Cheap & Well Made Chinese SE EL34 Amp

ttan98 · 12th August 2011, 03:43 AM

Hi,

I like share with all of you the Single Ended amp I bought recently and it arrives today. I have not powered it up as yet. Take a look at the images here.

I paid US$200 plus $100 postage by airmail. I think it is a bargain. All the parts alone will exceed $200.

As you can see the chassis is very well made, chromium plated both top and bottom plate covers. The components are mounted on PCB and finish is very good as well. The rear view, you can see a black button it selects between the 2 inputs.

It does not come with a manual but the seller will provide you with a circuit diagram. The circuit is pretty standard, no feedback the driver is 6N3 connected in parallel to drive the EL34 which is connected in UL mode. It claims to give 12 watts I guess more like 10watts.

My intention is listen to it for a while and then modify it to accommodate KT88 tubes which I have few lying around.

You can see better quality images here,
Flickr: ttan98's Photostream

Mr. Zenith · 12th August 2011, 03:56 AM

It would be interesting to see the schematic. Are the output transformers actually potted or are those just covers? Seems a nice find at any rate. Let us know how the future mods work out.

The name "TUBE" vacuum tube amplifier reminds me of the fad for generic products here in the states during the early '80's. They came in plain white packaging with the name of the item in bold black letters, along with the even-then-ubiquitous UPC codes. "SALTINES", "CIGARETTES" and "BEER" immediately spring to mind...

HollowState · 12th August 2011, 04:49 AM

Quote:

Originally Posted by ttan98

My intention is listen to it for a while and then modify it to accommodate KT88 tubes which I have few lying around.

Trying to adapt KT88s to this amplifier will not be very fruitful. Even if your power transformer has the extra filament current necessary, you will find that to make them perform well you'll need higher bias voltage and higher B+ voltage as well. Without that you'll still only get about the same wattage output. Power out is proportional to power in. Also, the output transformer primary impedance will not be the best match. This is assuming the Chicoms designed it right for EL34s. KT88s may look prettier, but that's about all you'll gain. Maybe a "difference" in sound. Sorry if I'm a party pooper.

ttan98 · 12th August 2011, 05:24 AM

Quote:

Originally Posted by HollowState

Trying to adapt KT88s to this amplifier will not be very fruitful. Even if your power transformer has the extra filament current necessary, you will find that to make them perform well you'll need higher bias voltage and higher B+ voltage as well. Without that you'll still only get about the same wattage output. Power out is proportional to power in. Also, the output transformer primary impedance will not be the best match. This is assuming the Chicoms designed it right for EL34s. KT88s may look prettier, but that's about all you'll gain. Maybe a "difference" in sound. Sorry if I'm a party pooper.

Most o/p transformer will work well with EL34, even if I bias KT88 at lower current it should work well. A 3.5K or 5K transformer will work.

ttan98 · 12th August 2011, 05:28 AM

Hi,

I powered it up and it worked fine, very quiet and no hum.

I cannot release the circuit without the supplier approval, it is quite straight forward very similar to this,

DIY Single-Ended KT88 / 6L6 / EL34 / 6CA7 Tube Amplifier

except the 6N3 twin triode is connected in parallel to give more current.

alexinthesky · 15th January 2012, 05:46 PM

Hi,

I just finised building the exact same amp I got as a kit for christmas (only difference is no PCB).
I replaced the 6N2J with 12AX7.
The amp is driving a pair of wharfedale 10.1( sensitivity rated 86Db).
Sound is good and no hum. Of course less power that with the gainclone LM3886 I had before.
One thing I have to say is that the power transformer is sizzling.
I tied the nuts holding it but no luck.
Do you experience the same?
Maybe the transformer is a little bit underdimentioned!

Alex

mace1337 · 15th January 2012, 08:20 PM

How much power supply filtering is there? Just those teeny caps?

alexinthesky · 15th January 2012, 08:26 PM

here is the schematic :

Alain Poitras · 15th January 2012, 10:00 PM

Very nice look and 6CA7/EL34 is a very good tube. I don't know about the output transformer quality but 200$ + 100$ shipping is a cheap price.

alexinthesky · 16th January 2012, 07:35 AM

OK, fixed the sizzling problem by tying more the bolds, all good now!

Now I have to listen to it for a while and see if I retube with better quality 12AX7s

Alex

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12th August 2011, 03:56 AM	#2
Mr. Zenith diyAudio Member Join Date: Aug 2009 Location: Central NC	It would be interesting to see the schematic. Are the output transformers actually potted or are those just covers? Seems a nice find at any rate. Let us know how the future mods work out. The name "TUBE" vacuum tube amplifier reminds me of the fad for generic products here in the states during the early '80's. They came in plain white packaging with the name of the item in bold black letters, along with the even-then-ubiquitous UPC codes. "SALTINES", "CIGARETTES" and "BEER" immediately spring to mind...

12th August 2011, 05:28 AM	#5
ttan98 diyAudio Member Join Date: Apr 2006 Location: Melb	Hi, I powered it up and it worked fine, very quiet and no hum. I cannot release the circuit without the supplier approval, it is quite straight forward very similar to this, DIY Single-Ended KT88 / 6L6 / EL34 / 6CA7 Tube Amplifier except the 6N3 twin triode is connected in parallel to give more current.

15th January 2012, 05:46 PM	#6
alexinthesky diyAudio Member Join Date: Aug 2010 Location: Toulouse	Hi, I just finised building the exact same amp I got as a kit for christmas (only difference is no PCB). I replaced the 6N2J with 12AX7. The amp is driving a pair of wharfedale 10.1( sensitivity rated 86Db). Sound is good and no hum. Of course less power that with the gainclone LM3886 I had before. One thing I have to say is that the power transformer is sizzling. I tied the nuts holding it but no luck. Do you experience the same? Maybe the transformer is a little bit underdimentioned! Alex

15th January 2012, 08:20 PM	#7
mace1337 diyAudio Member Join Date: Aug 2005	How much power supply filtering is there? Just those teeny caps?

15th January 2012, 08:26 PM	#8
alexinthesky diyAudio Member Join Date: Aug 2010 Location: Toulouse	here is the schematic :

15th January 2012, 10:00 PM	#9
Alain Poitras diyAudio Member Join Date: Aug 2011 Location: Laurentides QC Blog Entries: 1	Very nice look and 6CA7/EL34 is a very good tube. I don't know about the output transformer quality but 200$ + 100$ shipping is a cheap price.

16th January 2012, 07:35 AM	#10
alexinthesky diyAudio Member Join Date: Aug 2010 Location: Toulouse	OK, fixed the sizzling problem by tying more the bolds, all good now! Now I have to listen to it for a while and see if I retube with better quality 12AX7s Alex

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