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Boyuu EL34 A9 Tube Amp
Boyuu EL34 A9 Tube Amp
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Old 6th July 2019, 07:29 AM   #1021
huggygood is offline huggygood  France
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I just did a test with my little FX Audio plug-in preamp equipped with EF95 and the result is surprising in a good way.
The sound stage, the stereo sound separation is considerably improved, everything seems cleaner and less artificial.
I do not know why yet, but I will try to understand.
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Old 6th July 2019, 03:16 PM   #1022
nitrate is offline nitrate  United Kingdom
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@daniellu,

Did you find that giving the el34 output tubes reduced the noise floor further?
Normally i don't bother with the outlut tubes, just the small signal stages.

Have fun,
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Old 6th July 2019, 10:22 PM   #1023
huggygood is offline huggygood  France
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anyway, if you spend your pentode in triode you decrease your gain, so the question does not arise.
moreover, it is recognized that the EF86 gives the best in triode, so the E80F will be even better in this mode.
I started to have the tour of the tests and for now, it is still the kt66 that gives the best result at home.
I tried 6p3,6p6s-e, kt77, el34,6l6gc, 6l6wgb.
I still have 6CA7 to try but I'm happy like that and I do not want to look further
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Old 7th July 2019, 12:00 PM   #1024
daniellu is offline daniellu  Australia
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@ Nitrate,
I don't think it made much differences. overall I am quite happy with the baseline noise of my A9. I tried my solid state Amp, without signal , I could hear the faint noise within 5cm from the mid range speakers. The A9, if i listened carefully, i could hear faint noise within 10cm. Practically it will never bother me.
Good weekend!
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Old 7th July 2019, 12:17 PM   #1025
huggygood is offline huggygood  France
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Quote:
Originally Posted by huggygood View Post
anyway, if you spend your pentode in triode you decrease your gain, so the question does not arise.
moreover, it is recognized that the EF86 gives the best in triode, so the E80F will be even better in this mode.
[this answer is not for this thread]
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Old 7th July 2019, 01:34 PM   #1026
anatech is offline anatech  Canada
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Boyuu EL34 A9 Tube Amp
Hi huggygood,
I have to admit to preferring the 6CA7 over the EL34. Of course they are often mismarked. If its fat, it is a 6CA7 and not an EL34 (tall and skinny). The real 6CA7 is a beam power tube whereas the EL34 is a real pentode.

The KT66 is very close to a 7581A. That is a 6L6GC with 35 watt plate, and it does have the same plate characteristics as the 6L6GC from what I can tell.

-Chris
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Old 7th July 2019, 02:55 PM   #1027
nitrate is offline nitrate  United Kingdom
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Hmmm,

I wired my remaining stock channel to introduce a little feedback and bypassed the 6n9p cathode to increase gain to compensate for the loss of overall gain. Listening tests swaping from one channel to the other showed no noticable difference between the two ( if you read my earlier posts i heavily modified one of my channels ). The feedback was done by inserting a 100r resistor between the bypassing of the 6n9p and ground. There i injected the feedback via 2k from the speaker terminal. I also increased current on fhe driver to better bias the tube ( 1k cathode resistor ), and also added 1k to the el34 cathode making a total of 333r cathode.

Now i have a difficult decision on what scheme to keep on both channels. My latest attempt has better hf responce, better squares but higher 2nd harmonics and higher output impedance. It now requires 2500mv to drive into clipping compared with 500mv on my other channel. It does however retain the spirit of this amplifier and does not invert the output waveform.

What would you do?
Both sound equal even if my scope says different.
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Old 7th July 2019, 03:02 PM   #1028
huggygood is offline huggygood  France
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I too prefer 6CA7 to EL34. in the case of my A9, it is the EL34 which gives the least good result but it is the Electron Tubes sold with the kit so it is not representative. 6p3S-e and 6L6gc are very close in sound signature 6P3s is close to the EL34, flat and bland, I want to say gray and dull. KT66 is shining, goes down well in the low end, clean, and looks easy. my 6ca7 are already used with my clone Leak and I do not want to touch it, however I will try KT88 and maybe even kt150 with a separate power supply for heating.

what I can say more is that in any case, this little amp is inferior to my harman A300 a little modified, the Harman is a little more "noisy" but remains a real pleasure every day.

end of the story for this little Chinese beetle, I put it on sale. for who wants to have fun, it's a good amp but for the price, it is still better to find a TRUE amp with a TRUE scheme and a TRUE brand on the second hand market. I think the limiting factor is always the opt and you can not turn a donkey into a racehorse. yesterday, to "see" I confronted him with a 1030 marantz, the boyuu was ridiculous next to the marantz, I made my decision.

one last thing. do not use the power cable supplied with the kit there is a real danger to use it, it is not a 3x0.75 but rather a 3x0.25 with insulators of very poor quality that mimic the silicon but melt near the soldering iron.
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Old 14th July 2019, 03:24 PM   #1029
anatech is offline anatech  Canada
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Boyuu EL34 A9 Tube Amp
That is a good warning for people who aren't experienced and wouldn't know there was a problem with the power cord.

-Chris
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Old 18th September 2019, 05:50 PM   #1030
docdeule is offline docdeule
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Did someone also figured out that with the standard main switch at the front the left channel has 50 Hz hum. I put the twistet wire and the main switch out of the chassis and the 50Hz hum disappear. Just a small amount of 100Hz hum from the rectifier is still there, but I have the standard filter capacitor in place. Will be increased soon.

Does the GD24491 RMS1035 Lorlin decrese noise introduced in the left channel preamp?
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