Electrocompaniet 25W class A

[GIRAFON45]

Dear all

I'm wondering if someone knnow the input sensitivity of the 25W Class A ELECTROCOMPANIET amplifier ?
I bought one few days ago and I'm quite interesting by all the informations you can provide.

Thank you

Jérôme

[john curl]

It is VERY sensitive, but still OK.

[Iain McNeill]

Hi Jerome
I think you'll get better response with your own thread rather than take the Matti Otala thread off topic.

[AMV8]

Hi
I think these are great amps and still own a three of the 25 watt power amps and a couple of the pre amps.
Electrocompaniet quoted the input sensativity as 400mv for the 25 watt output. The gain is quoted as 36x (31db).
Nominal input impedance ik ohm and recommended source impedance below 50 ohms.
Output impedance at 1k ohms 250m ohms with a damping factor of 160 into 8 ohms.
Output 25 watt, continuous rms current 6 amp with a peak current of 20 amps.
Rated output 2x25w into 8 ohms
2x40 watt into 4 ohms
2x11 watt class a output
THD 1watt into 8 ohms 0.002%

Early ones ran very hot and I believe were more like 25 watt class A. I have adjusted all mine so that they are hand hot when warm. In my case the adjustable 1k ohm bias potentiometer is set to approv 750 ohm to make the heatsinks just hot enough to keep my hand on when fully hot.

I hope this helps.

Don

[GIRAFON45]

Great

Thank you Don

I was aware of the relativly low input impedance (1 KOhms is quite low) but never found the input sensitivity value.

With the information, I will try to find a preamplifier that can match as my ARC SP6B is realy not compatible (gain 28 dB, output impedance 500 Ohms).

Best regards

Jérôme

[john curl]

It is higher than normal due to an older European standard. Might be comparable to today's amps. I am using one with just a passive volume control in front being driven by a tuner. Works great.

[AMV8]

Hi

I find that they work ok with most pre amps or a passive pre amp; as john curl advises.

I have updated all the electrolytics in the power supply and on the pcb. Also it will be best to replace the output source resistors if the amp has been run hot as the resistors and the pcb track around the resistors can show signs of distress. It will be see this if it is happening. Updating ( modernising) the output transistors may also help.

I understand from e mail correspondence with Electrocompaniet that they were also planning to replace the input of the circuit with a balanced jfet arrangement. I may try that shortly. If John Curl is still reading this thread maybe he could advise if he thinks this is worth trying?

Don

Don

[GIRAFON45]

Hi Don

Unfortunatly, I have some problems when I connect my SP6B to the 25W amplifier.
With level at zero, I have a some FFFFFFFFFFFFFFFF in the loudspeakers, not a buz due to a ground default but a noise like tube can make.

Second point, the level knob have a very short travel to reach a high output level, for example at 7 o'clock position, I'm at zero, at 8 I can't hear anything, at 9, it's quite loud.

Do you have an idea ?

Best regards

Jérôme

[AMV8]

Hi

I can not at present think what would cause the noise unless it is a faulty component. As I mentioned above I would have a look at the resistors connected to the output transistors.

On your second point it sounds as though you need to attenuate ( reduce ) the volume from your preamp.

Don

[tiefbassuebertr]

perhaps the schematic about my post #9 helps:
Electrocompaniet original 25 W needs help (first Electrocompaniet 25W class A)
An interesting way was found to enhance the input impedance despite inverting mode instead non inverting mode.