Regency HF-80 Tube Amplifier Schematic 电路图.pdf

FOR GOLDEN EARS The Regency HF -80 amplifier; Pickering cartridge and tone arm; new records review RAPID expansion of the high -fidelity market into the mass consumer field has accelerated the design and production of simple, small, inexpensive units combining equaliza- tion, tone control and amplifier func- tions. They require only speakers, tuner and record player to make a complete system. Some of this equipment meets the standards of genuine high fidelity for home use surprisingly well. An excellent example is the Regency HF- 80 (Fig. 1), the lowest -priced unit in Regencys new line of hi -fi components. The essential performance factors are shown in Fig. 2. Curve A is obtained by positioning the controls as follows: volume, full on; bass, a third on; treble, a quarter on. This flat position was determined by feeding 200- and 2,000 - cycle square waves into the amplifier and adjusting the controls for flattest tops. Curve B was obtained with the bass and treble controls in the center position. Curve C is for maximum boost of bass and treble and curve D for maximum cut of bass and treble. The range of the tone control is clearly very wide. Four square -wave responses (Fig. 3), taken in the flat position with 500 - mw output, are shown and indicate a very acceptable transient response with- in the audio range. There was no sign of ringing or any other type of in- stability. The power output curve (Fig. 4) was obtained by feeding an input sig- nal at 15 different points in the fre- quency range from 20 to 30,000 cycles, increasing input until the scope trace showed clipping or distortion. The curve is flat from 50 to 30,000 cycles. Below 50 cycles the power output falls off to 8 watts at 30 cycles and just under 4 watts at 20 cycles before dis- tortion shows up. This might limit the usefulness of the amplifier in applica- tions -such as schools or small cafes - requiring high average power levels. But it is fully adequate for average home use and will take care even of the occasional demonstration at full JUNE, 1955 By MONITOR concert -hall level, particularly since almost no records or broadcasts pro- duce anything below 30 cycles. Fig. 5 shows the distortion curve from 100 mw to 10 watts. In compar- ing these figures with those of quality amplifiers without control units, keep in mind that these curves give the overall distortion, including that con- tributed by the tone- control stages - everything but the phono preamp, in fact. This is the lowest distortion I have registered on any commercial 6V6 amplifier. These are excellent curves; indeed as good or better than those obtainable with top components and designs a brief two or three years ago. They are improved upon in higher -priced equip- ment, principally in a flatter power curve below 50 cycles and a better square -wave response. The practical utility of both improvements for aver- age home use is debatable and is obtain- able only at a much higher price and larger size. The amplifier listens as well as it tests. It is very clean in the high end and the definition and transient re- sponse are very good throughout the range. A slight deficiency in the very low bass end, at very high outputs, is evident when highest -quality speakers are used. With run -of- the -mill systems which are flat to 50 cycles and cut off below 40 cycles, the sound is excellent all the way and I would judge that it is completely acceptable to all but the crankiest of listeners. The HF -80 provides three high -level input channels for tuners, tape re- corders or TV, and a single input with a two-position equalizer for magnetic pickups loaded with a 47,000 -ohm resistor. The curves of Fig. 6, obtained with a Pickering turnover cartridge and the Dubbings 101 test record, give the response of the phono channel. Position 1 yields excellent results with all four standard American curves. The bass -boost curve apparently is on the AES slope, which accounts for the small boost at the low end and the AUDIO -HIGH FIDELITY ONLY slight dip around 250 cycles. Most G -E cartridges will show a little more slope at the high end, just about flattening the LP and NARTB curves and pro- ducing slight rolloffs with the RIAA and AES. A rumble filter can be actuated by a switch on the chassis and is very effective without much effect on the musical range. Some readers may be at a loss to account for this excellent performance since there is nothing remarkable about the circuit. The answer is very simple: although the resistors are standard 10% and 20% units, the pairs in push - pull stages are matched on comparison bridges to 1% or better, and the output tubes are also matched closely. The unit is very compact, light and dissipates little heat; can be put in a restricted space easily. The craftsman- ship is excellent for a production unit. Despite the shallow and small chassis, individual components are easily acces- sible for replacement. All in all, the HF -80 is an excellent example of how much real high -fidelity quality can be provided at low cost by good design and care in manufacture. Pickering turnover cartridge and new tone arm The critical problem in the design and production of highest -fidelity pick- up cartridges is providing a flat, smooth and clean response above 10,000 cycles. One of the earliest cartridges to offer a response extending to 20,000 cycles was the Pickering, and its success is well attested by its wide acceptance. Not long ago Pickering issued a model 260 turnover version (see photos) which provides facilities for playing both 78- r.p.m. and microgroove record- ings at the turn of a lever. This is actually a combination of two cartridges mounted back to back. The cartridges can be disassembled in a few seconds for use independently if desired. Their performance is exceptional both by measurement and listening. Fig. 7 is the response, without an equalizer, directly off the pickup ter- 39 RadioFans.CN 收音机爱 好者资料库 AUDIO -HIGH FIDELITY INPUT JACKS MAG PHOND 4 SWI-a 5 .05 SWI6 v2 6AV6 V3 I2AX7 .03 12K 150ppf TREBLE IMEG 00K .03 GAIN I 50K 100K .03 IOOK .002 7 70K .03 IK 6V6-GT (2) V4 5 EG I00K 16n 6n 4 103K On SHIELD 22K T2 T2o 20 IOK IOOK vi I2AX7 VI 5 01 .03 RUMBLE FILTER .004 OUT 390K 33K I MEG 5Y3-GT v6 OUTLET 20 t 20 .001 B IMEG 560n 0047 T.007 minais on a Cook 10 -LP test record into a Heathkit a.c. v.t.v.m. The notable thing about the curve is the extreme linearity. The variations on the curve are largely variations on the test record which varies 1 db at various points. You will note that response is down only 1.5 db at 15,000 cycles, 6 db at 17,000 and 8 db at 20,000. Measure- ments in the range above 10,000 cycles with test records are difficult since various effects due to groove loading may occur. However, it is an entirely safe assumption that the Pickering is at least as good as indicated on the curves and possibly a few db flatter beyond 15,000 cycles. The linearity is borne out by the curves (Fig. 8) taken with a 27,000 - ohm load on the pickup, at the output of a preamplifier. To be sure, such curves are measures of the equalizer as well as the pickup. Nevertheless, they indicate the results which proper equalization can deliver. Again the linearity is very notable. The rise between 10 and 12 kc is not significant and probably repre- sents the result of needle coupling to the grooves on this specific record. This coupling can vary with different record materials and even from day to day on the same record. The curves speak for themselves. The only thing I need add is this: The sound of the Pickering in the high -high end -beyond 10,000 cycles especially - is exceptionally clean, smooth and sweet. Thoroughly pleasant to listen to, it is free of shrillness when used with tweet- ers which are themselves clean and sweet. I have used the pickup with several amplifiers and a number of speakers and, as near as I can deter- mine, the pickup has no influence on the character of the high- highs, which will be determined by the characteristics 40 5W ON GAIN CONT -o .7K 117VAC Fig. 1- Schematic diagram of the Re- gency HF -80 high -fidelity amplifier. of the tweeter. On clean records, even those which have been played scores of times with diamond points at low pres- sures, I found no need for rolloffs. Indeed, it is possible to boost the high end severely and still maintain a clean, sweet sound. This is by no means true of all wide -range cartridges. I made no measurements at 78 r.p.m. (my available test records stop at 10,000 cycles and up to that point the response was almost an exact duplicate of the microgroove cartridge). But listening tests reveal an exceptionally fine quality and a gratifyingly low scratch level, excellent evidence of a smooth, flat response free from peaks. Clearly the Pickering belongs in the top category of pickups and I cant imagine anyone, even the goldenest ear, being unhappy with it. Models 220 and 240 are avail- able separately for 78- and 45-33% - r.p.m. records, respectively. I was able to test the cartridges not only in my tone arms but also in the new Pickering arm (see photo). It is a worthy complement to the cartridges, makes no difference in the quality of reproduction, and is very convenient to mount and to use. It provides an adjustment for the height over the record. With most cartridges this adjustment can be made so that the needle will just miss the turntable when no record is on it and yet provide good tracking with a record. Pressure is adjustable with a knurled knob underneath the arm (but above the turntable), and the adjustment can be easily made. Incidentally the car- tridges tracked with as little as 3 grams, though 5 or 6 grams seem optimum and produce least distortion. The arm is made in two sections, rather like the G -E in principle. The cartridge mounts on a light small front section with very low vertical friction. In lifting the pickup off the record, only the cartridge and its mount are raised; the arm remains fixed. The vertical loading is therefore very slight and the arm will track extremely warped records with no difficulty what- ever and practically no risk of damag- ing either record or needle. The whole arm moves horizontally on fine bearings and has a large counter- weight at the rear which tends to damp out resonances, maintains a uniform 20 e RELATIVE DB +o 10 20 C MAIM I1M A 11:,I. = II/2/I 1!i1l11111l D 201. A D p0 INC lo FRED A- FLAT TEST POS7TGN; B- CENTER PoS7T01; C- MAX BOOST; D- MAX CUT Fig. 2 -Range of bass treble controls. NT 201. 604. 5KC 20KC Fig. 3 -HF -80 square -wave responses. 10 WATTS 0 201. 50 100 500 INC FRED Fig. 4 -Power output curve of HF -80. /Miii=INIiiiIMMEiiiNIMINIi 5 10 3% IM2% I% 0 A-.CLIPPING PONT (WATT 10 2 Fig. 5- Distortion curve of the HF -80. RADIO -ELECTRONICS RadioFans.CN 收音机爱 好者资料库 10 IC RIAA POS 1 10 + 0 o 10 LP IO +0 10 NARTB-P051 .00 OLD AES 10 POSI d P052 I P0S2 POSI 10 JOB SO 100 500 IK 5 10 FREQ Fig. 6- Response of the phono channel. Io + 0 IO 20 30 301, 100 IKC FREQ Fig. 7- Response of Pickering cartridge. IO 20 10. 10 m 10 +0 10 10 0 10 AES LP RIAA JJq, 50 100 500 IKC FREQ DUBBING5101 TEST RECORD INTO PREAMP Fig. 8- Curves of the Pickering cart- ridge at the preamplifier output. 5 to rhythm of movement as the arm travels toward the inside, offers considerable resistance to violent movement impart- ed by shock vibration, etc. The arm mounts with three screws which can be adjusted to level the arm. The method of holding the arm in the rest position is very clever and convenient. A small bar magnet mounted on the arm attracts it to the holder post and keeps it there firmly enough to resist any but the most violent accidental shock. The arm can be used with various other cartridges in permanent or slide mount- ing. New records NOTE : Practically all American mc- ords pressed since Sept. 1, 1954, use the standard RIAA curve or some modifica- tion of it which will be equalized to within 1 db by an RIAA equalizer. They can be equalized on the bass end exactly by the new RIAA equalizer and very closely with either the LP, NARTB or AES equalizer. Treble equalization is identical with the RCA ORTHO and calls for a slope of 13.7 db at 10,000 cycles. An LP treble equalizer will be -2 db at 10,000 cycles and an AES JUNE, 1955 AUDIO -HIGH FIDELITY The Pickering turnover cartridge (top left) installed in its arm (center). At right below, single -unit cartridges are also available, with 1- or 3 -mil styli. will be +2 db at the same point. The departures at intermediate points will be smaller. Therefore, in a pinch the new records can be equalized within 1 or 2 db by almost any of the four American playback curves: LP, NARTB, AES or ORTHO. Henceforth in my reviews I will not mention the recording curves unless the specific recording departs from the RIAA. An Adventure in High Fidelity RCA Victor LM -1802 RCA Victor left the pioneering in high -fidelity test records to others. But having at last risen to the challenge, it gives us a really remarkable test recording. Here in one disc is just about everything one needs to test, demonstrate or show off any high -fidelity system. It starts with An Adventure in High Fidelity, a special composition by Robert Russell Bennett. Whatever one may think of it as music, it is certainly deliberately composed to bring out al- most every possible hi -fi effect. The second band, The Orchestra in a Nutshell, is a unique test of realism and naturalness, presenting most of the instruments of the orchestra in solo passages from the Nutcracker Suite, ending with a short but very fine demonstration of the percussives. The recording of the instruments is extremely faithful to the natural sound and, given a low enough noise level, one can hear not only the characteristic tone of each instrument but often many of the noises which accompany its produc- tion. Listen especially for the valving and breathing of the tuba player. The first band on side B presents an excellent test for frequency range. It gives three switch bands, each succeeding one having a narrower bandwidth. Each test starts with a fast sweep of sine waves over the range covered. This is followed by a portion of Adventure in High Fidelity reproduced in the same bandwidth. A comparison of the effect of the three bands will quickly reveal the real range of any system and also demonstrate the difference between hi -fi and ordinary reproduction. However, the comparison is somewhat unfair to hi -fi since the 200 -5,000- 41 RadioFans.CN 收音机爱 好者资料库