Nobsound E6 Preamp Uses Directly Heated Tubes

[drjohnnyfeva]

@M70AB2 let us know. I was not aware of NOS Chinese tubes - but that's maybe what the E6 was shipped with. No idea. Anyway, let us know.

 

[M70AB2]

Maybe I was not clear? The 2P29L tubes are a similar tube to the stock 2J27L tubes included with the E6 as detailed previously in this thread.

I would like to hear them and the price was right, so why not?

 

[M70AB2]

Update: the eBay seller canceled my order, but are still listed on his eBay.

 

[Lenco803]

A lot of great info here! Purchased the E6 a few weeks ago. No hum, hiss or ringing at all with the stock tubes.
Here is my system:
Oliver Sayes custom 46/2A3 mono integrated amp.
RCA LC-1A Speaker.
Bluesound Node 2i with LPS mod (used as Streamer only).
MHDT Orchid DAC (modded a bit).

The RCA s an easy 16ohm load and is fairly efficient at 95dB but even with this setup I needed just a bit move gain. I first read about the E6 on Doctorjohn Cheapaudiotube website.

I have to say this little E6 is pretty amazing for the money. Yes it could be more transparent and extremes are rolled off a bit but the midrange performance is really good, not great. My plan is to upgrade the caps with these Russian PIO's and bypass the lytics with some teflon or polystyrene that I have in my stash. Obviously I have to remove the case and mount all of the rest on a small board. I also use the Moongel pads under some equipment.

 

[Lenco803]

Phase 1 complete:
Replaced the four gray coupling caps with Russian PIO’s (same values) mounted on PE crossover board. The E6 will be located behind the speaker cabinet out of site.

These caps made an immediate difference after cooking for 48 hours on lowish volume. Better dynamics, transparency, and tone.

 

[drjohnnyfeva]

Phase 1 complete:
Replaced the four gray coupling caps with Russian PIO’s (same values) mounted on PE crossover board. The E6 will be located behind the speaker cabinet out of site.

These caps made an immediate difference after cooking for 48 hours on lowish volume. Better dynamics, transparency, and tone.

I changed the coupling caps myself. I love these mods. Gives me more ideas! Kudos to you, @Lenco803 .

 

[Lenco803]

I’ve been messing with audio gear for like 45 years now. When manufacturers are coming out with their “Signature“ models what are they doing? They tweak the circuit a bit but mostly upgrading components especially capacitors and resistors.

Phase 2 has been implemented. An Acopian LPS. I’m a firm believer in good clean power and Acopians are good industrial units, cheap used.

Phase 3 will be replacing the lytics. I have the correct value ones in my stash.

I spent like $75 upgrading the E6.

 

[drjohnnyfeva]

I’ve been messing with audio gear for like 45 years now. When manufacturers are coming out with their “Signature“ models what are they doing? They tweak the circuit a bit but mostly upgrading components especially capacitors and resistors.

Phase 2 has been implemented. An Acopian LPS. I’m a firm believer in good clean power and Acopians are good industrial units, cheap used.

Phase 3 will be replacing the lytics. I have the correct value ones in my stash.

I spent like $75 upgrading the E6.

Nice!

I love that the tubes aren't "shelled." I had wanted to try that a couple years ago, and if you read the whole thread, we tinkered with minor ideas to do just that, but it didn't pan out. Since then, when I opened up the case to change the coupling caps, I had to shear off the top half of the case with the tube holes because the new caps were a mm or two too large and they wouldn't slide back into the case. lol. Missed it by that much! ...as the saying goes.

Anyway, the E6 is a good unit. I really like it. I use it to add gain to my school system, because the school issue laptop gives a weak signal. But I find it gives punch to whatever music or av I have going thru it.

One question, have you noticed any microphonics? I'm curious whether keeping the tubes in the shell - because there's quite a lot of damping material in there - is a kind of fail-safe against microphonics. I know the tubes are shelled because of aesthetics, but, certainly there's a reason for encasing them...plus, I kind of thought they looked cool as is, so I had designs - initially - on the case adjustment to accomplish keeping them as is and maybe eliminating the microphonics.

 

[Lenco803]

Nice!

I love that the tubes aren't "shelled." I had wanted to try that a couple years ago, and if you read the whole thread, we tinkered with minor ideas to do just that, but it didn't pan out. Since then, when I opened up the case to change the coupling caps, I had to shear off the top half of the case with the tube holes because the new caps were a mm or two too large and they wouldn't slide back into the case. lol. Missed it by that much! ...as the saying goes.

Anyway, the E6 is a good unit. I really like it. I use it to add gain to my school system, because the school issue laptop gives a weak signal. But I find it gives punch to whatever music or av I have going thru it.

One question, have you noticed any microphonics? I'm curious whether keeping the tubes in the shell - because there's quite a lot of damping material in there - is a kind of fail-safe against microphonics. I know the tubes are shelled because of aesthetics, but, certainly there's a reason for encasing them...plus, I kind of thought they looked cool as is, so I had designs - initially - on the case adjustment to accomplish keeping them as is and maybe eliminating the microphonics.

I never experienced microphonics with the original tubes or the 2P29L’s thou the volume pot is a bit squeaky at times. I‘m sure encasing the tubes is for microphonics and RF shielding. The fact that my modified E6 competes with my much much more expensive preamp in my main system is a real eye opener, ear opener.

 

[wearntear]

I never experienced microphonics with the original tubes or the 2P29L’s thou the volume pot is a bit squeaky at times. I‘m sure encasing the tubes is for microphonics and RF shielding. The fact that my modified E6 competes with my much much more expensive preamp in my main system is a real eye opener, ear opener.

Have you completed phase 3? What was the result?

 

[raycarr00]

Pio caps breaking in at 1amp 5v, even the 100v versions? Bet that the pre benefits from not being turned off. I'll now have to hook it up and give it a listen.

 

[Lenco803]

Have you completed phase 3? What was the result?

Not yet but you motivated me now so maybe this weekend.

 

[Lenco803]

Pio caps breaking in at 1amp 5v, even the 100v versions? Bet that the pre benefits from not being turned off. I'll now have to hook it up and give it a listen.

It’s fully broken in now and I never turn it off. I see Decware makes a gain stage device thou much more expensive than the E6.

 

[FlaCharlie]

Pio caps breaking in at 1amp 5v, even the 100v versions? Bet that the pre benefits from not being turned off. I'll now have to hook it up and give it a listen.

The PIO caps are not being subjected to 1A (1000mA) and 5v. I assume you’re referring to the rating of the external power supply that’s recommended for the E6.

The PIO caps he installed are coupling caps. Coupling caps block DC and allow AC (the music signal) to pass. Under normal conditions they have almost no current going through them. From what I’ve read it’s typically less than 1mA (1/1000 of an amp) and certainly no more than a few mA. The voltage rating of a coupling cap should be at least as high as the voltage that supplies the tube not the plate voltage, which is lower. That's in case there is a malfunction.

The 5v external PS may be capable of supplying up to 1A (or 5A or 10A) but with tubes it’s the device being powered that determines the actual current draw. There’s no way that the total current draw of the E6 is anywhere near 1A / 1000mA.

There are two factors that contribute to current draw - the tube heaters / filaments and the operating point of the tubes.

For a typical preamp tube, the heaters account for most of the current draw and that spec is listed in the tube’s data sheet. The filaments of the 2J27L only draw 56mA since they were designed to be used in battery powered radios. So that’s only 112mA for the pair. When it comes to heater current the main thing is to be sure you’re not exceeding the current capability of the portion of the power supply that runs the heaters. In a traditional PS this would be the heater winding of the power transformer. The voltages supplied to run the tube itself are separate from the heater / filament supply.

Since these are preamp tubes they have a plate load resistor so you can determine their operating current by measuring the voltage drop across the plate load resistor and calculating the current for each tube using Ohms Law.

I have yet to go into my E6 but, as an example, if you look at the schematic for the DIY 2P29L Preamp that I linked in Post #1 you’ll see that the supply voltage (B+) is 308v. The plate resistor is 15k and the voltage on the plate (measured to ground) is 114v. So voltage drop is 194v and 194 / 15,000 = 0.0129A, which is 12.9mA per tube. So 25.8mA total operating current is being drawn.

If @Lenco803 has taken any voltage readings or tried to draw a schematic of the E6 it would be great if he could post them. Nobsound says something about 105v in its description of the preamp. I'm wondering if that is the supply voltage or the plate voltage. That, along with the current, would tell us the operating point of the tube.

 

[raycarr00]

Looked for the e6 all last night and this morning; it disappeared. On the pio's, was thinking of my lack of success in using them in higher powered amps, they never seem to open up or make a significant difference in my ears. Doesn't mean they don't make a difference here. Was wanting to try the mods. Well. When it turns up.

 

[Lenco803]

Have you completed phase 3? What was the result?

Finished. Better bass and tone.

 

[raycarr00]

Wow! Good to hear. Would very much like to try, but still MIA.... Will have to buy another one.

 

[Lenco803]

Looked for the e6 all last night and this morning; it disappeared. On the pio's, was thinking of my lack of success in using them in higher powered amps, they never seem to open up or make a significant difference in my ears. Doesn't mean they don't make a difference here. Was wanting to try the mods. Well. When it turns up.

I’ve used the KBG-MN PIO’s in my 2A3 amp and in speaker crossovers with great succes.

 

[raycarr00]

Was about to order them when hearing about this new mod. Looked high and low yesterday, as well. It's so small...Where's Waldo?

 

[raycarr00]

Found it! Now, how do I make time for this and a Sherwood s-5000 ?