Searching for a valve line level pre to build

[Paul Bannister]

I have been trying to get a vinyl front end up and running but had some problems, which meant taking the turntable and phono back temporarily to the supplier for some TLC.

This included my preamp as there were also some matching issues. I borrowed a Canary pre, which had extraordinary powerful 'grippy' bass but thin female vocals and then a Tron Syren, which is sweet and has a certain rightness - however it's very expensive and although very good I am hoping I might be able to make something which sounded as good or better.

The reason for mentioning all this is that I was experiencing a problem of bloated bass I had put down to the WE 300B's in my WAD 300BPSE's is not the case. I hadn't realised the problem was the Art Audio preamp I was using. The different preamps are each have had their own signature sound, whilst the power amps just get on with what they are given. What I need is a realy good preamp circuit (or kit) to build and replace my own pre.

Any suggestions ? I want to try and do this just the once. I'm happy upgrading and fine tuning components but I don't want to end up with numerous preamps on the go. Is it worth looking beyond the original WAD pre or its promised WD replacement? I posted recently for any comments on the Bruce Berman's 76 pre which I had come accross in a Sound Practices magazine, but comments back appeared not to think it was particularly special.

All ideas welcome.

[The Shadow]

Hi Paul

You could try my 6J5 preamp. It is basically one 6J5 grounded cathode stage cascaded into another 6J5 configured as a cathode follower per channel. There are a couple of tweaks.

The two stages are direct coupled and the grid leak resistor for the final stage is bootstrapped to the base of a 1K resistor connected to the cathode of that stage. Below this resistor is the 22K load resistor.

James D spent quite a bit of time helping me optimise this preamp so you can be sure it has been done right.

I have since replaced the 6J5s with British equivalents CV1932 (L63s) which are much better sounding.

It sounds really rather good.

It did sterling service at EggFest 4 driving my PT15 amp with my Metronomes and Ed's TQWTS.

If you want the circuit PM me your email address.

Steve

[dave dove]

this is the best linestage i have built:

http://tubecad.com/2004/blog0011.htm

the one with 6n1p and 5687
but substitute 6n6p for 5687

broskie even does a nice PCB if you're that way inclined
he also does a pcb for octal valves
if you're that way inclined

i cannot recommend this preamp highly enough
there will be
no bloated bass
no weedy vocal
no sharp treble
no sibilance
no added warmth
no sterile presentation
no sloppy timing
and the revolution will not be televised....

dave

[Paul Bannister]

Just a quick reply before the battery on my laptop dies - I am 'on the road' tonight. I will be in touch and follow-up with you both later tomorrow.
Regards,
Paul

[Ianm2]

imo after trying quite a few topologies, none is better sounding than the simple single valve voltage amplifier, grounded cathode or whatever, I have tried a lot of the rest and they weren't for me as satisfying, ecc82, 6sn7,6922, 5687 any valve pretty much, some of the lesser known ones, of which I don't know a lot, others can help better with these,

imo all the efforts like active loading, paralleling, cathode followers, kill the sound.

dead easy, too. aikido was an easy build due to all the parts being the same, one of the easiest I have built, but a bit longer.

I do have an interesting circuit, I reckon its unique, I will try to get it optimised on paper and drawn out here, its got feedback so I may need some assistance from James or similar.....

I think it may well challenge Dave Dove's aikido!! may even get him to change it.... then again, he really loves that, so....

to me the aikdo was a touch to neutral.

Steve, if you are feeling ambitious, remove the cathode follower, and just take the otuput from the anode of the first valve, C coupled, I think that configuration sounds better, but ymmv. you can always replace to as it was.

Paul, does it have to be a kit? or a self build? how much to spend..

[Paul Bannister]

Just a quick reply, (still on the road.)

Steve,
Thanks for the email. I will look carefully at the circuit when I get home.

Dave,
Thanks for the link. I will study the info and I'm sure have some questions.

Ian,
As a quick answer - no, I am happy to build from scratch, and money whilst important will not prevent me using components for the job which will reap the best reward.

I will be able to say more when I am back home tomorrow.

[NickG]

but comments back appeared not to think it was particularly special.

You always need to check if the comments were from someone who had heard the thing in question.

76's are particually nice sounding valves IMHO, esp when choke loaded. the CF may of not be needed, it depends on what you are driving and the line length. Also, do you need gain?

Both Steve and Dave use the circuit they suggest so that does lend some safety to the suggestions.

IMHO, you should just build a few and use the one you prefer, forget the box, build on wood, then when you have the one you prefer build that for a keeper. Remember the power supply can be as important as the rest, and one supply could be used for several circuits so its never a case of starting from scratch.

Doing anything else is no different from reading What HiFi and picking what they says sounds better.

[dave dove]

i agree with you nick

i started with simon shilton's line level preamp project:

http://www.users.globalnet.co.uk/~valveamp/

in the "read it" section
learned absolutely loads from this
then messed with the operating points
i particularly liked the 417a

i then tried 417a and 6c45pi WOT - with output transformer -
then i moved on to the aikido
which again leaves plenty of room for messing
and i too think the power supply is the key
i don't understand how a linestage can be too neutral

i don't use the aikido linestage any more
as my power amp has a volume control

i think simon shilton's project is pretty essential
to understanding a linestage's function
and is not at all expensive

dave

[James D]

The Aikido is extremely neutral and natural. It has the lowest harmonic distortion, intermodulation distortion and wideband noise of any non global feedback amplifier by a factor of 100 or more (20dB+) and it sounds open, natural and transparent. It also has a very good ability to drive the next stage and to handle capacitive or inductive loads. It is as close to having no sound as any amplifier stage that I have heard.

So it doesn't add a certain degree of sweetness or 'magic' like, say, Steve's simple line stage will and it doesn't cover up any deficencies elsewhere in your system like a lot of lineamps do. It will show up any problems elsewhere in your system including what your psu sounds like In other words the better your system the better your Aikido will sound and this particularly applies to your frontend. It is ruthless in exposing its limitations but it won't exaggerate them like, say, a highend ss pre will...

I love the Aikido stage and think it is a real set forward for the audio amateur to have it available.

Dave mentioned that he no longer uses his Aikido pre as he doesn't need a pre in his system - what he didn't mention in this post is that his poweramp uses an Aikido stage to drive his 300BXLS

James