OK...
Tonight I finished building an active crossover for my home sub-amp and I was sitting in my office with the lights out listening to some music when i found myself mesmerized by the soft incandescent glow of the meter lamps on my tuner and amp, I got to thinking that I would like and should finally build my first tube amp.
About 4 years ago I purchased a collection of 108 various tube amplification schematics, so I pulled out the collection and began to peruse the various circuits but being "NEW" to the whole tube scene (it's funny I should say "NEW" cause when I was a youngster even the car radios had tubes in them) I have no experience to help me decide what configuration I should try.
What I am looking for here is some advice as to sound quality, I am not necessarily looking for measurably accurate sound but rather that TUBE sound that everyone always talks so fondly of and some nice glowing tubes on the top of the chassis would be nice too!
So what is your recommendation; single ended, push pull would you say one particular output tube is better than another?
I am not looking to go simple for my first tube project cause odds are that I will only build one set of mono blocs and that will be that.
So come on folks help a fellow DIY'er out. I am really quite fond of the McIntosh MC40 or MC-275 chassis so building something similar in appearance to that would be cool too but then if I wanted McIntosh maybe I should just buy one right? but there is no fun in that.
Thanks one and all for your time and consideration.
🙂
Tonight I finished building an active crossover for my home sub-amp and I was sitting in my office with the lights out listening to some music when i found myself mesmerized by the soft incandescent glow of the meter lamps on my tuner and amp, I got to thinking that I would like and should finally build my first tube amp.
About 4 years ago I purchased a collection of 108 various tube amplification schematics, so I pulled out the collection and began to peruse the various circuits but being "NEW" to the whole tube scene (it's funny I should say "NEW" cause when I was a youngster even the car radios had tubes in them) I have no experience to help me decide what configuration I should try.
What I am looking for here is some advice as to sound quality, I am not necessarily looking for measurably accurate sound but rather that TUBE sound that everyone always talks so fondly of and some nice glowing tubes on the top of the chassis would be nice too!
So what is your recommendation; single ended, push pull would you say one particular output tube is better than another?
I am not looking to go simple for my first tube project cause odds are that I will only build one set of mono blocs and that will be that.
So come on folks help a fellow DIY'er out. I am really quite fond of the McIntosh MC40 or MC-275 chassis so building something similar in appearance to that would be cool too but then if I wanted McIntosh maybe I should just buy one right? but there is no fun in that.
Thanks one and all for your time and consideration.
🙂
My 2c:
You might be surprised: a well designed tube amp will sound pretty accurate.
I would suggest the venerable williamson design, 6L6G or 807 push-pull with a long tailed pair 6SN7 or 12AU7 driver, perhaps a pentode front end like 6J7 or EF86? Vintage tubes are great when you can get them, dont worry about them being 40 years old! Power out would be 20-30W. Use vintage output transformers if you can get them.
I have found that a well designed PP amp comes close to a SET amp in sound quality, with the advantage of a decent amount of power.
Heard that before 🙂
You might be surprised: a well designed tube amp will sound pretty accurate.
I would suggest the venerable williamson design, 6L6G or 807 push-pull with a long tailed pair 6SN7 or 12AU7 driver, perhaps a pentode front end like 6J7 or EF86? Vintage tubes are great when you can get them, dont worry about them being 40 years old! Power out would be 20-30W. Use vintage output transformers if you can get them.
I have found that a well designed PP amp comes close to a SET amp in sound quality, with the advantage of a decent amount of power.
Heard that before 🙂
ShiFtY said:
How about something like this
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I'll bet 😉
Frazzled,
Where did the schematic come from? The 6L6s are triode wired. I question the ability of 12AX7 sections to drive the Miller capacitance of the "finals".
For sure, I'd change the 1 MOhm grid leak resistor at the circuit's I/P to 100 KOhms.
Where did the schematic come from? The 6L6s are triode wired. I question the ability of 12AX7 sections to drive the Miller capacitance of the "finals".
For sure, I'd change the 1 MOhm grid leak resistor at the circuit's I/P to 100 KOhms.
8SL7-6SN7-6L6
I think this may be what you are looking for:
http://www.dc-daylight.ltd.uk/Valve-Audio-Interest/Schematics/UL-H&K Fig3.pdf
I think this may be what you are looking for:
http://www.dc-daylight.ltd.uk/Valve-Audio-Interest/Schematics/UL-H&K Fig3.pdf
Re: 8SL7-6SN7-6L6
Hmmmm Interesting, this circuit is very similar to the one I posted, I guess tube amps are like SS amps in that there are some standardized circuit configurations that designers use to put their own parts into to obtain their own preferred sound.
Can anyone else chime in as to their favorite design, my speaker sensitivity is in the mid 90's and my budget could be just about anything, the more $$ I need to spend, the longer I will take to finish the project, I get more out of the process than the actual finished project cause it is more about filling my free time and learning more about my chosen hobby, really the only time I listen to music is when I am in my office working on a new audio project.
Thanks again everyone.
MIKET said:
Hmmmm Interesting, this circuit is very similar to the one I posted, I guess tube amps are like SS amps in that there are some standardized circuit configurations that designers use to put their own parts into to obtain their own preferred sound.
Can anyone else chime in as to their favorite design, my speaker sensitivity is in the mid 90's and my budget could be just about anything, the more $$ I need to spend, the longer I will take to finish the project, I get more out of the process than the actual finished project cause it is more about filling my free time and learning more about my chosen hobby, really the only time I listen to music is when I am in my office working on a new audio project.
Thanks again everyone.
Esthetic
Remember guys, as well as decent sound there is an esthetic I am going for here, I see some of the photos of tube amps that are posted here and some leave me wanting while others bring a big smile to my face, big glowing tubes just turn me on, kinda takes me back to my childhood sitting in front of my grandfathers console radio/record player, listening to his 78's, I used to love that bassy silky smooth sound, the first CD I ever played repulsed me, way too "tinny" ya know.
Remember guys, as well as decent sound there is an esthetic I am going for here, I see some of the photos of tube amps that are posted here and some leave me wanting while others bring a big smile to my face, big glowing tubes just turn me on, kinda takes me back to my childhood sitting in front of my grandfathers console radio/record player, listening to his 78's, I used to love that bassy silky smooth sound, the first CD I ever played repulsed me, way too "tinny" ya know.
Frazzled,
If your mid 90s SPL speakers have reasonably flat impedance curves, they are good candidates to be mated with single ended 300B based amplification of about 8 WPC O/P. You would get the tube sound "in spades". 300Bs are big coke bottle shaped tubes that will provide eye and ear candy.
If your mid 90s SPL speakers have reasonably flat impedance curves, they are good candidates to be mated with single ended 300B based amplification of about 8 WPC O/P. You would get the tube sound "in spades". 300Bs are big coke bottle shaped tubes that will provide eye and ear candy.
Stick to well-proved designs for your first go. You'll end up with something that works well and can last you a long, long time. Or at the least, a nice platform from which you can start experimenting. Shifty mentions Williamson, which is a very sound idea (ouch). I'd also recommend the Mullard 5-20.
Eli Duttman said:
Sweet, how about something like this...
An externally hosted image should be here but it was not working when we last tested it.
Frazzled said:
I am in the same boat as frazzled and I can relate to many of his comments. Half of the entertainment to me in building something of this sort is finding the best parts for that perfect look. I like the simplicity of this schematic design and the asthetics of the 300B tubes. I have also been looking at a PP 2A3 possibly because of looks. Of the two which will offer better sound with a set of JBL L40s ?
That 6SL7/300B circuit looks interesting. Before proceding, let's make sure that your speakers are really suitable, as this is not an inexpensive project. Are you speakers nominally 8 Ohms. 4 Ohm nominal commercial speakers frequently have fudged efficiency specs. Manufacturers will state a SPL at 2.83 V. of I/P. That's 2 W. into 4 Ohms and the efficiency is actually 3 dB. lower than stated. Even if the speakers are truly mid 90s sensitive driven by 1 W., you will be disappointed with the combination if there are significant dips in the impedance curve, particularly at low frequencies. Get the ducks lined up before parting with your money.
Assuming all is well with the speakers, I have some comments.
I am dubious about a 47 muF. cap. in the 1st position of the B+ filter, as it stresses both the power trafo and the 5U4. 20 muF. is plenty to keep the rail voltage up and will not stress the 5U4. You can add capacitance to the 2nd position and/or increase the choke to 10 H. If you can get a center tapped (CT) 5 V. winding for the 5U4 filament, take the B+ from the CT instead of taking it from the tube's pin 8.
Remarks have been made about "washed out" sonics when simple DC is used to energize the filaments of directly heated triodes (DHT) like the 300B. In addition, I wonder why a hum balance pot. is being used with DC heating. Current regulated DC has a good reputation, but is somewhat complicated to implement. An awful lot of good sounding 300B amps have been built using AC heating and hum balance pots. I'd go for the cost effective and simple AC heating.
The Locktal based 7F7 is electrically equivalent to the Octal based 6SL7 (different pin out) and is available at a lower price. In any event, I'd bias the voltage amp/driver heater at about 60 V. with a voltage divider on the B+ rail. Biasing the heater protects against exceeding the capability of the heater to cathode insulation.
Assuming all is well with the speakers, I have some comments.
I am dubious about a 47 muF. cap. in the 1st position of the B+ filter, as it stresses both the power trafo and the 5U4. 20 muF. is plenty to keep the rail voltage up and will not stress the 5U4. You can add capacitance to the 2nd position and/or increase the choke to 10 H. If you can get a center tapped (CT) 5 V. winding for the 5U4 filament, take the B+ from the CT instead of taking it from the tube's pin 8.
Remarks have been made about "washed out" sonics when simple DC is used to energize the filaments of directly heated triodes (DHT) like the 300B. In addition, I wonder why a hum balance pot. is being used with DC heating. Current regulated DC has a good reputation, but is somewhat complicated to implement. An awful lot of good sounding 300B amps have been built using AC heating and hum balance pots. I'd go for the cost effective and simple AC heating.
The Locktal based 7F7 is electrically equivalent to the Octal based 6SL7 (different pin out) and is available at a lower price. In any event, I'd bias the voltage amp/driver heater at about 60 V. with a voltage divider on the B+ rail. Biasing the heater protects against exceeding the capability of the heater to cathode insulation.
I am looking and pricing this 300B circuit out and I am shopping the transformers first. Looking at the Hammond products I should be able to use a 274AX transformer? Stupid question, but is there any reason why a person wouldn't hook all of the tube filaments up to the one transformers filament outputs?
This particular design is asking for a 3k OPT. how much would it effect things to put in a 2.5k or such ?
This particular design is asking for a 3k OPT. how much would it effect things to put in a 2.5k or such ?
For a Directly Heated Triode (DHT) like the 300B or a 2A3, the filament is the cathode. So you'll need separate filament transformers for both of those tubes, and be careful not to ground the secondaries of these transformers (just follow the schematics on the Angela/JE Labs website and you'll be fine). The driver tubes like the 6SL7 are indirectly heated, so you can, and would, hook up those to a single filament transformer. I used the 6.3V winding on my Hammond power transformer for the drivers, and 2 separate 2.5V transformers for the 2A3s.
P.S. Maybe you know this already, but check Angela.com for prices on Hammond transformers and chassis. I found them to be lower than any other place I looked.
Saurav said:
Thanks! Their prices are very good. That makes perfect sense. I am slowly puting this all together. It has been helpful for me to compare some of the different circuits that I have collected to see the differences in the schematics and it is interesting to determine what they are trying to achieve.
Eli Duttman said:
I think I should be OK with the speakers, I built them in high school electronics and was designed by the professor, we also built 2 watt SS amplifiers that drove these speakers for years until it bit the dust a few years back. (I should dig that out one of these days!) The whole concept of amp/speakers was to show the 500+ watt guys that with a good amplifier design and effecient speakers one could produce a suprising amount of sound pressure.
Thanks for the tip, but can you explain the reasoning behind taking B+ from the CT instead?
I also found this odd, I was going to ask if there was any reason why one couldn't just use AC heating. Thanks!
Again thank you for the tip, you are of course right about the prices but are there two tubes I could use instead of one, I am going for the "MORE GLOW THE BETTER" mantra...😀
A number of veteran builders, including Jim Dowdy (a man I respect highly), say the sound is better. I suspect it has to do with being equidistant from the filament's ends. Please observe that the "trick" works only with directly heated rectifiers, like the 5U4. In the case of a rectifier with a cathode sleeve, like the 5AR4, you have to take the B+ from pin 8, as that is where the sleeve is connected.
Let me chime in
Visit my site and check out my 300B.
http://home.midmaine.com/~talbot/talbot_audio_design/index.htm
6SL7 drivers are excellent as well.
Visit my site and check out my 300B.
http://home.midmaine.com/~talbot/talbot_audio_design/index.htm
6SL7 drivers are excellent as well.
OK I have settled on the 300B design with a few modifications and have started purchasing parts.
Whew doesn't take long to spend the $$, I plan to purchase all the parts now except the 300B tubes, once I am nearing completion of the project I will start shopping for the 300B's, of course I would love to be able to afford the coveted western electric 300B's but c'mon, US$1000 for a matched pair... YIKES
Anyway I won't start assembling anything until I have all of the parts, I am going to try and source some vintage stuff like the TRAFO's but I will be purchasing as much new as possible.
I will post pics and info as the project progresses but it may be a while before I start.
Thanks to everyone who had any input, especially Eli whom I am afraid is not off the hook quite yet, I am sure I will be consulting him in the future as he seems to be a willing if not knowledgeable participant in my quest for audio utopia.
😀
Whew doesn't take long to spend the $$, I plan to purchase all the parts now except the 300B tubes, once I am nearing completion of the project I will start shopping for the 300B's, of course I would love to be able to afford the coveted western electric 300B's but c'mon, US$1000 for a matched pair... YIKES
Anyway I won't start assembling anything until I have all of the parts, I am going to try and source some vintage stuff like the TRAFO's but I will be purchasing as much new as possible.
I will post pics and info as the project progresses but it may be a while before I start.
Thanks to everyone who had any input, especially Eli whom I am afraid is not off the hook quite yet, I am sure I will be consulting him in the future as he seems to be a willing if not knowledgeable participant in my quest for audio utopia.
😀
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