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EF86 wired as Triode in Mullard 5-10 - Cathode bypass capacitor?

I must admit that I haven't done measurements. I would be very curious to do that, but I don't have the equipment to do so.
I have compared it to my other amplifiers though.
I checked in my archive and with respect to feedback and gain, I can say the next:
The classic Mullard 5-10 (without tone controls) has an input sensitivity of 40 mV for 11W output with 26 dB feedback (according to the Mullard book).
According to r-type, the input sensitivity of the Elektor version is 200 mV for 10 or 12W output, again with 26 dB feedback.
Since the only difference between both is in the EF86, this would mean that the gain of the EF86 stage is reduced by a factor 4.
 
Essay said:
Since the only difference between both is in the EF86, this would mean that the gain of the EF86 stage is reduced by a factor 4.
Click to expand...
The difference in gain at the EF86 is about 6, but that's not the only difference. The Elektor is UL, which further reduces gain. It's difficult to directly compare the two without making measurements.

Jack
 
Essay said:
I must admit that I haven't done measurements. I would be very curious to do that, but I don't have the equipment to do so.
I have compared it to my other amplifiers though.
I checked in my archive and with respect to feedback and gain, I can say the next:
The classic Mullard 5-10 (without tone controls) has an input sensitivity of 40 mV for 11W output with 26 dB feedback (according to the Mullard book).
According to r-type, the input sensitivity of the Elektor version is 200 mV for 10 or 12W output, again with 26 dB feedback.
Since the only difference between both is in the EF86, this would mean that the gain of the EF86 stage is reduced by a factor 4.
Click to expand...
WAS wondering if you had any grounding issues .Did you use a single point ground .was there any other bumps in the road as you built this amp.Im just getting started building tube circuits .But i have been using them all my life and usually test and solve problems as they appear .things i have run into are hum or noise bad caps or loose connections drifting resisters that can start compounding in things way off ,tubes flashing over that ended up as a bad socket DIRT.ETC.. I figured its best to use proven schematics until i get more experience and an o scope Im a retired refrigeration renewable energy engineer -tech .so im covered in the theroy .but you all know how real world problems can be tough to track down . I learn new things all the time on AK and reading .This is a great site and thanks to each and everyone that ask and answer questions
 
Loose connections is basically a workmanship issue. Always check your solderwork very carefully.
Buzzing is always an issue. I use one thick copper ground bus bar that is connected to the chassis on one location. I try to connect the ground wires per tube on one location on the bus bar.
You have to keep the power and tube heater wires as far as possible from the incoming signal wire (which is not that easy). I have covered them with aluminium tape in the vicinity of my volume control potentiometer. Your incoming signal wire has to be shielded up to the point where it is attached to the EF86 input capacitor.
I went the masochistic way of having the power supply with 2 EZ81s running of a single transformer winding into a CRC power supply. With a second transformer, I could make it a dual mono, but there was not enough space on my chassis.
There is always some experimenting with the dropping resistors in order to get the voltages right, since you can never model everything exactly.

During the build, I got frustrated at some times, so I have had times where the amplifier stood aside for months. Especially getting rid of the 100Hz buzzing was a frustrating affair. You always learn when you build this kind of things.

If you have any specific questions, don't hesitate to let me know.
 
TriodeLuvr said:
The difference in gain at the EF86 is about 6, but that's not the only difference. The Elektor is UL, which further reduces gain. It's difficult to directly compare the two without making measurements.

Jack
Click to expand...
Actually, the Mullard book also suggests an ultralinear version of the amplifier.
 
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