by setup1 » Sun Jan 25, 2004 6:20 am
Hello,
We had a snowstorm and I'm stuck with some free time so I'll jump in here and contribute on my vintage experience.
I no longer own any vintage amps but still keep a bone stock PAS 3 for posterity and listen to a Scott LT110B FM mpx tuner. However when I burned out of high end in 1986 until I went SET/DHT in the mid 90s, I've collected, modified and serviced several classic amplifiers.
My frustration with high end stuff during the ragin' 80s was due to my c-j preamp going back and forth between McLean, VA and NYC for servicing. At that time, I had an AR/Merrill mod turntable with an FT-3 arm/Grado sig. 8, cj PV2Ar, Berning EA230 driving Magnepan SMGas. a decent entry level high end system for a grad student with some TAS and Stereophile credibility. While the cj was out being serviced, I sorely needed a preamp so I found a PAS/ST35 combo for less than $100 in downtown NYC to tide me over. I found out later that with a few mods and updating here and there, they possesed greater musicality than a lot of the touted and expensive high end tube amps of the time. First to go was the SMGa and I found the right speakers for classic amps in the LS3/5A and Quad ESLs.
Here are my faves driving LS3/5As.
PP EL34 UL [ultralinear amps] amps:
1. Eico HF series with Mullard derived input/driver stage EF86 or 12AX7--DC--> 6SN7GTB long tailed, HF 60 is tops due to monoblock construction and the Acro TO-330 OPT, the HF50 runs a close second albeit with a slightly inferior Chicago Standard OPT, nice sounding nonetheless. Stereo amps, I prefer the cathode biased HF87 to the fixed bias HF89 due to the softer clipping characteristics inherent in that biasing scheme. IMHO the HF 60 is in the same league as the Marantz 8B with budget cosmetics.
2. Pilot SA 260 - another nice amp with an input/driver circuit that is very similar to a Jadis, makes me wonder whether the Jadis folks based their design on this amp.
3. Dyna ST70/MKIV - great starting point for DIY/Mod experimentation, OPT quality is not the same as the Pilot or Eico, but good sounding nonetheless. This is how I formed my opinion that the Mullard circuit sounds best to my ears driving a push-pull design. Stock, they are musical if lacking in definition. If you want the utmost performance, graft the HF87 front end on an ST70 and it will be close to the best amps [within its power rating].
All these amps sound better triode connected if power is not an issue. This is also why I've lived with the 6SN7 as a driver tube and I've adhered to a similar topology for my SE designs. It's just a very linear tube with enough current and voltage swing to drive just about any power tube.
PP UL 6L6/5881/KT66
1. Heath W4 - classic Williamson design with Chicago OPTs, 6SN7s for the input driver stage, NICE!
2. Heath W5 - another Williamson, supposedly more deluxe than the W4, but they went with 9-pin equivalent 12AU7 for the input/driver. Saving grace is the Peerlees 16309 or 16508[?] OPTs, Acro standards of quality mated to MO KT66s.
3. W2 and W3 - classic two chassis Williamson, the early W2s had Peerless OPTs and some were even fitted with 807 outputs, the later W3 had 5881 with Acro TO-300 OPTs.
In stock form I place them on the same sonic level as Dynas. W1-3 series are even better.
I have a soft spot for PP UL EL84/6BQ5 in my experience sounded great driving Quad ESL57s. My all time favorites in alphabetical order are:
1. Acro 20/20 - this is a very simple Loftin-White adaptation into PP [12AX7 paraphase inverter---DC---PPEL84], no caps in the signal path, Almost Class A constant current [no SS devices though] operation. Very tiny deluxe chassis [looks like a mini Marantz 8B] and superior, potted Acro transformers.
2. Dyna ST35 - considered to have been fitted with the widest bandwidth Dyna OPTs, very simple cascaded/cathodyne inverter 7247 input tube [1st stage is a 12AX7, the second stage is a 12AU7]. Spartan looking but this sounded good.
3. Leak 20 - British response to the American counterparts, great OPT, Mullard style input/driver AND tube rectifier.
4. Pilot SA 232 - Similar input/driver stage 12AU7/12AX7 to its bigger brother SA260. Very sweet sounding and tube rectified also.
I held on to these 4 amps for the longest period of time until I sold them to finance my SET/Altec system.
Honorable mention goes to Eicos, stereo, mono blocks and integrateds and the Fisher SA100. Although these don't have ultralinear OPTs, they are good amps nonetheless. I wonder if anyone in the forum knows of the fate of my mint HF86 with the original box? I sold prior to leaving Manila in '92.
Classic Preamps:
1. Dyna PAS - mainly due to its flexibility for upgrades and experimentation. In stock form it will please the most avid music lover. Modified, it can be a high end beater. I still remember my ugly looking, early effort modded PAS 2 [phono stage and line stage was derived from the early Marantz Audio Consolette] trouncing an SP9.
2. Pilot SP215 and 216 - very nice looking with twin VU meters up front. Nice sounding too since they used 12AU7s in the line stage. Has a great tape head input wherein you can plug in the output heads of an open reel for true all tube open reel playback.
3. Eico ST84 - this is an ugly duckling but I serviced half a dozen of these for Angela Instruments and one time pitted it against a Marantz 7 and I preferred it to the 7.
4. Harman Kardon Citation 1 - very deluxe build, although if it was a kit built unit, be prepared for complex rebuilding/sleuthing to make them work. A bit dark sounding but very flexible I loved the tape head input sound mated to my Tandberg open reel transport.
I never was too enamoured of the Marantz 7 sound, it tended to sound comparatively thin and compressed and I think this was due to the 12AX7s in the line stage with a lot of negative feedback. Marantz got it right the first time when the early Marantz 1 audio consolette monos had a 12AU7 in the linestage. The phono stage of the 1 is also superior sounding to my ears.
I'm not an engineer and as you can see my empirical knowledge that led to the development of my present system was based on years of careful study of classic circuitry. Anyway I hope you get some cool ideas from reading this.
Regards,
Joseph
Last edited by
setup1 on Sun Jan 25, 2004 2:46 pm, edited 1 time in total.