Nobsound E6 Preamp Uses Directly Heated Tubes

[Nihilist]

FlaCharlie said :

"Under what conditions?

One way I test is to play music at a level that's considerably louder than I normally listen and then pause the music. If there is no residual ringing I'm happy."

It rings like a bell if you flick it. I know that's not normal usage.

If I have the music up @ the volume I normally listen, and I pause it, it is ringing. There is a high pitched tone that slowly fades away.


"If the chassis is picking up vibrations from the music at normal listening levels you might try putting it on some soft foam to isolate it or move it further from the speakers.

Vibration from the chassis is transferred to the tube through the socket whether the "teardrop" contacts the board or not. So I doubt that's the issue."

I suppose that's true. I thought about making a box with a hinged lid, lining the inside with acoustic foam, and having a small hole in the rear for the rca cables to exit. The box would be used "upside down" , with the E6 sitting on the "lid". The box would be hinged @ the back.

Kind of like a turntable's dust cover, but with acoustic foam inside.

"The metal casing of the tube will not fit through the hole in the top of the chassis. If you wanted to use the tube with the casing on you would need to put the board in a different chassis and use chassis mount sockets that have enough clearance underneath them for the locator pin, which is considerably longer than the "teardrop"."


I thought about fabricating a small hole saw from a piece of copper tubing and using it to cut out the PCB in the center of the tube socket. Obviously this would remove the LED in the process. I haven't tried this as I'm unsure if they are using the LED for anything other than a light show. I've seen some circuits where they use an LED for biasing.

This chassis could be used if the PCB center-ectomy was succesful, I would just have to enlarge the openings for the tubes. Easy enough with a step-bit or a Dremel.

I tried running it "naked", outside of the chassis, but it wasn't any better.

I just finished resoldering 90% of the joints. I didn't resolder the 8-legged semi-conductor, nor did I resolder the surface mount resistors. I resoldered EVERYTHING else (surface mount caps and diodes too).

Still rings. Although it does seem to be a bit better. Perhaps that's just expectation bias.

 

[FlaCharlie]

If I have the music up @ the volume I normally listen, and I pause it, it is ringing. There is a high pitched tone that slowly fades away.

Sorry to hear you're having problems. Again, I'd suggest putting the E6 on a piece of foam to isolate it from vibration that might be transmitted from whatever surface it's sitting on. And don't have the preamp and speakers sitting on the same surface.

Microphonics can also result from vibration that's transmitted through the air. So if you have the preamp close to, or in front of, the speakers you might try a different location.

Up till now the stock Chinese tubes have been hit and miss (mine were fine, others had issues) but until now all previous reports have indicated that using the Russian ones have solved the problem. Your experience indicates that at least some of the Russian tubes are also microphonic.

Microphonics in general, not just with these type of tubes, can be quite unpredictable and the problem can vary quite a bit between individual tubes. Even with tube types that are not considered problematic, some individual tubes will exhibit the problem.

So far, based on the experiences of other users, the issue is with the tubes. I'd just order some more - perhaps from a different seller - and try again rather than drill holes and mod the board. They are cheap enough that it wouldn't hurt to order more than one pair.

I had the same problem with a preamp I built many years ago that used American 12B4A tubes. The worst ones howled loudly with music playing, you didn't need to stop the music and listen for any residual ringing. Once I got some that were not microphonic installed it worked fine.

 

[drjohnnyfeva]

Just installed my matched Russian tubes from the same ebay seller. Still rings like a bell.

I think part of the issue is that the tubes have a glass "teardrop" in the middle of the pins, and if the teardrop is long enough, it contacts the circuit board. If you're lucky your "teardrop" is short and doesn't contact the chassis.

The circuit board is rigidly held in the metal chassis, but is suspended only by it's long outer edges. So the resonant metal chassis is connected to a fibreglass pcb which is suspended like a trampoline and the tube is in contact with it.

Thinking about cutting a hole through the pcb where the LED is located. This would allow the use of the tube in its metal casing, which has about 1\4" of paper rings inside of it to damp the tube body.....

I was considering - and still am with a second unit - adapting the chassis for the tube to be used as is without needing to remove it from the case. But, as FlaCharlie mentions, the loctal centering pin would need to be shortened or removed completely and that poses a problem because you'd have to work around the tube pins to do that. Shortening it to the length of the tube pins wouldn't be too difficult, but more than that could be a problem. Also of concern, for me, would be not knowing exactly where that "teardrop" portion of the tube is within the case. I imagine that it's pretty close to the point where the centering pin becomes flush with the case, but it could extend into the loctal centering pin a little too. Just don't know.

I considered enlarging the tube holes of the chassis to accommodate the tube case too. That's the easy part, to me, but the above issue is more of the roadblock. Until that is resolved, the mod is on hold.

Also, with the microphonics, I would definitely suggest putting a neoprene mouse pad or some other kind of "shock absorber" under the unit no matter where you have it placed. I have mine sitting on a speaker with four little cut out mouse pad squares under the feet and but for bumping the unit once, have not experienced the microphonics at all. I had the Chinese tubes in at the time and have adjusted the volume a few times with the Russian tubes in with no issues.

If you're concerned about the lower teardrop protrusion of the tube, you might also try a small piece of neoprene over the LED so there's at least cushioned contact...

 

[FlaCharlie]

I was considering - and still am with a second unit - adapting the chassis for the tube to be used as is without needing to remove it from the case. But, as FlaCharlie mentions, the loctal centering pin would need to be shortened or removed completely and that poses a problem because you'd have to work around the tube pins to do that. Shortening it to the length of the tube pins wouldn't be too difficult, but more than that could be a problem. Also of concern, for me, would be not knowing exactly where that "teardrop" portion of the tube is within the case. I imagine that it's pretty close to the point where the centering pin becomes flush with the case, but it could extend into the loctal centering pin a little too. Just don't know.

I considered enlarging the tube holes of the chassis to accommodate the tube case too. That's the easy part, to me, but the above issue is more of the roadblock. Until that is resolved, the mod is on hold.

Also, with the microphonics, I would definitely suggest putting a neoprene mouse pad or some other kind of "shock absorber" under the unit no matter where you have it placed. I have mine sitting on a speaker with four little cut out mouse pad squares under the feet and but for bumping the unit once, have not experienced the microphonics at all. I had the Chinese tubes in at the time and have adjusted the volume a few times with the Russian tubes in with no issues.

If you're concerned about the lower teardrop protrusion of the tube, you might also try a small piece of neoprene over the LED so there's at least cushioned contact...

If you're concerned about microphonics the last place you want to put the preamp is on top of a speaker, even if you do use some rubber pads under it. Assuming the speaker is hooked up, of course.

The most vibration resistant material I've seen is memory foam. If you can find something inexpensive that uses it, like a small pillow or something, that will isolate it better than mouse pad material. You could cut it to whatever size you like.

If you want to try the tube without removing the metal shell, use regular sockets instead of ones designed for a circuit board and mount them on a regular chassis with a top plate, or even a wooden box. Then you can just plug them in without doing any surgery. But, if you're not having issues in normal use, why bother?

To me the main appeal of transferring the thing into a different chassis would be to put all the RCA jacks on the back. But if I went that far I'm sure I would top mount the sockets too. Chassis mount sockets are much more solid so the solder joints are much less likely to be damaged by insertion and removal of the tubes. I'd probably replace the cheap volume pot with a decent, but inexpensive, stepped attenuator too. Not that the stock one is giving me any problems.

I'm happy with mine as is, though, and I've got too many other projects at the moment.

 

[fjdds]

Finally received the Russian tubes. No ringing whatsover.
My unit was unusable with the stock tubes. One, in fact, crumbled upon removal.

First use - Wiim Mini, the E6 to a Volt +D to Zenith 1045 OBs and plate amps driving 4- alpha 15s. Pretty good, but these speakers tend to be a bit harsh. I'm still experimenting with taming this, but the tone controls on the Tube-03 are very helpful in this regard. I don't think this is a reflection of the E6, as much as the speakers, which apparently, are still a work in progress.

Second use - Wiim Mini, the E6 to my Philips receiver (my favorite, much better than then Marantz 2270 to my ears) to Bozak Symphonys. (Loudness on, tone controls flat)
Wow!
The Bozaks excel at midrange clarity and a velvety smoothness, but when I inserted the E6, the smoothness was ratcheted up a couple of notches. Clear and beautiful, without being syrupy. Sounded like Lea Salonga was in the room with me. (Miss Saigon). Whether or not this is an accurate reproduction of the source material doesn't really matter to me as much as how pleasing the sound is, and with the E6 in this system, it's just great. Had it on for hours yesterday with nary a hint of fatigue, which the 16 tweeters in the Bozaks can produce in my system with certain material.

This is where the E6 will stay. Big improvement in the sound from the receiver alone, or with the Tube 03 in the loop.

I think most should consider just getting the Russian tubes when purchasing this unit. If the Chinese ones are good, you'll have backups.

Thanks to FlaCharlie for bring this to our attention, and drjonnyfeva for his very helpful comments.

YMMV, as always.

 

[FlaCharlie]

For those of you who don't want to go out and buy a tubing cutter, StepheK just posted a short video on her YT channel showing another method of removing the Russian replacement tubes from their aluminum shells.

 

[Sliphorn]

For those of you who don't want to go out and buy a tubing cutter, StepheK just posted a short video on her YT channel showing another method of removing the Russian replacement tubes from their aluminum shells.

..
Thanks for the video. I like how she did that. I look forward to the shootout she will be doing. One of my E6 started acting up with a scratchy volume pot. At least I think that’s what it is. Scratch scratch scratch and then the left channel cuts in and out. Bummer.
..

 

[drjohnnyfeva]

For those of you who don't want to go out and buy a tubing cutter, StepheK just posted a short video on her YT channel showing another method of removing the Russian replacement tubes from their aluminum shells.

I marked mine in the same manner that day I cut them open with the pipe cutter. I liked my marks, tho, and kept them. Thanks for posting that Charlie.

 

[Sliphorn]

..
I opened up the E6 with the scratchy volume pot. Sprayed a bit of Houdini 4-way lock lube in there and worked the knob a bunch. Lo and behold the scratchiness is gone. Reinstalled the tubes, fired her up and all is good. Yay!
..

 

[lazylistener]

Sorry if this has already been addressed in the thread! I've been considering getting one of these even though I've been very happy with my FX-Audio Tube 03 in a daisy-chain setup with a simple Aiyima tube pre.

Does this Nobsound E6 suffer the same issue of inverting polarity? I might just pair it up with my Tube-03 if so! Also, anyone knows is this benefits from a linear power supply? I might just get one out of convenience to power this + my Topping E30II (which I know wouldn't necessarily benefit from it, but I'd try because why not)

 

[drjohnnyfeva]

Sorry if this has already been addressed in the thread! I've been considering getting one of these even though I've been very happy with my FX-Audio Tube 03 in a daisy-chain setup with a simple Aiyima tube pre.

Does this Nobsound E6 suffer the same issue of inverting polarity? I might just pair it up with my Tube-03 if so! Also, anyone knows is this benefits from a linear power supply? I might just get one out of convenience to power this + my Topping E30II (which I know wouldn't necessarily benefit from it, but I'd try because why not)

That about sums it up. lol.

I don't know the answer about the polarity. I've done the polarity tests from time to time and the way that is said to be "correct" on all of them has been the way it has sounded the best for me. Mine goes from PC, to Nobsound Little Bear T7 (for gain), to the Nobsound E6, on/off Schitt Loki, and Fisher 170. I run the Loki on and off depending on my mood. But with A/Bing the Loki, I can't tell if there is any polarity shift. Sounds wonderful.

Just buy the damn thing and get back to us.

 

[lazylistener]

That about sums it up. lol.

I don't know the answer about the polarity. I've done the polarity tests from time to time and the way that is said to be "correct" on all of them has been the way it has sounded the best for me. Mine goes from PC, to Nobsound Little Bear T7 (for gain), to the Nobsound E6, on/off Schitt Loki, and Fisher 170. I run the Loki on and off depending on my mood. But with A/Bing the Loki, I can't tell if there is any polarity shift. Sounds wonderful.

Just buy the damn thing and get back to us.

You got me there...

I'll come back when I get the damn thing heheh

 

[Sliphorn]

Three days ago I received a new Dynaco ST-35 built by Kenny Russell. I am using the E6 in front of it and the combination sounds fantastic. It really is a great little preamp.

 

[cipriano]

If anybody was considering a purchase there currently is a 20% off coupon on ebay. The seller is doukmall.

I couldn't resist at $48, so I now have one on the way. For use with an integrated Class D (Volt D+) what are you all setting your amps volumes at? Maxed out, Noon, 9:00?

 

[lazylistener]

If anybody was considering a purchase there currently is a 20% off coupon on ebay. The seller is doukmall.

I couldn't resist at $48, so I now have one on the way. For use with an integrated Class D (Volt D+) what are you all setting your amps volumes at? Maxed out, Noon, 9:00?

I have one on the way as well! Didn't get it through ebay but it should be arriving in a couple of days. Eager to see how this will stack up against my Tube-03, and if it can play well with it in a daisy-chain set up.

 

[Sliphorn]

If anybody was considering a purchase there currently is a 20% off coupon on ebay. The seller is doukmall.

I couldn't resist at $48, so I now have one on the way. For use with an integrated Class D (Volt D+) what are you all setting your amps volumes at? Maxed out, Noon, 9:00?

..
My Dynaco runs full bore so I don’t have a choice as to a volume setting. When I used the E6 with class D amps I experimented with volume settings, though I ended up never maxing out the amp volume control because when I did that I barely got the E6 volume control off the bumper.

I strongly suggest ordering some Russian tubes because the Chinese tubes can be very microphonic.
..

 

[Sliphorn]

I have one on the way as well! Didn't get it through ebay but it should be arriving in a couple of days. Eager to see how this will stack up against my Tube-03, and if it can play well with it in a daisy-chain set up.

..
Please tell me why you would use it with a Tube-03. Also consider getting some Russian tubes for the E6.

 

[drjohnnyfeva]

If anybody was considering a purchase there currently is a 20% off coupon on ebay. The seller is doukmall.

I couldn't resist at $48, so I now have one on the way. For use with an integrated Class D (Volt D+) what are you all setting your amps volumes at? Maxed out, Noon, 9:00?

Great info on the price. Thanks!

I'm really interested to see how it performs with the Volt+D. I have an Aiyama A07 that I got on sale to play around with as my first Class D amp. Had the Volt+D in the cart at Xmas time, but it sold out the before I could pull the trigger. I found the A07 a little lacking in overall sound quality by itself, but once the Tube03 was added in I really liked how it blossomed. I haven't had the chance to play with the A07 and E6, so I'm really anxious to hear what you think of the combination you have.

I have the E6 daisy-chained with an older Little Bear T7 tube pre and sometimes a Schiit Loki that I A/B into my Fisher 170. I've sort of settled on the E6 almost full-bore... maybe 3 or 4 o'clock. The T7 gives me some needed gain from my PC. That it's a tube pre is a bonus. I removed a modded FX Audio Tube03 as the E6 was a superior replacement. So T7 to E6 to Loki +/- to receiver. Nice.

Do get the Russian tubes as suggested. They are far superior to the stock Chinese tubes. Good luck with it. Don't sweat a little ringing with the unit until you get it settled and once the Russian tubes go in you should have no problems at all.

 

[Sliphorn]

Great info on the price. Thanks!

I'm really interested to see how it performs with the Volt+D. I have an Aiyama A07 that I got on sale to play around with as my first Class D amp. Had the Volt+D in the cart at Xmas time, but it sold out the before I could pull the trigger. I found the A07 a little lacking in overall sound quality by itself, but once the Tube03 was added in I really liked how it blossomed. I haven't had the chance to play with the A07 and E6, so I'm really anxious to hear what you think of the combination you have.

I have the E6 daisy-chained with an older Little Bear T7 tube pre and sometimes a Schiit Loki that I A/B into my Fisher 170. I've sort of settled on the E6 almost full-bore... maybe 3 or 4 o'clock. The T7 gives me some needed gain from my PC. That it's a tube pre is a bonus. I removed a modded FX Audio Tube03 as the E6 was a superior replacement. So T7 to E6 to Loki +/- to receiver. Nice.

Do get the Russian tubes as suggested. They are far superior to the stock Chinese tubes. Good luck with it. Don't sweat a little ringing with the unit until you get it settled and once the Russian tubes go in you should have no problems at all.

..
I used the E6 in front of my A07 with the upgraded opamp, and it was excellent. In fact, my second E6 is going back in with the A07 chained to a TubeCube7 driving two pair of speakers.

Hey cipriano, thanks for the heads up on the E6 sale. I’m gonna check it out in a moment and if it’s still on sale I’m gonna grab one. You never know when they’ll stop making it, and I like it so much I might as well grab another.
..

 

[lazylistener]

..
Please tell me why you would use it with a Tube-03. Also consider getting some Russian tubes for the E6.

No specific reason other than that it's right there on my desktop already lmao, with switched op-amps and a linear power supply.

But it's really that some have still noted the inverse polarity in the E6 (like here), which was the same case for the Tube-03. And ever since I daisy-chained the latter with an AIYIMA tube pre, the sound leaped forward in ways I never would've expected! So just going by the rule of polarity (odd number of tube preamps in the chain resulting in inversed polarity, even numbers restoring it, etc. – at least how I remember it) I figure it wouldn't hurt pairing them up.

Still, when the E6 gets here I wanna use it by itself for a week-ish, just to see how it sounds. I have the Russian tubes ordered, but considering where I live, where I'm much closer to China than Ukraine, I'm anticipating a long wait.

I read that damper rings help reduce microphonics from the Chinese tubes, so I'm waiting on those to arrive as well. The E6 should arrive next week so I'll let it settle in when it does and come back here to report!