The Hypex input probably is very low impedance, perhaps 5k ohms, or perhaps 10k ohms. I doubt it will be higher (although I could be wrong).
It might be a good idea to use a 10k ohm volume pot, and use your 12AU7 cathode follower either after the input switch/volume control (to present an easy-to-drive high impedance load there) or after the input switch but before the volume control (to drive the volume control from a low impedance with some current to drive the vol ctrl and interconnect cable capacitance).
Swap the buffer in.
Swap the buffer out.
Move the buffer around.
Figure out if it makes a difference in the sound you get.
Experiment.
Have fun with it.
A cathode follower has about 0.95x gain.
As said, it is better to focus on what is needed and then pick out the necessary stuff looking at their specific known properties (not assumptions) and only then if it is executed with opamps, tubes, transformers and what not. If this sequence would be understood correctly we would not be looking at the 2858934758th post with the same issue/subject.
BTW the Merrill Audio Thor has a gain of 26 dB and input impedance is 50 kOhm so a very easy load. I think we can conclude that the Yaqin preamp was chosen wrongly. The focus was on "tube" and the results are "suboptimal".
BTW the Merrill Audio Thor has a gain of 26 dB and input impedance is 50 kOhm so a very easy load. I think we can conclude that the Yaqin preamp was chosen wrongly. The focus was on "tube" and the results are "suboptimal".
Very true.
As I keep posting, "This subject keeps coming up, over and over again...."
And then, silly me... I try to explain things... again.
Then there's this, which is slightly different:
https://www.diyaudio.com/community/threads/why-does-no-one-use-the-anode-follower.359355/
As I keep posting, "This subject keeps coming up, over and over again...."
And then, silly me... I try to explain things... again.
Then there's this, which is slightly different:
https://www.diyaudio.com/community/threads/why-does-no-one-use-the-anode-follower.359355/
A few RCA connectors, a box, a source selector switch followed by a good 10 kOhm logarithmic stereo potentiometer could very well be your perfect preamp. You do not need any extra gain at all. If you like to live dangerously you could try out a source (or DAC) with built in volume control connected directly to the power amplifier(s). Make sure volume is set to 0 at power on then test, check, listen. Tell us if you liked it.
If there MUST be a tube in it then look at low gain devices which are not standard in the tube world.
If there MUST be a tube in it then look at low gain devices which are not standard in the tube world.
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Well, if it wasn't clear, this is a commercial product that I was hoping to just tweak a bit, not fully redesign. As suggested earlier in the thread, I'm going to try swapping the 2, 12ax7 tubes for some 12au7 tubes, and see how that works out. It seems the least invasive, and doable. And if that isn't satisfactory, I'll probably put this up for sale and look into something with the gain structure I need...
2023-04-04_05-47-24 by Barry, on Flickr
Category "just doing something" is also a habit in the tube world. You now have the knowledge and know what you need. Random actions won't give you the desired results. You could try out the passive mode just to....................................
4 mini crocodile clips and 2 pieces of wire.
4 mini crocodile clips and 2 pieces of wire.
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With 40k or 50k input impedance and digital sources with Zout that's no more than 1k ohms, there is no need for a buffer unless you're driving 25 feet or more of interconnect cables.
In that original preamp, there's no input coupling cap to block DC, so there's no easy way to redesign it to be just a cathode follower.
If you really just want to do something that involves tubes, perhaps it's time to build something. A simple cathode follower in a box is a very simple project, and has a very good chance of working on the first try.
In that original preamp, there's no input coupling cap to block DC, so there's no easy way to redesign it to be just a cathode follower.
If you really just want to do something that involves tubes, perhaps it's time to build something. A simple cathode follower in a box is a very simple project, and has a very good chance of working on the first try.
What gain structure do you need? No gain? The solution is simple and readily available.
Maybe this: https://www.schiit.com/products/sys
If you want to go high end with it, there's this: https://intactaudio.com/atten.html (which will drive Jean-Paul nuts! lol)
While infuriating Jean-Paul would be fun, that's out of my budget, though this holds potential...
https://www.schiit.com/products/saga-2
https://www.schiit.com/products/saga-2
That is probably a device that will bring what you want. Making well thought out choices will never infuriate any sane person I guess. It sure checks many boxes and the volume control is way better than the usual. It can be used actively and passively which is nice. I just hope Schiit designed it with muting at power on/off.
With solid state sources and solid state amplifiers this Saga+ would be one of my choices (FWIW). The price is low for a western build device. One can not build that DIY for that price with relay based volume control, remote control and also a nice looking casing.
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Well, my only advice for what it's worth is to remind you to use your ears as well as your logic around a choice of what works for you in your system.Well, if it wasn't clear, this is a commercial product that I was hoping to just tweak a bit, not fully redesign. As suggested earlier in the thread, I'm going to try swapping the 2, 12ax7 tubes for some 12au7 tubes, and see how that works out. It seems the least invasive, and doable. And if that isn't satisfactory, I'll probably put this up for sale and look into something with the gain structure I need...
2023-04-04_05-47-24 by Barry, on Flickr
I have many cases of measurements, and logic (e.g. in room measured response of subwoofers to reduce room modes) and (low gain, passive and noise free feedback setting) that all SHOULD sound and work better, BUT simply don't.
The most expensive, and sensitive piece of test equipment you have are your ears (even down to measuring hum for example in my experience) so don't let too much logic spoil your fun.
No, I didn't think the Saga+ would infuriate you, it was the $1,000 volume control that rongon had suggested would infuriate you, which I can't really afford, that would have infuriated you 😉
Yeah we agree listen and logic
"remind you to use your ears as well as your logic around a choice of what works for you "
My point was that the final decision should come from your ears, and of course the journey to get there by guided by good logic. BUT relying on logic will not in my experience result in the most enjoyable sound.
Hence my earlier post about my comparable experience with a high gain preamp (which I am now definitely keeping having tried a lot of alternatives!)
Does Barry, like the sound but dislike the inconvenience of high gain?
I'm absolutely more in the listen camp, but there are some basics that one should be aware of when making decisions. I'm not fully against the inconvenience of the high-gain pre, but the buzzing/spitting noises that seem to come with that gain are a bit off-putting. The recordings below don't seem to fully capture the noise, there is the buzz that waxes and wanes a bit and also a pfft/spit type noise made too. These noises can be heard at the listening position, about 10 feet (3 meters) away from the speakers, with no signal present, or during quiet passages when program material is being played. The volume knob doesn't have a big impact on the intensity of this background noise.
Phone recording of noise 1
Phone recording of noise 2
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Barry NJ,
I believe we might have solved your preamp problems quicker, if you originally said in post # 1:
The problem is "the buzzing/spitting noises" (Your Post # 78).
I can not remember if you ever said that in a Post between # 2 and # 77.
My 77 year old mind's memory is not real good.
Do not assume that the cause of "the buzzing/spitting noises" is only caused by high gain.
Might be true, might not be true. Ground loops, poor design, and a few other causes.
Assuming that in your case: high gain is the only cause of "the buzzing/spitting noises", Then . . .
Changing from a high gain 12AX7 SRPP input stage, to a 12AU7 SRPP medium/low gain input stage is simple, even if your circuit is all on a PCB.
Changing two resistors in the input stage, and changing one in the B+ to the input stage should do the trick.
You want to run a little more current in a 12AU7 than in a 12AX7. If your preamp is a quality design, it can handle the slight extra B+ current.
And, it is easily and completely reversible, if you later need to sell the preamp.
Happy modifying!
If you are unwilling to "ruin" that commercial preamp by doing as simple a modification as that, then sell that preamp.
Then purchase one that is more suited to your system.
I hope you solve your problem soon, and get back to enjoyable listening!
Just my opinions and experience.
Your Mileage May Vary.
I believe we might have solved your preamp problems quicker, if you originally said in post # 1:
The problem is "the buzzing/spitting noises" (Your Post # 78).
I can not remember if you ever said that in a Post between # 2 and # 77.
My 77 year old mind's memory is not real good.
Do not assume that the cause of "the buzzing/spitting noises" is only caused by high gain.
Might be true, might not be true. Ground loops, poor design, and a few other causes.
Assuming that in your case: high gain is the only cause of "the buzzing/spitting noises", Then . . .
Changing from a high gain 12AX7 SRPP input stage, to a 12AU7 SRPP medium/low gain input stage is simple, even if your circuit is all on a PCB.
Changing two resistors in the input stage, and changing one in the B+ to the input stage should do the trick.
You want to run a little more current in a 12AU7 than in a 12AX7. If your preamp is a quality design, it can handle the slight extra B+ current.
And, it is easily and completely reversible, if you later need to sell the preamp.
Happy modifying!
If you are unwilling to "ruin" that commercial preamp by doing as simple a modification as that, then sell that preamp.
Then purchase one that is more suited to your system.
I hope you solve your problem soon, and get back to enjoyable listening!
Just my opinions and experience.
Your Mileage May Vary.
Yeah, I would not accept pfft/spit noises or any hum that I can hear from the listening position. I got mine to a level that was just about perceived on a quiet evening from stood in between the speakers and not really able to hear it at all from the listening position 3.5m away. During the day due to higher background noise you would swear it was completely silent.
I would have loved the excuse for a new amplifier when I first had the amp working and the hum was at an unacceptable level. I listened to a Tron 7, and a Luxman CL-38 and had them at home for a couple of weeks, both were silent, both felt lovely to use, both sounded good, BUT that damn high gain humming vintage lump just sounded more alive, more tangible, more musical - I just preferred it. So I set to work minimising the hum as best as I could. It's now at a level that you would think me obsessive to keep trying to improve.
I would have loved the excuse for a new amplifier when I first had the amp working and the hum was at an unacceptable level. I listened to a Tron 7, and a Luxman CL-38 and had them at home for a couple of weeks, both were silent, both felt lovely to use, both sounded good, BUT that damn high gain humming vintage lump just sounded more alive, more tangible, more musical - I just preferred it. So I set to work minimising the hum as best as I could. It's now at a level that you would think me obsessive to keep trying to improve.