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Nobsound EL34 Single-ended Class A tube amplifier

Discussion in 'New Gear - Values' started by Frank Sol, Jul 13, 2015.

  1. mjw21a

    mjw21a Super Member

    Messages:
    3,160
    Location:
    Brisbane, Australia
    Mmmm, I've just finished pimping my Oldchen SEP amp. Looks much prettier now. My wife was complaining that it didn't match the room so it either had to go or it needed to look better:

    Before:

    IMG_20180107_105740.jpg

    After:

    IMG_20180108_160026.jpg IMG_20180108_160013.jpg

    I'm sure others can do a better job than I, though it is still an improvement.
     

     

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  2. Frank Sol

    Frank Sol Addicted Member

    Messages:
    8,166
    Location:
    SoCal

    I like :thumbsup:
     
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  3. jadobbins77

    jadobbins77 New Member

    Messages:
    14
    Location:
    The Land of Enchantment
  4. DavidTT

    DavidTT AK Subscriber Subscriber

    Messages:
    531
    Just purchased the Gemtune X-1 from Amazon. Should be here Tuesday and I'm looking forward to adding it to my home office set up. Now I need to purchase a set of desktop/bookshelf speakers to compliment it. I've been leaning toward something like the Klipsch R-15M but haven't finalized. Here's hoping my first foray into Chi-Fi power amping goes well!
     
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  5. Nixxuz

    Nixxuz AK Subscriber Subscriber

    Messages:
    803
    Location:
    Minnesota
    Klipsch with the fairly high sensitivity rating is probably a good bet for the lower wattage the Gemtune is putting oit.
     
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  6. Poultrygeist

    Poultrygeist Lunatic Member

    A great speaker match for the single ended EL34 are these easy to build Betsy open baffles. If you lack the tools, Home Depot will make the straight cuts provided you buy their wood. I have a pair that I use with a single ended 3 watt APPJ amp and the sound is nothing short of amazing. These are true audiophile speakers that you can build for under $200.

    If you own one of these flea watt EL34's the next step is unleashing it's full resolution. To me that means high efficiency full range single drivers like the Betsy. Unlike conventional speakers there are no crossovers in the signal path to mar the sound as the amp is wired directly to each driver. But most important the Betsy's offer all the benefits that come with open baffles and I could write volumes on that but not here. :)

    http://www.wildburroaudio.com/projects.php
     
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  7. DavidTT

    DavidTT AK Subscriber Subscriber

    Messages:
    531
    So, the Gemtune X-1 arrived this morning along with a set of Klipsch R-15Ms. Setting them up was simple enough and I'm breaking them in as I write this. First thoughts are that the sound is very, very good right out of the box, at least in my desktop near field listening environment. This amp puts out more power (at 8W/channel) than I'll ever use in this environment, especially with these efficient speakers.

    Second thought is that these tube amps run quite hot don't they? I'm not looking forward to the A/C usage in the summer that's for sure! Not much time for a better review now, but will add thoughts in the next couple of weeks. All I know is that it seems great to run a turntable directly through tubes and into speakers. Loving it.
     
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  8. DavidTT

    DavidTT AK Subscriber Subscriber

    Messages:
    531
    Question for those who use low power SET EL34 amps. As noted above, I bought a Gemtune X-1 (same as Nobsound NS-13D) and have been using it for about 8 hours now, 4 hours each time. So far it's been great, aside from the obvious varnish odor it's emitting. All good and sounds really great with a new pair of Klipsch R-15Ms on my desktop. Anyway, its placement is such that getting to the gain control is a little inconvenient so I added a FX-audio tube-01 preamp to the chain, mainly because I own it and I can place it such that getting to its gain control is easy. It sounds good in front of the Gemtune and I have the gain on the Gemtune set very low, using the gain control on the FX-audio as a volume controller.

    So, I have no experience with preamps to speak of, other than this little FX-audio unit, which I originally purchased to add to a SS chain. Is there anything I should keep in mind regarding adding gain control in front of an EL34 amp? I assume that I can overdrive the unit if I crank the gain on the preamp, or not? Anything else I need to think about here?
     
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  9. Poultrygeist

    Poultrygeist Lunatic Member

    When using a preamp with an integrated amp I max the latter and use the preamp to control the volume.
     
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  10. DavidTT

    DavidTT AK Subscriber Subscriber

    Messages:
    531
    Great and thanks for the reply. This has been a great little amplifier so far. Really enjoying the sound.
     
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  11. DavidTT

    DavidTT AK Subscriber Subscriber

    Messages:
    531
    I've continued to enjoy this amp a ton. A week or so ago the amp blew a fuse, then another, then another the next day. Instead of remaining rational and searching for a reason, including the tubes themselves, I emailed the seller. I will give them credit, because the unit was beyond the amazon return window, but the seller agreed to refund my money once I returned the unit. Gemtune/Nobsound/Gold Dust is very responsive as it turns out.

    Because of the hassles associated with shipping, I decided to do some googling and found the problem in short order. When I first received the unit I had replaced the rectifier with a JJ 5AR4, and the preamp tube with a Sovtek SL67. Well, I never saw a flash in the rectifier but it must have gone south on me, which apparently is common with JJ rectifiers early in their lives. Once I installed the original tube set, the unit worked like a champ and has continued to do so ever since. I guess I'll order a Tung Sol or Sovtek rectifier to have on hand.

    So, now I have a little baby APPJ miniwatt on the way from MassDrop, which will go on the desk where the Gemtune is now. The Gemtune has much more power than I need for desktop Klipsch R-15Ms, so I'll find another spot for it. 8 watts per side is overkill in my offie system! Go figure. It's a good problem to have, to have an extra tube amp on hand. I have a set of OBs in the basement so maybe I'll find a way to drive two of the OB drivers with the Gemtune and figure out the other half of the equation from there.

    Anyway, sorry to reawaken this thread, but the Nobsound/Gemtune 8W EL34 units are really great in the right applications.
     
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  12. Frank Sol

    Frank Sol Addicted Member

    Messages:
    8,166
    Location:
    SoCal

    No problem :)

    Played mine about 3 hrs last Thursday night...
     
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  13. Poultrygeist

    Poultrygeist Lunatic Member

    Glad it worked out for you. Spare tube amps are good to have. I think I have four but none over 4 watts and they all sound different. Mix and match is where the fun is.
     
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  14. KlipschFan61

    KlipschFan61 Smooth Jazzer

    Messages:
    938
    Location:
    Manchester, NH
    The Gemtune GS-02 is also a nice little amp for the money. Put a quality 5U4G rectifier in it and some decent input tubes and you have one sweet little single-ended tuber.
     
  15. Frank Sol

    Frank Sol Addicted Member

    Messages:
    8,166
    Location:
    SoCal

    Got these coming , maybe on Tuesday

    JJ-E34L
    Matching
    24-Hour Burn-In

    From Tube Depot


    [​IMG]
     
  16. Poultrygeist

    Poultrygeist Lunatic Member

    Frank, I hope those JJ's work OK for you. I bought a quad of JJ EL-84's a few years ago and within a few months two popped.
     

     

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  17. Frank Sol

    Frank Sol Addicted Member

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    8,166
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    SoCal

    wow

    my fingers are crossed

    Listening to Tung-Sol KT66s now
     
  18. premington

    premington New Member

    Messages:
    14
    Hey folks (Frank and everyone)!

    Well, it's been some time since I last gave a report about my Nobsound NS-13D amp. I bought it over a year and a half ago. I had a question about it, but need to explain what's happened with this amp. The last post, I reported I liked the amp but didn't care for the speaker hummmmm, regardless of which input was used (computer/turntable). Well, things got interesting in a very bad way.

    The hum increased gradually to become so violent, it shook the upper part of the cabinet, where the transformers are housed. I opened the chassis and found the two smaller transformers were shaking like an SOB! The vibration was so pronounced, you could hear it in the other room. I took the top part of the case off and installed seven layers of electric tape and then remounted the top of the chassis on the bed of electric tape. This quieted the chassis down quite a bit, but you could still hear a loud hum from the amp PLUS the usual hum from the speakers.

    Shortly after, the entire amp died. :-(

    I looked everywhere and didn't see a fuse. Since I need it for work, I replace it with a new one from Amazon. Got it two days ago. I plugged all my OLD tubes in and fired it up. Immediately, the old stock rectifier tube flashed and the new amp went dead. <sigh> The rectifier tube blew, and now I had TWO dead amps! :-( I opened the chassis of my OLD dead amp, plugged it in, and decided to trace back where the voltage was dying out. This is where I feel VERY stupid! (I'm not a technician... I'm a hobbyist!) I noticed no power was coming off the back of the plug--I mean, nothing. The red "hot" lead read 0V. The plug had 120V coming off it. WTF! After close inspection, I noticed there was a fuse inside the plug housing. OMG! I didn't notice that. But it had a spare. Awesome! I changed the fuse.

    Since the new amp came with tubes, I now used the new rectifier tube with all the old tubes. I plugged them into the old amp, crossed my fingers, cringed, and flipped the power switch. The tubes lit! A minute or so later, the old amp was playing! I didn't play it for long, so I don't know yet if it's actually fixed. The transformer hum normally took five or ten minutes to begin buzzing. I have no other spare rectifier tube (I ordered two new ones). So I don't want to run this old amp until I have a spare (I have three sets of all the other tubes). I'm only running the new amp now.

    So after telling this looooong story, my question relates to the rectifier tube. I'm beginning to wonder if that was faulty from day one and contributing to the old amp's hum (both in the speaker and, later, the transformers and chassis). The old amp, I thought the transformers were faulty. Maybe it was all the rectifier tube? Can a bad rectifier tube cause AC hum through the speakers or buzzing/shaking transformers? Anyone have any thoughts on this?

    Now that both amps are running, comparing the two, I think the new amp is what the old amp should have been. The old amp was always a little left-channel dominant with a mild hum and thin soundstage. This new amp has a balanced output with both channels presenting equally. Also, there's a much cleaner soundstage that's louder, richer, and deeper. You can hear the audible placement of instruments. The old amp sounded like you were listening to two speakers with a little bit going on in between them. The new amp, when I turn it full volume with no source playing, it's so quiet. I can hear only a little hiss at full volume. The old amp was a mashup of hiss and hum.

    I appreciate any comments...
     
    Last edited: Oct 7, 2018
  19. Frank Sol

    Frank Sol Addicted Member

    Messages:
    8,166
    Location:
    SoCal
    What a rough journey , premington :(

    Maybe someone can help
     
  20. Frank Sol

    Frank Sol Addicted Member

    Messages:
    8,166
    Location:
    SoCal

    Got them today... already plugged in and driving a pair of SP-5500X

    fingers still crossed
     

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