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Old 19th September 2011, 07:46 AM   #1
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Default Cheap ($235) SE Tube amp kit, transformer and chassis on ebay

Hi all,
Saw this http://www.ebay.com/itm/HIFI-Audio-T...item3a69a3ea41 recently online and wondered if anyone had built it. The cost is pretty reasonable (US$235) as is postage to get it to me.

I've queried the seller and I'm waiting on a copy of the schematic, but whilst I wait, any thoughts?

Last edited by aspringv; 19th September 2011 at 07:53 AM.
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Old 19th September 2011, 07:56 AM   #2
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Default ...and the schematic

That was quite quick! FYI I'm not associated with the seller in any way, I'm just looking to get informed feedback before I consider a purchace.
Attached Images
File Type: jpg Schematic - ebay tube amp.jpg (61.2 KB, 1834 views)

Last edited by aspringv; 19th September 2011 at 07:59 AM.
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Old 19th September 2011, 08:05 AM   #3
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Output is a pentode without any feedback, either local or global? Highly not recommended by any expert... BUT, you can triode connect it with a slight modification, and get 4 - 5 watts, which may or may not be enough for you.

Last edited by costis_n; 19th September 2011 at 08:22 AM.
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Old 19th September 2011, 08:49 AM   #4
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Cool thanks. Power's not a major issue, and I guess in the end it's a set of parts and a chassis to suit, and after that I suppose I could make whatever design that I felt like.

Hmm, I'll do a bit more thinking.
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Old 19th September 2011, 09:39 AM   #5
Grega is offline Grega  Australia
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depends what you are looking for.
you could try the oatley elec kits (also not affiliated with them - the k281) if you are like me and looking for a bit of experience.
oatley are also up nth in NSW so local(ish) to us. also is a smaller investment. depends what you want

cheers mate
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Old 19th September 2011, 10:57 AM   #6
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Quote:
Originally Posted by aspringv View Post
Hi all,
Saw this HIFI Audio Tube Amplifier SE EL34B Amp DIY Kit Stereo | eBay recently online and wondered if anyone had built it. The cost is pretty reasonable (US$235) as is postage to get it to me.

I've queried the seller and I'm waiting on a copy of the schematic, but whilst I wait, any thoughts?
That's 235$ + 90$ shipping = 325$ ... But it is a good price ...

Suppose you build it yourself not with a kit :

If you buy all those Shuguang tubes brand new on eBay, you will paid about 80$
If you buy the transformers from Edcor, you will paid about 170$
Figure out 10$ for the sockets, 20$ for the frame, 20$ for the volume pot, 10$ for the plugs, 30$ for all the resistors and good capacitors, 20$ for different hardware ...

All that cost about 360$, maybe a little less ...

Cheers,

Alain. .
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Old 19th September 2011, 11:07 AM   #7
ttan98 is offline ttan98  Australia
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Hi,

From the cct diagram, it appears the EL34E is triode connected, hence lower output power, I don't think you can get 10W from each channel. the o/p transformer is not an ultra-linear one so you cannot modified the cct diagram to operate in ultra-linear mode, in this mode you can get about 12Watts.

If you are interested in this type of amp try this site:Shuguang,Shuguang treasure,Fullmusic,Guiguang tubes,amplifier chassis,tube sockets,capacitor,resistors,coil meters,toggle switches,tag boards,transformer covers,various parts for tube guitar amps diy <meta name="keywords" content="tube sockets,shugua

look under vacuum tube amplifier heading, model GDAP 01. I bought a unit. the o/p transformer is ultra-linear type. For the money I am quite happy with it but it is not operating in its ideal state, I have to modify it to apply operate feedback to the cct.

BTW I am not associated with the company.
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Old 19th September 2011, 11:18 AM   #8
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Quote:
Originally Posted by aspringv View Post
That was quite quick! FYI I'm not associated with the seller in any way, I'm just looking to get informed feedback before I consider a purchace.
That is the circuit ...

With a 340 ohms cathode resistor, the bias most be very high and there will be more than 10% distortion at full power for sure ... And there is no feedback to attenuate it ...

I also notice the voltage of the screen grid is higher than the plate voltage because the voltage drop in the primary of the output transformer ... It suppose to be equal or lower ...

All that is a bit suspicious but you can modify it to get a better sound, but less power. The 6CA7 / EL34 have a separate suppressor grid from the cathode, it can be reliate to the screen grid and plate to make "a real triode connexion" ... The power will be much less but the distortion too.

Cheers,

Alain.
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Old 19th September 2011, 11:32 AM   #9
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Originally Posted by ttan98 View Post
From the cct diagram, it appears the EL34E is triode connected ...
On the aspringv schematic, the EL34B is not triode connected ...
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Old 19th September 2011, 12:34 PM   #10
ttan98 is offline ttan98  Australia
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Quote:
Originally Posted by Alain Poitras View Post
On the aspringv schematic, the EL34B is not triode connected ...
sorry my mistake, it is pentode----> higher distortion and o/p impedance than triode or ultralinear hence more feedback is required.
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