Pro’s and Cons tube phono preamps

seriously considering purchasing an Icon2 phono preamp and just wanted some feedback on tube phono preamps before committing to the purchase.

 

Tube preamps deliver a 3 dimensional soundstage rather easily. They also have more coloration and noise than nice solid state units. I like to place the tubes in the linestage while leaving the more demanding jobs of high gain and low noise to solid state devices. Some designs, both tube and SS, will incorporate step-up transformers for the LOMC section and so reduce active amplification in that way. No matter how it is done, it gets rather expensive to get all of the best parts and few of the drawbacks from any design.
-Bill

 

What's the rest of your system like?

Generally, I'm a big fan of tubed phono stages. Units like the Rogue Ares, Manley Chinook and even the Line Magnetic LP-33 are generally considered some of the top choices on the market in their respective price ranges (granted I don't much about the particular model you are considering).

 

rx1070 Yamaha amp, Mofi ultradeck with master tracker cartridge. The icon ps2 runs about $1200. Their out of England.

 

High Overload margin, which I consider to be of primary importance in phono stage performance, comes pretty naturally to any decent performing tube phono stage.

 

I never buy anything anymore where critical specs are omitted from the manufacturer's and retailer's info sheets/web sites. So I would not buy this, if it were my money. I also wouldn't buy anything for $1200 without a home audition or return period that is generous enough to fully audition in home.

RE: tube phono stages, lots of different types from full tube units to gimmick hybrid units. Not sure what this one is because info is scant. With any type of tube unit (esp. full tube), there will typically be more noise and sonic coloration, as said above.

I personally prefer solid state phono stages but some people do like tube units.

 

I think I better slow down and do some more research. Ty

 

I used a Pro-ject several years ago. I already had a wide assortment of 12ax7 tubes from owning tube equipment. I enjoyed it and can think of nothing negative about using it.

 

'The preamp section uses the "cascade effect" of pairing to valves together to attain high gain'
Supposing that first valve is a triode, there will be substantial Miller effect input capacitance, which impacts high frequency response with moving magnet and other high impedance cartridges.
High gain valve amplifiers are also liable to microphonics.

 

Tube preamps tend to sound much more 3-D, and a little "sweeter" in the mids and highs than do most SS preamps in general. They can be (but don't have to be) more colored as well.

Noise is always going to be a bit higher with a tube design. Achieving really low noise with tubes is always going to be more expensive with tubes, since either you have to start putting tubes in parallel or you have to use a step-up transformer. But this only becomes an issue if you are running low output moving coils. Normally the noise of a tube preamp is well below that of the vinyl, so this isn't usually noticeable in practice.

IMO a good tube preamp is worth the effort. And I love the ability to roll tubes to get the sound perfect.

But I would stay away from cheap gimmicky designs which use Op-amps to amplify and then just throw a tube in as a buffer. If the tube isn't doing most of the amplification work, then its not worth bothering IMO.

 

That's an important point if you use a cart that requires low capacitance. A vintage cart with a higher capacitance requirement, like 400-500pf may be a better choice for that type of tube phono pre.

 

Icon Audio makes some nice gear, and relatively low cost compared to much of the competition, may be assembled in China, not sure, and it does get quite a bit more expensive from US dealers (but some pretty nice deals around if you don't mind buying from UK sources) . The phono stages are nice designs, I like that they don't use any global negative feedback, which is important to me. As a consequence, it will never have the low distortion of competing SS products that use lots of negative feedback, especially opamp-based designs, but I think the sound is more natural. The PS2 is also not the quietest of designs, that usually comes with a cost in tube designs, such as the use of parallel sections (for example, my Conrad Johnson phono stage uses four dual triodes in the input stage, so four 12AX7 sections in parallel for each channel). And as mentioned above, tube designs with their high voltage power supplies, usually don't have marginal input overload margins like many of the low voltage SS designs.

In any case, I think the Icon Audio line really shines at the PS1 MKII level, with the separate tube rectified and choke input power supply that allows you to avoid use of bad sounding electrolytic caps, though I honestly haven't seen what's inside these units (my CJ only uses electrolytics in the high current tube heater power supply).

 

Not always. For most tube phono preamps, you are certainly right, but it is in fact possible to make a very quiet tube phono. Mine for example. It uses a simple two-stage circuit with one Siemens D3a per channel for the input stage and a 5687 on the output. For a low output MC I use a SUT but the basic circuit works just fine with a MM. This phono stage is virtually dead quiet even with the volume cranked way up. It is quieter, much quieter, than any of the solid state phono preamps I have owned which include Threshold Fet 10e, ARC PH-1, Emotive Audio Circa and Lehman Black Cube.

This tube phono preamp is my own design but there’s no reason why a mfr couldn’t build the same circuit today except for the fact the D3a is no longer being made. NOS tubes can still be bought in small quantities though.

Your comment about noise from tube phono stages is certainly true with designs that use tubes like the 12ax7 or 6dj8 but it is not fair to assume from these tubes that all tubes are noisy.

 

I wouldn’t even consider buying this just to run it through a home theater receiver. You’d get much better music if you invested that budget in a two channel amp with home theater bypass.

 

Interesting. I have no experience with the D3A, and have never even heard of that tube before. In pulling out my trusty RCA receiving tube manual, I can't find any type of listing for that tube.

Might I inquire as to the topology you used? Since you specified an input and an output tube, I'm guessing that it might be a cascaded design of some sort.

 

i have experienced the pristine sound quality of driving my LOMC with highly filtered quality power supply solid state phono preamp and that is my preference.
if i did not have tube amplication i would try a tube phono pre again. a noise and distortion free signal makes low output moving coil cartridges shine.

 

The D3a is a Siemens tube. It’s a fairly high gain pentode but I use it in triode. The data sheet is online.

The topology is very simple. The D3a is cap coupled to the 5687 with passive RIAA eq in between. Each tube has LEDs on the cathode to set the bias. The 5687 has a CCS for plate loading and is cap coupled to the output jacks.

 

More noise but cool soundstage. I’m getting a Sutherland as I prefer SS for the phono but I do have both options. And everything else of mine is tube.

 

I have a 2014 Icon Audio PS2 which I bought here for just $425 (yeah classifieds!). It is a phenomenal sounding phono stage and will benefit greatly from installing vintage tubes, but not necessarily any that cost very much. It has tremendous gain, it actually amplifies even LOMC carts quite well, but you lose the full dynamics without a step up device, I use a Lounge Copla.

I’ve used the PS2 into a Pioneer SX-850, a Luxman L-85v, and currently a Fisher 800c, it plays well with them all.

There’s been an Icon Audio PS1 listed in the classiest for a long time, currently at $1675, if you can stretch your budget a bit this is quite a deal. I have no affiliation with the seller.

 

No cons only pros with a tube phono preamp

 

Any properly designed 12AX7 moving magnet preamplifier without defective components should have a noise floor well below that of
the quietest LP being played. For low output moving coils with 12AX7's, step-up transformers are wanted IME.

 

I agree with you. And I believe that I stated this above as well.

The noise is usually only a problem for those silly people who insist on lifting their stylus, and then turning-up the volume until they hear the noise-floor of the preamp. With a record playing this noise is normally completely masked.

 

OP, is it possible for you to audition at all?

 

Ty for your input. How often have you had to replace the tubes?

 

I've only replaced the tubes to try a different sound, none have gone bad on me and I play a lot of records, sometimes throughout the day if I'm working at home. I currently have a pair of Westinghouse 12AX7 Tubes in along with a Mullard 12AT7 that I bought from the unit's Seller. I see on the Icon Audio site they now spec for three 12AX7 tubes. Also of note they have their snazzy silver version on sale for $208 off (I did the conversion).