Nobsound E6 Preamp Uses Directly Heated Tubes

[drjohnnyfeva]

I'm interested in knowing what might be the outcome if I changed the two round capacitors next to the film caps I already changed; and what value I should go with. I know some of the mods of the Tube03 included taking out the round capacitors but I don't know what line they are in in the E6, so not sure if it would make a difference or not...

I think the change in filter caps changed the sound profile of my E6 a little. I've been using my modded Tube03 because I preferred it over both the modded and unmodded E6. I'm going to take the E6 to school and put it in my little system there just to use. I've got a crappy little tube pre in there now that I use just for the gain, but I'm not really pleased with it.

I have not experienced any flatness in the E6. The highs are crisp, the mids are presented well, and the bass has a nice bottom. But the sound of it has changed from the stock since I changed the film caps.

 

[raycarr00]

I just add a few uf's directly to the existing caps and listen for results. I try to avoid unsoldering caps to minimize damage until I've decided on a valve I like; sound wise. I haven't opened up the one I have, but I would determine what caps go to the tubes and start adding and listening. Certainly, one can add bipolars directly to the smd's after determining which ones are caps with a dmm.

 

[M70AB2]

I'm interested in knowing what might be the outcome if I changed the two round capacitors next to the film caps I already changed; and what value I should go with. I know some of the mods of the Tube03 included taking out the round capacitors but I don't know what line they are in in the E6, so not sure if it would make a difference or not...

I think the change in filter caps changed the sound profile of my E6 a little. I've been using my modded Tube03 because I preferred it over both the modded and unmodded E6. I'm going to take the E6 to school and put it in my little system there just to use. I've got a crappy little tube pre in there now that I use just for the gain, but I'm not really pleased with it.

I have not experienced any flatness in the E6. The highs are crisp, the mids are presented well, and the bass has a nice bottom. But the sound of it has changed from the stock since I changed the film caps.

The film capacitors are not filter capacitors. They are input and output capacitors.

Filter capacitors filter rectified DC of ripple to varying degrees.

Theoretically, you could go up in value, but you must stay at the same voltage or higher.

I have found that swapping out no-name filter capacitors for say, Panasonic FC or Nichicon can improve things a bit.

I suppose the conventional wisdom is going up in value by 50 percent at most.

 

[M70AB2]

Something occurred to me last night: this would be an easier method of marking which pins ought to be facing the sockets’ keyway.

Instead of removing the tube after visually lining up the top of the tube with the metal key at the base and marking it, mark each pin on both sides of the key with a Sharpie before cutting open the metal shield.

Then remove the tube from the metal shield. Next, use the marked pins as a guide to mark the bottom of the glass next to the marked pins. Clean off the Sharpie markings from the two pins with Isopropyl alcohol.

Done. And you cannot fail to get it right each time.

 

[Sliphorn]

Something occurred to me last night: this would be an easier method of marking which pins ought to be facing the sockets’ keyway.

Instead of removing the tube after visually lining up the top of the tube with the metal key at the base and marking it, mark each pin on both sides of the key with a Sharpie before cutting open the metal shield.

Then remove the tube from the metal shield. Next, use the marked pins as a guide to mark the bottom of the glass next to the marked pins. Clean off the Sharpie markings from the two pins with Isopropyl alcohol.

Done. And you cannot fail to get it right each time.

..
Just align the metal tab found at the top of the tube with the keyway. Done.
..

 

[drjohnnyfeva]

Something occurred to me last night: this would be an easier method of marking which pins ought to be facing the sockets’ keyway.

Instead of removing the tube after visually lining up the top of the tube with the metal key at the base and marking it, mark each pin on both sides of the key with a Sharpie before cutting open the metal shield.

Then remove the tube from the metal shield. Next, use the marked pins as a guide to mark the bottom of the glass next to the marked pins. Clean off the Sharpie markings from the two pins with Isopropyl alcohol.

Done. And you cannot fail to get it right each time.

Somewhere earlier in the thread that's what I did. If you mark those two pins and pull the tube out afterwards, you can mark the top of the tube with an arrow to the direction of the key and keyway. You should mark the tube in some way, because Sharpie does wear off the pins and becomes hard to see.

There was also some talk of drilling thru the board and widening the tube holes in the case to accommodate the entire tube, as is, without removing the case. As I know nothing about the electronics of boards like this one, drilling a hole thru the board seemed nuclear, not know what might be affected; other than, certainly, the LEDs in the middle of the sockets. I know on some boards, LEDs can be used as a resistor or something in a circuit... not sure.

However, I will add that I've considered buying a replacement for the unit I modded. I kind of want to hear it in it's virgin, factory state to compare to what the result is with the mod I did. That being said, once compared, I would not be opposed to experimenting with doing some of the changes discussed earlier in this thread. Primarily, making a new case altogether to move the jacks to the back of the unit, raising the sockets or installing new sockets that would accept the tube, case and all, and a better volume control. I just haven't had the time to really plan all that out.

@FlaCharlie has suggested a couple ways to raise the tube sockets earlier in the thread, but I don't think he is particularly interested in doing them himself as he builds his own pre's from scratch and he has been vocal about his appreciation of the E6 in it's stock form.

 

[M70AB2]

As mentioned, I have super bright orange SMD LEDs with which I intend to replace the stock LEDs.

Many think this sort of thing is goofy, but I got to thinking that Nobsound had to put them in there.

Either that or semi-intelligible online reviews with something like, “Tubes don’t work are turned off total joke they could of put some real tubes in not these junk tubes that don’t do nothin this thing probably has chips in it for sound and tubes don’t do nothin don’t buy this I sent it back…”

I just know it. I see this kind of thing a lot with various gear, guitar gear, etc. There are more than a few who do not understand what the gear does, how it works, what it doesn’t do, etc.

Off the top of my head, I read a review of a DAC in which the reviewer complained that the DAC does not provide sound to his gear when he plugs in his headphones.

Geez. Yeah, it is supposed to do exactly that.

About the tube shields, I wouldn’t mind being able to leave them on, but that’s surely not a look many or most would prefer.

The tiny size of the E6 is a bit off-putting. It’s easily moved. Got to thinking that I may mount it with Velcro eventually if I don’t rehouse it.

And rehousing it, I could install an indicator LED as well.

 

[drjohnnyfeva]

The only reason keeping the case on the tube has been discussed is that the reported microphonics might be diminished by having it remain encased with the dampers and shield intact. If you follow this thread back to it's beginning, a few of us commented on the Amazon reviews because one of the reviews was utterly wrong. And since this is the first inexpensive tube pre that uses directly heated tubes, it seemed a shame to have such a terrible review impacting others from trying what is actually a really sweet sounding unit.

Whenever I get around to dealing with moving the inputs and changing the volume control, I'm gonna put it in a larger case, probably wood. I'm also going to have the tube socket on top of the unit so the tube case can stay on and the loctal key can pass thru. If I don't like the look with the case on the tube, I can always cut it off.

 

[raycarr00]

Just got a second e6 and I'm in the process of slowly powering it up with a variac. Noticed that before reaching 50v, it emitted a clicking sound. On the first e6 I purchased, I did not hear the clicking. But come to think of it, I was hearing a clicking sound and while playing it. Just didn't know where the clicking was coming from. I'm hoping it sounds better. The clicking is obviously a sign of being underpowered. But I did use a 4amp 5v power adapter on the first e6. Mailing it back, anyway. Will hear what the second one sounds like and go from there.

 

[raycarr00]

on the second e5, the sound was also flat and hardly any bass. after swapping the tubes from the first e6 to the 2nd, the bass is back and there's a bit more treble. seems like the tubes are having a significant effect on the sound(no kidding!).

 

[raycarr00]

tube alignment can be easily determined by a tab on the top of the tube. the tab corresponds to the location of the 2 pins.

 

[M70AB2]

Quick thoughts: the Soviet tubes, for lack of a better description, seem for me to sit between GE 5654W and the Russian 6Zh1P-EV.

That is, they seem to enhance female vocals like the GE tube while while retaining the precise detail of the Russian tube.

Of course, this is a bit or a lot of an apples and oranges comparison, but I am going by the previous use of the FXAUDIO TUBE-01 in my modest garage system.

So I seem to get the best of both worlds.

I don’t have even an hour on these tubes. As mentioned, it’s cold in there. So things may change.

But briefly last night, I was listening to Secret Rule - “The Key To The World.” Liked what I heard.

Worth mentioning that as crazy as it sounds, I also like the Chinese tubes. A little less push in the midrange, a little more delicate sounding.

 

[lazylistener]

Quick thoughts: the Soviet tubes, for lack of a better description, seem for me to sit between GE 5654W and the Russian 6Zh1P-EV.

That is, they seem to enhance female vocals like the GE tube while while retaining the precise detail of the Russian tube.

Of course, this is a bit or a lot of an apples and oranges comparison, but I am going by the previous use of the FXAUDIO TUBE-01 in my modest garage system.

So I seem to get the best of both worlds.

I don’t have even an hour on these tubes. As mentioned, it’s cold in there. So things may change.

But briefly last night, I was listening to Secret Rule - “The Key To The World.” Liked what I heard.

Worth mentioning that as crazy as it sounds, I also like the Chinese tubes. A little less push in the midrange, a little more delicate sounding.

I remember having the Chinese tubes for a good week or two, and they weren't bad at all! Certainly better as stock tubes than the ones that come with the Tube-03. Weirdly enough, they were also less microphonic than the Russian pairs I've tried.

 

[M70AB2]

Then that’s two of us.

And as I previously wrote, zero microphonic issues with my Chinese tubes.

 

[drjohnnyfeva]

Then that’s two of us.

And as I previously wrote, zero microphonic issues with my Chinese tubes.

You both are actually the only two in this thread thus far that have had fewer microphincs problems with the Chinese tubes than the Russian tubes...Most who had issues right out of the box with the stock Chinese tubes and ringing, it was resolved by using Russian tubes. Personally, I've only experienced the microphonics twice. First when I bumped the unit inadvertently, before I got the Russian tubes, but had no issues before or after with the stock tubes either. So that was clearly the bump. I've bumped the unit once or twice with the Russian tubes and had no microphonics, tho. The worst micro phonics were with Russian tubes in, but that was a signal strength issue and it persisted with the Chinese tubes because I took the Russian ones out to see if the tubes had been damaged.

In that case, the signal strength to the E6 was not adequate and turning up the volume to compensate produced a ringing, which was amplified by boosting the volume on the amp. Lowering both the unit and the amp and boosting the PC signal strength was the only avenue that stopped the ringing. I have asked others to try to confirm the signal strength issue - this is also common with some Class D amps using pre's like the Tube03. If the Class D is weak, the effect of the pre is diminished and even negative. But this is a "power" problem in that case. I properly powered Class D with a pre like the Tube03 has been called "the icing on the cake," by some. I think the same is true with this unit, but specifically when it comes to the strength of the signal it receives.

My experience was that no matter what I did after the unit to try to make up for the weak signal, it increased the ringing. But when the signal had the right amount of gain, the E6 didn't display any microphonic qualities. I stuck my Little Bear tube pre back in the line to get the gain the E6 was craving and no issues since. But I don't know of anyone else facing that specific problem.

 

[raycarr00]

You both are actually the only two in this thread thus far that have had fewer microphincs problems with the Chinese tubes than the Russian tubes...Most who had issues right out of the box with the stock Chinese tubes and ringing, it was resolved by using Russian tubes. Personally, I've only experienced the microphonics twice. First when I bumped the unit inadvertently, before I got the Russian tubes, but had no issues before or after with the stock tubes either. So that was clearly the bump. I've bumped the unit once or twice with the Russian tubes and had no microphonics, tho. The worst micro phonics were with Russian tubes in, but that was a signal strength issue and it persisted with the Chinese tubes because I took the Russian ones out to see if the tubes had been damaged.

In that case, the signal strength to the E6 was not adequate and turning up the volume to compensate produced a ringing, which was amplified by boosting the volume on the amp. Lowering both the unit and the amp and boosting the PC signal strength was the only avenue that stopped the ringing. I have asked others to try to confirm the signal strength issue - this is also common with some Class D amps using pre's like the Tube03. If the Class D is weak, the effect of the pre is diminished and even negative. But this is a "power" problem in that case. I properly powered Class D with a pre like the Tube03 has been called "the icing on the cake," by some. I think the same is true with this unit, but specifically when it comes to the strength of the signal it receives.

My experience was that no matter what I did after the unit to try to make up for the weak signal, it increased the ringing. But when the signal had the right amount of gain, the E6 didn't display any microphonic qualities. I stuck my Little Bear tube pre back in the line to get the gain the E6 was craving and no issues since. But I don't know of anyone else facing that specific problem.

No microphonics yet, with either tubes. Just no treble. Russian tubes did sound better to me. I've paralleled caps to several caps, but with no significant changes. Added/ paralleled one to the tubes, but have yet to test it. Have new caps coming in. Will hear, then.

 

[M70AB2]

Maybe try parallel capacitors .01uF - .1uF instead.

 

[drjohnnyfeva]

No microphonics yet, with either tubes. Just no treble. Russian tubes did sound better to me. I've paralleled caps to several caps, but with no significant changes. Added/ paralleled one to the tubes, but have yet to test it. Have new caps coming in. Will hear, then.

I didn't notice any change when I changed the film caps, but I can't say that I've heard any deficiency in treble either with either version of the film caps.

 

[raycarr00]

after about 7 hours of continuous play(yesterday), the excessive bass diminished and the treble improved a bit. All parallel caps were removed(no change). will continue testing; figure to just apply a cap at low volume to the existing smd caps and listen for a change. it's quiet and clear. just needs a tad bit more treble. Seems like this pre might benefit by leaving it on around the clock. woke-up to 50 deg f and the pre's been on about 24 hrs. waiting on new caps.

 

[drjohnnyfeva]

I have my E6 on my school system now. It gets turned off now at the end of each school day, but when I first got it, it stayed on 24/7 in my regular system. I only turned off the receiver and both of my tube units stayed on always. I do think they need a bit of a burn in period - all of the tube pre's. I know that the Tube03 I changed the filter caps on was noticeably better from the moment of the change, but that has gotten even better since I've been using it, over six months now.