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Telefunken EL153 SE circuity
Telefunken EL153 SE circuity
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Old 28th December 2012, 05:10 AM   #1
TBL is offline TBL  Hong Kong
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Default Telefunken EL153 SE circuity

Hi All!

I wonder anyone has a good circuitry reference for a Single Ended configuration of a pair of EL153?

I have an SE AMP running 1 EL153 in Single Ended configuration. It was made DIY by a friend of mine around 12 years ago.

It has been given a change in power transformer and two EZ80 in the power supply for the input stage PCC88, and the pair of EL153 respectively.

However, no matter what my friend has done, since the power transformer change, the amp has been giving loud hum sound, like a combination of 50Hz signal with multiple high order intermodulation noises above it. I hate to trash the amp for its noise, but I have now where to do
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Old 28th December 2012, 06:23 AM   #2
astouffer is offline astouffer  United States
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Are the heater supplies floating?
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Old 28th December 2012, 06:37 AM   #3
yagoolar is offline yagoolar  Poland
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Send a message via ICQ to yagoolar Telefunken EL153 SE circuity
Can you be more specific about the xformer "change"? Is the "new" xformer the same as far as # of windings, voltages and current ratings are concerned?

The schematic of your amp is essential for fault finding. I suspect the hum is caused by improper grounding - check if all leads are connected, tubes are properly sit in sockets etc.
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Old 29th December 2012, 04:29 PM   #4
Funker is offline Funker  Germany
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probably your amp are going to oscillate in the radio frequency range. The EL153 ist a RF output valve designed to operate on frequencies up to 150 MHz. Did you checked it with an oscilloscope?
If the circuit behave like this, insert grid stoppers or/and plate chokes.

Here are the original Telefunken spec sheet(german language):


This valve were widely used in shipboard transmitters & and in base stations of land mobile radio services.

Ground your devices before they ground you
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Old 29th December 2012, 05:14 PM   #5
TBL is offline TBL  Hong Kong
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I know the EL153 is different from its brother EL153 in its frequency operating frequency range. With the Audion Sterling in mind when designing a SE amp, My friend chose the EL153 for its wide bandwith. The first PSU was a conventional design, until the current draw was so high it burnt out in just two years' time.

This is now replaced by a toroidal power transformer. That was when the loud hum bagan. I disconnected the ground wire running to the line power plug. This helped reduce the IM noise above the 50HZ-ish noise which is staying decidly.

I do not have the schematic now but I think I can take some pictures if you do not mind taking a look see.

Thanks in advance!
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Old 3rd January 2013, 09:23 AM   #6
LAZAROIU is offline LAZAROIU  Romania
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EL153 tube proposing this project in SE configuration and output power of 15W.
The design is complete and voltages and currents are marked important points.
EL153 power dissipation for final tube is 30W and is located beneath the anode dissipation hyperbole.
For EL153 tube can go casual with power dissipation up to 40W.
A draft tube must be done with care and attention to the points table and routes filaments, and location of transformers on the chassis must be done properly.
Output transformer has a 10K Ra and the practical problems will not, of course, be done with air gap so as not to saturate the core.
Attached Images
File Type: png EL153 15W SE.png (53.3 KB, 1292 views)
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Old 5th August 2013, 02:08 AM   #7
carageae is offline carageae  Romania
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TBL, some pictures would be useful to diagnose the source of the noise - if the electrical compatibility is assured, it remains the possibility of electromagnetic induced noise, how is the new transformers position relative to the tubes? Did it change a lot? If yes, try to enclose the transformer in an iron pot, even temporary, trying to listen to the difference...
On the other hand...do you have separate heater windings for the EZ80? I understand you added them lately...if no, that's the noise source for sure - the heater windings must be separate for the rectifier tubes, even for those with indirect heating...the cathode-heater leakage is not to be neglected...if your power transformer hasn't separate winding for the rectifiers, get rid of the EZ80 and try using simple diodes - eventually with some resistors in series to compensate the voltage gain - about 50-100 ohms could be ok.
Because I have a pair of NOS EL153 made by Telefunken in Germany, I'm planning to build this summer the amplifier design proposed by LAZAROIU, stay tuned!
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Old 5th August 2013, 09:45 PM   #8
v4lve lover is offline v4lve lover  Netherlands
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Telefunken EL153 SE circuity
The GU50 is basically the same tube, why not use that one?
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Old 6th August 2013, 12:17 PM   #9
carageae is offline carageae  Romania
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Default GU50 alternative...

Yes, it is, but primary I don't like the aspect of this tube and secondary I trust more the TFK quality than the soviet-russian made GU50.
Still, it could be a good idea for those who don't have the quite rare EL153...
As far as I know, LAZAROIU has the simulated schematic also for the GU50 SE version, you can search the GU50 topics...
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Old 6th August 2013, 02:16 PM   #10
es345 is offline es345  Germany
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Just to be precise: EL153 is a tetrode.
GU50 is a pentode, and the equivalent is the FL152. (12,6V heater voltage)/ EL152 (6,3V heater voltage)

Last edited by es345; 6th August 2013 at 02:28 PM.
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