Nobsound E6 Preamp Uses Directly Heated Tubes

[raycarr00]

Houston, we have a problem...

So I took the aluminum case off of the unit. Not difficult, but tighter than the FX to slide out of the case.

To answer a couple questions first.

1- the aluminum cover on the Russian tube will not fit into the tube socket of the Nobsound without either cutting off the entire cover OR taking off the part of the centering pin.

2- the Russian tube with the centering pin aligns into the socket, but the centering pin is too long to allow the tube pins to seat into the socket.

3- the holes in the case of the Nobsound, designed for the Chinese tubes without the cover, are a couple millimeters too small in diameter to accommodate the Russian tube WITH the aluminum cover.

Decisions, decisions... I think what I am going to do is take the avenue of least resistance and cost. There are socket extenders on the bay. Some are $2, but they don't particularly seem to be extenders as much as savers. There are others that are extenders, but they either don't have the protrusion that the centering pin has and the center "post" is the same height as the Russian tube minus the extended "nipple" at the extreme base of the case. Those are $18 plus delivery.

Plan: I'm going to leave the cover on the Russian tube. I'm going to cut off the bottom "nipple" of the tube cover and use a Dremmel tool to grind it down further so it fits into the socket correctly. Next, I'm going to use the same grinder to shave a few mm off of the existing holes in the case.

Basis for adaptation decisions: I'm a bit concerned about damaging the tube by getting the cover off, the cost of my plan is low, and if any tube rolling occurs in the future, the unit is ready for it without having to do anything to arriving tubes other than cutting and grinding the bases. Low effort, quick turnaround.

I'd appreciate some feedback on the type of Dremmel grinder to use for aluminum. I'll have the tube in a vice, but I'm going to need to have good, steady control of the tool so it doesn't careen into the tube pins.

That's the plan. Pictures of the unit below.
View attachment 2740537 View attachment 2740538 View attachment 2740539 View attachment 2740540

Yeez! Looks like it could be easily built. Might have read somewhere that it has smd electronics. Don't see them.

 

[M70AB2]

Yeez! Looks like it could be easily built. Might have read somewhere that it has smd electronics. Don't see them.

Bottom of circuit card.

 

[M70AB2]

Additional thoughts: The E6 pairs nicely with my FX Audio DAC in which I installed a MUSES8820 opamp.

It’s difficult to put into words, but the E6 seems to enhance the inherent characteristics of the MUSES8820.

As mentioned on another site, there is some coloration. This is not always a bad thing. Furthermore, everything colors a signal to some degree. It’s inescapable. “Wire with gain” is an unobtainable goal.

So with that in mind, why not shape the sound to your liking? The equally unobtainable “as the artist intended” is practically laughable to anyone who had done any recording at all.

How many times has a musician said in bafflement and disappointment, “Why does it sound like that???”

A name most would recognize told me directly of the severe emotional distress he experienced upon first hearing a final mix of his band’s album.

Musicians very often rank last in many decisions and as some will know, very few, if any band members are always in perfect agreement in the studio.

It would be far more accurate to declare As The Producer, A&R Reps Who Didn’t Like The Initial Mix, Attorneys, Engineers and Management Company Intended and Totally Fought It Out While The Artist Was Sidelined and What You Have Here is Something With Which No One is Completely Happy.

So I don’t worry about “wire with gain.” I especially don’t worry about “As The Artist Intended.”

So, with that in mind and out of the way, the sound rendered through these tubes is very pleasing. “Digititis” seems absent as that other site mentioned.

In keeping with fairly obscure CDs, I intend to fire in Maxine Petrucci - “Don’t Hate Me” in order to see if the E6 tames any of that spiky guitar tone.

Low end is punchy and seems to have some extension. Quote from the wife:

“Hey, can you turn that down? It’s so loud my feet are vibrating on the upstairs bathroom floor from that!”

I ordered more WIMA 1uF capacitors, both 160v and 250v. I will see if it’s possible to install them without modification.

Also ordered Soviet tubes and super bright SMD LEDs. While surely some will consider tubes lit by orange LEDs as goofy, it does serve as a power indicator. I could also find the resistor before the LEDs and lower the value, within reason.

As is, the stock LEDs are dim and I cannot see any illumination with my workbench light on.

My garage system is certainly unlike the de rigueur personal injury attorney audiophile systems in which a single AC cord cost more than my house.

I’m running some RCA CD changer into the aforementioned DAC, the E6, a Kenwood KA-3500 and some kind of KLH speakers. But the point here is how nicely the E6 complements these. I find myself wanting to work in the garage in order to listen to CDs. Speaking for myself, it was a very nice surprise.

 

[M70AB2]

Addendum: Still no microphonics. Regardless, I added tube dampers — specifically Danco #19 O Rings purchased at Lowe’s in the Plumbing section for $3 and change.

The Maxine Petrucci CD I also used as a test track CD was tamed slightly without seeming to lose detail, if that’s possible or makes any sense.

Her guitar tone is a very distorted and edgy scooped-mid metal sound. Sounds close-miked with no ambient miking. Surely digitally recorded, etc.

Be certain to turn on the E6 and wait a minute or so before turning on your receiver or integrated amplifier.

Turn the E6 off last. This of course is to avoid loud pops through the speakers.

As with the FX-Audio Tube 01, the E6 seems to work best for me with the control set between 10 and 11 o’clock.

 

[drjohnnyfeva]

Nice to see the E6 being rediscovered. It is a sweet little unit. I changed out the filter caps to WIMAs. I don't think it made much difference. Maybe a slightly different value would have been better, but I just replaced them with the same value. I'm interested in trying to figure out whether this thing is as gain dependent as I experienced when I had it as the only component between my PC and receiver. That line has no noise in it at all, but it is not a super strong signal. Partially because I moderate it with the computer volume set pretty low allowing another pre, the LittleBear T7 supply some tuby gain before either the E6 or a Tube03. I'm still sort of stuck on the Tube03 at the moment, but over my Christmas break, I'm gonna play with the E6 some more.

I still think that the E6 unit, right out of the box, has the best sound of any tube pre I've used. I leave the pre's on all the time. I just turn off the receiver and forget the rest. They have been running this way, depending on the unit for up to 4 years with no issues, no burned out tubes, and no microphonics with the E6 other than bumping it once and not supplying enough gain and getting a ringing when trying to compensate with the receiver.

I'm interested to hear about the different value caps and if anyone can confirm the gain issue I had. I know that some other small tube pre's can have issues with Class D amps when the power is lower in either of the units, but that when the power is correct, a tube pre on a Class D has been considered the icing on the cake.

Anyway, good to see this thing getting some traction again.

 

[M70AB2]

The issue with capacitor changes to WIMA and other values (I think you mean input and output capacitors) is fitment.

It could be advantageous to go up in value on the output capacitors, but this is likely difficult to impossible.

I was looking at 2.2uF, etc. WIMA capacitors online, but the dimensions are too big to fit.

Also looked at Mundorf, but these seem problematic as well.

Is it just me though? Is there a perceptible greater instrument separation?

I was listening to a track I had loved since my teens and found myself noticing the bass guitar lines to a degree that I don’t believe I had before.

And I didn’t go in with the idea of well, now I will listen for greater instrument separation for a preplanned “A-HA!” moment. I’m just enjoying listening.

It may seem counterintuitive to some that something this inexpensive could sound so nice, and it’s rather likely they would contend that as a “distortion generator,” it can’t possibly sound good anyway. And that’s okay.

It also reminds me of when I was a child, my parents let me have an ARVIN tube shortwave radio. Even then, it sounded very nice to me. So does the E6 now.

 

[WizardWG4]

Has anyone sketched out a schematic for the E6?

I tried searching but no luck.

 

[drjohnnyfeva]

The issue with capacitor changes to WIMA and other values (I think you mean input and output capacitors) is fitment.

It could be advantageous to go up in value on the output capacitors, but this is likely difficult to impossible.

I was looking at 2.2uF, etc. WIMA capacitors online, but the dimensions are too big to fit.

Also looked at Mundorf, but these seem problematic as well.

Is it just me though? Is there a perceptible greater instrument separation?

I was listening to a track I had loved since my teens and found myself noticing the bass guitar lines to a degree that I don’t believe I had before.

And I didn’t go in with the idea of well, now I will listen for greater instrument separation for a preplanned “A-HA!” moment. I’m just enjoying listening.

It may seem counterintuitive to some that something this inexpensive could sound so nice, and it’s rather likely they would contend that as a “distortion generator,” it can’t possibly sound good anyway. And that’s okay.

It also reminds me of when I was a child, my parents let me have an ARVIN tube shortwave radio. Even then, it sounded very nice to me. So does the E6 now.

The fit was an issue. I posted a couple pics on post 213. I had to saw the top off because the WIMA's were just a hair too tall. Fearful of damaging the caps by shaving anything off, I erred on hacking the thing up. lol. It still sounds great, in fact I don't think it did much of anything and I could have probably done without the change and the extra labor that went along with it.

I didn't go into it expecting anything spectacular nor an a-ha moment either. But I think the comments thru-out the thread show a pretty solid thumbs up to the E6. I also noticed aspects of songs I either hadn't heard before, like clearer baselines, or the vibration of strings in acoustic Cash, that were just more realistic and vivid.

The guys on the testing site have been dismissive of the unit and, basically, anyone trying the thing out. Calling it a noise box or a distortion box. The later is more acceptable because it probably is distortion being added, but it's very pleasing to my ear. So I really don't care how they feel about it, I enjoy it and other units like it AND, as you say, they are all part of MY system that I enjoy listening to with the characteristics of the mix I create for myself by using these units and MY system itself. I like a syrupy bottom end, solid middle, I don't like piercing highs, and I don't like sibilance. I do what I can to minimize the negatives and support the positives of my tastes. The E6 at 1:30 on the volume dial does a really good job of doing just that.

 

[M70AB2]

In the wise words of the late Ed Van Halen, if it sounds good, it is good.

I can certainly understand interest in assessing both with precise testing equipment and the selflessly-blessed Golden Eared (whose finely-tuned ears unfortunately somehow missed the entire MoFi digital source debacle, but I digress). That is perfectly fine too.

On the face of it, what I don’t get is the Debbie Downer self-appointed mission of crapping on others’ gear choices and the fact that as a family man as one example, many don’t have unlimited incomes from trust funds, lawsuits and the like.

So how long before the Secret Audio Police conduct Search & Seizure raids? “Is this your 6J1 preamp? Oh, you’re just keeping it for a friend you say? What if we told you we saw your online posts?”

Now about the capacitors, if you will look at the photo, you will see small tabs on the bottom of the capacitors. If we’re talking a half millimeter, shaving these off may provide the clearance.

 

[drjohnnyfeva]

@M70AB2 Yep, hindsight, but I don't even think it was a millimeter, I just didn't want to force it. Plus, sawing the case in half opened the door to lifting the tube sockets enough off of the board so the tubes could go in in their locktal socket as intended without the need of removing the aluminum casing.

What I'm probably going to do is build an inexpensive wood case where I can have all of the jacks at the back, put new sockets on the top of the case, and a new volume knob on the front. But I'm not in any rush.

 

[M70AB2]

@M70AB2 Yep, hindsight, but I don't even think it was a millimeter, I just didn't want to force it. Plus, sawing the case in half opened the door to lifting the tube sockets enough off of the board so the tubes could go in in their locktal socket as intended without the need of removing the aluminum casing.

What I'm probably going to do is build an inexpensive wood case where I can have all of the jacks at the back, put new sockets on the top of the case, and a new volume knob on the front. But I'm not in any rush.

I’ve seen a lot of nice enclosures on eBay.

I think I have a Greenlee punch the correct size for the tubes.

But like you, I am in no rush to rehouse it.

 

[raycarr00]

got one yesterday and allowed it to break-in over night(about 17 hours) before playing anything through it. no ringing. just a clear, quiet, detailed and flat sounding. running it with a 5v/ 1a cell phone charger at 109v ac(variac). using a 6bq5 amp and a cd player. appears to need a tad bit more treble. has plenty of gain. will try a variety of different factors- transistorized amp, higher amperage cell adapters, plugging it in directly to the mains, alternate speakers....for a few weeks before I tear into it and experiment with a variety of capacitors, tubes. alexi has them for about 38 bucks free ship. 4 bucks tax. got it on amazon for 70+.

 

[drjohnnyfeva]

got one yesterday and allowed it to break-in over night(about 17 hours) before playing anything through it. no ringing. just a clear, quiet, detailed and flat sounding. running it with a 5v/ 1a cell phone charger at 109v ac(variac). using a 6bq5 amp and a cd player. appears to need a tad bit more treble. has plenty of gain. will try a variety of different factors- transistorized amp, higher amperage cell adapters, plugging it in directly to the mains, alternate speakers....for a few weeks before I tear into it and experiment with a variety of capacitors, tubes. alexi has them for about 38 bucks free ship. 4 bucks tax. got it on amazon for 70+.

I think it says in the literature it needs 2 or 2.5 amps to function at its best...

 

[raycarr00]

5V 3.0A US Plug

 

[drjohnnyfeva]

Raspberry Pi 4 Power Supply Adapter ON/OFF Switch USB-C 5V 3.0A US Plug

That should work better than the 1amp... I have the supplied usb power wire plugged into a power strip usb port that is labelled 2.4amp max. Powerstrip usb ports are almost universally 5V...

 

[M70AB2]

I’m using a double USB plug. I figured it would provide enough current. But I should check.

 

[M70AB2]

Just got four Soviet tubes from a seller in Romania. Included is a datasheet in Russian. Has that de rigueur Soviet-era font and paper.

Reportedly, these tubes are exactly matched. Of course, I need to cut away the metal. Then we will see, er, hear.

 

[M70AB2]

Got two tubes out of their metal shells and installed them.

Only a very short time listening, but they seem to provide more bass. Guitars are detailed, maybe slightly more?

I noticed that at the very top of the tube, there is a small metal tab that aligns with the keyway. This ought to help with proper alignment. I will post a photo of this.

 

[raycarr00]

Got two tubes out of their metal shells and installed them.

Only a very short time listening, but they seem to provide more bass. Guitars are detailed, maybe slightly more?

I noticed that at the very top of the tube, there is a small metal tab that aligns with the keyway. This ought to help with proper alignment. I will post a photo of this.

Good to know. Does it, or did it have, plenty of treble? I don't have an adequate amount; it's flat or muffled. Tons of bass. Waiting for Russian tubes to arrive. Might need caps that are in spec. using 3amp pwr supply.

 

[M70AB2]

Given that I am using the E6 with a garage system that could scarcely be termed “audiophile,” it’s difficult for me to give definitive answers.

I only had a very brief time listening with the Soviet tubes. Also, it was with a CD I just grabbed and not a CD I with which I typically test.

As a lifelong musician, I naturally will tend to listen for aspects that relate to my instruments.

It would seem that some digital spikiness on the distorted electric guitar is ameliorated without reducing treble.

I haven’t tried any of my Classical CDs, so I can’t comment.

I seem to notice a bit more midrange “push,” but again, I only listened very briefly. And it’s cold in there too.