el95 single ended amp project needs help with preamp

[isidoros]

Hello everyone!

This is my first post on the forum so i would like to greet everyone.Bare with me for any stupid questions etc.

So, i wanted to build a tube amp and i found an old Philips AM radio and took the output and power transformers in order to use them with the tubes i also found in there.The output tube is an EL95, the rectifier is an EZ80 and the preamp an EBC81.I found some old schematics about el95 and ebc81,i combined them, made some modifications and everything was great.No buzz at all, very nice and clean sound with very clear high freqs but kinda poor low freqs(wich is not the case as soon as this is my first project).

The problem is that preamp stage was not enough to drive the input of turntable-record player.So i decided to add another stage of preamp with an ech81.I did the same combining proccess and mods to the schematic i found but now something is wrong.

I hear a buzzing sound from the speaker every 1 sec aprox.Would this be some wrong "coordination" of an RC circuit or something else might be happening?Any suggestions for what i should check?

If this won't go well, i though of removing all the preamp stages i 've built so far and use an ECC83: the first triode as amplifier and the second for treble/bass adjustments as long as ECC83 has a way higher gain factor.
I can upload the schematics i based my project on if needed.

Every opinion and request for more information is more than welcome.
Thanks in advance.

[DF96]

It may simply be that you have too much gain. If the buzz varies every second or so then you may have low frequency instability too (known as motorboating).

Post your circuit and we will have a look. Bear in mind that the ECH81 was not really intended for audio purposes.

[gaborbela]

Hello

I would be interested on a good schematic since I have a box (20-25) EL95.
Unfortunately I didn't found any schematic on the net which uses EL95..
Can be PP or SE. I think we can parallel the power tubes for SE to get about 4-5W.
I had a Philips amplifier (I sold her so all the extra tubes it remain on my hand)
I would build a small amp with these tubes just for fun..

Greetings gabor

[mltube]

Originally Posted by gaborbela

Hello

I would be interested on a good schematic since I have a box (20-25) EL95.
Unfortunately I didn't found any schematic on the net which uses EL95..
Can be PP or SE. I think we can parallel the power tubes for SE to get about 4-5W.
I had a Philips amplifier (I sold her so all the extra tubes it remain on my hand)
I would build a small amp with these tubes just for fun..

Greetings gabor

I have this in my archive, I hope it helps...

[gaborbela]

Hello
These is similar like my little Philips amp was. A bit over crowded and abot 2W.
I will see if someone has a bit something simple or PP. If not I go with Russian EL84 power tubes.
I just thought because I have some Telefunken, Valvo etc EL95 at hand.
By the way thank you very much!
Greetings
gabor

[mltube]

Originally Posted by gaborbela

Hello

I would be interested on a good schematic since I have a box (20-25) EL95.
Unfortunately I didn't found any schematic on the net which uses EL95..
Can be PP or SE. I think we can parallel the power tubes for SE to get about 4-5W.
I had a Philips amplifier (I sold her so all the extra tubes it remain on my hand)
I would build a small amp with these tubes just for fun..

Greetings gabor

Found it deeper in my hard drive, this is push pull.
This may be closer to what you are looking for...

[planet10]

Here are 3 more. One is a 2.1 way circuit.

dave

[planet10]

The ELL80 is essentially 2 EL95 in one bottle.

dave

[planet10]

And this is one we built.

dave

[gaborbela]

Hello
Thank you very much!
At first I like the Normende 3/683 PP. I saved the picture and printed out , impossible to read the parts unfortunately.
PP would give me (I think) 6-8W.
For 2W I need a min.90db sensitive or higher! My Visaton only 87db. That is why I sold my Philips tube amp.
When I listened classical and the sound went up lot of distortion.
May be I wait until I finish my 3 way speaker, that will be around 90db.
I also had a nice SE amp circuit, I attache the schematic.
Here some info in English
Weeny vacuum tube amplifier on 12AX7 and EL95
The original in Polish
Malutki wzmacniacz lampowy na 12AX7 i EL95
I don't know if I can parallel the power tubes to get a bit more power. The question can the half ECC83 drive the 2 paralleled EL95?
I don't want to use a extra preamp, extra cables, connectors etc.
Another question if I parallel the EL95 how much distortion I get?
Thank you one more time
Greetings gabor