Hello. This is my first tube-based amplifier I've ever built, and I'm experiencing a strange issue with it.
The amplifier works well when the EL504 is heating up, but it stops working when fully heated. It works also when cooling down.
I'm following an schematic made for the PL504 but modified (I've just added another transformer for the 6.3VAC the EL504 uses)
Here's the schematic:
The output of the rectified voltage measures about 31VDC (vs the original 27V the original amplifier used)
Thanks
The amplifier works well when the EL504 is heating up, but it stops working when fully heated. It works also when cooling down.
I'm following an schematic made for the PL504 but modified (I've just added another transformer for the 6.3VAC the EL504 uses)
Here's the schematic:
An externally hosted image should be here but it was not working when we last tested it.
The output of the rectified voltage measures about 31VDC (vs the original 27V the original amplifier used)
Thanks
I don't want (or need) an HiFi quality, I'm just interested in building a very simple amp with tubes, then try building some more complex
The schematic is from the famous electronics magazine Elector:
http://www.gtlab.net/gtlab2/filemanager/userpix/igor/low_anode_1.pdf
http://www.gtlab.net/gtlab2/filemanager/userpix/igor/low_anode_2.pdf
Also there are videos on YT with PL504 working at an even lower voltage, this one for example: Amplificator cu tubul PL504 la 27V - YouTube
Thanks for your answer
The schematic is from the famous electronics magazine Elector:
http://www.gtlab.net/gtlab2/filemanager/userpix/igor/low_anode_1.pdf
http://www.gtlab.net/gtlab2/filemanager/userpix/igor/low_anode_2.pdf
Also there are videos on YT with PL504 working at an even lower voltage, this one for example: Amplificator cu tubul PL504 la 27V - YouTube
Thanks for your answer
I have no 1 Ohm resistors. The lowest resistor I have are 75 Ohm resistors. Can I use these to obtain for example 7.5Ohm, then bias with that value?
So the correct schematic is this one, right?
Which resistor adjusts the bias?
Sorry if these questions seems too basic or stupid, but it's my first project using tubes. Thanks for your patience
So the correct schematic is this one, right?
An externally hosted image should be here but it was not working when we last tested it.
Which resistor adjusts the bias?
Sorry if these questions seems too basic or stupid, but it's my first project using tubes. Thanks for your patience
Thanks! That worked. I've put a 1kOhm resistor on the G1 and removed the capacitor. Now it sounds more clear than before.
A bit offtopic: would be possible to use this exact circuit with this other tube? http://tubedata.tubes.se/sheets/127/1/17DQ6B.pdf . They're both dirty cheap, but these use a more common octal socket
A bit offtopic: would be possible to use this exact circuit with this other tube? http://tubedata.tubes.se/sheets/127/1/17DQ6B.pdf . They're both dirty cheap, but these use a more common octal socket
The difference between "working" and "working well" is made by the right supply voltage.
Sure, it "works" with 30V but that is still in the unlinear region of the tube (knee), so you will have lots of distortions, especially at low level passages.
Phillips recomens supply voltages between 170-230V for 504 tubes.
The second tube is a horisontal deflection tube. Very high voltage, low current, works best in pulses... not an audio device.
Sure, it "works" with 30V but that is still in the unlinear region of the tube (knee), so you will have lots of distortions, especially at low level passages.
Phillips recomens supply voltages between 170-230V for 504 tubes.
The second tube is a horisontal deflection tube. Very high voltage, low current, works best in pulses... not an audio device.
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AFAIK, both the xL504 and xDQ6B are horizontal deflection tubes :/The difference between "working" and "working well" is made by the right supply voltage.
Sure, it "works" with 30V but that is still in the unlinear region of the tube (knee), so you will have lots of distortions, especially at low level passages.
Phillips recomens supply voltages between 170-230V for 504 tubes.
The second tube is a horisontal deflection tube. Very high voltage, low current, works best in pulses... not an audio device.
Also, I'm using ~30V because it's my first tube project, so I don't want to play with high voltages yet.
I can get these locally for less than 2€, so the amount of tubes is not really a problem. I'm looking here using the search for circuits using the 17DQ6B or 6DQ6B, but I haven't found any. Do you have a link?actually, the (X)dq6b has been used successfully as an output tube, but only in PP circuits (or OTL). It seriously sucks as an SE tube...
Thanks to everybody for your help
Yup--Thee are some Real Gems in the Compactron Collection and curently Dirt Cheap too....
I aint saying which ones!
Actually I have a 6AR11 double pentode compactron.
This is the full list of tubes I have:
- 2 EL95 small audio pentode
- 2 6AS6 RF pentode
- 3 EL504 horizontal deflection pentode
- 1 17DQ6B horizontal deflection pentode
- 2 ECC89 VHF double triode
- 2 6N1P double triode
- 1 UCH84 RF stage triode & pentode
- 1 UBC81 RF diode triode
- 2 Z806W neon discharge tube
- 4 0RP30 selenium light sensor
And the said 6AR11
If there is anything interesting let me know. There is a local store who sells old NOS tubes (but they don't have any classic audiotube, EL84, EL34, KT88, ...
This is the full list of tubes I have:
- 2 EL95 small audio pentode
- 2 6AS6 RF pentode
- 3 EL504 horizontal deflection pentode
- 1 17DQ6B horizontal deflection pentode
- 2 ECC89 VHF double triode
- 2 6N1P double triode
- 1 UCH84 RF stage triode & pentode
- 1 UBC81 RF diode triode
- 2 Z806W neon discharge tube
- 4 0RP30 selenium light sensor
And the said 6AR11
If there is anything interesting let me know. There is a local store who sells old NOS tubes (but they don't have any classic audiotube, EL84, EL34, KT88, ...
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UCH84? Never thought that ever has been there any! It's - presumed- counterpart ECH84 once has been derived from the elder ECH81 especially for TV services (line sweep oscillator, sync separation), not for radio sets, and never has been there any TV set with a 100 mA series heater chain. Also can't find any datasheet of this tube...
Maybe you might have an UCH81?
Best regards!
Maybe you might have an UCH81?
Best regards!
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30V B+ is going to be VERY disappointing, - to all intents and purposes impossible and not a learning step at all (unless you count learning that 30V is not enough).
At 150V, you start getting into a usable operating point. It will certainly do more than tickle if you accidentally touch it, but is not likely to be deadly unless you are already unwell and you take extreme risks eg using a line supply
At 150V, you start getting into a usable operating point. It will certainly do more than tickle if you accidentally touch it, but is not likely to be deadly unless you are already unwell and you take extreme risks eg using a line supply
I have a 230V to 125V transformer. I only have to replace the input transformer, or I have to change something more?30V B+ is going to be VERY disappointing, - to all intents and purposes impossible and not a learning step at all (unless you count learning that 30V is not enough).
At 150V, you start getting into a usable operating point. It will certainly do more than tickle if you accidentally touch it, but is not likely to be deadly unless you are already unwell and you take extreme risks eg using a line supply
With EL95 and 6N1P you can do very decent things, but you will need proper power and output transformers....
Yep, thats the way I would go too. Lots of very simple designs and cheap otp's. The power transformer that the op has MAY be able to be voltage doubled to give a useful supply...
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