I received a few PM’s asking for my impressions. Not surprisingly many are interested in what Peter McAlister has to offer. His prices are reasonable (very reasonable) and his designs unique. If your interested in obtain a McAlister component, all I can say is don’t’ be in a rush! It took about 3 months to get mine and this seems to be about average waiting time. He has a tall list of clients. Good news is that a used McAlister sells for just a little less then what it cost new – there is little reason to discount his components. Their cheap enough already and not having to wait to get one has a value all its own!
Well I’m going to reserve the right to change my mind while it breaks in. I’ve been running my new McAlister PL-10 preamp/headphone amp overnight all week long, at the very least. I estimate I have about 80 hours on it now and its been somewhat of a rollercoaster ride.
At one point while listening late at night through my headphone my feeling was that it was bright and edgy and lacked bass, but right now I’m listening and the bass is certainly not lacking and it’s not nearly as bright. I’m expecting it will settle down at about 150 hours or so. What’s consistent is the sheer amount of detail, especially through my CD player. I’ve been breaking it in mostly from my PC through a Scott Nixon USB Tube DAC listening to a mixture of WAV’s and MP3’s. My CD player is leagues better and the layers of sound and detail is really surprising me, subtle things I never noticed before. Soundstage depth and focus is great, even through my Sennheiser 600’s. I can’t wait to here my buddies AKG 1000’s with this amp.
I’ve said this many times before and it still holds true; too much detail can be like a double edged sword – all the imperfections in the recording become evident, loud and clear! What I sometimes perceive as distortion ends up being in the recording. One of the things about tube gear that many people like, they tend to soften or blur some of the detail making for a more tolerable presentation. Not so with this preamp and really not so with my Decware SET amp, so I’m very open or exposed to what the recordings has to offer. I’ve gone out of my way choosing cables/wire/cords and tube’s that aid in musicality. The Scott Nixon is very forgiving and somewhat lush; this is perfect for MP3’s. Something I find that lots of tube HiFi gear do well is richen up the bass and midbass which makes more ‘lesser quality’ recordings sound musical – tube bloom is what I believe they call it. If done right you can retain all the detail and transparency without the fatigue. If done more typically (mid-fi rather then hi-fi) the tube bloom becomes fat and bloated, somewhat disjointed from the midrange and top end. High end can be bright with a sibilance. This preamp is far from that, handling everything in a correct manner so far, again transparency is wonderful making for a great soundstage and tolerable detail. Soundstage is the most important part of a components presentation to me. It’s the reason I steered into the direction of low powered amps and simple crossoverless speaker designs. This PL-10 fits right in.
Peter said that he choose to change the design somewhat substituting two PL500 sweep tubes for 12SN7’s in the power stage. He said this added about 2 volts of gain which he thought I would like with my lower powered amp. He also added a 6BQ6 sweep as a power regulator. Peter sent me a quad of RCA branded 12SN7GTA’s, Canadian made. He also sent a Roggers 5AR4 rectifier made in Holland and a Japanese made 6BQ6. I found some cool looking 6BQ6’s for pennies – literally! A Tung-Sol for $0.99, a Sylvania ST bottle from the 40’s for $1.99 and a slew of others of varying styles all well under $5. Even if they have little audible differences, they look cool. Rectifiers can be a trip all in their own and in my SET amp it makes a significant difference. 5AR4/GZ34’s can be expensive for premium brands made my Mullard and Amprex.
From what I have read the 12SN7 is identical to the 6SN7 just in a 12v version and since the need for this 12v version was much less then its 6v sister there were a lot less of them made. The good news is that the stock of 6SN7’s are being used up at an alarming rate while the 12SN7’s gather more dust. Since they were literally made side by side, the sound chrematistics of these tubes are said to be nearly identical, many saying the 12SN7 having a touch more detail. The cost of 6SN7’s are high, especially the older, more sought after ones. $50 to $150 has become common for a single 6SN7.
These tubes come in two distinctive types; a GT and a GTA. The GTA’s are a more rugged version but are almost unanimously said to sound inferior to the GT’s most commonly made in the 1940’s and 1950’s. Unfortunately the GTA’s are more abundant making finding the older GT’s difficult.
Also, it appears that there weren’t many makers of SN7GT’s so regardless of the ‘brand’ you can usually track down the manufacturer to just a few.
My experience with these tubes are limited to 6SN7’s so far. I based my selection of 12SN7’s on that and once this preamp/headphone amp is broken in I’ll be able to determine the differences providing the preamps topography allows for it. According to Peter the sound character will be nearly identical regardless of tube brand or variant. We’ll see!
I’ve only rolled through just three pairs of 12SN7GT’s so far and I really can’t comment on the differences yet, the unit needs to settle down before I can trust what I am hearing.
I’m currently listening to a pair of Westinghouse 12SN7GT’s.
The most sought after xxSN7 is the Tung-Sol round plate/oval mica black plate made in the early 40’s. Versions of these in a 6SN7 can cost well over $100 each. I found a couple of 12SN7GT’s for less then half that and I think that was way too much to pay for a 12SN7 but they are rare and I want to hear them. Another popular SN7 is the Tung-sol with ‘mouse ears’ that came in both gray and black plates made through the 50’s as well as a clear glass black plate version commonly branded Tung-sol but believed to have been made by Sylvania. These are all considered ‘premium’ 12SN7’s and although hard to find, seldom sell for more then $20 each.
Other more common premium 12SN7GT’s are branded RCA, Westinghouse, Western Union and Ken Rad made in the USA some for the military that have the JAN (Joint Army Navy) designation. Philips branded GT’s made in Holland can be found at a premium too as well as British made GT’s branded National but made in the Blackburn Mullard plant.
Once you move to GTA’s the list of brands and types open up a lot. These are fairly abundant and were made through the 60’s into the 1970’s and generally sell for about $5 each but again are said not to sound as good overall.
Here is a list of tubes I have so far in pairs:
12SN7GT - Tung-sol round black plate/oval mica
12SN7GT - Tung-sol ‘mouse ear’ gray plate
12SN7GT - Tung-sol ‘mouse ear’ black plate
12SN7GT - Tung-sol black plates, half mica
12SN7GT – RCA smoked glass, full mica.
12SN7GT – Ken Rad JAN-CKR black plate
12SN7GT – Westinghouse (tall bottle) gray plate
12SN7GT – Philips ‘Holland’ black bottle
12SN7GT – National ‘British’ black plate
12SN7GTA – RCA black p-late, Canadian
12SN7GTA – Raytheon short gray plates, side getter.
12SN7GTA – Western Union gray plate
I bought a hard to find pair of PL500’s made by Mullard which I no longer need. If any of you McAlister owners are interested in them, I’m selling them for less then I paid. I listed them here:
http://www.audiocircle.com/index.php?topic=30957.msg275430#msg275430
