Hovland HP-100 phono vs Audio Research REF Phono 2

12AX7 = ECC83. ECC88 are 6DJ8 or 6922 equivalents. The ECC88 et al are VERY different from a 12AX7 in both electrical parameters and in pin configuration. You could damage your gear or the tubes by inserting an ECC88/6DJ8/6922 into a socket set up for a 12AX7. Variants of the ECC83 include the ECC803, 803S, and probably some others using the English naming system adopted by Mullard. (Mullard CV4024 are 12AT7s, for example, but I don't know the 12AX7 equivalent name.) The 5751 is often sub'd for a 12AX7, but it is not electrically identical. The 5751 has a lower "mu", for one thing. This means that you will have a little less gain with it, so if your phono gain is at all marginal, you might find that it is insufficient with a 5751. However, 5751 will "work", and lots of folks seem to like it in circuits designed for 12AX7. Larryi, I disagree that all-in-one preamps are inevitably inferior to separate line and phono stages. In fact there are many inherent advantages to the one-box solution, but you have to pay the big bucks for the best ones, just as with separates.

A bit off topic but somewhat relevant regarding 5751 tubes.

They are similar but often not drop-in replacements for 12AX7.

Check with your retailer or manufacturer before substituting.

The biggest issue with the Hovland is noise; it's not the most quiet phono/pre you've ever heard. Use it with Khorns and that makes things worse... However, it sounds pretty darn good; just not quite as good overall as an Audio Research Ref Phono Two...

Lewm,

Thanks for the detailed information on the various tube types. Yes, the 5751 is a lower gain tube, but in almost all applications it does work in place of a 12AX7 or 12AT7. But, I think it is also worth mentioning that tube swapping MAY be problematic with phonostages if RIAA equalization is not done passively.

By the way, I did not say that one-box preamps are inevitably inferior. I said that most of the ones I heard were not that impressive and noted that the Audionote M-8 is one exception. I think that the M-8 costs over $30k. I have, though I don't current use it, a Mark Levinson No. 32 with a built-in phonostage. Contrary to the opinion of reviewers, I think that that phonostage (built on two cards that slot into the back of the unit) is not very good (the No. 32 is a pretty expensive preamp). I've heard Shindo preamps that sounded very good, though I don't specifically recall whether the built-in phono was outstanding too.

You are correct that there is a big advantage to building in the phonostage -- a long run of interconnect cable and inevitably crappy RCA jack interface is eliminated. But, many of the better phonostages cannot be built into another component because they take up WAY too much space. For instance, my current phonostage has a separate power supply that is bigger than most power amplifiers (it uses two 300B tubes as rectifiers).

Larryi, I see your point. As I was saying too, to get a great phono stage built in to a fine linestage, you need to spend more than a little money or you need to build it yourself. IMO, superb all-in-one preamps can be had at the $10,000-ish price point. To get similar quality phono reproduction from separates, you would have to spend much more than that, again IMO.