Fosi ZP3 Preamp- Vintage Audio Review Episode #200

Fozzy ZP3 Preamplifier Review

Introduction to the Fozzy ZP3

• The episode introduces the Fozzy ZP3 preamplifier, highlighting its compatibility with vintage power amplifiers.

• The reviewer discloses that Fozzy provided the unit for review and mentions it as a paid promotion, clarifying their independence in editorial content.

Features of the Fozzy ZP3

• The ZP3 includes balanced inputs/outputs, two unbalanced inputs, a subwoofer output, and a high-pass filter for frequency management.

• Unique features include bypass controls for bass and treble adjustments and a balance control not commonly found in lower-priced preamps.

• A remote control is included, which is compatible with other Fozzy equipment.

Performance Overview

• The reviewer plans to demonstrate the performance of the ZP3 on a bench setup while discussing user experience.

• Notably, there is no headphone jack; however, this feature is deemed unimportant by the reviewer.

Operational Insights

• The power button also functions as an input selector. An LED indicates when powered on.

• Volume control lacks motorization; thus users cannot easily track volume levels due to continuous rotation without stop points.

Control Functionality

• Each RCA input retains separate volume settings, which is beneficial for user convenience.

• Feedback was given regarding knob labeling; it would be more accessible if labels were positioned on top rather than underneath.

Back Panel Features

• The underside features switches for high-pass filtering (with multiple frequency options), along with tone bypass functionality.

• A standard main power switch replaces wall wart designs. However, concerns are raised about the short length of the supplied power cord.

Input Configuration

• The review notes that measurements will primarily use unbalanced RCA input number one while adjusting bass and treble controls to mid-position.

Audio Performance Analysis of ZP3

Initial Measurements and Bypass Control

• The ZP3 is in bypass mode, with tone controls and balance control set to their detented positions. Signal-to-noise ratios (SNR) are above 98 dB, and total harmonic distortion (THD) is better than 0.001%.

• Upon switching the bypass control on, SNR increased by approximately 4-5 dB while THD slightly worsened to 0.002%, still maintaining low levels.

• The setup uses balanced inputs/outputs with tone defeat engaged, achieving a zero dB gain with a 12 dBV input signal at 1 kHz.

Frequency Response Analysis

• With balanced connections, SNR improved by about 8-9 dB compared to unbalanced inputs; THD remained similar.

• Frequency response testing from 10 Hz to 30 kHz shows a high-pass filter set for the range of 20 Hz to 20 kHz; results indicate slight deviations from specifications.

• At low frequencies (20 Hz), the output is down by half a dB, missing the specification slightly; at high frequencies (20 kHz), it’s only down by 0.02 dB.

Tone Controls Impact

• Engaging tone controls affects channel balance minimally but increases loss at lower frequencies (from -0.5 dB to -1 dB at 20 Hz).

• High-frequency response remains relatively unchanged when tone controls are activated; minor adjustments noted in the frequency response curve.

Further Testing with Balanced Inputs

• Using a standard input level of +6dBV for frequency response measurements yields consistent results between balanced and unbalanced setups.

• A zero dBV signal applied shows an achievable gain of up to +8dB; SNR recorded at around 105 dB, which is commendable despite not meeting specified conditions (>115 dB).

Total Harmonic Distortion Observations

• THD versus frequency analysis indicates performance below specified limits (<0.008%), yet still demonstrates good overall quality.

• Harmonics analysis reveals that even harmonics exceed odd harmonics under certain conditions when using RCA input one with bypass off.

Changes in Harmonic Structure

• When connected through balanced inputs/outputs, odd harmonics become more prominent than even ones, indicating a shift in distortion characteristics based on connection type.

• The balance control's influence persists regardless of bypass switch position; this highlights its importance in overall sound quality management.

This structured summary encapsulates key insights from the audio performance analysis of the ZP3 device as discussed in the transcript provided.

Audio System Performance Analysis

System Noise and Distortion Measurements

• The system noise is measured from 20 Hz to 20 kHz, with RCA number two inputs terminated into shorts, showing a low level of noise at approximately 0.0000 volts, which is well below the specification limit of four microvolts.

• The isolation between RCA number one and RCA number two inputs shows a worst-case scenario of about 80 dB across the frequency range of interest (20 Hz to 20 kHz) with zero dB gain set on the volume control.

Crosstalk and Phase Differences

• Crosstalk measurements indicate that at worst case, there is about 75 dB crosstalk when a 6 dBV signal is applied to the active channel while maintaining zero dB gain. No specific crosstalk specifications are provided for this analysis.

• A phase difference measurement reveals no significant change at 1 kHz between input and output signals; however, at lower frequencies (100 Hz), a phase delta of around 22 degrees is observed, while at higher frequencies (10 kHz), it’s about 12 degrees. These observations lack formal specifications but provide insight into performance characteristics.

Rise Time and Channel Comparison

• The rise time for a 1 kHz square wave input measures approximately 1.6 microseconds across various frequencies (100 Hz and 10 kHz). This consistency suggests stable performance in response times across different signal conditions.

• When comparing left and right channels using a sine wave input at different frequencies, minimal phase differences are noted: around 3–4 degrees at 10 kHz and approximately 12 degrees at lower frequencies like 100 Hz. This indicates good channel alignment in terms of phase response under test conditions.

Tone Control Effects

• Adjustments to tone controls show significant effects on bass response: maximum settings yield about +14 dB gain at low frequencies (20 Hz), while minimum settings result in -15 dB loss under similar conditions. Treble adjustments also demonstrate notable variations from -67 dB to +7 dB depending on settings made at high frequencies (20 kHz).

• The device retains volume control settings per input source; switching from RCA input two back to one successfully recalls previous settings without manual adjustment needed, showcasing user-friendly design features in audio management systems.

Volume Control Functionality

• Testing volume control functionality reveals consistent changes: each remote press or knob turn results in an approximate change of ±2dB in gain levels, indicating predictable behavior during operation which enhances user experience during audio playback adjustments.

• Mute functionality effectively drops output levels significantly by around -92 dB when engaged, demonstrating effective silencing capabilities within the system's operational parameters without introducing unwanted noise artifacts upon re-engagement post-mute state.

Frequency Response Analysis

• Analyzing frequency response for both sub out and left line out shows flat responses when bypassing tone controls; however, engaging tone controls introduces minor variances that do not significantly alter overall sound quality as indicated by overlapping traces during testing phases across multiple configurations including high-pass filter adjustments from various cutoff points (80 Hz to120 Hz).

Analysis of Subwoofer Output and Volume Control

Overview of Frequency Response and Volume Control

• The speaker sweeps frequencies from 20 Hz to 20 kHz, showing the line out (left channel) and sub out (right channel) outputs.

• The volume control is set at zero dB gain with a zero dBV signal; the aim is to observe how changes in volume affect both outputs.

• Initial measurements show a delta of 7.2 dB between outputs; after adjusting the volume control by three clicks, the delta remains consistent at approximately 7.25 dB.

Performance Insights

• Adjusting volume affects subwoofer levels proportionally, indicating reliable performance across different settings.

• The Fozzy ZP3's frequency response shows a slight dip of half a dB at 20 Hz compared to P4, which had better performance in this range.

• Overall frequency response is flat within one-tenth of a dB from 100 Hz to 20 kHz, suggesting good performance despite minor low-frequency discrepancies.

Noise Floor and Input Isolation

• Balanced inputs improve signal-to-noise ratio (SNR), achieving up to 104 dB versus 98 dB for unbalanced inputs.

• Notably, the subwoofer output boosts bass frequencies compared to normal frequency responses when using high-pass filters.

Phase Response and Gain Characteristics

• Rise time across measured frequencies was excellent; phase differences were typical with about a 20° delta at low frequencies like 100 Hz.

• The unit provides around 8 dB gain, sufficient for driving most audio equipment effectively without distortion.

User Experience and Recommendations

• Channel balance accuracy is impressive, within two-tenths of a dB without needing adjustments on balance controls.

• While it performs well overall, there are concerns regarding lack of visual indicators for volume levels which could lead to sudden loudness when switching inputs.

• Suggestions include adding an LED indicator for mute status or volume changes to enhance user experience and safety during operation.

Performance Review of the ZP3 Preamplifier

Signal-to-Noise Ratio (SNR) and Distortion Measurements

• The SNR for balanced inputs was measured at 104 dB, while unbalanced inputs showed 98 dB, indicating excellent performance.

• The noise floor was around four microvolts, with distortion levels significantly low beyond three decimal points. Overall, the ZP3 performs exceptionally well despite slight measurement discrepancies compared to manufacturer claims.

Op-Amp Replacement Considerations

• The ZP3 features socketed op-amps that can be replaced; however, the speaker expresses skepticism about this practice. He believes replacing op-amps may cause more harm than good based on existing data.

• Recommendations against swapping out op-amps are supported by evidence suggesting minimal improvement or potential degradation in sound quality when replacements are made. This feature is available for those who wish to experiment but is not advised.

Listening Experience with Equipment Pairing

• The reviewer connected the ZP3 to a Carver M400A amplifier and Wilson Watt 3 Puppy 2 loudspeakers, noting it as an excellent match for vintage audio setups. They found this combination produced dynamic and lively sound quality.

• While acknowledging some criticisms of the Carver M400A's design complexity, he emphasizes its power capabilities and suitability for most music types without overheating issues during short listening sessions.

Recommendations for Vintage Audio Setups

• For those seeking a vintage amplifier to pair with the ZP3, the Carver M400A is highly recommended due to its performance when properly maintained and recapped. Variants like T models are also mentioned as comparable options with similar circuitry capabilities.

• The reviewer's personal experience led him to reconnect his M400A after a period of inactivity, resulting in satisfaction with both sound quality and equipment compatibility during testing sessions with various music genres.

Conclusion and Viewer Engagement

• The speaker encourages viewers to engage by liking the video or leaving comments/questions for further discussion while expressing hope that they will consider subscribing for future content related to audio equipment reviews and recommendations.