Phono preamp valve kit?

[Ruthann]

Hi, not sure this should go in the homebrew section as I'm mostly seeking advice on a kit. If necessary, mods, feel free to move.

Anyway, can anyone recommend a CHEAP phono preamp valve kit?

I did a search here but couldn't find an answer related to kits.

I want to hook an amplifier up to a record player, and would prefer it to be tubes/valves. This would be my first amplifier build, so I'd prefer a kit.

I've done some googling and it's throwing up kits in the $600 to $900 range! I was thinking more in the 50 pounds range... max.... Something basic and easily assembled that gets the job done.

Preferably something smallish and relatively compact, as the reason for this in the first place is the original setup got moved to the garage due to its large size.

Any info/recommendations much appreciated. Thanks!

[Peter.N.]

Dont know of any kits but something built around an EF86 would give you a good low noise pre amp.

Peter.N.

[Mullard]

Try the Mullard Circuits for Audio Amplifiers on Paul's Valve Data CD-ROM (http://www.service-data.com/cd-roms/...data/index.htm) is full of classic valve audio amplifier circuits. I built several of the pre-amps (and amps) some years back and they all performed extremely well. The EF86 + ECC83 unit is extremely good and relatively cheap if you source your own components. Easily built on a small aluminium chassis with the controls on the front.

[Mike Phelan]

I'd second that - I made the preamp and a couple of 3-3's from the Mullard book years ago, and it performed really well considering what little was in it.

[ALANS ANITAS]

The Mullard circuits are excellent, but I do not know of any kits available in this country. Try a worldwide Google. I would expect someone in the USA would have something available, although Australia is another possibility.

ALAN

[Mullard]

Sorry, I was wrong about the valve line up - memory playing tricks. I seem to think it was 2 EF86s.
John

[Ed_Dinning]

I would certainly agree with the comments above on the Mullard designs; however there does not seem to be a source of kits anymore and you would have to get the parts yourself and probably do some chassis bashing.
Try looking at the Elektor website as I'm sure they have had valve pre-amps in the past and may well have suppliers who still stock the parts.

Good luck, Ed

[Mike-repairman]

You could scrounge the LT/HT mains transformer from an old scrap valve radio, as well as some of the other parts, and a couple of ECC83 valves would probably suffice. You could probably make up the whole thing for £20 or less; depending on how well your component box is stocked.

I have no idea where some of these manufacturers get their prices from?
Extortionate is the word that springs to mind.
£100 would be enough and they'd make a profit at that as well.

Mike.

[Chris55000]

Hi!

I admit its probably sacrilige to say so but the chassis from a Heathkit RF-1U or C3-U (or US equivalent) are ideal construction platforms for preamps, TC units or replacement reel-to-reel amplifiers!

Chris Williams

[barretter]

John Broskie is offering a kit on his website www.tubecad.com, an unpopulated circuit board for $59 or a kit with all the parts and valves, but no power supply for $270. Alternatively you could buy or borrow from the library Morgan Jones's Valve Amplifiers book (preferably the 2nd or 3rd edition) which has several designs for phono preamps. I've built a couple myself, using the principles he describes but with different valves and it's a very satisfying thing to do.

[paolo]

There's always this:

http://www.project-audio.com/main.ph...=boxes&lang=en

[Herald1360]

Originally Posted by paolo

There's always this:

http://www.project-audio.com/main.ph...=boxes&lang=en

Looks like the biz, if a bit OTT. No sign of a price, though, and it looks like that might be somewhat stratospheric from the general tone of the site. (Gold plated RCA connectors.....). There's mention of an additional PSU required too....

Chris

[flyingtech55]

There is a magazine called Hi-Fi World which used to do DIY supplements of valve kit. They did a couple of phono pre-amps. One was a fairly simple thing comprising a kind of cascode first stage followed by a passive equalisation network followed by a normal common cathode triode stage buffer to prevent loading of the EQ. network by the following stage. The output is by a further triode in common cathode mode and incorporating a bit of NFB. The overall output of the pre-amp is 180 degrees out of phase though. It incorporates a regulated PSU with active smoothing and the usual DC heater supplies. It uses ECC88 (6922) valves

The second one they did was a bit OTT which had three parallel ECC88s as the lower element of the cascoded front end. It also had a passive EG network which drove what they called an SRPP buffer stage from which the output is taken. There is no feedback used. The PSU has two separate stages of active smoothing the second incorporating a series regulator to reduce the HT from 340V to 210V. This second circuit is a phono stage only and is designed to drive an AUX. input to a normal amplifier. There is no overall phase reversal with this circuit.

Both are competent enough designs which will be easy enough to build. The power supply circuits are a bit pretentious and can be simplified somewhat without compromising the performance to any significant degree.

I have both of these circuits to hand along with the relatated supplements. If you want to see these, PM me.

TimR

Both are

[phase_splitter]

^^Yes, they were World Audio Design kits who went bust. They now appear to be called World Designs. They are/were both affiliated in some way with Hi-Fi World Magazine.
I remember their preamp kit; called the KPL1 or something; I recall it wasn't terribly highly thought of; although I don't recall why. (Haven't got any details to hand)

Mind you, to buy their current preamp kit; you'll need deep pockets.

http://wduk.worldomain.net/acatalog/AmpKits.html

I would concur with a previous poster, build the ECC88 preamp from Valve Amplifiers by Morgan Jones.
Sounds outstanding and doesn't need to cost a fortune. And as with all of Morgan's designs; good, solid engineering and no audiophool nonsense.


Footnote>
900 quid for a KT88 PP amp; good grief! Looks a bit chav, too.

[flyingtech55]

Hi Phase_Splitter

I bought some of the Hi Fi World magazines with the supplements and was also given some others. I never heard any of their stuff actually running and have never built any of it so can't comment on the sound quality but...they were a very pretentious lot. You'd have thought, when reading their descriptions, that they had completely re-invented valve circuitry personally, by hand, from original research. I remember that they 'redesigned' the famous Mullard 20W EL34 valve amp...the one with the EF86 input stage. They made a completely fundamental error in their interpretation of how the original circuit worked. ISTR that their 'modification' involved returning the screen grid decoupling to chassis earth instead of to the cathode. Some correspondents, who obviously knew what they were talking about, wrote in and absolutely ripped them apart over that one.

TimR

[jjl]

Originally Posted by flyingtech55

There is a magazine called Hi-Fi World which used to do DIY supplements of valve kit. They did a couple of phono pre-amps. One was a fairly simple thing comprising a kind of cascode first stage followed by a passive equalisation network followed by a normal common cathode triode stage buffer to prevent loading of the EQ. network by the following stage. The output is by a further triode in common cathode mode and incorporating a bit of NFB. The overall output of the pre-amp is 180 degrees out of phase though. It incorporates a regulated PSU with active smoothing and the usual DC heater supplies. It uses ECC88 (6922) valves

I've got one of these that I built from the kit 10 or 11 years ago, I believe it it is known as the KLP1. It works well and is decently quiet for a valve phono pre-amp, the DC heater supplies and regulated HT probably help with this. The circuit bears some resemblance to Morgan Jones designs but is a fair bit simpler.
I agree that building one of these should be easy. The audiophoolery with silver wire, special volume pot etc. is best ignored though.

John

[paolo]

Originally Posted by Herald1360

Looks like the biz, if a bit OTT. No sign of a price, though, and it looks like that might be somewhat stratospheric from the general tone of the site. (Gold plated RCA connectors.....). There's mention of an additional PSU required too....

Chris

I think that they are around 250 pounds. The PSU comes with it so its not too bad for what you get. I have the non-tube version and its great (and a fair bit cheaper).

[Ruthann]

Thanks so much to you all for your helpful responses. I expected one or two replies at most.

I've decided not to go with a kit. I'll be brave and work off a circuit.

Seems I'll go with this one:

http://i3.photobucket.com/albums/y91...odephono-1.gif

I already have most of the necessary components, with a large collection of resistors and caps.

I'm absolutely keeping the expenditure as far below 100 euros as possible!

I bought a box for it through Maplin. Got a transformer there too.

Picked up the remainder of the components (valve bases, etc) through Farnell, as I deal with them through work.

So we'll see what I can throw together!

If it doesn't look too horrible when it's done, I'll post some pics.

Again, thanks to you all for your help!

[Trevor]

I built something very similar to your schematic but put the output and feedback stage through a cathode follower
Results were wonderfull and well worth the effort!!!
Regards Trev

[Top Cap]

I also could not believe the price asked for valve phono amps. People recommended a solid state device going for about £40 but I decided to build a 'Chinese Copy' of the WAD phono amp. The power supply was built into a separate enclosure whilst the actual amp was constructed into a very small die-cast box. The results to my ears were superb and I did a level check on both channels using a swept constant output audio generator. After carefully selecting the ECC83's, both channels were virtually identical in gain and response and followed very close to the RIAA characteristic. The attached photos show the PSU internals, the phono amp before construction and the finished amp sat on its power supply. It does not live there in normal use as there is sufficient vibration from the mains transformer to rattle one of the ECC83's but kept apart they really deliver the goods.
The 6N1 cathode follower was replaced by an ECC82 as the unit gave just a tadge too much output for my PC soundcard.
The point of it all though was the fun obtained in building, getting it going and then sitting back to enjoy listening to your handywork.