Hi,
I have some questions...
When I built my Hybrid GC, I noticed a faint hum when I put my ears near my speakers. Is this normal?
What would be the advantage/s to make it worth regulating the tube supply? Less noise? Better sound? Perhaps a schematic to start with will be helpful or should I just use LM317/337?
Would slowly turning up the tube supply eliminate the loud thump during turn on? (The trafo for the tube and GC share the same switch).
Best Regards,
JojoD
I have some questions...
When I built my Hybrid GC, I noticed a faint hum when I put my ears near my speakers. Is this normal?
What would be the advantage/s to make it worth regulating the tube supply? Less noise? Better sound? Perhaps a schematic to start with will be helpful or should I just use LM317/337?
Would slowly turning up the tube supply eliminate the loud thump during turn on? (The trafo for the tube and GC share the same switch).
Best Regards,
JojoD
When I built my first Hybrid GC I connected small, cheap speakers. If something went wrong I wouldn't regret. Comparing to my others not tube buffered Gainclones that one played really well. To my taste the best. I gave it a few hours of work at moderate volume level to make sure everything was OK. There was no hum no hiss. After test finally real loudspeakers were connected and I did notice the faint hum and a bit of hiss. I don't know what could cause that. I'm sure the speaker cable has a lot of capacitance (Kimber biwire 4TC/8TC) and speakers are more sensitive. I also noticed thump when using separate switch for the LM3875's, tube stage is permanently on. In my design I skipped 0R22 resistor at the output of the amp. Wondering if that would improve things a little.
🙄
Thanks
🙄
Thanks
"I also noticed thump when using separate switch for the LM3875's"
Do you mean turn on thump ? If yes, I found one simple solution. Basically connect a switch after the coupling cap (3.3 uf) to ground. Each time before turning on the power chips, momentarily toggle the switch to discharge the coupling cap.
regards,
will.
Do you mean turn on thump ? If yes, I found one simple solution. Basically connect a switch after the coupling cap (3.3 uf) to ground. Each time before turning on the power chips, momentarily toggle the switch to discharge the coupling cap.
regards,
will.
Will
Turn on and turn off thump. They are different. Turn on makes speaker cones move. I almost don't hear it. Turn off thump makes noticable pop. Do you suggest to put grounding switch after 3.3uF signal cap coming from tube stage ?
JoJod818
Can you explain or point me to where I could find information about capacitance multiplier
Is 0R22 output resistor could help? A little ?
Could hiss be a result of high gain ?
Thanks
Turn on and turn off thump. They are different. Turn on makes speaker cones move. I almost don't hear it. Turn off thump makes noticable pop. Do you suggest to put grounding switch after 3.3uF signal cap coming from tube stage ?
JoJod818
Can you explain or point me to where I could find information about capacitance multiplier
Is 0R22 output resistor could help? A little ?
Could hiss be a result of high gain ?
Thanks
I don't know the exact url but you can do a search at google.
I use a relay to switch my speakers after a delay.
I use a relay to switch my speakers after a delay.
Hi
I will keep bothering you for some time untill all my questions are aswered.
Thanks to you guys I went through on and off switching noise quite nicely. No more pops and thumps.
I'm really happy with the sound my amp reproduces. Particularly I love midrange which gives beautiful vocals.
. There are no more laid back and are more open and natural. Little warm like and sweet. Is this tube? Connection between low and high range is seemless. However I have tiny problem with low end bass and highs. I used 1n6 cap in LPF so that could be the problem. Going a bit lower to or than recommended < 1n3 will add more "air" which I need. I get feeling of grain, sand. Like there is no final touch. I like fuller highs with present cap and I'm afraid to loose it. I need to experiment. The bass is another story. It's well controlled and faster than with other Gainclones. Correct me if I'm wrong but according to me this is the result of not going low enough. Could it be that in that design I should have used bigger cap reservoir by the LM3875 or it's just the way tube works. What if I change the 3u3 signal cap? Is it to be a bigger or smaller value for lower "cut" point in frequency range? Yeap I'm not sure even abut that. 
When I "fix" abovementioned things I will definitely implement second tube for better soundstage. Currently using only one per 2 channels.
Well, conclusion is one. I'm the beginner and so far this is the best piece of audio I've ever built from the scratch. So if it stays the way it plays now anyway I'll be one happy man. 😀
I will keep bothering you for some time untill all my questions are aswered.
Thanks to you guys I went through on and off switching noise quite nicely. No more pops and thumps.
I'm really happy with the sound my amp reproduces. Particularly I love midrange which gives beautiful vocals.
. There are no more laid back and are more open and natural. Little warm like and sweet. Is this tube? Connection between low and high range is seemless. However I have tiny problem with low end bass and highs. I used 1n6 cap in LPF so that could be the problem. Going a bit lower to or than recommended < 1n3 will add more "air" which I need. I get feeling of grain, sand. Like there is no final touch. I like fuller highs with present cap and I'm afraid to loose it. I need to experiment. The bass is another story. It's well controlled and faster than with other Gainclones. Correct me if I'm wrong but according to me this is the result of not going low enough. Could it be that in that design I should have used bigger cap reservoir by the LM3875 or it's just the way tube works. What if I change the 3u3 signal cap? Is it to be a bigger or smaller value for lower "cut" point in frequency range? Yeap I'm not sure even abut that. When I "fix" abovementioned things I will definitely implement second tube for better soundstage. Currently using only one per 2 channels.
Well, conclusion is one. I'm the beginner and so far this is the best piece of audio I've ever built from the scratch. So if it stays the way it plays now anyway I'll be one happy man. 😀
Hi,
Bigger...Note that too big a cap will also slow down transient response giving a subjectively "slower" sound.
Better forget that notion....
Cheers,😉
Bigger...Note that too big a cap will also slow down transient response giving a subjectively "slower" sound.
Better forget that notion....
Cheers,😉
Hi,
I agree with Frank, no need to use individual tubes for this project. The version I built with just one tube for two channels sounds great!
My only mission now is how to reduce further that hum. Would a capacitance multiplier or a LM317/337 for the tube psu help on this hum reduction?
Cheers!
JojoD
I agree with Frank, no need to use individual tubes for this project. The version I built with just one tube for two channels sounds great!
My only mission now is how to reduce further that hum. Would a capacitance multiplier or a LM317/337 for the tube psu help on this hum reduction?
Cheers!
JojoD
Hi,
Thomashek,
As I read your post prior to having my cup of black poison this morning, I didn't quite catch the idea....
If you want better channel separation form the tube stage, just ground pin # 9 and keep signal carrying wires apart.
Jojo (sounds like a jacques brel song),
Isn't the heater supply regulated yet?If it is, it should be totally hum free.
Cheers,😉
Thomashek,
As I read your post prior to having my cup of black poison this morning, I didn't quite catch the idea....
If you want better channel separation form the tube stage, just ground pin # 9 and keep signal carrying wires apart.
Jojo (sounds like a jacques brel song),
Isn't the heater supply regulated yet?If it is, it should be totally hum free.
Cheers,😉
Frank,
Your right on target! I did ground pin 9 and kept those signal wires apart. I guess I did the right thing there! 😀
Now for the hum, the heaters are already regulated. I noticed that when I disconnect the tube from it's socket and power up the gc only, the hum is still there???
Star grounding maybe? Well, I am not annoyed with the hum siince I have to put my ears very near the speakers to hear hum. If others find this behaviour then I rest my case.
JojoD
Your right on target! I did ground pin 9 and kept those signal wires apart. I guess I did the right thing there! 😀
Now for the hum, the heaters are already regulated. I noticed that when I disconnect the tube from it's socket and power up the gc only, the hum is still there???
Star grounding maybe? Well, I am not annoyed with the hum siince I have to put my ears very near the speakers to hear hum. If others find this behaviour then I rest my case.
JojoD
Hi,
This always difficult to solve from a far, still you could try a number of things out:
Disconnect anything on the RCA inputs and short it with a cheater plug or some clip on leads, see if the hum is still present.
Try rearranging some of the internal wiring, the heaters do carry about 360 mA.
Maybe you grounded the ground pin of the heater regulator and the negative side of the heater as well?
It could be induced hum from nearby powerxformer? Try to turn it untill the hum disappears.
Ask a knowledgeable friend to have a look, maybe it's obvious to him...
Cheers,😉
This always difficult to solve from a far, still you could try a number of things out:
Disconnect anything on the RCA inputs and short it with a cheater plug or some clip on leads, see if the hum is still present.
Try rearranging some of the internal wiring, the heaters do carry about 360 mA.
Maybe you grounded the ground pin of the heater regulator and the negative side of the heater as well?
It could be induced hum from nearby powerxformer? Try to turn it untill the hum disappears.
Ask a knowledgeable friend to have a look, maybe it's obvious to him...
Cheers,😉
fdegrove
Thanks for your reply concerning second tube. I did ground 9th pin of tube so can't tell what would be the difference without that. Don't want to mess with circuit only to hear that it was OK before. After all idea of adding second tube for better soundstage was taken from the forum. Explanation seems reasonable. Don't remember exactly but it was about cross-signal etc.
In my project I used 2 transformers (one 200VA per channel) providing power to LM3875 so here it helps. You can tell difference at once between one and two transformers if we talk about sounstage. I always try to keep everything in dual mono so in one tube design I just cannot "see" dual mono topology. Well it could be that this is lack of knowledge and I need learn more about tubes. On the other hand if I look at many tube amp schematics they make me feel I'm right.
Regarding better bass. I still need clear answer to my question. Does the tube somehow limit low frequency ? In that case is it worth to put bigger signal cap (3u3 now) to achieve better- lower bas. I don't mind the present but without the tube buffer the bass is lower.
DIY has that advantage that you can experiment and built to suit your needs. I give it a try and will keep you posted.
Thanks for your reply concerning second tube. I did ground 9th pin of tube so can't tell what would be the difference without that. Don't want to mess with circuit only to hear that it was OK before. After all idea of adding second tube for better soundstage was taken from the forum. Explanation seems reasonable. Don't remember exactly but it was about cross-signal etc.
In my project I used 2 transformers (one 200VA per channel) providing power to LM3875 so here it helps. You can tell difference at once between one and two transformers if we talk about sounstage. I always try to keep everything in dual mono so in one tube design I just cannot "see" dual mono topology. Well it could be that this is lack of knowledge and I need learn more about tubes. On the other hand if I look at many tube amp schematics they make me feel I'm right.
Regarding better bass. I still need clear answer to my question. Does the tube somehow limit low frequency ? In that case is it worth to put bigger signal cap (3u3 now) to achieve better- lower bas. I don't mind the present but without the tube buffer the bass is lower.
DIY has that advantage that you can experiment and built to suit your needs. I give it a try and will keep you posted.
Hi,
With careful layout AND the shield (pin #9 on the socket) grounded there shouldn't be any interchannel crosstalk worth mentioning or measuring.
Sure, you avoided interwinding capacitive coupling.
From my experience, it's not just the fact that you have 2 separate xformers, the way the xformers are made is also important.
For audio projects I usually have mine custom made, always of the EI or C-core type, never toroidals as they're just too wide in bandwidth to stop RF from entering the audio circuit.
There's more you can do but this gives you an idea already....
So do I and for really sensitive circuits like a MC phono preamp I even push it so far as to use a dedicated regulated PS per amplification stage, separate left-right volume controls etc...
Going dual mono for GC is not a bad idea if you want to carry the extra cost involved. As far as the tube stage goes you can wire them in mirror image so you can interchange the tubes after a few years of use so you don't use up the same section on both channels.
No, it does not.
Depends where you want to have the LF pole and what the input impedance of the next stage is.
IRCC, this is the cap that couples the cathode follower to the chip?
You could try a bigger cap but I doubt you'd notice a difference for the better, bigger caps have a slower discharge time and that's audible.
I think the LPF cap is the one you'd better experiment a little with so you find the value that suits your system/taste best.
Cheers,😉
With careful layout AND the shield (pin #9 on the socket) grounded there shouldn't be any interchannel crosstalk worth mentioning or measuring.
Sure, you avoided interwinding capacitive coupling.
From my experience, it's not just the fact that you have 2 separate xformers, the way the xformers are made is also important.
For audio projects I usually have mine custom made, always of the EI or C-core type, never toroidals as they're just too wide in bandwidth to stop RF from entering the audio circuit.
There's more you can do but this gives you an idea already....
So do I and for really sensitive circuits like a MC phono preamp I even push it so far as to use a dedicated regulated PS per amplification stage, separate left-right volume controls etc...
Going dual mono for GC is not a bad idea if you want to carry the extra cost involved. As far as the tube stage goes you can wire them in mirror image so you can interchange the tubes after a few years of use so you don't use up the same section on both channels.
No, it does not.
Depends where you want to have the LF pole and what the input impedance of the next stage is.
IRCC, this is the cap that couples the cathode follower to the chip?
You could try a bigger cap but I doubt you'd notice a difference for the better, bigger caps have a slower discharge time and that's audible.
I think the LPF cap is the one you'd better experiment a little with so you find the value that suits your system/taste best.
Cheers,😉
Hi,
Most of the regulators used for heater supplies are of the 78XX series.
They have their middle pin and ground tab internally connected.
When you break of the center pin and screw the tab to a grounded area such as the chassis and then also ground the cold end of the heater at the socket side you have a ground loop.
This can be a source of hum.
Cheers,😉
Most of the regulators used for heater supplies are of the 78XX series.
They have their middle pin and ground tab internally connected.
When you break of the center pin and screw the tab to a grounded area such as the chassis and then also ground the cold end of the heater at the socket side you have a ground loop.
This can be a source of hum.
Cheers,😉
fdegrove said:
Ok ok, this is what I will do, use insulators for the LM7806 and ground of heaters connected directly to center pin of LM7806.
Thanks Frank!
If I put my ear next to the speaker and can just hear the sounds of a radio braodcast coming through, what modifications to the Tube bufferd gainclone should i make ?
As a first step Ive desoldered most of the leads going to chassis ground and signal ground and jury rigged them with temporary leads to find a configuration which a) produces minimum hum and b) get rid of that pesky radio noise
Ive found a good enough solution to a) but not b)
Some details which may or may not be relevant
1 Input leads from RCA plugs to circuit are 2 strands CAT5
2 Two tubes used, one for each channel
3 Layout is as recommended by Joe in latest iteration
Any suggestions appreciated . ill try and get some pics up
As a first step Ive desoldered most of the leads going to chassis ground and signal ground and jury rigged them with temporary leads to find a configuration which a) produces minimum hum and b) get rid of that pesky radio noise
Ive found a good enough solution to a) but not b)
Some details which may or may not be relevant
1 Input leads from RCA plugs to circuit are 2 strands CAT5
2 Two tubes used, one for each channel
3 Layout is as recommended by Joe in latest iteration
Any suggestions appreciated . ill try and get some pics up
Is your case shielded and if so is it connected to ground and the the power star ground via a resistor/cap?
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