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Boyuu EL34 A9 Tube Amp
Boyuu EL34 A9 Tube Amp
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Old 18th January 2019, 01:01 AM   #751
LongRoad is offline LongRoad  Russian Federation
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Quote:
Originally Posted by gregas View Post
So if the a9 has an put sensitivity of 750mv and my CD player outputs 2 volts, would this be the reason for Distortion at higher volumes?
that over 750mV will be fed to the amplifier causing signal distortion.
Be sure that the sensitivity of the input amplifier circuit must match the level of the output signal of the head unit. Input sensitivity is adjustable in the amplifier and sets the magnification factor, but high input sensitivity can lead to large signal distortions.
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Old 18th January 2019, 01:40 AM   #752
VictoriaGuy is offline VictoriaGuy  Canada
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Boyuu EL34 A9 Tube Amp
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Originally Posted by navydiver View Post
I do also note that when the amp is powered off, music still plays through the speakers until the caps have significantly discharged.
If you take out the rectifier tube and power up the amp with speakers attached, do you still hear the hum?

Quote:
Originally Posted by navydiver View Post
I hear you 6A3sUMMER....snip.... Thing works very well for my needs.
I agree with 6A3sUmmer that a bleeder resistor should be added to the B+ supply, if one isn't already fitted. You should be able to find spots for connection of the bleeder resistor on the PCB.
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Old 19th January 2019, 01:38 PM   #753
LongRoad is offline LongRoad  Russian Federation
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Made an amplifier input divider, it works well, it is controlled by a regular source selection button.
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File Type: jpg -750mv.jpg (52.8 KB, 188 views)
File Type: jpg back.jpg (50.9 KB, 196 views)
File Type: jpg back1.jpg (71.7 KB, 193 views)
File Type: jpg back2.jpg (91.8 KB, 195 views)
File Type: jpg back4.jpg (163.1 KB, 194 views)
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Old 21st January 2019, 10:36 PM   #754
VictoriaGuy is offline VictoriaGuy  Canada
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Boyuu EL34 A9 Tube Amp
Quote:
Originally Posted by LongRoad View Post
Made an amplifier input divider, it works well, it is controlled by a regular source selection button.
Looks useful - it creates a 'Hi Level' (CD) input and a 'Lo Level' (Aux) input.
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Old 22nd January 2019, 05:07 AM   #755
6A3sUMMER is offline 6A3sUMMER  United States
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A little excess gain in the amplifier is why we have volume controls.

Many CD players (with the DAC at full scale) have 2Vrms out.

Suppose you set the amplifier gain so that it is just below clipping (or just below high distortion) when the CD player puts out 2Vrms (DAC at full scale). But when you play a typical Chesky Records CD, the loudest section of the recording is -10dB below full scale. Now, your 10 Watt amplifier can only put out 1 Watt when listening to that CD (so you have to turn the gain up, but you can only do that if you have the excess gain available).

Last edited by 6A3sUMMER; 22nd January 2019 at 05:11 AM.
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Old 22nd January 2019, 05:21 AM   #756
navydiver is offline navydiver  Canada
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Great success. Explained herein: YouTube

I am sure there is room for tweaking once I get to know this A9 a bit better. Got some listening to do to find any warts but for now am very happy with outcome!
Cheers and thanks all!
TMF

Another question I have:YouTube

Short and to the point, anyone know where I can get a cage for this amp (see linked video)?
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Old 22nd January 2019, 10:24 AM   #757
LongRoad is offline LongRoad  Russian Federation
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Quote:
Originally Posted by 6A3sUMMER View Post
A little excess gain in the amplifier is why we have volume controls.

Many CD players (with the DAC at full scale) have 2Vrms out
I tried to explain clearly, but you persistently with one friend drank beer when I explained.
I do not urge everyone to make a divider, but in my case it is necessary.
Conclusion from my DAC 2.5V, send such a signal to your amplifier (750mv), then you will understand.


navydiver
BOYUU EL34 tube protection grill cover Reisong BOYUU A10 EL34 tube protection grill cover-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
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Last edited by LongRoad; 22nd January 2019 at 10:53 AM.
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Old 22nd January 2019, 07:11 PM   #758
navydiver is offline navydiver  Canada
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Thank you - I think that is for the A10 amp. Mine is the A9 which I believe is a different size? Will look at the site to see if they have an A9 version....
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Old 22nd January 2019, 07:40 PM   #759
VictoriaGuy is offline VictoriaGuy  Canada
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Boyuu EL34 A9 Tube Amp
Quote:
Originally Posted by navydiver View Post
Short and to the point, anyone know where I can get a cage for this amp (see linked video)?
If you're concerned about safety, and possibly fingers getting in the wrong places (kids, adults moving the amp or dusting), a (perforated?) bottom cover/panel could go on your list. Pretty easy DIY with a piece of Al from MetalSupermarket or something steel from old commercial gear. Al is easier to cut...

It's baffling to me how many DIY-type units come without bottom covers (Bottlehead Crack Headphone amp was the same @ $400+...)

Good work in finding the wiring error/errors and getting the amp running properly!
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Last edited by VictoriaGuy; 22nd January 2019 at 07:44 PM.
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Old 22nd January 2019, 08:54 PM   #760
navydiver is offline navydiver  Canada
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Will look at the dimensions of the A10 when I get home and compare - thinking I might be able to DIY that one. Here is my A9 Sound Check video to give folks a feel as to how good one of these sound (of course the crappy phone mic doesn't really do it justice):

YouTube
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