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Nobsound E6 Preamp Uses Directly Heated Tubes

Thanks for your comments FlaCharlie. Using passive volume control isn't really possible in my case, since the poweramp has quite a low input impedance, so some sort of a buffer is needed. I thought a small dht would be the kicks, but it looks like the input voltage sens is simply to high like you say. I wonder if theres a fix to it.

Regarding bass, in my case, I have noticed a considerable reduction in the low end as the tubes/amp "burned in". I'm actually sad that it went away, as the fullrange drivers without xo-s are a bit dry, but on a warmer system I can see this initial bass boost being like dipping everything in honey. This was oem chinese tubes, bass went fully "away" in a week or so. Now its possibly even a bit rolled off at the bottom.
 
@FlaCharlie I appreciate your suggestions in approaching the E6 and I considered ordering another one, but the single arbiter for me was reliability.

I just don't want to spend that kind of time and aggravation to get something that will probably work if the right input/output characteristics are in place. The howling feedback can easily be harmful to speakers and ears.

That being said, I heard the preamp performing nicely at the AK Peekskill meet in NY which is what got me interested. I was just looking for something portable but reliable under different circumstances, so for my needs, this doesn't really fit the bill. Also, no matter what, after the outlay with new tubes, it's not really that inexpensive and the fact that many simply do not work without intervention violates some of my personal basic gear criteria. But I can see that tinkering for gold can be an enjoyable pursuit to audio fans and the E6 can indeed be fertile ground! Have fun!
 
Supercool! said:
@FlaCharlie I appreciate your suggestions in approaching the E6 and I considered ordering another one, but the single arbiter for me was reliability.

I just don't want to spend that kind of time and aggravation to get something that will probably work if the right input/output characteristics are in place.
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Yeah, I fully understand the frustration with these.

The two amps that I use it with are able to deal with its idiosyncrasies because the tube one has an unusually low input sensitivity and the Ayima A-07 is an integrated so its volume control can be adjusted to make it work.

As for reliability, they don't seem to be reliable in the sense that you can't count on them to be plug and play into any system. I was able to get it to work fine with the amp I was recently modding because I just happened to have a DIY "passive preamp" sitting around so inserting it between the E6 and the amp is the equivalent of having an amp with a volume control. Without that "intervention" it would have been unusable with that amp.

I haven't heard any reports of them dying but it wouldn't surprise me if some of them are defective upon delivery. That's why I asked if your amp has a volume control. If it does and you still couldn't get it to work with the volume set low, then the unit was probably defective. Stringent quality control in not something I associate with inexpensive Chinese gear. Most initial complaints seem to be about the Chinese tubes but that's a common complaint with all inexpensive Chinese tube gear.

So what kind of amp were you using with it? Does it have its own volume control?
 
Yes it probably does as the amp is an el84 DIY tube amp. That being said, I've used this amp on many different occasions with everything from passive to active pre amps, tube and otherwise. In this case, I only had that amp and a set of Minimus 7's available which I was willing to gamble because of the noise reported. As it turned out I ultimately experienced this in person. Unfortunately, the two other systems I have in that room would be very costly to repair. Not worth the risc/reward

I'm sure further exploration would yield better results but one of the requirements I have is reliability, and I should add, reliability with compatibility. The pre I need will be confronted with different equipment in timely demo situations. I've never had a pre amp behave like this one and in fact it may have been defective. Ultimately though, when I run into gear like this I move away quickly and the pre has already been returned and refunded.

I do love and respect your zeal and willingness to share and document the E6. Were I younger and equipped with more lifetime years than choices, I might jump into the endeavor. This hobby is actually just so cool because of folks like you!

It's funny, in the 50's and early 60's "hi-fi" was very DIY with thriving kit building and modification. Now with inexpensive options becoming available from China and other countries it's kind of happening again!
 
Supercool! said:
Yes it probably does as the amp is an el84 DIY tube amp. That being said, I've used this amp on many different occasions with everything from passive to active pre amps, tube and otherwise. In this case, I only had that amp and a set of Minimus 7's available which I was willing to gamble because of the noise reported. As it turned out I ultimately experienced this in person. Unfortunately, the two other systems I have in that room would be very costly to repair. Not worth the risc/reward

I'm sure further exploration would yield better results but one of the requirements I have is reliability, and I should add, reliability with compatibility. The pre I need will be confronted with different equipment in timely demo situations. I've never had a pre amp behave like this one and in fact it may have been defective. Ultimately though, when I run into gear like this I move away quickly and the pre has already been returned and refunded.

I do love and respect your zeal and willingness to share and document the E6. Were I younger and equipped with more lifetime years than choices, I might jump into the endeavor. This hobby is actually just so cool because of folks like you!

It's funny, in the 50's and early 60's "hi-fi" was very DIY with thriving kit building and modification. Now with inexpensive options becoming available from China and other countries it's kind of happening again!
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My comment about a possible amp fix was actually directed at bridger2086.

But it certainly sounds like your DIY EL84 reacted the same way that my PP 6N6G Magnavox mod did. Adding the "passive pre" between them worked but there was no way that it would have without that addition.

I started the thread about the E6 simply because, with its directly heated tubes, it is so unique. I only use it occasionally and only with the two amps I mentioned. So I don't really participate in the thread all that often. I'm sure others here use their E6s more regularly, perhaps daily.

You mentioned that you heard one at an AK meet in NY. Do you recall what type of amp it was paired with?

At 72 I'm not exactly young either! I started collecting vintage gear and restoring it almost 25 years ago but for the past several years my main focus has been on DIY builds. I'm always trying to get others interested in that aspect of the hobby.

Here's a thread about my most recent effort to encourage more DIYing:

Build This Tube Amp With A Screwdriver

So a few years ago I picked up a Switch Mode Power Supply (SMPS) that's designed for tube circuits. It has separate outputs for 6.3v and 12.6v heaters and a 300v output for the B+. But other projects took precedence so it sat on the shelf for a long time. Some folks over at DIYAudio had...
www.audiokarma.org
 
I'll only chime in briefly here, because I have had little trouble with the E6.

I've had the microphonics issue twice - once when I bumped it inadvertently while in operation (user error) and another time that I used it without the additional gain I deliver to it from my PC and Little Bear T7 Tube Pre. No matter what I set the PC volume at or the Fisher 170 receiver volume, the E6 rang like a bell and got louder when the volume on the E6 was increased. E6 on low volume, PC on low and normal use of the receiver volume saw ringing starting at 3 and becoming unbearable by 4. Same with low volume on E6 and receiver but controling volume on PC - starting ringing at maybe 25% and by 30% it overcame the music. Suffice it to say that no combination of controls yielded a signal without significant ringing. But when I put the Little Bear back in the chain after the PC, then to the E6, and then to the receiver it worked like a charm again.

I've been using the E6 in a Fisher 295 at school. I have it running thru the tape loop as you would with the pre in/ main out to boost the volume of a school laptop so that kids can hear the audio of the videos I need to play as part of my tech instruction. I also play music thru it that way and it sounds great. No microphonics at all.
 
got around to playing with the Nobsound E6 and believe I have reached the treble I was listening for: on the 10uf cap, changed it to a wima 10uf and it did nothing. incrementally changed it to 1330uf and it's improved for me from a flat sound, to much added treble(I can now hear the cymbals and the flutists breathing). it's still clear and quiet. the bass is no longer as pronounced as before, though. played classical, jazz, blues, rock and reggae to test it. added 220uf to the 1000uf cap or 1220uf total in the center of the pre and then eliminated it. produces sound notes better, or more drive, with the added 220uf to the 1000uf; might try changing it to 1330uf. but it's good as is, now. even accidentally dropped a vape on the tubes and they still play.
 

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Just had a listening session with the included Chinese tubes over the Russian tubes I began my experiment with, and the treble was a bit high, good midrange, less bass and higher gain. I suspect the Russian tubes might have been weak to begin with.
 
drjohnnyfeva said:
https://audiokarma.org/forums/index...-tube-preamp-a-31-wonder.848535/post-17284011

Above is an introduction to a new Nobsound DHT preamp. Seems interesting and indicates, thankfully, that the DHT experiment started with the E6, might continue with more units.
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Appreciate you moving the conversation here!

I looked through Douk's most recent offerings, and so far, I've found that their T6PRO promises the same tube performance (and with the same 6J1 tube types too). A promising sign that this is the way to go for them with tube stuff.
 
drjohnnyfeva said:
https://audiokarma.org/forums/index...-tube-preamp-a-31-wonder.848535/post-17284011

Above is an introduction to a new Nobsound DHT preamp. Seems interesting and indicates, thankfully, that the DHT experiment started with the E6, might continue with more units.
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The tubes used in the new Douk P1 Plus are the same types used in the FX. They are not directly heated triodes (DHTs). They are indirectly heated pentodes that are wired as triodes. The main change is that they are now being run at higher voltages.

I tried to download the graphic of the schematics to see the details. Unfortunately, it's some odd file type that can't be opened on my computer. I took a screen shot but the images are too blurry to read when they're enlarged. But at least they are releasing schematics so perhaps at some point they can be examined.

The new model just combines several features into a single model. It includes a DAC, a variety of inputs (usb, coax, optical and Bluetooth), digital and analog outputs, a headphone output and some useless eye candy (a VU meter) at a jacked up price of $269.
 
FlaCharlie said:
The tubes used in the new Douk P1 Plus are the same types used in the FX. They are not directly heated triodes (DHTs). They are indirectly heated pentodes that are wired as triodes. The main change is that they are now being run at higher voltages.

I tried to download the graphic of the schematics to see the details. Unfortunately, it's some odd file type that can't be opened on my computer. I took a screen shot but the images are too blurry to read when they're enlarged. But at least they are releasing schematics so perhaps at some point they can be examined.

The new model just combines several features into a single model. It includes a DAC, a variety of inputs (usb, coax, optical and Bluetooth), digital and analog outputs, a headphone output and some useless eye candy (a VU meter) at a jacked up price of $269.
Click to expand...

Thanks for clarifying. Yeah, if they were to do the same approach with the tubes but release something like the Tube-01 with no op-amps, I'll be down for it.
 
lazylistener said:
Thanks for clarifying. Yeah, if they were to do the same approach with the tubes but release something like the Tube-01 with no op-amps, I'll be down for it.
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I wouldn't hold my breath . . . the chance of them putting out a new version of the Tube-01 that simply runs the tubes at higher voltages seems unlikely. The trend with new products is to add more features and sell the resulting product at a considerably higher price. The new model that was mentioned is a prime example.

From a marketing standpoint, the fact that the tubes are being run at higher voltages is only a minor technical difference to the vast majority of their potential customers. It's probably the least appealing aspect when compared to functional "features" like Bluetooth, remote control or an integral DAC. Most people will be much more interested in the VU meter that has a choice of backlight colors - even though it's totally useless eye candy.

If commercial offerings don't fit your needs the answer, as I've often suggested, is DIY. As my most recent DIY threads show, it's not that difficult. One is linked in Post #306 above. Here's the most recent one:

My 10 Year Old Granddaughter Builds a Tube Amp

This was actually the first circuit I developed with the convenient SMPS used in the Simplissimo, the breadboard style SE EL34 that I posted previously: https://www.audiokarma.org/forums/index.php?threads/build-this-tube-amp-with-a-screwdriver.1061713/ While the circuit used here is different...
www.audiokarma.org

If you're set on using a Class D or SS amp the same build techniques could be used to build a tube preamp.
 
Wow, Charlie! The one you built with your granddaughter is super. Puts me to shame a bit for not getting over the butterflies of attempting the Boogie Factor. I really like the no solder idea and those tube boards look like they'd be pretty easy to deal with.
 
Hello everyone

i am new to this site and a noob about modifying electronics. I bought an E6 because I wanted a tube preamp. So far I am enjoying it. I did have the microphonics people talked about but it went away when I sat it on a pile of bubble wrap. The reason I am writing is the E6 comes with 2j27s tubes but the stream on this site talks about ordering 2j27L tubes as a replacement. Are these tubes interchangeable?
 
wearntear said:
Hello everyone

i am new to this site and a noob about modifying electronics. I bought an E6 because I wanted a tube preamp. So far I am enjoying it. I did have the microphonics people talked about but it went away when I sat it on a pile of bubble wrap. The reason I am writing is the E6 comes with 2j27s tubes but the stream on this site talks about ordering 2j27L tubes as a replacement. Are these tubes interchangeable?
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I rolled the Russian tubes in. I've tried both the 2j27L and 2p29L's. They both work. The 2j27L's have more gain and I needed that for my system. Mine is still running strong and sounding great. I use it on the system I took to school to help amplify the crappy laptop output we have. The original tubes are hit and miss. There are a lot of complaints about microphonics, in general, with this unit. The problem seems more apparent with the stock tubes, but when they work without incident, the sound reports have been positive, so don't give up on them. Anyway, good luck with it. It's a fun unit to mess around with and out of the box I think it sounded better than the much discussed FX Audio Tube03... which I have messed around with a lot.
 
As previously mentioned, seems I won the Chinese tube lottery as mine sound perfectly fine, no problems with my garage system.

Thinking of popping them back in as I did like the slightly sweeter sound and I am curious to know how it might sound with the WIMA 1uF capacitor replacements.

I also ordered a pair of NOS Chinese 2P29L tubes, so we’ll see, er, hear.

Will report back.
 
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