simple hi-fi phono amp

[TUBEDUDE]

As far as the turntable goes, check out the orbit from U turn. It was a project developed with a kickstarter campaign. $179 for the basic table, a little more with other cartridge options. Great specs and stunning reviews from Analog Planet and others.

[JazzGuitarGimp]

I've been thinking about phono stages lately too. I'll be moving soon, and I plan to finally take my turntable out of storage (it's been about 7 years). CUrrently, my Nakamichi 410 preamp is out on loan - and besides, I've done some research on it lately, and it apparently doesn't get good reviews anyway.

I was traveling the inter webs this morning, and I happened across this design, which looks very interesting:

[http://www.diyaudio.com/forums/diyaudio ... reamp.html]

I might have a go at it once I get moved and settled in.

[passfan]

Here is a link to a fella that has experimented and tweaked the old Magnavox paraphase circuit. He also has a SE 2A3 as well. I've built them both and they sound really nice.

http://gabevee.tripod.com/ezindex.html

[gingertube]

I would definitely use a tube power amp BUT tube phono preamps to match or better the performance of modern op amp circuits are very expensive to build.

If you really want tube phono pre I would probably opt for a John Broskie kit:
http://glass-ware.stores.yahoo.net/aiphpcb.html

For poweramp options are:
1) Look around for an old Pioneer SA400 or something similar you can fix up
2) A low power (4 to 5 Watt per Channel) single ended design - lookup RH84 as an example.
3) For a 12 to 15 watt per channel, push pull there are a lot of designs but I would pointv you to 3:
- My own Baby Huey Design, Post number 604 here; http://www.diyaudio.com/forums/tubes-va ... ey-61.html for what I'm running at home, or see the Baby Huey Wiki for a simpler version:
http://www.diyaudio.com/wiki/Baby_Huey_ ... +Baby+Huey

- Sy's Red Light Ditrict here:
http://www.diyaudio.com/forums/tubes-va ... 4-amp.html

Eli's El-Cheapo - a search should turn it up.

For simple SS phono pre use this circuit:
http://sound.westhost.com/project06.htm
I would use a different op-amp, this one: http://www.ti.com/product/OPA2134/techn ... s#doctype2

So what Phono pre do I use? This one: http://www.customanalogue.com/jlti_phono_stage.htm BUT it is very expensive. (I bought a loaded and tested PCB from Joe and put it a box etc. myself. That worked out about 1/2 the listed price)
HINT: If you want to know more about the guts of this I can tell you it uses an Analog Devices AD844.

Lots of options there for your consideration.

A picture of my 6V6/6SL7 Baby Huey HiFI Power Amp as documented in the DIYAudio link above. This is my everyday HiFi Amp, it does everything beautifully but does guitar music and female vocals stunningly.


Cheers,
Ian

[TUBEDUDE]

Have a look at the aikido tube and hybrid phono stages on John Broskie's site. He has stages using small noval tubes and large octal tubes, 6sn7, 6sl7, etc. He sells cards for these, and power supplies. Many, many options.

[Meat&Beer]

I've been kicking around the phono preamp stuff for a while too, haven't completed any of it yet. I DID, however, mock up this attached schematic. I remember adjusting the coupling caps to taste, and liking it quite a bit before trying a different design.

If I may ask a question, while we're on the subject, why no cathode resistor on the second tube half? I showed one of my vastly advanced tube buddies and he kind of scoffed at this... Just curious as to what I'm missing, and if a triode can actually be set up like this, or if this is purely poo-poo'd upon.

Oh, and thanks for all the ideas and suggestions from all the knowledgeable folks here! Totally been creeping on this thread.

[gingertube]

The 3M3 puts that stage into grid leak bias.
Grid Leak bias is noisy and should never be used in a phono preamp.

Floating around the web is a modern version of teh RCA phono premap which uses 1 off 12AX7 for each channel. The modern version adds a mosfet source follower buffer to improve its peformance.

Ah! Here it is:


Cheers,
Ian

[Meat&Beer]

Thoughts on the mighty Marantz 7c? I know the OP was for simple... Diversifying this thread a tad I suppose.

Gotten from here: http://www.preservationsound.com/?p=3187

[gingertube]

There are certainly more knowledgable people that me in this area but for what its worth, these are my comments.

The Maratz uses feedback based RIAA whereas the Modified RCA uses passive RIAA.

I like the Marantz circuit as gain has been maximized by use of those 270K anode loads.

Those 270K loads to maximize gain are not suitable for the passive RCA circuit as the Zout needs to be kept low so as to not influence the passive RIAA compensation.

The 3rd 12AX7 triode in the Marantz circuit is a cathode follower and can be replaced by a MOSFET source follower as in the Modified RCA. That would be worth doing as it gets you back to a single 12AX7/7025/6N2P for each channel of the phono.

I see above that someone else has also suggested getting a kit or at least a PCB from John Broskie. That is probably easiest/cheapest/best results option. John is reknown for really good build/assembly instructions.

Cheers,
Ian

[jazbo8]

I would definitely use a tube power amp BUT tube phono preamps to match or better the performance of modern op amp circuits are very expensive to build.

Cheers,
Ian

+1, a "good" phono preamp is not an easy DIY project. If it's cool tube look that you want, there are many Chinese hybrid designs that can fit the bill.

[Synchu]

I built these
http://diyaudioprojects.com/Tubes/EL84-Mini-Block-Amps/
for my brother with the said Edcor transformers.

Relatively easy build, except the power supply I used NOS Russian PIO coupling caps (supposedly add some mojo according to the hi-fi crowd), Vishy Beischlag 1% precision resistors, some Solens in the PS.

They do sound incredibly good, albeit not too loud, due to the Class A, ultralinear design.

These are about the first time I seem to like EL84 in an amp (not a guitar one though ).
Niki

[rp]

I built these
http://diyaudioprojects.com/Tubes/EL84-Mini-Block-Amps/
for my brother with the said Edcor transformers.

Those are cute!

BTW to the OP keep in mind the speakers you intend to use, if they are inefficient, sensitivity below 88db or if they are sealed/non ported, you'll need at least 15W IMO and that will provide only modest volume levels. Those little SE amps running a couple of watts are for horns or other speaker into the +90bd range. Background music? active listening? party? - or all three? Is your son using these as a desktop w/ tiny speakers, trying to fill up a decent size bedroom or a living room? Is he into rock or jazz or classical, chamber or orchestral? What's the bass range of the speakers? Bass reproduction sucks up big watts. That TT won't do too much bass so you'll be ok. Maybe best with speakers that cut off at 80htz to avoid rumble from cheap bearing and arm.

Keep in mind Hifi isn't guitar amps where hitting the power limit can equal joy, ie distortion and compression. In hifi you want tons of headroom to reproduce dynamics without distortion or the tone skewing or the soundstage collapsing, the latter happen pretty quick when the power supply or the output stage can't deliver.

I personally wouldn't built any cult SE stuff, but suggest a tried and true classic PP with feedback, at least to start, minimum 2xEL84/6V6. If the kid wants to party now and them you need to go with 2X6L6 style in PP w/NFB.

And, rock is actually easier to reproduce as it's recorded compressed and less dynamic, orchestral music you need 35-50W just for modest volumes if you want to keep the sound stable.

Also just on the mojo side you might want to decide if you want to go pure retro - no silicon ie tube rectifier, some silicon - ss rectifier, maybe heater regulation, lots of silicon - all stages regulated. The boards and kits let you mess with later. SS rectifier helps drive rock and roll, tube rectifier helps classical and jazz bloom.

Lots of choices, but keep in mind the critical importance of power reserves.

[rp]

one more if you are doing your budget/BOM building a stereo chassis rather than dual mono will save you $, you'll only need one chassis, one PS, one PT. Remember the PT needs to provide current, HV and heaters to two sides.

[didit]

I personally wouldn't built any cult SE stuff, but suggest a tried and true classic PP with feedback, at least to start, minimum 2xEL84/6V6.

Completely agree with this recommendation. Though 2xEL84 for me hits the sweet spot. I'd recommend working up a Dynaco ST-35. Power sufficient for modern home use when paired with reasonably efficient speakers. Portability is much better. Full kits are readily available. Also some trade in originals that can be restored. It's a simple design so scratch build would be straightforward if you've got requisite experience. Lots of experience with these on other forums so if do get into sticky issues you'll find the help to get unstuck. On the phono preamp, I'm siding with folks recommending solid state.

Best .. Ian

[rp]

Occurred to me to mention these old Eicos, time tested and well loved variant on the Mullard 5-20 circuit. Capacitance is upped and the circuit tweaked for a commercial product, which is good.

EL84
http://www.vintageshifi.com/repertoire- ... Manual.pdf

HF-35 / EL34
http://www.acousticpsychos.com/Files/Ei ... manual.pdf

HF-50 / EL34 w/ fixed bias
http://www.acousticpsychos.com/Files/Ei ... manual.pdf

This post got me all worked up over tube hifi again, found this surfing, kind of cool as it seems so faithful to a hoary old circuit. The Matamp provenance might make it of interest to peeps here:

http://www.hifiwigwam.com/showthread.ph ... 20-circuit