I've been meaning to use the 6C4C with one of my better OPTs - an O-Netics 3.5K, the one Bud built for Wright Sound 2a3 amps. I just got it up and running, and I'm shocked!!! I'm familiar with this OPT with 300b outputs and I prefer the 6C4C. More low level detail and just very musical. Operating point is the book 250v, -45v, 60mA.
Since I don't need the power in my smallish listening room I may start replacing my 300b outputs one by one with 6C4C. It's that good. This goes against the almost universal 300b fan club. If you can deal with the lower power it's a real contender.
Is anybody else using 6C4C outputs?
Since I don't need the power in my smallish listening room I may start replacing my 300b outputs one by one with 6C4C. It's that good. This goes against the almost universal 300b fan club. If you can deal with the lower power it's a real contender.
Is anybody else using 6C4C outputs?
I have recently purchased a pair of winged C Svetlana 6C4C, but didn't have time to put them in a set-up to test them. I'm currently still working with the 4P1Ls, which, by the way, finally proved that I like them better than the 2A3.
Thanks for that! I'm surprised that you prefer 4P1L to 2a3. Do you mean a pair of 4P1L in PSE? Could you tell us more about how you came to that preference? Some details of sound quality?
You may think that's a simple analogy but it actually isn't. Authors have written books about blue for instance. There's a lot in colours, technological, physiological, aesthetic and so on. Same with music.
Amazon.co.uk "On Being Blue" 2014, William Gass
Also have a look at the Colour Quiz. Surprisingly interesting results! ColorQuiz.com - The free five minute personality test!
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Hi Andy,
I mean one 4P1L in SE.
Comparing the two, I had the feeling that the sound of the 4P1L was more detailed, with better articulation and slightly more extended in the top end part of the spectrum.
Of course, all this is my personal sense of how those sounded, but it was also confirmed by a good friend of mine, whose opinion I highly appreciate (in fact, my friend is a maker of high-end horn loudspeakers and, usually, our opinions coincide).
Also, I must note that the 2A3 was probably not loaded the best way, since I used the same parafeed transformer that I use for the 4P1L and the load impedance was 5 kOhms. Soon I will try it with a lower load impedance. Namely, a local winder is winding for me a rather "extreme" OPT with some exotic amporphous double-C core. I have designed the OPT myself, using a rather less than optimal scheme, that is 5 primary and 4 secondary sections (optimally, for such a low outpit power, a 4p3s sectioning would be better, but this would not give me the versatility I wanted). This is designed sort of a "passe par tout" transformer, as the 4 secondary sections allow me to use it as 4, 8 or 16 Ohm. So, with 4 secondary sections in series, I get a load impedance of 2,8 kOhm to 8 Ohm. Also, I could use it as a push-pull OPT, since I have predicted for a center tap.
Soon as I get in hand and try the new OPTs, I will update my findings.
Regards,
Evangelos
Thanks! That's very useful. I did much prefer a single 4P1L to a pair in PSE but didn't use it much since I needed a bit more power. The 4P1L is certainly detailed with a good top end. I find it a bit thin in the midrange, though. Needs a lot of current. I wonder how far you can over-drive a single 4P1L since it's very cheap to replace. It's nominally 9W dissipation max. Talking triode here.
Yes, running 4P1L in SE requires quite sensitive speakers.; Mine are ca. 96 dB, so no worries about power - 1 watt is more than enough to drive them to unbearable levels, so with 2 watts from the 4P1L I have plenty of headroom 🙂.
Regarding the midrange, I haven't noticed a lack of volume. On the contrary, mids are just full and magical.
In the current configuration, I run them (triode connected, of course) at a cathode current of 38 mA and an anode-cathode voltage of 240 V. That gives me ca. 2 W at the start of clipping, as I notice on the oscilloscope (sorry, no set-up for FFT measurements yet...)
Sorry, but it's not a matter of taste. My personal judgement of reproduced music is based on my experience of listening to live music and being myself an amateur musician. So, I always compare the music reproduced from my system to the sound of (mainly) physical instruments, as far as my acoustic memory can help me.
You took the words out of my mouth. I trained at the Royal Academy of Music and worked as a freelance musician for many years - orchestras, theatre pits, jazz and rock bands, modern gospel, even bluegrass and a few further out things. Acoustic sounds become very familiar after so many years. It's all about timbre and the reproduction of lifelike timbre.
A fellow audiophile came over today and we listened to the same input stage with
1. 300b SE outputs - NP amorphous OPT 3.5K, 4300 tubes.
2. 6C4C SE outputs - O-Netics 3.5K OPT, Svetlana 6C4C.
We switched between the output sections with a variety of music. We were in complete agreement that the 6C4C stage was clearer, more neutral, more low level detail, had more attack on the leading edge of notes and was more foot-tapping on music with a beat.
The 300b was warmer in the mids, with a sweet tone that got in the way of the music. The 6C4C seemed almost totally transparent. Nothing added, just the music. With the 300b you were aware that you were listening to a 300b. My colleague had owned a 300b amp for 10 years and remarked "that's the 300b sound I've been used to" (he moved on to an 833 amp). I'm well aware that there are other variables here. The power supplies were almost identical but the 6C4C amp had a 5Z3 RCA rectifier and the 300b amp has a VT244 Sylvania rectifier. Both 5U4 types but I'd say the RCA was more neutral. Both the output stages had choke input filament supplies with Rod's regs. The input stage is complete with its own PSU so that didn't change.
The differences were not subtle. I was rather surprised, having assumed that the 300b was the output of choice. Note that I haven't tried the 300b-N mesh types, nor any of the expensive ones. The 4300 dates back a little but was a decent mid-range 300b. The 6C4C were the standard Svetlana types.
So a turn in the road for me. I'll be building with 2a3s and 6C4Cs in the immediate future and probably converting my 300b amps. I didn't expect this. I'm sure the 2a3 fans will smile and think "yeah, we've been there...".
Right at the start of the thread Eli said "The #45 and 2A3 are honest. The 300B is a "showman". Lots of folks like the 300B's euphony, but it (IMO) generates excessive 2nd order harmonic distortion." Tony Tecson added "I've heard those comments from a lot of folks".
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1. 300b SE outputs - NP amorphous OPT 3.5K, 4300 tubes.
2. 6C4C SE outputs - O-Netics 3.5K OPT, Svetlana 6C4C.
We switched between the output sections with a variety of music. We were in complete agreement that the 6C4C stage was clearer, more neutral, more low level detail, had more attack on the leading edge of notes and was more foot-tapping on music with a beat.
The 300b was warmer in the mids, with a sweet tone that got in the way of the music. The 6C4C seemed almost totally transparent. Nothing added, just the music. With the 300b you were aware that you were listening to a 300b. My colleague had owned a 300b amp for 10 years and remarked "that's the 300b sound I've been used to" (he moved on to an 833 amp). I'm well aware that there are other variables here. The power supplies were almost identical but the 6C4C amp had a 5Z3 RCA rectifier and the 300b amp has a VT244 Sylvania rectifier. Both 5U4 types but I'd say the RCA was more neutral. Both the output stages had choke input filament supplies with Rod's regs. The input stage is complete with its own PSU so that didn't change.
The differences were not subtle. I was rather surprised, having assumed that the 300b was the output of choice. Note that I haven't tried the 300b-N mesh types, nor any of the expensive ones. The 4300 dates back a little but was a decent mid-range 300b. The 6C4C were the standard Svetlana types.
So a turn in the road for me. I'll be building with 2a3s and 6C4Cs in the immediate future and probably converting my 300b amps. I didn't expect this. I'm sure the 2a3 fans will smile and think "yeah, we've been there...".
Right at the start of the thread Eli said "The #45 and 2A3 are honest. The 300B is a "showman". Lots of folks like the 300B's euphony, but it (IMO) generates excessive 2nd order harmonic distortion." Tony Tecson added "I've heard those comments from a lot of folks".
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andyjevans,
Very interesting!
It was great, you used the same input stage on both amplifiers.
1. 300b SE outputs - NP amorphous OPT 3.5K, 4300 tubes.
2. 6C4C SE outputs - O-Netics 3.5K OPT, Svetlana 6C4C.
Other than the different output tubes, you used different output transformers.
3.5k amorphous is not the same as 3.5k O-netics . . . Right?
With a little (lot) more work, one of those two amplifiers can be modified for an even better test.
Pick one amp, and one output transformer.
Make one amplifier able to switch from 300B to 6C4C.
I know, easier said than done, sockets and filaments are different?
You will have to adjust the bias, so that . . . the quiescent operating current is the same for both tubes (same DC current in the one output transformer).
Now, change the output transformer, and repeat on the same modified amplifier, again comparing the 300B and 6C4C (rather than drill holes to mount the other transformer, just wire it off chassis, and ground the transformer frame to the chassis).
I would be real interested in hearing the results of a listening session if you do that.
Thanks!
Very interesting!
It was great, you used the same input stage on both amplifiers.
1. 300b SE outputs - NP amorphous OPT 3.5K, 4300 tubes.
2. 6C4C SE outputs - O-Netics 3.5K OPT, Svetlana 6C4C.
Other than the different output tubes, you used different output transformers.
3.5k amorphous is not the same as 3.5k O-netics . . . Right?
With a little (lot) more work, one of those two amplifiers can be modified for an even better test.
Pick one amp, and one output transformer.
Make one amplifier able to switch from 300B to 6C4C.
I know, easier said than done, sockets and filaments are different?
You will have to adjust the bias, so that . . . the quiescent operating current is the same for both tubes (same DC current in the one output transformer).
Now, change the output transformer, and repeat on the same modified amplifier, again comparing the 300B and 6C4C (rather than drill holes to mount the other transformer, just wire it off chassis, and ground the transformer frame to the chassis).
I would be real interested in hearing the results of a listening session if you do that.
Thanks!
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Thanks 6a3. Your very name shows some investment in these output tubes.
I could indeed make it a closer match. Two things holding me back - first I now have an order for an amp as close as possible to my present 6C4C amp from my colleague who loved it. Plus i have to get a couple of 26 preamps out of the door as well. So I'm busy. I'm also selling off tubes on eBay as fast as I can to make some space.
Second - I don't have any really good 300b tubes. I might be able to borrow some.
In terms of motivation, having lived with the 300b sound for many years I'm coming with fresh ears to the 2a3 variants. Knowing me I'll start collecting them. I don't have any of the US monoplates and not sure I want to get into those - they won't be cheap. I do have some Sovtek 6B4G which are monoplates and I have those in the amp right now. I love all this stuff!
I could indeed make it a closer match. Two things holding me back - first I now have an order for an amp as close as possible to my present 6C4C amp from my colleague who loved it. Plus i have to get a couple of 26 preamps out of the door as well. So I'm busy. I'm also selling off tubes on eBay as fast as I can to make some space.
Second - I don't have any really good 300b tubes. I might be able to borrow some.
In terms of motivation, having lived with the 300b sound for many years I'm coming with fresh ears to the 2a3 variants. Knowing me I'll start collecting them. I don't have any of the US monoplates and not sure I want to get into those - they won't be cheap. I do have some Sovtek 6B4G which are monoplates and I have those in the amp right now. I love all this stuff!
Operating points will be different for 6C4C and 300B.
Making them equal means that one of them is not sounding to his best.
i have a question - are the internal structures of the US 2a3 and 6B4G tubes the same?
I can see there are a few varieties. Even some 6B4G with straight glass.
I can see there are a few varieties. Even some 6B4G with straight glass.
Andy,
A while ago, I did the same test, comparing 2A3 (RCA) to 300B (TJ FullMusic), using the same driver and same OPT (although, at 5K load instead of a more optimal at 3K). Listening tests were conducted in mono, since I only have one pair of OPTs. Probably not ideal, but, since I listen with horn speakers, dispersion is wide, so you don't get the feeling of lack of the musical scene and I can come to a conclusion regarding the quality of the sound.
My findings coincide exactly with yours. The 300B may have this lust in the midrange, but lacks bass control, low level detail, speed and transparency. The 2A3 proved to be more detailed, with punch, attack, extension and bass control.
As I wrote previously, currently, I prefer the 4P1L over the 2A3, but I plan to try the 2A3 (and 6C4C) with a more optimally loaded OPT.
A while ago, I did the same test, comparing 2A3 (RCA) to 300B (TJ FullMusic), using the same driver and same OPT (although, at 5K load instead of a more optimal at 3K). Listening tests were conducted in mono, since I only have one pair of OPTs. Probably not ideal, but, since I listen with horn speakers, dispersion is wide, so you don't get the feeling of lack of the musical scene and I can come to a conclusion regarding the quality of the sound.
My findings coincide exactly with yours. The 300B may have this lust in the midrange, but lacks bass control, low level detail, speed and transparency. The 2A3 proved to be more detailed, with punch, attack, extension and bass control.
As I wrote previously, currently, I prefer the 4P1L over the 2A3, but I plan to try the 2A3 (and 6C4C) with a more optimally loaded OPT.
I just don't have the budget for high price tubes, I'm afraid. You may well be right but I have a ceiling on what I'm willing to spend on a tube. My system is on 24/7 because everything on my computer goes through it, so I use cheaper tubes where possible and don't run them close to max operating conditions. So I favour tubes up to a certain price, not beyond. And in particular I can't buy in an "experimental" way without hearing a tube. I've never borrowed tubes, but I could look into that. Maybe even set up a listening session now people are starting to mix again.
It may be the internal structure of these 2a3 and 300b that matters most. Mesh or solid, monoplate or biplate, filament structure etc. I'm looking at a lot of tube photos online to see if I can divide the tubes into different "families" regarding structure. I know some have large collections of these tubes, especially those in the USA, but here in Europe the US tubes are less plentiful and more expensive. There's Russia and China and sometimes these produce a really good tube. I've started collecting a bit - already I prefer the 6C4C to the Sovtek 6B4G monoplate for instance. I favour the 6B4G types with DC heating through Rod's regs. Adding a choke to the supply is a nice upgrade too. A bit easier to execute than DC heating a 2a3.
Hopefully this thread will go on for a while and give us more experiences and answers
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daanve,
Please consider the many varied operating conditions that are listed for the WE 300B in the WE 300B datasheet.
Which is the 'optimum' quiescent setting, and why?
Power, 2nd harmonic D., 3rd harmonic D., damping factor, available real good SE transformers of different primary impedances, tube life, etc.
Given that, then operate the 300B and the 6C4C (6S4S) at 250V plate to filament, 60mA plate current, with a 3.5k output transformer primary.
Yes, the bias voltage will be slightly different, and the plate impedance, rp.
Use self bias, and have 2 resistors and a switch to get the current at 60mA for each tube.
Of course the filament voltage is different too, but that could be a 6.3V DC supply for the 6C4C, and a switchable series resistor for the 300B filament.
Very few listening tests are 100% fair, but that is about as close of a setup as you can get for a comparison of a 300B versus a 6C4C.
When I did the comparison of Parallel 300B SE, versus 300B Push Pull at VSAC 2008 . . .
I learned the main problem was not how close the two amplifiers were in tube operating conditions, circuit topology, load lines, damping factor, etc.
The main problem (I discovered too late) was the setup that used 2 loudspeakers, not 1 loudspeaker (an audience needs to have the same spacial position for each amplifier (so that interfering objects like the listener in front of another listener, and persons with only one good ear, etc. does not change the listening characteristics during the test).
Just my opinions.
Please consider the many varied operating conditions that are listed for the WE 300B in the WE 300B datasheet.
Which is the 'optimum' quiescent setting, and why?
Power, 2nd harmonic D., 3rd harmonic D., damping factor, available real good SE transformers of different primary impedances, tube life, etc.
Given that, then operate the 300B and the 6C4C (6S4S) at 250V plate to filament, 60mA plate current, with a 3.5k output transformer primary.
Yes, the bias voltage will be slightly different, and the plate impedance, rp.
Use self bias, and have 2 resistors and a switch to get the current at 60mA for each tube.
Of course the filament voltage is different too, but that could be a 6.3V DC supply for the 6C4C, and a switchable series resistor for the 300B filament.
Very few listening tests are 100% fair, but that is about as close of a setup as you can get for a comparison of a 300B versus a 6C4C.
When I did the comparison of Parallel 300B SE, versus 300B Push Pull at VSAC 2008 . . .
I learned the main problem was not how close the two amplifiers were in tube operating conditions, circuit topology, load lines, damping factor, etc.
The main problem (I discovered too late) was the setup that used 2 loudspeakers, not 1 loudspeaker (an audience needs to have the same spacial position for each amplifier (so that interfering objects like the listener in front of another listener, and persons with only one good ear, etc. does not change the listening characteristics during the test).
Just my opinions.
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