Monday, June 22, 2015

Building a new Dynaco PAS-3 tube preamplifier

The existing Dynaco PAS preamplifiers are now all getting a little long in the tooth - with a history that goes back to the Golden Age of stereo, this simple circuit has provided many of an hour of audio enjoyment.  Sure there are more transparent and detailed units out there, along with newer products with better reliability. 

But I do have many fond memories of the Dynaco PAS - the first time I heard Quad ESL-63s, and with surprising results coupled with a simple Mosfet amplifier from Stereo Cost Cutters driving a pair of Wharfedale Diamond V speakers.  Both had huge soundstages - both in depth and width - along with a thoroughly musical presentation.  In an effort to capture those glory days, I decided to give this preamplifier another whirl, but this time decided I wanted to build it from scratch. 

Chassis and many of the parts from Dynakits.com, while everything else was from various Ebay sellers, along with a few stops at Mouser.

For now this will just be a picture presentation.  Updates later.











Friday, March 13, 2015

Review: Adcom GFT-555 tuner


I'm not a radio guy since most of the program material in my area is pretty bad - overplayed classic rock and a plethora of bro country stations.  But I do fancy some classical music once in a while, and perhaps a little sports radio if I'm in the mood to experience some Red Wings hockey.  So with that in mind, and to keep the rest of my family happy, I purchased an Adcom GFT-555 tuner to match the GFP-555 preamplifier.

Together they make a handsome pair with black metalwork, red LEDs, and matching dials.  Such a setup would have been common for an entry-level audiophile of the early 1990s.  Inputs are for separate AM and FM antennas, while the output is a single pair of RCA jacks.  Digital tuning between station is using tap-a tap-a buttons, and there are also buttons for presets and whatnot.

Sound quality is nothing to get excited about - this is, after all, a compressed, eq'd, and limited format - but what does come through has that Adcom trademark sound: slightly warm, inoffensive, and just a tad grayed out.  This is no Marantz 10B or McIntosh MR78, but is instead a good working man's tuner.   Reception is better than the (probably misaligned) Sansui AU-777 in my collection, but the latter does have an even warmer sound and one of the coolest dials around.

Old school radio is a dying format versus satellite and Internet services, but there still is a nostalgic place for a peace of gear like this.  So if you need a tuner, then the Adcom GFT-555 tuner is worth it provided you don't pay more than $100.

Thursday, October 2, 2014

Review: Adcom GFP-555 preamplifier

 (Image from Google)

Note:  This review is of the original incarnation of this model, not the latter Series II model.  The "Series 1", for lack of a better term, features a moving-coil head-amp that can be turned on via a switch on the back.

History: Adcom.  There's a company that brings memories of the late 80s and early 90s, back when their gear seemed to be everywhere.  The famed GFA-555 amplifier drove a lot of high-end speakers, and as proof of their longevity, one of these amplifiers has been in continuous service at my father's house for over twenty years.  My very first "high-end" preamplifier was the Adcom GFP-565 which was once on Stereophile's Class B list.  I never liked the unit, or, to be fair, I never liked the sound I got out of it when matched with a Harman Kardon Citation V.  I've also owned the GTP-400 tuner-preamplifier; not exactly a stellar performer but good for mid-fi duty.

So how did I end up with a GFP-555 in my system?  It was mostly a matter of need since I recently bought a McIntosh 2100 amplifer.  For now I decided to wait until a good McIntosh preamplifier comes along but I required something serviceable until then.  For $129 via Ebay, the Adcom GFP-555 is certainly affordable, and, as I was to find out, is actually quite listenable.

Ins & Outs: A rather boring, er, conservative black metal case.  The tone controls that are defeatable.  A Mono button.  Two outputs - one with capacitors on the output and a "Lab" output that is DC coupled.  Switchable MC (with a 100ohm load) head amp, and a regular ol' MM phono stage.  Dual tape outs - hey, you remember cassette tapes! - and, more important for the McIntosh 2100, switchable two-prong AC jacks.  No video switching or subwoofer outs.

The Sound: Paired with the McIntosh 2100 - a rather strange combination in terms of years - the sound is actually quite good.  Fairly warm without that upper midrange/lower treble grit that I normally associate with solid-state gear.  The bass goes down low with nice control and the treble is fairly clean too, at least not intrusive with the transparent B&W tweeters.  Not bad for a bunch of op-amps.  However, compared to the departed Quicksilver tube preamplifier, the Adcom suffers from less detail, a flatter, more 2-D sound, and, for lack of a better word, some greying of the musical palette.  But such weaknesses are only obvious with active "between the speakers" listening, and does not normally interfere with my current listening habits.

For us vinylphiles, the phono stage is very good - quiet is the first word that comes to mind.  Perhaps I'm too used to tube gear, but with the Adcom the music comes out of the speakers from a black background.  There is no tube hiss or rush anymore.

Conclusion: The Adcom GFP-555 is a sensible - but perhaps a touch boring - option for any entry-level system.  Where it fails - definition, detail, and dimensionality - will only be noticeable as the quality of the front-end and speakers begin to outpace this classic piece.  So this preamplifier does get a recommendation, but only within the confines of the partnering gear.  For example I certainly wouldn't use the GFP-555 to drive a pair of Eico HF-60s into the UREI loudspeakers because only then would I start to hear the deficiencies of this budget piece.  But partnered up with an Adcom amplifier, or any other budget solid-state powerhouse, and some decent speakers, this preamplifier is a good starting point. 

System:
Dual CS5000 turntable with Nagaoka MP-110
Pioneer DVD-V7400
McIntosh MC2100
B&W Matrix 805s on stands
Wire: Various brands

Thursday, September 25, 2014

Review: McIntosh MC2100 power amplifier


It was vintage McIntosh tube gear that launched my interest in high-end audio which is a bit funny since - and I'll be sure to get some flack for this - these older preamplifiers and amps aren't necessarily the greatest in the world.  But I will give them credit for making a piece of gear that is certainly memorable; the lit glass fronts and layouts are visually striking while the sound coming out of the speakers is warm and robust.

As I already mentioned in the previous post, I've sold off my previous system, retaining only the UREI 813A loudspeakers - for now.  Part of this was due to the location of the system - the dark basement isn't exactly my favorite place to hang out - and the realization that I was spending thousands of dollars on something that was only being used a few hours a month.  So with that in mind, I decided to simplify; concentrating on the musical aspects of reproduction instead of the ultimate fidelity.  Since the B&W 805 speakers like power I thought it best to replace the Nakimichi receiver in my upstairs system with something with a little more drive.


I remembered how much I liked my departed McIntosh MC-250.  I also noticed that prices are rising on these vintage amplifiers.  But my luck held out and I managed to find the 250's big brother, the heavy-duty MC2100 for only six hundred dollars.  It has twice the power and the same utilitarian (some might say industrial) look of its smaller sibling.  When funds permit, I may go for a matching McIntosh preamplifier - though of a later vintage - and tuner, but for now I've gone the budget route with a first-generation Adcom GFP-555.

The McIntosh MC2100 is rated - very conservatively - at 105WPC and features autoformers on the output.  It can, at least according to various sources, easily exceed that value.  And after hooking it up to my B&W Matrix 805 speakers, the first thing that I noticed was more bass oomph and dynamic drive.  The little 5" woofer of 805s don't exactly move a lot of air, so this was a pleasant surprise over the Nak receiver.  Perhaps it is the nature of having an autoformer on the transistor output stage, but this bass had a slight (and I mean very, very small) loosey-goosey nature.  It wasn't sloppy, but was just a touch less tight and less sterile than the Japanese receiver.  In my book that's a good thing.


With these early SS pieced of McIntosh there have been many comparisons to tubes.  The midrange, with well-recorded pieces like Steve Forbert's Jackrabbit Slim, or Gary Numan's Splinter had a warm character, but lacked that ultimate finesse and clarity that the best tube amplifiers have.  Instead I'm vaguely reminded of the venerable B&K ST-140, which has a (non-linear?) dc-blocking electrolytic capacitor on the input stage.  It adds some "FM Radio" character that is pleasant and conducive to long-term listening but should not be mistaken for uber-fidelity.  Of course that's not what I'm striving for here so there are no disappointments in this area, but just something to be noted for any readers looking for the "ultimate" amplifier.

It is the upper-mids and treble where most solid-state amps fall on their face.  I would give the McIntosh MC2100 a high passing grade here.  It suffers from the sins of omission, clouding some detail and rolling off the treble.  Again we are talking about musicality over the ultimate extension and pin-point imaging.  A rough analog: perhaps the MC2100 is closer to a good moving magnet instead of a hyper-detailed moving-coil cartridge.  As a side note: when I had a MC250 around, I noticed some grain in the texture, but, at least with this current setup, I'm not hearing that same kind of effect


Imaging and depth are good but not superlative.  Of course some of this is the fault of my speaker setup, the limitations of the Dual CS5000 turntable and Nagaoka MP-110, and perhaps the use of an Adcom preamplifier, which isn't exactly the best in the world.  Future upgrades will give a clearer picture of the limitations of this amplifier.

At least to my ears, the McIntosh MC2100 is a fine solid-state piece of gear if - and this is an important point - one is not reaching for the ultimate fidelity, but instead prefers emotion.  It is here where this amplifier shines, being a sort of "poor man's tube amp."   No, it doesn't sound like a Dynaco 70 or even come close to my departed Eico HF-60s, but it does capture the essence of the musical performance and minimizes the worst aspects of a budget system.  So in that regard, the McIntosh MC2100 is a clear winner.

System:
Dual CS5000 turntable with Nagaoka MP-110
Pioneer DVD-V7400
Adcom GFP-555
B&W Matrix 805s on stands
Wire: Various brands

Tuesday, August 19, 2014

Major Stereo Changes Coming


I've sold off my Eico HF-60 monoblocks, Quicksilver preamplifier, and, most important of all, the VPI Aries 1 turntable.  As to why this large step was made, it was a matter of listening habit.  My main system, which was located in the basement, just wasn't getting the airtime that it needed.  Instead I've been doing most of my listening upstairs on my family orientated stereo.  Yes, this second system does not have the high fidelity bonafides of my main rig, but it certainly is more enjoyable over a wide variety of music.  What it does lack is some sort of soundstaging and ultimate dynamics.
Instead of fruitlessly trying to pursue the impossible dream of an ultimate stereo - and all the trouble that brings - I've decided to scale back my aspirations and concentrate on the joys of music.

With that in mind, I will be using the Dynavector 10X5 cartridge paired with the Dual CS-5000 turntable.  I will then replace the Nakamichi receiver with a McIntosh 2100 amplifier and some sort of preamplifier, possibly the McIntosh C-27.  These older pieces will not have the definition of my old main system, but I am hoping to reach a happy medium of musicality and audiophile sound quality - truly a difficult balancing act.

More later!