Honestly Andy
''So what would I do with a 12B4A with a mu of 6.5? I've made a preamp before with the 12B4A and it's no DHT, not in the same ballpark as a 4P1L in triode.''
A common cathode amplifier is not the only tube circuit in the tube manual....
The diyAudio search function yielded a goldmine of circiuts...
https://www.google.com/url?client=i...FjAAegQIARAB&usg=AOvVaw0Z8BM2aYD37HcLpMKvHQvE
Or just type anode or plate follower amplifier in the advanced search function.Now your choice of valve has expanded and valve datasheets are you friend.
All the best in your valve ventures.
''So what would I do with a 12B4A with a mu of 6.5? I've made a preamp before with the 12B4A and it's no DHT, not in the same ballpark as a 4P1L in triode.''
A common cathode amplifier is not the only tube circuit in the tube manual....
The diyAudio search function yielded a goldmine of circiuts...
https://www.google.com/url?client=i...FjAAegQIARAB&usg=AOvVaw0Z8BM2aYD37HcLpMKvHQvE
Or just type anode or plate follower amplifier in the advanced search function.Now your choice of valve has expanded and valve datasheets are you friend.
All the best in your valve ventures.
Thanks. I could indeed look at SRPP or other kind of input stage using 4P1L, however for simplicity I'm going to optimise the op-amp stage. Also it's new stuff for me so a healthy bit of learning.
I could toss it back to you - why don't you try a x3 gain op-amp input stage?
I could toss it back to you - why don't you try a x3 gain op-amp input stage?
Good news - my new dual supply op-amp setup is now working. Did some fault finding, installed protection diodes, earthed the centre point of the 20-0-20 toroid. No hum, music coming out now. Now I can start optimising the setup.
I have a few different op-amps to play with -
NE5532
LM4562
OPA2134
LM6172
OPA2228
also NE5534, interesting and will be a future project.
I also have two setups - the new dual supply stage and my existing single supply chi-fi board which sounds pretty good in fact. All SMD except the socketed op-amp. Right now listening to a LM4562 in the single supply board. Better than the NE5532, particularly in the treble, and more detail. It's pretty nice. The idea of an initial op-amp stage is clearly realistic in my tube setup. Now I have good sound and enough gain and just 2 DHT tube stages. Exactly what I set out to do.
Listening to my usual audio demo list and very pleased with the sound. If it gets better than this I'll be delighted. If any of you guys want to try it, here's the single supply board I'm listening to right now with a LM4562 in it. Unbelievably cheap for such a good sound.
NE5532 Dynamic Microphone Stereo Preamp Amplifier Board DIY DC9-24V AC8-16V | eBay
I have a few different op-amps to play with -
NE5532
LM4562
OPA2134
LM6172
OPA2228
also NE5534, interesting and will be a future project.
I also have two setups - the new dual supply stage and my existing single supply chi-fi board which sounds pretty good in fact. All SMD except the socketed op-amp. Right now listening to a LM4562 in the single supply board. Better than the NE5532, particularly in the treble, and more detail. It's pretty nice. The idea of an initial op-amp stage is clearly realistic in my tube setup. Now I have good sound and enough gain and just 2 DHT tube stages. Exactly what I set out to do.
Listening to my usual audio demo list and very pleased with the sound. If it gets better than this I'll be delighted. If any of you guys want to try it, here's the single supply board I'm listening to right now with a LM4562 in it. Unbelievably cheap for such a good sound.
NE5532 Dynamic Microphone Stereo Preamp Amplifier Board DIY DC9-24V AC8-16V | eBay
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please stop this crazyness !
here is a decent discret jfet line stage 😀
HIFI Stereo Class A FET Preamplifier Board / kit base on JC-2 Preamp circuit | eBay
here is a decent discret jfet line stage 😀
HIFI Stereo Class A FET Preamplifier Board / kit base on JC-2 Preamp circuit | eBay
Aha! Now we move on to JFETs. I'm totally sold on a solid state pre-amp stage now.
Do you think this will out-perform my LM4562 op-amp stage? Tell me more.
Do you think this will out-perform my LM4562 op-amp stage? Tell me more.
What's the amplification factor of this board? I need something quick and dirty to boost the output of the Bluetooth receiver module for one of my builds 🙂
Op-amp testing starts in my NE5532 chi-fi single supply board....
NE5532 - baseline. OK, nothing special but generally good.
OPA2228 - improvement on NE5532 but not as good as others tried. Smooth, low distortion, good vocal timbre, lacks ultra transparency. Musical. A bit down in extreme treble. Less detailed and airy than LM4562, less inner detail in orchestral textures, can sound a bit duller, not so involving, less punch.
LM4562
Very detailed, airy highs, transparent. Strings can be a little thin. Plenty of punch in the bass. Overall sound is similar to the OPA2134 and LM6172, which is to say better than the OPA2228
OPA2134
FET input. Very neutral, does everything well, smooth, good voices, even frequency response, good tone. Overall very nice. Versus OPA2228, better in all ways. Versus LM4562 smoother, more balanced FR, less extreme highs and air, but highs nicely there. Could live with this one.
LM6172
Very similar sound to OPA2134 plus just a tiny bit more transparent. Very neutral, does everything well, smooth, good voices, even frequency response, good tone. Versus LM4562 again smoother, more balanced FR, less extreme highs and air, but highs nicely there. High slew rate and would need to be checked for oscillation (I don't have the means). If correctly implemented this could be very good, but more fussy than OPA2134.
Overall it would need more listening to decide between LM4562, OPA2134 and LM6172. I just used 8 pin DIP devices here, and by using a SOIC adapter some of the latest op-amps may exceed the ones tried here. These are all duals, no singles tried yet. For further op-amp shootouts it's over to the chip amp forum. I'm very encouraged by what I'm hearing. Neutral, transparent sound with good instrumental tone.
NE5532 - baseline. OK, nothing special but generally good.
OPA2228 - improvement on NE5532 but not as good as others tried. Smooth, low distortion, good vocal timbre, lacks ultra transparency. Musical. A bit down in extreme treble. Less detailed and airy than LM4562, less inner detail in orchestral textures, can sound a bit duller, not so involving, less punch.
LM4562
Very detailed, airy highs, transparent. Strings can be a little thin. Plenty of punch in the bass. Overall sound is similar to the OPA2134 and LM6172, which is to say better than the OPA2228
OPA2134
FET input. Very neutral, does everything well, smooth, good voices, even frequency response, good tone. Overall very nice. Versus OPA2228, better in all ways. Versus LM4562 smoother, more balanced FR, less extreme highs and air, but highs nicely there. Could live with this one.
LM6172
Very similar sound to OPA2134 plus just a tiny bit more transparent. Very neutral, does everything well, smooth, good voices, even frequency response, good tone. Versus LM4562 again smoother, more balanced FR, less extreme highs and air, but highs nicely there. High slew rate and would need to be checked for oscillation (I don't have the means). If correctly implemented this could be very good, but more fussy than OPA2134.
Overall it would need more listening to decide between LM4562, OPA2134 and LM6172. I just used 8 pin DIP devices here, and by using a SOIC adapter some of the latest op-amps may exceed the ones tried here. These are all duals, no singles tried yet. For further op-amp shootouts it's over to the chip amp forum. I'm very encouraged by what I'm hearing. Neutral, transparent sound with good instrumental tone.
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One month after starting this thread I'm now completely sold on using a solid state input stage to a 2-stage all DHT amplifier. The level of transparency and detail surpasses everything I've experienced with other topologies.
As many have pointed out, the signal that comes into your amplification has probably gone through innumerable solid state devices already, including everything in your DAC, so all you are doing is "extending" the solid state devices a little further into your amplifier. Obviously you could go all the say and eliminate the tubes, but I still believe in DHTs for their tonal qualities. The only thing that comes close that I've heard in my system is a Class A SE FET amp, things like Passlabs are producing. I admit that's pretty close, but optimum devices aren't plentiful or NLA and heatsinks are massive.
If I had more knowledge of solid state I'd use discreet devices. Anyway, the advance for me was hearing what op-amps can do. I've been pretty amazed. I wish I'd started using them years ago.
Using a solid state first stage in an amplifier has been done, of course, but it doesn't seem to have become popular. I'm not sure why this is the case. Except maybe it requires builders who are equally at home in both tubes and solid state.
I don't think op-amps could drive a 300b because of the voltage swing necessary, but I'm starting to wonder about directly driving something like a PSE 4P1L output stage where the bias can be 16-18v. Or a 6V6 or EL84 at -15v bias
Antique Radio Forums • View topic - Using TI's LME49724 Op-Amp For A Hybrid Audio Amplifier
Sofrito Preamplifier – wauwatosa tube factory
As many have pointed out, the signal that comes into your amplification has probably gone through innumerable solid state devices already, including everything in your DAC, so all you are doing is "extending" the solid state devices a little further into your amplifier. Obviously you could go all the say and eliminate the tubes, but I still believe in DHTs for their tonal qualities. The only thing that comes close that I've heard in my system is a Class A SE FET amp, things like Passlabs are producing. I admit that's pretty close, but optimum devices aren't plentiful or NLA and heatsinks are massive.
If I had more knowledge of solid state I'd use discreet devices. Anyway, the advance for me was hearing what op-amps can do. I've been pretty amazed. I wish I'd started using them years ago.
Using a solid state first stage in an amplifier has been done, of course, but it doesn't seem to have become popular. I'm not sure why this is the case. Except maybe it requires builders who are equally at home in both tubes and solid state.
I don't think op-amps could drive a 300b because of the voltage swing necessary, but I'm starting to wonder about directly driving something like a PSE 4P1L output stage where the bias can be 16-18v. Or a 6V6 or EL84 at -15v bias
Antique Radio Forums • View topic - Using TI's LME49724 Op-Amp For A Hybrid Audio Amplifier
Sofrito Preamplifier – wauwatosa tube factory
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Hi Andy
I think you should try a folded Cascode to have a single stage to drive the 300B. You can ask Rod Coleman for a board and use the 4P1L in triode
Also if you want to experiment with SMD op amps I could solder for you some op amps of your choice in DIL adaptors. Just get some recommendations on SMD ones as I’m not that familiarised and surely there are a lot of experienced people here who can suggest good ones
Cheers
Ale
I think you should try a folded Cascode to have a single stage to drive the 300B. You can ask Rod Coleman for a board and use the 4P1L in triode
Also if you want to experiment with SMD op amps I could solder for you some op amps of your choice in DIL adaptors. Just get some recommendations on SMD ones as I’m not that familiarised and surely there are a lot of experienced people here who can suggest good ones
Cheers
Ale
Hi Ale! I did indeed think of a cascode. It's certainly a possibility.
But I'm getting fired up about op-amps for the first time ever - it's all new to me. A learning experience. After at least 12 years of building with tubes it's a good exercise in neuroplasticity, which as we know is very good for the brain!
I may well take up your offer of turning SOICs into DIPs. First I need to try out some circuits with the DIP8s I have. I haven't started on single op-amps yet. Maybe over this weekend. When the circuits are ready I can think of some SOIC alternatives. Still reading up on the theory and watching YT videos. Something to do in lockdown.
But I'm getting fired up about op-amps for the first time ever - it's all new to me. A learning experience. After at least 12 years of building with tubes it's a good exercise in neuroplasticity, which as we know is very good for the brain!
I may well take up your offer of turning SOICs into DIPs. First I need to try out some circuits with the DIP8s I have. I haven't started on single op-amps yet. Maybe over this weekend. When the circuits are ready I can think of some SOIC alternatives. Still reading up on the theory and watching YT videos. Something to do in lockdown.
While Andy is all fired up about solid state first input stages, I'd like to ask you opinion about power supply solid state rectifiers vs. tube rectifiers. Please share your thoughts on using a high quality Cree/Schottky/Hexfred bridge rectifier in lieu of a tube rectifier. In the end, sound is the thing that matters the most to me. Ease of use and reliability is secondary. Thoughts?
I think by that you mean a totally solid state amplifier! I haven't yet heard anything that sounds better than DHTs, but as I said, class A SE SIT amps are contenders. What did you have in mind?