Hi-fi Components

Some observations on hi-fi components we have serviced.

Power Amplifiers

Item Picture Description
Harmon Kardon Citation 12

The Harman Kardon Citation series is very under-appreciated. We recently serviced a Citation 12 whose performance was quite stunning, far in advance of its specifications. The channel separation, bandwidth, and signal-to-noise ratio are exceptional, and the total harmonic distortion was far below the modest 0.1% specified.

Leak Point One series

LeakPointOne

This consists of:

  • Point One 15W (1948-50)
  • Point One 25W (1948-50)

We service all Leak valve amplifiers at a fixed price per channel. We specialize in undoing prior modifications by well-meaning amateurs, or in some cases professionals, and restoring them to factory condition.

Leak Stereo series

LeakStereo20LeakStereo50LeakStereo60

This consists of:

  • Stereo 20 (1957-67)
  • Stereo 50 (1957-63)
  • Stereo 60 (1963-7)

We service all Leak valve amplifiers at a fixed price per channel. We specialize in undoing prior modifications by well-meaning amateurs, or in some cases professionals, and restoring them to factory condition.

Leak TL series

LeakTL12

This consists of:

  • TL/12 (1949-57)
  • TL/25 (1949-51)
  • TL/25A (1951-7)

 

We service all Leak valve amplifiers at a fixed price per channel. We specialize in undoing prior modifications by well-meaning amateurs, or in some cases professionals, and restoring them to factory condition.

Leak TL/Plus series

LeakTL10LeakTL12PlusLeakTL25LeakTL50

This consists of:

  • TL/10 (1954-7) (not called Plus but it is 'ultra-linear', see below)
  • TL/12 Plus (1957-67)
  • TL/25 Plus (1957-67)
  • TL/50 Plus (1957-68)

These are all 'ultra-linear' amplifiers, i.e. using pentodes with a tapped screen winding in the output transformer. Power and efficiency are up and price is down as compared to the TL series.

We service all Leak valve amplifiers at a fixed price per channel. We specialize in undoing prior modifications by well-meaning amateurs, or in some cases professionals, and restoring them to factory condition.

McIntosh McIntosh MC240

McIntosh have been shipping a range of superb valve amplifiers since the late 1940s. They are built to battleship standards and feature a remarkable output stage free of crossover distortion.

Mullard

The Mullard 5/10 and 5/20 amplifier circuits formed the basis (in many cases, the entirety) of many British and Australian amplifiers in the 1950s.

Quad 303 Quad 303

The Quad 303 is especially noteworthy as being an absolute bargain at present, selling for only a few hundreds of dollars. Some audiophiles have rated this amplifier in the $1500 value class. We have restored hundreds of 303s and we have now added a complete rebuild option beyond the standard service, where we also replace every single PCB-level component, to assure correct and trouble-free running for decades.

Quad 405/306/520/606/707/909

405306520606707909 These are the famous Quad 'current dumping' amplifiers. We can adjust the sensitivity of 405s, 606s, 707s, and 909s at no extra charge. Many users find these too sensitive: a 2x or 3x gain reduction makes them more usable. The selected Berndt Ludwig 405 modifications we perform are sufficient to more or less transform a 405-1 into a 405-2.

Quad 50E We have serviced this fairly rare model, and we can adjust the outputs to practically any impedance level including multiple different impedances, suitable for bi-wiring. If you buy these units make sure the irreplaceable input and output plugs are included in the sale.
Quad II

Quad II The Quad II is one of the most sought-after classic amplifiers of the valve era. We have serviced many of these and can also replace the outmoded mains input sockets with IEC sockets.

Quad QII-40/80/Classic Quad QII-40

These are reissues of the original Quad II with substantially the same circuitry and appearance, but three different power levels, built to modern standards.

Radford MA series Radford MA25

These are the mono valve amplifers MA-15 and MA-25. Higher-wattage versions exist but are rare.

Radford SPA/HD/ZD series

These comprise a range of superb solid-state power and integrated amplifiers.

Radford STA series

These are the stereo valve amplifiers STA-15 and STA-25. Higher wattage versions exist but are rare.

Preamps

Item Picture Comments
Leak valve preamps RC/PU , Point One , Varislope , Varislope II , Varislope Stereo

Leak released an astonishing number of valve preamps over quite a short period of about a decade, often having four models in production at the same time (Point One/Varislope and mono/stereo). See the Services tab for a chronology.

They suffer from enormous output impedance due to not having a final buffer stage, which severely limits the length of the umbilical interconnect cable; and from the tape-out being taken off after the tone controls and filters, and the balance control where present, which makes it basically useless. The design before the high-impedance filter stage and balance control is elegant, and economical in using the same gain stage for everything from 5mV phono to 2V tuners: however this inevitably compromises the distortion performance of the phono input.

Not all of the Leak preamps interconnect with all the valve power amplifiers, due to differing umbilical socket connections. We can advise on or modify the umbilical cable, which Leak must have provided in different versions, mutually incompatible. See the following table.

Leak Umbilical Cable pinouts
Unit 1 2 3 4 5 6 7 8
RC/PA, RC/PA/U, Varislope E   HT Heater Heater     Output
Point One Output E HT Heater Heater HT   E
Varislope II Output   HT Heater Heater HT   E
Varislope III, Varislope III Series N, Point One Plus, Varislope Mono Output     Heater Heater HT   E
Point One Stereo, Varislope Stereo, Varislope 2 Stereo Output L     Heater Heater HT Output R E
Point One amplifier Type 15, Point One amplifier 25W No umbilical socket, only a meter socket
TL/12, TL/25, TL/25A, TL/10 E   HT Heater Heater HT E Input
TL/12 Plus, TL/25 Plus, Tl/50 Plus E   HT Heater Heater   E Input
Stereo 20, Stereo 50, Stereo 60 E Input R HT Heater Heater   E Input L
Source: published Leak schematics. No responsibility is taken for any errors or omissions.
Quad preamps Quad QCII , Quad 22 , Quad 33 , Quad 34 , Quad 44 , Quad 66pre

Quad 22s and 33s often require replacement of panel lamps, not included in the service but available for a small fee. We can adjust your Quad 22 Phono adapter can, 33, 34, 44, or 66pre to match your phono cartridge exactly if required, for no extra charge.

Quad QC24 preamp Quad QC24

This late model harks back to the original QCII in appearance, with the round pushbuttons and large volume control, but inside it is a state-of-the-art valve preamplifier. It is normally shipped without a phono stage, which is an optional extra. We can supply and fit it.

Radford preamps

We have serviced all of the Radford preamps, from the valve SC22 to the solid-state SC24 and ZD-22, the latter being also built into the HD and ZD power amplifier series. They are all remarkable, especially the SC22, which however does exhibit a not quite flat frequency response 20-20kHz (±0.3dB) due to the tone control section design, and not startlingly accurate RIAA phono equalization.

The umbilical cable used between the SC22 and the MA- and STA- power amplifiers is wired as shown in the table below. It is wired 1-1, 2-2, 3-3, 4-4, 5-5, 6-6, 7-7, 8-8. Please note that this is NOT COMPATIBLE with the majority of Leak umbilical cables.

Radford Umbilical Cable pinouts
Unit 1 2 3 4 5 6 7 8
SC22 Heater E via R42 56R AC   AC AC=3, switched HT Heater
SC22P No socket: this unit is self-powered.
MA series Heater E AC=4 AC AC AC=4, switched HT Heater
STA series Heater E AC=4 AC AC AC=4, switched HT Heater
Source: published Radford schematics. No responsibility is taken for any errors or omissions.

Tuners

Item Picture Comments
Acoustical A.M. Tuner ('half-moon') Quad AM half-moon

This unit is part of the Quad II/22 setup with the same power requirements. It is an audiophile-grade AM tuner with two bands, LW and MW, and two switchable bandwidths, 'tune' and 'wideband' (12KHz). This rare early version is reputed to be the best-sounding of all Quad AM tuners

Dynaco FM3 Dynaco FM3

The legendary Dynaco FM-3 was one of the best-sounding valve tuners of the era. They were produced in enormous numbers, largely as kits. After all this time an FM-3 will certainly need alignment, and possibly renovation, including coupling capacitor upgrades and PEC filter correction. We have serviced this model and can correct the de-emphasis to 50μS for UK/European/Australia/New Zealand broadcast conditions.

Leak Stereofetic Leak Stereofetic

These are not among the most sought-after of all British tuners, for reasons which escape us. They have superb technical specifications, and audio performance quite similar to the Troughline series.

Leak Troughline Troughline 2 , Troughline 3

These are among the most sought-after of all British valve tuners, with exceptionally stable tuning due to three separate design elements; two stages of limiting; and quite remarkable sound. The original factory stereo decoder is now of historical interest only: we can either service and align it, or we can replace it with a modern unit.

McIntosh

McIntosh made fine valve tuners, notably the MR66/67/71 and MAC1700 series, which we have serviced, including the MR66's outboard MA-6 MPX decoder.

Quad /R Quad /R AM tuner

These exceedingly rare units (fewer than 1000 /R units built in 1954-5 only) were low-sensitivity high-fidelity AM tuners. The /R had 3 preset stations (BBC Home, Light, and Third Programmes), plus a phono feed-through connection. It was connected directly to a Quad I or II power amplifier at 20mV level.

Quad AM tuner (European/export)

The correct name for this is 'the AM tuner', although it is often known as the AM1. This unit is part of the Quad II/22 setup with the same power requirements. It is an audiophile-grade AM tuner with several bands and switchable bandwidths. European models had LW, MW, and SW bands; export models had MW, SW1, and SW2 bands. Both models had three selectable bandwidths: 'narrow' for tuning; 'filter' which provides a 10KHz notch filter which needs to be retuned to 9KHz since AM frequencies were reallocated to 9KHz spacing in the 1970s; 'wide' providing a 12KHz wideband unfiltered output, which sadly is more than double what any AM station broadcasts these days.

Quad AM3

This is essentially an 'AM tuner' in an FM2-sized case with an independent power supply. Like its predecessor, it is an audiophile-grade AM tuner with LW, MW, and SW bands and switchable bandwidths. This was Quad's last valve tuner and also their last AM tuner. Only 2000 were made and they are now much sought-after, changing hands for four-figure (AUD) prices.

Quad FM

The correct name for this is 'the FM tuner', although it is often known as the FM1. This is part of the Quad II/22 setup, needing to be powered by the 22 control unit or a separate 330VDC supply. When well-aligned, it is a very serious audiophile contender among valve FM tuners. There are four or five circuit variations, depending on serial number, including valve changes. The original factory 'bird-cage' decoder is now of historical interest only, and should generally be replaced with a modern unit. However we can certainly align and renovate this original MPX unit, which will substantially improve the sound.

Quad FM2

This is essentially an 'FM tuner' in an AM3 case to match the 33 preamp, with an independent mains supply, and with somewhat better stereo performance than the 'FM tuner' due to minor circuit tweaks, and an internal stereo decoder. Not to be confused with the later solid-state FM3 which superceded the FM2: see below. Although the FM3 is a most competent performer, many audiophiles and collectors prefer the FM2, especially with a modern stereo decoder. We can replace the FM2 decoder with a much better-performing modern unit.

Quad FM3

This is the solid-state replacement for the FM2 above, fitting into the same case as the 33 preamp and looking almost identical to the FM2 from the front, except that the indicator lights are in the reverse positions. There are three distinct versions: serial nos. 1-5884, 5885-9999, and 10,000 upwards. To our ears the early FM3 before serial number 5885 sounds better than the later one, although it is more of a servicing headache: the MC1305P decoder chip used early in the production run has seven adjustments to the two required by the MC1310P used subsequently.

Quad FM4

The FM4 tuner matches the 34 and 44 preamps and is a superb piece of work, with 7-preset station memory, and a laid-back sound to die for. We can now supply and fit a new CPU made by Quad for this tuner, which not only allows for 14 pre-set stations but also eliminates the battery. We can also supply and fit a factory modification for early models with long-term frequency drift.

Quad FM66/77/99

The FM66 and subsequent FM77 and FM99 Quad tuners are substantially similar to the FM4, but with a revised RF section and remote control.

Quad HR1 Quad HR1 AM tuner

These exceedingly rare units were low-sensitivity high-fidelity AM tuners. The HR1 made 'no attempt at sensitivity' and was designed to listen to nearby BBC transmitters only. It was connected directly to a Quad I or II power amplifier at 20mV level.

Radford FM tuners

The Radford FMT1/2/3 FM tuners were built to complement the SC22 (valve) and SC24 (solid state) preamps. The FMT1 is a valve design using 1xECC85 in the RF and mixer stage, 3xEF89 in the IF strip, 1xEF80 as the limiter, an EM84 tuning indicator valve, a ratio detector, and an optional muting circuit. No stereo decoder was supplied but a modern one can easily be fitted. The FMT2 and FMT3 are solid state designs, again with ratio detectors, and with a quite nice stereo decoder fitted as an optional extra. We can fit a modern IC-based stereo decoder to any of these models.