Cheap and Easy Tube Phono Preamp

[Geek]

Hi,

Have a look at Mr. Allen Wright's paper about this here:

RIAA

Good link! A wee bit opinionated, but his facts look OK

 

[JojoD818]

Hi,



Should have read 965R. Typo.

BTW, regarding PCBs, it's really worth a try to make two identical preamps except for one with PCB, the other P2P and compare the two.
You're in for a big surprise I promise.

Since you're two persons building, why not do one each?



Afterwards you can combine different values to arrive at the calculated value of 965R, I just picked the easiest two at the time out of the E96 table.

Cheers,

Good news Frank! My brother can get me 1% resistors at 909R and 56R values for a total of 965R! With proper matching of course.

I'm not sure what you mean by the surprise difference of a p2p version with a pcb version. Anyway, I already have the parts (tubes, resistors, caps, etc) except for the power trafo coming this monday and this would be built in a p2p manner,

If the pcb version do push through, it would be very tempting to build one also. Especially for the surprise part, care to elaborate on that?

Thanks,
JojoD

 

[JojoD818]

Good link! A wee bit opinionated, but his facts look OK

The CC+SLCF ckt is very tempting too. Wonder if someone already had the chance to build one. Ah... focus Jojo, focus.

 

[fdegrove]

Hi,

If the pcb version do push through, it would be very tempting to build one also. Especially for the surprise part, care to elaborate on that?

Ah...The surprise being that the P2P version should sound much better than the PCB version all else kept equal.

It's also much more "upgrade friendly" than PCB in that you don't have to worry about PCB tracks coming lose and you can arrange components much more in a way that signal path is kept shorter instead of wondering if it will fit onto the PCB etc.

My entire system doesn't contain a single PCB, not one...
Quite often when I hear some device sounding really good, I can't help but wonder how much better it could sound if it were built P2P.

Cheers,

EDIT:

Ah... focus Jojo, focus.

Grashopper?

 

[JojoD818]

Frank,

I knew you would say that. I'd go p2p now and if the guys here insist on testing a pcb version then I'd get the chance to compare both.

Need to focus on which project to do first. Your ultimate tube preamp, a SLCF (thanks to you also for showing me ), tube phono stage, and the list goes on. It has to start somewhere so I picked the phono stage.

Thanks!
JojoD

PS, maybe that's why 47 Labs built their gaincard virtually in a p2p fashion, using a pcb just to support the component leads?

 

[kmj]

a little of topic, but it seems like the comment "no one builds just ONE amp" is quite on the mark '

start with an integrated and find yourself with line/pre, power, RIAA, +3ch for the homecinema, speakers and one small toy for the kitchen and toilet (far away fron the tub)

 

[Kofi Annan]

OK-- I did a lot of soul searching on this one (not my soul, but someone's anyway) and I am trying to enact a plan for a tube phono preamp now.

I think I want to go with the RCA circuit that Dave (Planet 10) posted. It seems easy enough and, since this wil be my first foray into non-kit tube amp bulding, easy is what I need right now. Experience is the important issue here for me.

A few weeks ago, I found an old Pilot tube amp (see my post here) at a TV repair joint and, rather than restoring it (it needs some real attention, plus I have yet to find a schematic), I'm thinking of using the transformers and possibly any salvageable resistors, caps, tubes, knobs, screws, rubber feet, wire, paper, oil, film, aluminum, casing, switches, smells, light (particles), light (waves) etc. to build the phono pre (in homage to P-10's Frugal-phile(tm) concept).

It looks like the power Tx puts out about 340V in the secondary so, like a big boy, I tried to design a power supply using the Duncan Amps PSU designer. Attached is a screen grab of what I came up with.

So I'm asking politely, please rip apart my PSU design for the RCA phono preamp, dress me down and advise why a stupid Secretary General of the United Nations should have even considered DIY Audio in the first place. While you're doing this, if you could advise why this would or would not work, that would be very helpful.

One issue-- I made the load a 30ma current. I did this because Kuei Yang Wang had this as the load in his PSU designer attachment, but I'm too stupid to understand why this is. I think it means that I will need to have some sort of transistor-regulated constant current source in the PSU, but I'm not sure how to build one or if that is even the case. Any help on this one would be much appreciated.

Thanks again for all the ideas and all the help.

Kofi

 

[chipco3434]

LOVE the ID tag! Whan a novel idea! Good luck on your tube project ~ don't kill yourself ~ 340VAC will leave a mark, and possibly a widow.

Are you insured? Please send picture of wife and any watercraft you own. On second thought, just send the boat pictures.

 

[Kofi Annan]

No watercraft, but Mrs. Annan has added a little junk to the trunk in the last few years and has actually become quite buoyant! I'd attach a photo of the aforementioned "flotation device", but decency prevents such an action.

Now back to the audio-- any remarks on the PSU? C'mon... I'm wide open for criticism here. Can't believe no one wants to humiliate a guy for tryin'!

Kofi

 

[Kofi Annan]

El bump-o

 

[pedroskova]

The RCA circuit doesn't consume 30 Ma. . . and you need more filtration for a phono stage. Since this is DIY, throw a choke or two in their, have fun ... build Alan's circuit.