Jan E Veiset Mini EL84 pp

kopite · 4th August 2006, 02:07 AM

Hi Jan,

I really like your Mini EL84 pp circuit, can you tell me what value of feedback resisitor you settled on. I can't read your website page about it but would like to know more, can you explain the circuit in english please.

jane · 4th August 2006, 07:13 AM

Hi,
The design is very simple and more or less a class A design. It moves into class AB, but not far into AB, so if you are looking for plenty of power this is not the way to go.

The local shunt feedback is ~9dB and will lower the output resistance of the EL84. Global NFB is approx 10dB set by a 1k2 feedback resistor (I have to check this out, I’m not at home now..)
I achieved a damping factor of 8 (Zo=1 ohm) with 10dB gNFB. The distortion figures are also quite low, 3rd harmonic <0.3% and higher order harmonic less than 0.1% at half power output.
The amplifier sounds very transparent and does not have any dominant sound signature.

After some experimenting I found the best sonic working point for the EL84s to be ~41mA cathode current: Rk=2k2/10W and Vk=90V. The cathode voltage (Vk) is adjusted by trimming the CCS.

(I will upload the updated schematic later today).

Jan E Veiset
NO-6600

jane · 4th August 2006, 08:33 AM

Here is the current schematic for the miniPP:

Jan E Veiset
NO-6600

corbato · 4th August 2006, 02:46 PM

Hi Jan

Cute design!

Do you have any measurements?

jane · 4th August 2006, 03:55 PM

Key figures:
Max Po: 7V rms into 8 ohm. (40Hz - 25kHz)
Frequency response (1W, -3dB) 22Hz - 40kHz
DF: 8 (Zo = 1 ohm)
THD: Less then 0.3% (5V rms output)

Distortion pattern 400Hz input (5V rms output):

But if you are looking for power, take a walk to SY's red light district: EL84 in pentode mode with very stiff cathode bias is the way to go for some real good spanking.

Jan E Veiset
NO-6600

kopite · 4th August 2006, 07:26 PM

Hello Jan,
Thank you for the updaye on your circuit. I'm not looking for a lot of power. Can you tell me the power out in watts please.

I also like Sy's circuit but I'm not sure if I can fit the led board into my space.

Thanks again for your time.

jane · 5th August 2006, 10:17 AM

Hi,
Power output = Vo*Vo/R. If Vo = 7V rms, Po = 6.1W
I think that is close to what's possible to achieve in class A in this circuit.
(max theoretical class A Po = (2xIq)^2 x Rl/4 = (2x0,04)^2x8000/4 = 6.4W)

Jan E Veiset
NO-6600

4th August 2006, 02:07 AM	#1
kopite diyAudio Member Join Date: May 2005 Location: NZ	Jan E Veiset Mini EL84 pp Hi Jan, I really like your Mini EL84 pp circuit, can you tell me what value of feedback resisitor you settled on. I can't read your website page about it but would like to know more, can you explain the circuit in english please.

4th August 2006, 07:13 AM	#2
jane diyAudio Member Join Date: Jul 2004 Location: Norway	Hi, The design is very simple and more or less a class A design. It moves into class AB, but not far into AB, so if you are looking for plenty of power this is not the way to go. The local shunt feedback is ~9dB and will lower the output resistance of the EL84. Global NFB is approx 10dB set by a 1k2 feedback resistor (I have to check this out, I’m not at home now..) I achieved a damping factor of 8 (Zo=1 ohm) with 10dB gNFB. The distortion figures are also quite low, 3rd harmonic <0.3% and higher order harmonic less than 0.1% at half power output. The amplifier sounds very transparent and does not have any dominant sound signature. After some experimenting I found the best sonic working point for the EL84s to be ~41mA cathode current: Rk=2k2/10W and Vk=90V. The cathode voltage (Vk) is adjusted by trimming the CCS. (I will upload the updated schematic later today). Jan E Veiset NO-6600 __________________ Life is hard - Then you die.

4th August 2006, 08:33 AM	#3
jane diyAudio Member Join Date: Jul 2004 Location: Norway	Here is the current schematic for the miniPP: Jan E Veiset NO-6600 __________________ Life is hard - Then you die.

4th August 2006, 03:55 PM	#5
jane diyAudio Member Join Date: Jul 2004 Location: Norway	Key figures: Max Po: 7V rms into 8 ohm. (40Hz - 25kHz) Frequency response (1W, -3dB) 22Hz - 40kHz DF: 8 (Zo = 1 ohm) THD: Less then 0.3% (5V rms output) Distortion pattern 400Hz input (5V rms output): But if you are looking for power, take a walk to SY's red light district: EL84 in pentode mode with very stiff cathode bias is the way to go for some real good spanking. Jan E Veiset NO-6600 __________________ Life is hard - Then you die.

5th August 2006, 10:17 AM	#7
jane diyAudio Member Join Date: Jul 2004 Location: Norway	Hi, Power output = Vo*Vo/R. If Vo = 7V rms, Po = 6.1W I think that is close to what's possible to achieve in class A in this circuit. (max theoretical class A Po = (2xIq)^2 x Rl/4 = (2x0,04)^2x8000/4 = 6.4W) Jan E Veiset NO-6600 __________________ Life is hard - Then you die.


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

4th August 2006, 02:46 PM	#4
corbato diyAudio Member Join Date: Jan 2003 Location: India	Hi Jan Cute design! Do you have any measurements?

4th August 2006, 07:26 PM	#6
kopite diyAudio Member Join Date: May 2005 Location: NZ	Hello Jan, Thank you for the updaye on your circuit. I'm not looking for a lot of power. Can you tell me the power out in watts please. I also like Sy's circuit but I'm not sure if I can fit the led board into my space. Thanks again for your time.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
5W EL84 drive EL84 SE	Audio_idiot	Tubes / Valves	31	31st May 2012 08:38 PM
Mini EL84 Amp Done	sorenj07	Tubes / Valves	21	25th June 2007 03:26 PM
Mini 98 El84 PP amplifier	Tubesin	Tubes / Valves	0	3rd March 2007 01:48 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read