advice on choosing preamp project needed

Who is Andreja Jelen?
IOAUDIO, your circuit seems very simple. So you suggest input trafo and penthode-triode switch for the first tube. And capacitor for output. Did you ever have problems with noise or other unwanted components? Which in Trafo did you use? Preamp seems to be very simple and parts are easy to find. I'm wondering about sound of this pre. When i used EF86 for the first time i was very surprised about it's sound. And with good trafo preamp like this could be very good to warm up DAW.

hey rotation,

i stumbled into the idea of making my first preamp when i bought a old wheel-to-wheel recorder on viennas flea market. i bought various models, telefunken, grundig and even stuzzi recorders.
i dont know where you are located, but you will likely find a flea market in ljubljana. i remember one morning after a gig i bought a telefunken wheel-to-wheel in a very small austrian city, on a very small flea market near the church...i paid 5 euro for a box containing a psu, telefunken ef86´s and ecc81´s sockets and stuff. i then ordered some oep´s from rs-components and some caps and resistors and where done. http://www.groupdiy.com/index.php?topic=11456
the circuit is different from the mullard (which i dont have the schematics from, just heard of) the output stage in my pre´s is srpp. i used that topology one some preamps, with and without output transformer, with ef83 instead of ef86, ecc81 instead of ecc82, with, without negative feedback or even with positive feedback - which doesnt oscillate but i still cant figure out why...

with a good psu and good tubes you can get a very nice, silent preamp, i believe. headroom is a matter of gain structure and distortion, or saturation, or simply nice sound. when i breadboard things and replace parts or values, i do first the listen and than the measuring, just in case i do measure something but voltages at all.
some of my psu´s are made with back to back toroids like in the g9, with regulated heaters, others with 6,3v windings rectified and filtered with some 4700µ caps and 1ohm resistors. way too many possibilities...you can play around with a certain amp topology for years, i guess.
point to point soldering and layout is fun, you can change parts easily, make a nice star grounding, avoid oscillations and so on.
my friends complain i do talk too much about tube preamps and such...
:wink:
hmm. however, i should go and build something.
i´m sure you`ll get this certain vibe about diy soon.
max

Hi!
I live in Ljubljana and we have flea market here. I bought some old radios there, but they all have strange tubes which are difficult to find and use. Tell me, why do you use these pre's for? The on with cash box looks really good. Much better than any commercial stuff. I'm wondering what it sound like. Did you ever have problems with signal penthodes as gain block? Mullards circuit with this tubes was not quiet at all, and from then on i never used them again. But that was my fault because i didn't put any trafo at the input..
So tell me about it's sound. I also like to talk about this stuff, so don't worry talking too much :grin:
Miha

hi micha,

i uploaded one sample where i use the di of my micpre.
you can find it in the thread http://www.groupdiy.com/index.php?topic=187470#187470

Andreja Jelen= Cassandra!

Nice!

I'll throw my .02$ in. I use my 1272's more than any of my other preamps. They aren't the cheapest but I just can't get by without them.

I still haven't tried Analag's firebottle/FET hybrid yet.. Something tells me that it rocks.

Hmm, very nice sounding bass. What about vocals? If that is ok than circuit is very interesting because of simplicity and easy to find parts.

hi miha,

i like it very for vocals, somewhat depending on the input transformer of course. i do like the oep input transformers(1:6,3) in this application, but i also got good results with the beyerdynamics. of course they tend to saturate easier, so i put a switchable pad for hot condensor mics.
i also tryed the ef83 as input tube (which is supposed to be a remote cutoff tube) and got quite nice results, gain is a little less. you can find these for 5,88 euro at http://www.btb-elektronik.de/de/preise_lager_europ.htm
please dont buy all of them, as i´ll need some more for myself :wink:

Hi Max!
I'm getting more and more interested in this pre. It's very simple and cheaper than many solid state. I will slowly start to buy components and make it.
Did you ever compare it to Green Pre or something similar? I'm familiar with this kind of sound. But this doesn't mean i don't like different ! Are you running a studio? What kind? I'm mostly working as a sound technician for live acts and sometimes concerts. Electronics is my hobby, but it's getting serious latelly. Lots of small studio owners is asking me to make compressors, preamps, simple repairs, cables..I really enjoy doing this, specially pres. I mentioned situation here and for some people diy is the only way to get big sounding gear. That's why we have this part of forum: www.planetaudio.si/viewforum.php?f=29 Sorry, it's in slovenian, but we accept english speaking people. Visitors are slovenian producers, studio owners, musicians..
What means remote cutoff tube? And how are marked OEP and Beyerdinamic trafos for this pre? I think i can get OEP from Farnell in Ljubljana. Tubes are also easy to find. For testing i could even use an old EF86 from radios or other old stuff.
I never been to Vienna, but my girlfriend knows some promotors for concerts there. They are sending musicians here. And we run a small underground club Channel Zero.
I can't forget the sound of bass guitar you posted. This pre seems to be ideal candidat for our needs. If vocals are on the same level as bass than i have nothing to think. So thanks again for helping me.
Have a nice weekend!

hi miha,

i´m running a small studio, but i do most of my recordings on different locations, bringing along my own equipment. i think this kind of recording gets more common recently. and i do like working in different places, its always something "new" and "fresh" when you listen to an unknown room while setting up the drum mics.
i didnt compare it to the green pre, i´ve never had one. but i´m sure its something completely different, soundwise.
do a search about remote cutoff tubes, they are used in vari mu compressors. lots of information in the metas, invaluable posts by prr and others. look up tube data sheets here: http://frank.pocnet.net/

nice you have a small club running, maybe i´ll stop by when i come to ljuljana next time.

You are welcome to our club Channel Zero. Maybe you could even have a concert there. Contact me about this if you want. We could try your pres and my stuff
Do you have any particular supplyer for transformers? Here we only have Farnell where they only have OEP. Our market for this kind of products is very small but people seem to be interested for diy. When i wrote about my Gssl i got a lot of answers, questions..
Is that switch in feedback circuit a kind of pad? And when you switch from penthode to triode you get less gain? Am i right? Sound should change also..