Hovland HP-100 Tube Analog Line Level Preamp - Stunning Inside and Out!

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General:

Absolutely stunning piece of kit from Hovland.

Volume is controlled via a 31-position silver-contact attenuator, featuring 2dB steps, using Holco resistors.

On the back of the fully loaded HP-100 there are seven single-ended line inputs, a tape loop, and two sets of single-ended outputs.

*Note the Phono/Aux input functions as a normal line level input, as no phono module is installed.

The preamp is tube-based using two 12AX7 tubes and a 12AU7 in the line stage (which provides 14dB of gain).

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Specs:

Description: Vacuum-tube full-function preamplifier with built-in phono stage and optional MC step-up transformer module (SkyFi Note: Not installed on this model). Line-stage tube complement: two 12AX7s, one 12AT7. Phono stage tube complement: two 12AX7s, one 12AU7. 

Line-stage: Voltage gain: 14dB. Frequency response: 10Hz-25kHz, +0/-0.25dB. S/N Ratio: 80dB (wideband) ref. 3V out, (with level control fully clockwise). THD: ±1% at rated output. Output impedance: approximately 2500 ohms. Input impedance: 100k ohms.

Dimensions: 18.25" W by 5.25" H (including feet) by 17.375" D (including knobs and rear jacks). Weight: 27 lbs.

Manufacturer: Hovland Company, 1545A Pontius Avenue, Los Angeles, CA 90025. 

Recommended Cables:

Kimber Kable - RCA Interconnects - Better

Kimber Kable - RCA Interconnects - Best

Kimber Kable - Phono Interconnects - Better

Kimber Kable - Flagship Tonearm Interconnects - Best

Kimber Kable - Power Cords - Better

Kimber Kable - Power Cords - Best

The SkyFi Testing Process for Preamps:

We start with a visual inspection of all internal components to make sure that there are no signs of heat stress or damage. Capacitors are checked for telltale signs of predictive failure including bulging, shrunken wrappers, or physical leakage. We also inspect the PCBs for discoloration from resistors or transistors that may have been running hot. On vintage units we often spot check select capacitors for value and ESR.

When we first power on a preamplifier we connect its RCA output to a Sencore PA81 Power Analyzer which simulates real world loading conditions and gives us an oscilloscope interface. The first order of business is checking that the volume control works smoothly throughout its entire range with acceptable channel balance. This is accomplished by feeding a 1KHz sine wave into one of the preamp’s line level inputs while monitoring the preamp’s output on an oscilloscope. We then switch to a 1KHz square wave to test the tone controls, loudness function, and filters where applicable. During this step we are watching for equal alteration of the test signal by both channels. This also helps us identify dirty controls that will need treatment. Once the basic line stage functions are verified, we test each input individually. This is especially important for devices that use relays to select their sources. If the preamp is equipped with a phono stage we test that as well. We use an inverse RIAA filter which allows us to feed a reference test signal into the phono input with the proper RIAA equalization and level. A square wave or sine sweep is used to verify that the device’s phono stage is faithfully reproducing the RIAA curve. If the preamp under test has balanced inputs and/or outputs these are tested as well.

We finish up our bench testing with a listening test with our bench amplifier and reference speakers. During this test we check for hum or hiss that may not have shown up in earlier testing. We also check that all of the tone controls and filters perform as expected. If the preamplifier has remote control functions these are also tested. Preamps with tube circuits or complicated power supply topologies are connected at our long term test rig for extended stress testing under real world conditions.