efficency more than anything.
The small pentodes are easy to drive, inexpencive and make a fun amp.
I would search the forum for power amps, both PP and SE and read what was discussed. Lots of great information on this forum.
Good Luck;
Doug
Speakers to be driven.
If I ever get the cabinets made I will most likely be driving some Buschhorn MkII with vintage AlNiCo Foster FE-103a or a pair of AlNiCo Coral 4" full range. The other current possibilities are a fantastic sounding pair of Janszen Z-412 HP or some Infinity 2000AXT. I'd say all of these are about 90 - 91 db efficient. Of course most of the time I'm not playing them all that loud anyway so it doesn't matter to much how many watts I have. When I do play them loud it's usually something that's not quite as sound quality critical so I have a big Yamaha 125 x 2 integrated for that. Maybe if I make something around 2 x 10 or so now, like that PP Svetlana, later I can make another 2 x 20 or 30 and bi-amp my Janszen's. That'd probably sound pretty ab-fab.
Thanks,
Bryan
If I ever get the cabinets made I will most likely be driving some Buschhorn MkII with vintage AlNiCo Foster FE-103a or a pair of AlNiCo Coral 4" full range. The other current possibilities are a fantastic sounding pair of Janszen Z-412 HP or some Infinity 2000AXT. I'd say all of these are about 90 - 91 db efficient. Of course most of the time I'm not playing them all that loud anyway so it doesn't matter to much how many watts I have. When I do play them loud it's usually something that's not quite as sound quality critical so I have a big Yamaha 125 x 2 integrated for that. Maybe if I make something around 2 x 10 or so now, like that PP Svetlana, later I can make another 2 x 20 or 30 and bi-amp my Janszen's. That'd probably sound pretty ab-fab.
Thanks,
Bryan
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