• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Preamp suggest, please.

kacernator

Member
2008-01-09 10:38 pm
Hi,

I am planning to build HiFi line preamp. I have searched and read on this site alot. I want to use just the following tubes as I already have bunch of them: 12AX7, 12AU7, ECC88.

Can you please recommend very good sounding preamp with these tubes?

I have just build this one: http://hlava.webpark.cz/Predzes/preampecc83.gif

What about Aikido? Is it good, or it does have the type of sound which might not everyone like?

Thank you.
 
Trade some of your tubes for some 6FQ7's and 5687's. Use the 6FQ7 as the input tube.

Read the Aikido threads. Bas started one on a Aikido group buy and it shows schematics of the audio and power supply. You can build a flawless Aikido from just reading this thread.

The Aikido will outperform the schematic you listed.
 
Unfortunately, I cant get those tubes in my country. Is the Aikido worth building with ECC82,3,ECC88 or are these not good sounding tubes for HIFI?

There is nothing wrong with a 12AU7 / ECC82. However, since there are common tubes that match every characteristic and have better distortion, it does not have a strong following. Look up "fart bottle" in the search engine.

IMHO, an aikido is worth building with ECC82 or ECC88 tubes.
The ECC88 is very attractive as the CF tube in Aikido.

Let me ask, how much gain do you need?
If you need a buffer, look at Heretical. It uses ECC88 and looks to be very well designed.

An all ECC88 Aikido should have an gain of about 16.

I personally am building my Aikido with 6H6pi, which I got from eBay @ $4 each. 6N1pi and 6H30 are also very well respected choices.

Let us know a little more about your needs, and we can advise you better

HTH

Doug
 

kacernator

Member
2008-01-09 10:38 pm
On my current preamp I have volume set to 10 o´clock. So all ECC88 Aikido will not have enough gain, am I right?

Looking at the Aikido scheme, I have one more question: Is it OK to run TWO tubes from the same B+ supply capacitator? Is it better to have for EACH tube its own ps RC filter?

Thank you.
 

euro21

Member
Paid Member
2004-09-17 12:16 pm
Budapest
Try this PSU
 

Attachments

  • aikido_psu_v1.jpg
    aikido_psu_v1.jpg
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If not I can swap first tube for ECC83.

I used to think I needed mega gain also.

You will find that the 6N1P or 6922 or 6DJ8 will be fine in the first tube position.

You do not need nor will you want the 12AX7 with a gain of 100 as the input tube. You will have two much gain and also a noticable amount of noise.

I suggest that you read all the threads on the Aikido on this forum as well as Mr. Broskie's site WWW.tubecad.com

You may come to the realization that more is not better.
 

kacernator

Member
2008-01-09 10:38 pm
OK, so I will be building Aikido preamp.

My last question is about power supply. I will post schematics of my PS design later today. Anyway is it better to have big supply caps or smaller one? How can I know if the value of capacitor is big enough or when it is big TOO much.
 

Yaho

Member
2008-01-08 12:22 am
How about for phono stage?

Hi everyone

Hope I am not hijacking the thread. But I do want to add a question if I may. I am hoping to build a linestage for both CD and MM phonostage. What preamp would you suggest for that? The first stage of phono is 12ax7 and the final stage is 6922. My power amp is driven by 12ax7 and el84. So, I am thinking of mixing some tubes. Sor far, I am looking at 12b4, 6sn7, and 6t4. But I am opened.

Thanks.

Yaho
 
The psu is ok., but I suggest al small change;
start with 47 uF after the rectifiers, then the first 220 uF after the choke, also 220 uF after the resistor with a good quality MKP or paper/oil (1 to 4,7uF) parallel to this last cap.

If you want a pre amp that also drives headphone's and 5687 or other of this kind of tubes is hard to find, try a ECC99 or 6N6P.
These tubes must be very easy to get in your neighbourhood!!!

As first tube you can use the Ecc 82 or the ECC 88 or whatever you like.

Have fun!
 

kacernator

Member
2008-01-09 10:38 pm
Why 47uF first ad the 440uF after choke? What is advantage of this compared to my posted design?

I will parallel with some foil definately, I just didnt draw it in the scheme.

I can get ECC99 no problem, but my PT will not handle it. ECC99 has 5W max Pa. I will have roughly 150V on plates, so for 4W tube will need 26mA, double that is 52mA and for two ECC88 is 16mA. Maybe bias ECC99 little colder, but the preamp is not mentioned to be used as headphone amp, anyway I just have very low impedance headphones (cca 100 Ohm).
 
If you use the aikido just as a preamp, biasing the second tube at 10 mA's is more than ok!
The 5687/6N6/Ecc99 will dissipate less than 2 Watts per triode.

You also keep a low output resistance, very important!
Then your preamp is does not have to worry about cable capacities, lenghts en input restance of the power amp.

My expierience is, if you use a relatively high value capacitor for the choke, during turning on and off you get a lot of overshoot, swinging en momentarily oscillation at the power supply output.
Just mostly for a short time, but still long enough......

Choosing a cap, what is smaller than the cap after the choke, the chance of an unstable psu is almost zero!!

When you use a relatively big choke and big capacitors, the choke and second cap are responsible for a smooth and ripple free output voltage.
A nice idea is to download the power supply designer on the page of Ducan's amps.
This gives you a big help todesign and simulate a diy power supply.
Have fun, greetings
Hansel