The Series III builds on improvements made to the Series II for an even higher level of performance. The new design features an extensively revised power supply based on current-sourced shunt regulator technology that minimizes impact on the audio signal by eliminating high voltage gain. Far more precise power regulation yields dramatically improved rejection of noise and AC fluctuation.
The completely redesigned high current gain stage utilizes newly available FET technology developed for green technologies such as solar panels and electric cars that require a normally-on state. Unlike MOSFETs that need to be biased on, normally-on devices operate more like vacuum tubes in the audio output stage, with simpler circuits that continuously conduct current, resulting in a more tube-like sound. The high-current gain stage has been further optimized for linearity with zero global negative feedback in the circuit.
Also included in the upgrade are new specially selected audiophile grade capacitors and a fully bi-directional RS-232 control interface for increased compatibility with modern home theater systems.
Enhancements to the Series III result in an even higher level of coherence, integration and transparency of sound, with dramatically improved mid-bass and midrange, and a more tube-like sonic character.
Product features
- Isolated Control Unit chassis with 12 separate fully regulated power supplies
- Separate Audio Unit chassis with zero internal digital activity and isolated from AC and power supply noise
Audio unit features
- Fully balanced differential circuit with balanced in and out, and mirror-image layout
- Simple 2-stage circuit topology with differential gain stage and output buffers for musical purity and integrity
- Ultra low impedance output stage to drive any length of cable and any power amplifier/paralleled amplifier/subwoofer load
- 30 microfarad output capacitors for vastly improved bass control
- Tube complement: 2 – 12AU7 tubes
- Gain switching between normal gain and low gain with 6dB gain reduction
- Single fully balanced differential 95-step 70dB discrete resistor relay attenuator for all attenuation functions, using low signal instrumentation ruthenium relays for greatest resolution
- Microphonically damped tube gain stage for greater vibration noise elimination
Control power supply unit features
- Ramped B+ filament soft-start power up for extended tube life
- Huge energy storage power supply for elimination of AC fluctuation and noise rejection
- Low noise processor control design for all functions
User interface features
- Processor loop – any of 8 inputs can be assigned as fixed unity gain pass through
- Tape monitor function for both tape loops
- 4 separately programmable trigger outputs
- Bi-directional RS-232 interface
- Programmable input offsets
- Selectable padded inputs
- Rigid Combination steel and non-magnetic chassis and machined aluminum remote wand
- Factory upgradeable from Series I and Series II
Additional feature list of the TL7.5 Series III Reference Preamplifier
Audio unit features
- New FET device output stage for more tube-like sound and simpler circuit
- New device in the gain stage current source for improved musicality and better single-ended operation
- Zero Global NFB for vastly improved faster dynamic and tonal resolution, and unconditionally stable circuit, without any phase shift.
- All audiophile grade Mundorf capacitors in signal path with bypass system for improved HF resolution
Control power supply unit features
- Vastly improved lower impact and greater precision-regulated current-sourced shunt power supply
- Teflon power supply bypass caps for improved top end
Documentation
TL7.5 Data Sheet
Technical Specifications
| Vacuum Tube Complement | 2 x 12AU7 | |||
| Inputs | 4 pairs balanced/XLR or RCA single-ended, 4 pairs single-ended/RCA | |||
| Outputs | 2 pair balanced out, 2 pairs single-ended RCA out, 2 pairs single-ended RCA buffered Tape Out | |||
| Remote control functions | Power, Source Select, Volume up/down, Mute, Fade, Balance Control, Phase Reverse | |||
| Gain | Balanced in and Balanced out: 19.2 dB, Single-ended in and Balanced out: 19.2 dB Balanced in and Single-ended out: 13.2 dB, Single-ended in and Single-ended out: 13.2 dB |
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| Output impedance | 25Ω, Max 150Ω @ 10Hz | |||
| Input impedance | 50kΩ, 20kΩ min | |||
| Frequency Response +0 -1 dB | 1Hz – 100kHz (20Hz – 100kHz +0 –1dB into 600Ω with 900pF 20’ interconnect cable) | |||
| Maximum Output Voltage <1% THD | 30V into 10kΩ or above (10Hz – 200kHz +/-1dB) 10V into 600Ω |
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| Channel separation | >100dB @ 1kHz (>80dB @ 20kHz) | |||
| Power consuption | 150W | |||
| Dimensions W x D x H | Control chassis – 17.5 x 17.5 x 4 inches (44.5 x 44.5 x 10.2 cm) Audio chassis – 17.5 x 17.5 x 6 inches (44.5 x 44.5 x 15.3 cm) |
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| Weight | 90 lbs (40.82 Kg) Fully packed in two boxes Unpacked weight: Audio Unit – 38lbs (17.24Kg), Control Unit – 32lbs (14.50Kg) |
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The VTL TL7.5 Series III Line-stage (and MB450 Series III mono-blocs)
…If you want the music AND the message, and you want it right there right now, then the TL7.5 Series III is a great place to start, the MB450 Series IIIs the perfect partners. Costly to purchase and demanding to house they may be, but these electronics will deliver the warm, beating heart of a truly great system; for once, value really isn’t an issue. Read the full review here…
- Roy Gregory, HiFi+, UK, Issue 97
TL-7.5 Series III
VTL TL-7.5 Series III Reference Line Preamplifier Read the full review here…
- Jacob Heilbrunn, The Absolute Sound, April 2012
TL-7.5 Series III
VTL’s new [TL-7.5 Series III] line stage is the best one it has produced. Its transient fidelity, dynamic power, enormous soundstage, and sheer grip are mesmerizing.
- Jacob Heilbrunn, The Absolute Sound, Editor's Choice Awards 2013, Issue 231
VTL TL-7.5 Series III Reference Preamplifier
Excerpts and quotes from the Paul Bolin review:
It is the finest line stage I have heard, tube or solid-state.
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It does more — by doing less to the signals that pass through it — than any piece of audio equipment I have heard to date.
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the TL-7.5 Series III somehow manages to combine the full portfolio of harmonic virtues that only tubes can provide, even at this late day, with the kind of bandwidth and speed of the very finest solid state.
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The ‘7.5 simply made it easier, much easier, to pay attention to all of the threads in the fabric of music — and to hear that music as a complete entity.
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Excerpt from Marc Mickelson’s comments in the Paul Bolin review:“It comes by detail honestly” with “dynamic prowess that is state of the art here and now.”
- Paul Bolin, The Audio Beat, January, 2013
Comments on the TL7.5 III
The way the [TL7.5] III unravels the musical lines … and rocks the room is awesome. Read more here…
- Lee Schwartz, published in the What’s Best Forum, 2011
VTL TL-7.5 Series 3 Preamplifier | purity like water
…I listened to Jacintha’s “Here’s to Ben” to find out how low is the TL7.5 III’s noise floor. With this recording, I can hear more of the nuances in her voice, the image of the instruments become much better defined and three dimensional, and the overall low level details of her voice is much clearer. The feeling is like drinking water that is so pure and unadulterated…From “Here’s to Ben” I can start to comprehend the benefits of the “Clean Box – Dirty Box” design …… In this recording, TL7.5 III is as neutral as vegetables and tofu and at first you don’t feel the excitement at all, however, when you listen longer you’ll find out that it is so clean, so natural, so airy that there is no stress whatsoever on your ears…
Vegetables and tofu are very common ingredients and most people would not have any special impressions after eating them. The reason is because when the vegetables are not fresh and the tofu quality is not high, they would not give you any special impression. However, if you eat vegetables that were freshly picked and tofu made with very high quality ingredients, you will be surprised that such ordinary food could be so tasty and delicious. The reason is that these high quality ingredients are cooked in very simple way with a balanced flavoring. This is exactly the feeling I get from the TL7.5 Series III.
- Jack Liu, Audio Art, Taiwan, January 2012
VTL TL7.5 Series III
TL7.5 the 3 Series has regained the throne of my reference system, after a few months when the old model Series 2 had been replaced by Audio Research Anniversary Edition, the fight for supremacy between the two leading exponents of the American school of the valves continues rigorously, and this round goes in favor of VTL. We speak of an object from the high price, but in line with the market, in fact, slightly cheaper than the contender. We also talk about a product built superbly and characterized by refined technical solutions, such as exceptional volume control, and very convenient to use. The quality of the sound has been further improved in the Series III. In short, fans of the brand will not be disappointed, but this level of quality should also appeal to solid state fans as well…- Marco Benedetti, Audio Review Italy, n. 324, August, 2011