PJ MIAOLIA SA-1000 Vacuum Tube Preamp with GE JAN 5670 Tubes
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- Опубликовано: 18 окт 2024
- I saw a number of videos on RUclips about this little voltage amplifier with tone controls and how it was claimed that the GE JAN 5670 tubes improved it. Thought I should document what I find comparing the original 6H3N with the 5670
I always wait for your videos. You have taught all of us who watch you so much. Thank you for that and I look forward to the next one. Be safe out there :)
I just want to say that I'm happy, so happy to see you and hear your voice again especially in three consecutive videos. I love your take on things and your positive outlook. Thank you so much what you do. It really does inspire some of us out there to get back on the bench and keep experimenting
I recently fell in love with the GE 5670, sounds incredible, is super rugged and reliable and it’s a fraction of the cost of more popular dual triodes….
I knew nothing of them until this event and remembered I might have some in the military odd tube box. I like them also and the basing diagram is a beautiful physical layout for RF work. Their characteristic curves are nice and straight and should make a great audio tube. I may have to build something with them also. Thanks for your comments.
I have this tube pre-amp and am impressed with the overall sound quality. I took your advice and turned the volume up all the way up from ten o'clock and I must say that the SQ improved some. Just make sure your bass setting is no more than 12 o'clock or it might distort on bass heavy tracks. I do plan on trying out the GE jan 5670 tubes sometime later. I appreciate the info you've provided in this video.
I was just looking a this pre-amp about a week ago under the name of "xuefu Audiophile Tube Preamp". I think you sold me.... I'll pursue the 5670's as well... Nice Job. Seems like you've been on a Roll!!!
Back in 2012, there was another pre-amp buffer circuit based on 6N3 tubes running at 170V. It was a Matisse Fantasy circuit and you could swap JAN 5670 tubes. This newer model looks like it has a few more bells and whistles. It is likely the tube portion of the schematic is similar. Very cool to see your experiments!
Gotta concur with the other commenters that It's good to see videos, especially audio videos, from you again. I've never thought to do harmonic profiles on different brands of the same tube. I'll have to remedy that soon! I do know from various listening tests on my CJ amplifiers that NOS British made GEC KT88's sound significantly sweeter than any current production tubes. I'd love to know what they did differently and why it can't be or isn't being duplicated. Metallurgy? Dunno.
It is difficult to measure the "sound" of a tube and THD is not the whole answer, that is for sure. I have believed for a long time that the nuances in harmonic profiles is the best answer to how a tube sounds but every slight differences in harmonic profile are going to sound very different so, maybe this is the simplest answer so far and especially with the inexpensive FFT software available for PC. Thanks for your comments.
Howdy from the East Side:)
I have looked at that preamp before. Was wondering how well it worked. I'm in the process of building a tube preamp using some of the boards available from China. Using the 3 - 12ax7 C22 McIntosh clone and the 12ax7 Baxandall tone control board. Going to add an RIAA phono preamp on the one input. Going to use a 4 input relay selector. Been wanting to try this for a while. Also have a couple nice VU meters a may put on it. Commented on your video the other day. Hope you are doing well. Thanks for the videos.
I never got into preamps except for maybe a single channel for a special purpose. I have a Mac C-20 and it is the best preamp I have ever had. There is something special about those old preamps that just can't beat. I remember my uncle had the Fisher 50-C and 70-A preamp and amp. That was the best sounding system my ears ever heard - that was back when I was 13 years old. I have the 70-A but could never find the 50-C that I could afford. Building the clone Mac C-22 sounds like a nice project. You got me interested. I will be 75 soon and life goes on and doesn't stop here so there is always something to look forward to.
Hey good to see you in another video. I used to go by bluestoneamps until I changed my profile to the doggo. I have a weird question for you, if I ever get down to El Paso would you be willing to meet for coffee or host a tour of your setup? You share an immeasurable wealth of information online, it would be great to chat with you in person. Cheers, great to see you online again.
Sure, sounds good. Let me know ahead of time to make sure I am here. I still have my astronomy hobby and have been getting back into that lately and like to go off to Aguirre Springs in NM.
@ElPasoTubeAmps That's cool. I've been just recently thinking about getting into astronomy a little more. Been watching the meteor showers lately? I have a cheap telescope which I've had since the 80s. Bought it for my son at the time and he wasn't really interested. More into teenage ninja turtles. Been thinking about getting a better one. Getting up in age we need more hobbies to fill the time. Do a little metal detecting also.
@@kgsalvage6306 I have been back into my astronomy a good bit lately. My big telescope is just, too big, for me to haul around anymore but I picked up an iOptron tracker and use my camera lens when I go to a federal park just up the road from me called, Aguirre Springs, NM. I am the only real geek in my family. My son and grandsons are not interested in hardly anything I do but my passion for this stuff more than make up for four people. 🙂 Yes, it is good for us to get out. It is an hour drive to the park but therapeutic for me to go there. Good to hear you like astronomy. I have an old metal detector. I bet I throw it in the van next trip to the park. Thanks for the thought.
I was just curious. How do they get the plate voltage in these and what is it? The tubes do not have an operating voltage at 12v.
That is a really good question. I didn't take the time or think much about measuring it. I will see if I can get around to making those measurements
and put a link to it as an unlisted video and show what I found. I know the filaments are in series and the tubes have to warm up before there is any
output so I "assumed" the tubes are actually an active component in the audio chain but without proof, the whole thing could be a spoof. Thanks
for your comments.
@ElPasoTubeAmps The only way I can think of is if there's a small boost converter in the circuit. It would need an inductor, switcher, and control IC. Only needs to handle maybe 20ma. I would think that it would need probably 50v @ 10ma per tube.
@@kgsalvage6306 That makes sense and probably is what develops the HV but I didn't pay attention when I had it open. I will try to check it out tonight. 🙂
How hard are you driving that preamp and what is the impedance of the load it's looking into? Because those Distortion figures seem to be three orders of magnitude higher than normal for a preamplifier. If the output is being pushed to plus 40 dbm I can see maybe that would be the reason.
Agree that a preamp should be ultra clean. My Mac preamps are almost as clean as the SG505. In the video I am driving it at -10 dBm (0.244 V across 600 ohm) for 2.45 V output - seems reasonable for full output for line level. If I lower it to -20 dBm input, that gives me 782 mV out and THD drops to 0.57%. All this is at 2 KHz. It is disappointing for a high-end device but serves it purpose in other ways.
@@ElPasoTubeAmpsTalking about levels, when you in earlier video compared EL34 tubes at high output power and did some FFT analysis using FFT software in computer, what audio interface did you use, and if, how did you attenuate the output signal of a amp which is presumably giving 20 volts RMS, 56 Vpp if load is 8 ohms? Or was the load only 4 ohms so that output level was smaller?
@@jutukka I don't know which video you might be referencing but, yes, the output of most any amplifier has to be attenuated to at least line level voltages to put into the outboard USB sound units. In my break-out box mounted on the wall where I put a signal in and distribuite it to all the equipment, I have two ports that are attenuated 10x and frequency compensated. I also have another, that was on the bench next to the PC in these last videos that is an adjustable and compensated attenuator. Devices like the Tektronix and HP can handle pretty high levels of voltage without overload or harm. Even just a 10K pot parallel with the 8 ohm load will allow you to attenuate the voltage down to a level that the PC and equipment can handle. Hope this helps.
@@ElPasoTubeAmps Well, that possible frq compensation was what I was thinking of. However, the output impedances of those amps are so low that the need of compensation is supposedly quite minimal and simple voltage divider gives pretty satisfactory results unless very long cables etc. are used. And I just today compared some virtual distortion effects and virtual tube amps with virtual FFT analyzer, when using VST plug-ins in DAW, and I did not think about compensations at all because those virtual devices seemed to be connected to virtual FFT analyzer using virtual cables which had no inductance and capacitance. 😁