Hey there! I know that this is a pretty common discussion topic, but I've looked around and haven't found the exact answers that I'm looking for.
It seems like a lot of people look to tackle the the 300B SET as their first build and are cautioned from doing so. While I'm not super experienced in the world of building from scratch, I've done quite a few restorations of various amps, and I recently built a Darling just to see if building was something I enjoyed. I did, and it just made me want to build more, so here I am. I spent some time reading about sonic qualities of different projects employing the 45, 46, 2a3, 300B, etc. The 300B sounded enticing, but I wasn't sure if it was quite right for me. My speakers are quite efficient (a 3-way JBL system using the 130A, 2410, and 075), so no tube is really off the table, and the power of a 300B isn't fully necessary.
A friend of mine brought over his amp recently, which is a 5U4 rectified, single ended 300B, driven by 2x C3g's per channel. I really loved what I heard–everything just sounded effortless in a way that I haven't heard before. Recordings where I would usually have to dial in tone adjustments just sounded great from the start, and crisp bass was present like I haven't heard from my speakers before. It seemed to suit just about any type of music that we auditioned with, from jazz to stoner metal. So, I'm seriously thinking about going for the 300B. His was done by a Japanese builder using current production ISO transformers and choke (FC-20s for outputs), and I'd like to use the same iron.
I don't know if I want to copy the amp that he has, as the 4x C3g will just add another $400+ to the cost of tubes (I know $400-500 isn't a lot in the grand scheme of building a 300B amp, but I'm also not looking to spend more than I absolutely have to). I also don't want to get into a design that's incredibly different or blows my budget, so I've been looking at the Sun Audio SV-300BE and the Audio Note Quest as other schematics to work from. My question is, would I be disappointed by the sound produced by an amp driven with the 6SN7 after liking what I heard from my friend's amp?
Any thoughts are appreciated. Thank you!
It seems like a lot of people look to tackle the the 300B SET as their first build and are cautioned from doing so. While I'm not super experienced in the world of building from scratch, I've done quite a few restorations of various amps, and I recently built a Darling just to see if building was something I enjoyed. I did, and it just made me want to build more, so here I am. I spent some time reading about sonic qualities of different projects employing the 45, 46, 2a3, 300B, etc. The 300B sounded enticing, but I wasn't sure if it was quite right for me. My speakers are quite efficient (a 3-way JBL system using the 130A, 2410, and 075), so no tube is really off the table, and the power of a 300B isn't fully necessary.
A friend of mine brought over his amp recently, which is a 5U4 rectified, single ended 300B, driven by 2x C3g's per channel. I really loved what I heard–everything just sounded effortless in a way that I haven't heard before. Recordings where I would usually have to dial in tone adjustments just sounded great from the start, and crisp bass was present like I haven't heard from my speakers before. It seemed to suit just about any type of music that we auditioned with, from jazz to stoner metal. So, I'm seriously thinking about going for the 300B. His was done by a Japanese builder using current production ISO transformers and choke (FC-20s for outputs), and I'd like to use the same iron.
I don't know if I want to copy the amp that he has, as the 4x C3g will just add another $400+ to the cost of tubes (I know $400-500 isn't a lot in the grand scheme of building a 300B amp, but I'm also not looking to spend more than I absolutely have to). I also don't want to get into a design that's incredibly different or blows my budget, so I've been looking at the Sun Audio SV-300BE and the Audio Note Quest as other schematics to work from. My question is, would I be disappointed by the sound produced by an amp driven with the 6SN7 after liking what I heard from my friend's amp?
Any thoughts are appreciated. Thank you!
300B SE "sound" IMO depends on 50% of OPT, 20% type of power tube, 10% PSU, 10% structure of amplifier, and 10% other components.
The "last" 10% even may costs more (if you are quite a maniac HiFi fan 😁), than other components -except OPT-.
C3g is excellent driver tube.
I don't really understand why he used 4 pieces, only one enough per channel, if you are satisfied with 6-7W (A1 mode).
BTW choosing of SE amplifier begins with chasing of "tube friendly" loudspeaker. If you don't have it, the final result may be disappointing.
The "last" 10% even may costs more (if you are quite a maniac HiFi fan 😁), than other components -except OPT-.
C3g is excellent driver tube.
I don't really understand why he used 4 pieces, only one enough per channel, if you are satisfied with 6-7W (A1 mode).
BTW choosing of SE amplifier begins with chasing of "tube friendly" loudspeaker. If you don't have it, the final result may be disappointing.
The 3Cg is a high transconductance pentode commonly configured as a triode with a Mu of 40. It is possible that two 3Cg are cascaded to give enough drive voltage for a 300B. There are other popular high transconductance pentodes with higher Mu that could be used to build a two stage amp. The 6688/E180F is one of several pentodes that are normally triode connected and became popular a decade or two ago. Among them are the 6688/E180F, 7721/D3a, 7722/E280F and 7788. When I bought my 6688s, they were very cheap and were available in quantity on epay. Now, all these tubes have become more expensive, but the 6688 has remained the least expensive. I have tried most of the triode connected pentodes and find them quite similar sounding in my application e.g., a two stage amp driving a 45, 2A3 or 300B.
@Nick
I have been through this recently myself starting from more or less your level of experience and knowing what I know now (that is, just enough), I would pass on the sunaudio designs.
There are better sounding solutions using very cheap 10-20$ driver tubes - besides the 300b.
The 3 main questions are:
-include SS parts in the amp. My answer: yes
-AC or DC heater(s): For me, DC all the way.
-finally auto bias or fixed bias. I did auto bias. It's very safe and I know how that sounds and now I am switching over to fixed.
I have been through this recently myself starting from more or less your level of experience and knowing what I know now (that is, just enough), I would pass on the sunaudio designs.
There are better sounding solutions using very cheap 10-20$ driver tubes - besides the 300b.
The 3 main questions are:
-include SS parts in the amp. My answer: yes
-AC or DC heater(s): For me, DC all the way.
-finally auto bias or fixed bias. I did auto bias. It's very safe and I know how that sounds and now I am switching over to fixed.
Can you tell us who that is?His was done by a Japanese builder
@Hearinspace Ken Uesugi / Otomon Labs. He receives mixed reviews for customer service, but I liked what I heard.
Good to know! Is the 6SN7 the reason you would pass on the Sun Audio design, or just that you feel there are better options out there? Just curious.@Nick
I have been through this recently myself starting from more or less your level of experience and knowing what I know now (that is, just enough), I would pass on the sunaudio designs.
There are better sounding solutions using very cheap 10-20$ driver tubes - besides the 300b.
The 3 main questions are:
-include SS parts in the amp. My answer: yes
-AC or DC heater(s): For me, DC all the way.
-finally auto bias or fixed bias. I did auto bias. It's very safe and I know how that sounds and now I am switching over to fixed.
SS Parts - I'm not opposed as the Darling I built was solid state rectified. I think I'm leaning toward tube rectification with the 300B.
AC or DC - My friend's amp was AC. There was a low level hum with my speakers which wasn't awful, but I wouldn't mind that being gone.
Fixed or Auto Bias - I'd like to do fixed
The Sun Audio only puts out a few watts with a 300B as there is insufficient drive for full output power. It is really a 2A3 amp and was designed for very efficient speakers nearfield listening for a small apartment in Japan.
I asked because there's a number of Japanese builders who have a web-page and post their designs. If thinking of drivers that will give you a sound in the same family as the one you heard, it would be helpful to know what the circuit was.
Was it an integrated amp? If so , perhaps one C3g input and one as driver ?
If power amp only , maybe SRPP or mu follower?
If your friend can take a look under the hood and scribble a diagram . . . . . . . .
Was it an integrated amp? If so , perhaps one C3g input and one as driver ?
If power amp only , maybe SRPP or mu follower?
If your friend can take a look under the hood and scribble a diagram . . . . . . . .
An SE 300B amp is really not that difficult, and no one should be discouraged from building one! ;-) The Joe Roberts "Sound Practices" version of the Western Electric 91A was my first DIY project 30 years ago. I sprang for Magnequest transformers, Black Gate caps, etc., and I was gobsmacked at the quality of sound that came out of what I had built with my own hands. My wife still thinks I should have stopped there. ;-)
A STUNNING 300B amp can be as simple as a Dennis Had Inspire with a 6SL7 driver, or as complicated as the one you cite. Gordon Rankin used a 417A driver to create one of his legendary Wavelength amps.
Here's the trick, IMO. Every component in an SE 300B amp matters. You can hear EVERYTHING. If you're on a budget, the best way to start is with a breadboard amp. They're not at all difficult to construct. Leave plenty of room to experiment. Start with a simple circuit, some affordable output transformers, and then work your way up. Do not be discouraged! It'sd enormous fun, but will suck up some of your monthly food budget. ;-)
A STUNNING 300B amp can be as simple as a Dennis Had Inspire with a 6SL7 driver, or as complicated as the one you cite. Gordon Rankin used a 417A driver to create one of his legendary Wavelength amps.
Here's the trick, IMO. Every component in an SE 300B amp matters. You can hear EVERYTHING. If you're on a budget, the best way to start is with a breadboard amp. They're not at all difficult to construct. Leave plenty of room to experiment. Start with a simple circuit, some affordable output transformers, and then work your way up. Do not be discouraged! It'sd enormous fun, but will suck up some of your monthly food budget. ;-)
I don't know if it's because of the no feedback circuitry but I second @grover on the fact that everything makes a sonic difference. Aside from the PS type, which I have not played with at all, all the caps in the amp make a HUGE difference. I did not appreciate that until I tried. You'll eliminate the cathode bypass cap with fixed bias. Bartola Valves (Ale M.) uses SiC diodes for the driver bias thereby eliminating that cap too.
While I don't necessarily need the full output for my speakers, I'd rather build something that will fully utilize the tubes. Just because I'm curious, is there any benefit to under-driving them?The Sun Audio only puts out a few watts with a 300B as there is insufficient drive for full output power. It is really a 2A3 amp and was designed for very efficient speakers nearfield listening for a small apartment in Japan.
Power amp only. I actually have a decent under the hood photo:I asked because there's a number of Japanese builders who have a web-page and post their designs. If thinking of drivers that will give you a sound in the same family as the one you heard, it would be helpful to know what the circuit was.
Was it an integrated amp? If so , perhaps one C3g input and one as driver ?
If power amp only , maybe SRPP or mu follower?
If your friend can take a look under the hood and scribble a diagram . . . . . . . .
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Love this photo, and thank you for the encouragement!An SE 300B amp is really not that difficult, and no one should be discouraged from building one! ;-) The Joe Roberts "Sound Practices" version of the Western Electric 91A was my first DIY project 30 years ago. I sprang for Magnequest transformers, Black Gate caps, etc., and I was gobsmacked at the quality of sound that came out of what I had built with my own hands. My wife still thinks I should have stopped there. ;-)
View attachment 1321378
A STUNNING 300B amp can be as simple as a Dennis Had Inspire with a 6SL7 driver, or as complicated as the one you cite. Gordon Rankin used a 417A driver to create one of his legendary Wavelength amps.
Here's the trick, IMO. Every component in an SE 300B amp matters. You can hear EVERYTHING. If you're on a budget, the best way to start is with a breadboard amp. They're not at all difficult to construct. Leave plenty of room to experiment. Start with a simple circuit, some affordable output transformers, and then work your way up. Do not be discouraged! It'sd enormous fun, but will suck up some of your monthly food budget. ;-)
I'm really interested to see how different components will change the sound. That's something that I haven't really been able to notice to a huge extent with previous projects that employed far more parts (Fisher receivers, Dynaco ST-70s, a Marantz 8B). I've always opted for nice, but not bank-breaking coupling caps and such, because as long as it was something of decent quality, I didn't notice much of a difference.
I don't know if it's because of the no feedback circuitry but I second @grover on the fact that everything makes a sonic difference. Aside from the PS type, which I have not played with at all, all the caps in the amp make a HUGE difference. I did not appreciate that until I tried. You'll eliminate the cathode bypass cap with fixed bias. Bartola Valves (Ale M.) uses SiC diodes for the driver bias thereby eliminating that cap too.
Feedback will certainly smooth out a lot of anomalies with passive components--though not all. I'm pretty fussy about the cathode bypass caps in my Williamson amps, which employ 20dB feedback. But certainly a no-feedback amp will reveal any flaws in the design or components.
Did a quick pinout , poor image quality but good enough to get the idea. One above the other , Looks to me that plate of right socket connects to cathode of left through resistor. Detail of other resistor connections is less certain , but have other things to attend to. Guess is SRPP (or Mu).
Attachments
I first build my 300B amp using that sun audio/JC Morrison schematic that's all over the web and it just didn't perform well. That direct coupled cascade 6SN7 design just doesn't have enough drive for a 300B tube. I ended up changing to a cascode 6SN7 design and it worked well for me. Quite a few folks have build one like mine and they seem to like the way it sounds. I love mine 🙂 I originally built it with all Edcor iron, the power transformer died after about 2 years so I swapped for a Hammond. Later swapped in some ISO FC30-3.5K transformers, which were a nice upgrade! I'm really liking these new Psvane Horizon 300B tubes as well.
https://www.skunkiedesigns.com/300b
https://www.skunkiedesigns.com/300b
Just my Generalized Opinions . . .
When a part (resistor, capacitor, tube, etc.) is Inside of a negative feedback loop (local or global) . . .
When you change that part to another one of the same value, the difference in the sound is harder to hear.
If the part is Not Inside of a negative feedback loop, changing that part to another one of the same value, the difference in the sound is easier to hear.
And, for all of my 45, 2A3, and 300B amplifiers (single ended 45, 2A3, and 300B; and push pull 2A3 and 300B) . . . I Never used negative feedback.
For DHT tubes, use DC for the filaments.
Whenever I can, my B+ uses solid state rectifiers, and Choke Input Filters.
Caution: use aluminum chassis, not magnetic steel, keep the choke away from the SE output transformer, and rotate the choke and output transformer coils at right angles (90 degrees).
Then, with careful control of all hum ground loops, I have less than 100uV into 8 Ohms.
One more thing: If you use an output transformer that saturates at some low frequency and power level . . . then if you apply global negative feedback around the output transformer, expecting to get more power without saturating, it actually makes the saturation worse, not better.
Your Mileage May Vary!
When a part (resistor, capacitor, tube, etc.) is Inside of a negative feedback loop (local or global) . . .
When you change that part to another one of the same value, the difference in the sound is harder to hear.
If the part is Not Inside of a negative feedback loop, changing that part to another one of the same value, the difference in the sound is easier to hear.
And, for all of my 45, 2A3, and 300B amplifiers (single ended 45, 2A3, and 300B; and push pull 2A3 and 300B) . . . I Never used negative feedback.
For DHT tubes, use DC for the filaments.
Whenever I can, my B+ uses solid state rectifiers, and Choke Input Filters.
Caution: use aluminum chassis, not magnetic steel, keep the choke away from the SE output transformer, and rotate the choke and output transformer coils at right angles (90 degrees).
Then, with careful control of all hum ground loops, I have less than 100uV into 8 Ohms.
One more thing: If you use an output transformer that saturates at some low frequency and power level . . . then if you apply global negative feedback around the output transformer, expecting to get more power without saturating, it actually makes the saturation worse, not better.
Your Mileage May Vary!
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poxdiconsvoice,
Thanks!
As I often do, I added some more comments to my Post # 18 After you read it.
You might want to read it again.
Thanks!
As I often do, I added some more comments to my Post # 18 After you read it.
You might want to read it again.
Have you considered the Bottlehead Kaiju?
Sounds great. My friend has one. I've built several Bottlehead kits and they are excellently done. Among the best build support and troubleshooting there is. Highly recommended. Simplify your life by ordering domestic (have you seen how many people complain about Otomon Labs shipping?) and not overly fetishizing specific tubes. You will spend less and end up with some really great-sounding gear.
Sounds great. My friend has one. I've built several Bottlehead kits and they are excellently done. Among the best build support and troubleshooting there is. Highly recommended. Simplify your life by ordering domestic (have you seen how many people complain about Otomon Labs shipping?) and not overly fetishizing specific tubes. You will spend less and end up with some really great-sounding gear.
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