When I became aware of the F4's ability to be driven by a main amplifier's output, I started wondering if I could use it to drive a wider range of speakers with my SET - and still have the SET character?
I'm not sure how significant this is, but the 300B is a Tubelab SE.
Aside from 300B's any descriptions about the F4 being driven by low power SET amplifiers would be great! Please include your speaker. Thanks!
I'm not sure how significant this is, but the 300B is a Tubelab SE.
Aside from 300B's any descriptions about the F4 being driven by low power SET amplifiers would be great! Please include your speaker. Thanks!
ZM, I wish I would have understood it before ordering all the parts I did. That's a really cool project. I have read the NP writing on it. If there's more, could you please recommend?
F4 is Chameleon, with intrinsic THD low enough, so preceding (source) THD Spectra is transfered practically unspoiled
if you need more voltage than your 300B is giving to 8R speaker, jut use 16R dummy load on 300B output, prior to feedng it to F4
lesser THD and greater swing on output of 300B, comparing to situation with 8R (speaker) and F4 is adding muscle to it
build and try
btw. if you search for "Papa's Koan" around, you'll see what's my everyday's amp
if you need more voltage than your 300B is giving to 8R speaker, jut use 16R dummy load on 300B output, prior to feedng it to F4
lesser THD and greater swing on output of 300B, comparing to situation with 8R (speaker) and F4 is adding muscle to it
build and try
btw. if you search for "Papa's Koan" around, you'll see what's my everyday's amp
Search the F4 thread for posts by DebK. If I recall correctly, she did some great experiments with 300B and 45 and posted thoughts.
I haven't done it yet with mine, but it's on the ever-growing list of things to experiment with.
I haven't done it yet with mine, but it's on the ever-growing list of things to experiment with.
Not the answer to your question, but I have a simple 2C51 based triode preamp driving the F4.
I wanted to hear the mids, palpable texture and sound-stage triodes provide.
I got it with a tube triode and F4.
I have heard parallel 300b mono-blocks and 300b with $1200 tubes alone, without the F4. I think what I have is as good, but of course I'm biased. The only way I can explain it is those systems didn't draw me in like the 2C51 preamp and F4 combo.
I kept waiting for the magic to happen, but wasn't really getting there.
With that said, I'm sure a 300b and F4 will sound great.
I am building a second F4 but ran out of power supply caps.
Someone said the F4 doesn't sound good as mono-blocks, but I want to see for myself.
Good luck and let us know if you try the F4 with a 300b.
I wanted to hear the mids, palpable texture and sound-stage triodes provide.
I got it with a tube triode and F4.
I have heard parallel 300b mono-blocks and 300b with $1200 tubes alone, without the F4. I think what I have is as good, but of course I'm biased. The only way I can explain it is those systems didn't draw me in like the 2C51 preamp and F4 combo.
I kept waiting for the magic to happen, but wasn't really getting there.
With that said, I'm sure a 300b and F4 will sound great.
I am building a second F4 but ran out of power supply caps.
Someone said the F4 doesn't sound good as mono-blocks, but I want to see for myself.
Good luck and let us know if you try the F4 with a 300b.
Forgot. Speakers are Sonus Faber Grand Piano 87db sensitivity, 6 ohm nomonal.
F4 drives them well.
F4 drives them well.
That’s the brilliant thing about the F4, if you’ve got Vout, then yes. So, a resistor of appropriate wattage will allow you to drive the F4.
The best scenario would be an OTL driving the F4.
Also, I have just enough voltage out of my cathode follower tube dac to drive it. So, I’m building an F4.
Cheers,
Greg
The best scenario would be an OTL driving the F4.
Also, I have just enough voltage out of my cathode follower tube dac to drive it. So, I’m building an F4.
Cheers,
Greg
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You will get more current from the F4 for sure. If you have a 16 ohm tap on your 300b amp you will get more voltage as well. If all you want to do is use the F4 for a buffer for 300b amps then you won’t need to build it with high voltage supplies. Running a 300b for typically 8w on the 16 ohm tap would give something just over 11 volts rms. It looks like building a 50w at 8 ohm version of F4 (20volts rms) would be plenty. That would also give you enough power for general use without getting into huge power transformers, heatsinks etc. If your 6 ohm speakers dip to 4 ohms then you would have close to 100w available versus 8 for the 300b.
One difference with the F4 compared to 300b would be output impedance. You may want to experiment with this and have some high power 1-4 ohm resistors on hand so you can put them in series with the F4 output. This will help the solid state amp to more or less mimic the frequency response of the tube amp when driving your particular speakers. If you like what you hear, and space permitting, you could build the resistors into the amp, either using a switch or separate binding posts to put them into use.
This sounds like a great project. If you go for it, please document the build and results here.
One difference with the F4 compared to 300b would be output impedance. You may want to experiment with this and have some high power 1-4 ohm resistors on hand so you can put them in series with the F4 output. This will help the solid state amp to more or less mimic the frequency response of the tube amp when driving your particular speakers. If you like what you hear, and space permitting, you could build the resistors into the amp, either using a switch or separate binding posts to put them into use.
This sounds like a great project. If you go for it, please document the build and results here.
Sjrajan in his review found nirvana with an ~8R 2W in series between his Yamamoto DHT and the F4(s).
The brilliant move would be to build a linestage with your favorite tube without OPTs. Even a universal linestage if you will (tubelab).
Plus, playing with the F4s bias from 200mv to 300mv could bring more happiness.
Cheers,
Greg
The brilliant move would be to build a linestage with your favorite tube without OPTs. Even a universal linestage if you will (tubelab).
Plus, playing with the F4s bias from 200mv to 300mv could bring more happiness.
Cheers,
Greg
anyway, that's why I wrote that using higher values of shunt resistor at output of toob amp is possible: output toob itself is more than happy to see higher load, overall THD is lower, while you can have double swing with 16R or even quadruple swing with 32R, in place of usual 8R
Thanks for all the feedback, everyone.
I enjoyed reading about your amp, ZM.
This will definitely be my next project. I always loved the mids out of my 300B, and had heard them well through a Madisound horn kit using Fostex FE166NV (budget build).
The inability to get good low frequency response without a horn the size of a car was frustrating, given how much I loved other parts of the reproduction.
I also considered getting a super tweeter to fill in the missing highs; but I was on a more limited budget at the time; and the $1k (or more) expense of a Fostex super, without knowing what the actual results would be, was outside my comfort level. To be honest, it still is 🙂
I can't wait to try this!
I enjoyed reading about your amp, ZM.
This will definitely be my next project. I always loved the mids out of my 300B, and had heard them well through a Madisound horn kit using Fostex FE166NV (budget build).
The inability to get good low frequency response without a horn the size of a car was frustrating, given how much I loved other parts of the reproduction.
I also considered getting a super tweeter to fill in the missing highs; but I was on a more limited budget at the time; and the $1k (or more) expense of a Fostex super, without knowing what the actual results would be, was outside my comfort level. To be honest, it still is 🙂
I can't wait to try this!
in case that I'm living on your side of Big Splash, while thinking of 2 ways- I would go for biggest Heil AMT1 today, directly from factory (bargain) , and will mate it with something appropriate down , no smaller than 12"
Heil AMT | ESS Laboratories, LLC
I was lucky enough to have those tweeters to listen to as a kid because my dad was into this stuff. They are pretty amazing.