A Chapter of HFR’s Buyer’s Guide to High-End Audio
Amplifiers hand-built in Cave Creek, Arizona by the engineer who defined American solid-state high-end. This is the reference for buying Dan D’Agostino Master Audio Systems gear on the used market — the current lineup, the factory upgrade path that keeps decade-old Momentums competitive with new ones, what to look for on inspection, and what a fair price looks like today.
Daniel D’Agostino has been designing high-power, high-current solid-state amplifiers for four and a half decades. In 1980, he co-founded Krell Industries with fellow Mark Levinson colleague Rondi Halling — the two later married, and she remained his creative and business partner (as Rondi D’Agostino) long after their divorce. D’Agostino ran Krell as CEO and chief engineer for twenty-nine years. Under D’Agostino, Krell became synonymous with a certain kind of American high-end sound — massive linear power supplies, sustained Class A operation, fully balanced topologies, and the ability to drive nearly any loudspeaker to its limits without breathing hard.
In 2009, D’Agostino was pushed out of Krell after the company brought in new investors (KP Partners) who — despite holding a minority equity stake — gained voting control and, within months, escorted the entire D’Agostino family off the premises. After exhausting his legal options, he moved on. In 2011, working from a facility in Cave Creek, Arizona, he founded Dan D’Agostino Master Audio Systems (DDMAS) and began designing amplifiers under his own name.
The company today runs on a small, tight team. D’Agostino remains founder and chief designer. Bill McKiegan, who worked with D’Agostino at Krell, serves as company president. Petra D’Agostino handles operations and customer relations. Everything is hand-built and individually tested in the Cave Creek facility.
The design philosophy departs from Krell in one significant way. Where Krell was often defined by the pursuit of raw specification supremacy, D’Agostino has been explicit that DDMAS pursues the emotional experience of the recorded performance ahead of any measurement. In an interview, he put it directly: “In the past, I was always searching for the latest and greatest technology in audio. Sometimes, that pursuit became more important than the end result... With D’Agostino, I am only interested in the emotional connection that comes with listening to music.”
That philosophy hasn’t softened the engineering ambition. D’Agostino remains an advocate of high-power, high-current, fully balanced, direct-coupled solid-state amplification. The flagship Relentless monoblock, introduced in 2018, delivers over 1,600 watts into 8 ohms. Copper heatsinks flank every amplifier for their superior heat dissipation. Illuminated meters, inspired by 18th-century Parisian watchmaker Abraham-Louis Breguet, sit centered on the fascia.
The current lineup breaks into four families. Progression is the entry, Momentum sits in the middle, Relentless is the flagship, and the Pendulum (introduced in 2025) sits outside the three-tier hierarchy as a compact integrated for buyers who want the sonic and aesthetic identity in a single, more accessible chassis. Each series has evolved through multiple generations. All of them can be brought up to current specification through the factory.
D’Agostino has kept the lineup narrow by design. Four product families, each with a small number of models, and — critically — every unit ever built by DDMAS can be returned to the factory and upgraded to the current specification of its family. This section walks the current active models and the significant legacy pieces you’re likely to encounter on the used market.
The most accessible entry into DDMAS ownership. The Progression Integrated Amplifier ($20,950–$30,100 depending on modules) delivers 200 watts into 8 ohms and 400 into 4, with a 2000VA transformer and optional integrated phono (~$2,100) and DAC/streamer (~$6,950) modules. Its industrial design is more restrained than the Momentum line — smaller footprint, still two illuminated meters, still the signature volume dial with gold-plated outer edge. The line also includes the larger Progression M550 Monoblock ($47,500/pair, 125 lb, 500 watts into 8 ohms).
In June 2026 at High End Vienna, D’Agostino announced the Progression Neo Series — a new Progression Neo Preamplifier, Neo Monoblock, and Neo Stereo Amplifier, positioned as a step up from the standard Progression models with refined aesthetics and technical advancements. This brings meaningful trickle-down from the top of the line into the accessible entry tier and reshapes the used-market calculus for pre-Neo Progression pieces.
The flagship for most of the last decade and still the most-photographed amplifier line at hi-fi shows. The company’s inaugural product was the Momentum Monoblock, launched in 2011. The Momentum Stereo followed in 2012. The Momentum Preamplifier arrived in 2014 at $32,000. Over the years the line evolved through the S200 and S250 stereo amplifiers, the M300 monoblock, and the M400 monoblock in 2016.
The single largest generational shift in the Momentum family came with the MxV upgrade — announced in December 2021, first shipping in January 2022. MxV stands for Mass times Velocity, the physics equation for momentum, and it’s the fullest expression of the Momentum circuitry to date. Every major section (power supply, input, driver, output stage) is enhanced with technology developed for the Relentless line. The Momentum M400 MxV Monoblock ($79,500/pair) delivers 400/800/1,600 watts into 8/4/2 ohms in a 95-lb chassis, using 28 new high-output transistors running at 69 MHz, a 2,200 VA linear transformer, and a nearly 100,000 μF capacitor bank. The Momentum S250 MxV Stereo Amplifier is the stereo counterpart. The Momentum HD Preamplifier ($40,000) has since been superseded by the Momentum C2 (2024) and the flagship Momentum C4 ($61,000, 2024) with its external power supply.
The most recent Momentum evolution is Momentum Z technology, which brings a new preamplifier–amplifier coupling architecture. The current top-tier Momentum pair is the Momentum C2Z Preamplifier and Momentum MZ Monoblock, showcased together at High End Vienna 2026.
The flagship. The original Relentless Monoblock ($385,000/pair in its Epic 1600 form) delivers over 1,600 watts and weighs 570 lb per chassis. The three-chassis Relentless Preamplifier followed at $165,000.
At High End Vienna in June 2026, D’Agostino announced the Relentless Z Series — a Relentless Z Preamplifier, Relentless 800Z Monoblock (1,200 watts into 8 ohms), and Relentless Epic 1600Z Monoblock (2,200 watts into 8 ohms), centered on a reworked FET-based output stage intended to strengthen the electrical coupling between preamp and power amp.
Sits outside the three-family hierarchy. Announced as a prototype at High End Munich in May 2024 and launched into full production in 2025, the Pendulum Integrated Amplifier is D’Agostino’s most compact and most accessible design. US base price is $15,000 (£18,000 inc. VAT in the UK; €19,990–€25,490 inc. VAT in Europe depending on modules). It delivers 120 watts into 8 ohms (240 into 4) from a 750 VA toroidal transformer. The JFET input stage is derived directly from the Momentum C2 Preamplifier. Modular design supports optional DAC/streaming and phono modules. Became Roon Ready in early 2026. The Pendulum brings the D’Agostino sonic and aesthetic identity into a compact chassis, with an LCD display replacing the traditional illuminated meter.
You may encounter on the used market the Momentum M-Life (Momentum Integrated variant with streaming in place of tone controls), the original Momentum Preamplifier (pre-HD), and the original M400 (pre-MxV). All are eligible for factory upgrade to current spec — which is the subject of the next section.
If you’re buying used D’Agostino, the single most important thing to understand is the factory upgrade path. There is no formal Certified Pre-Owned program in the way some brands operate them, and there is no manufacturer-issued extended warranty for units purchased on the secondary market. What D’Agostino has instead — and it’s genuinely rare in high-end audio — is an active, ongoing factory retrofit path that lets any Momentum monoblock ever built (going back to the 2011 originals) be returned to Cave Creek and brought up to current M400 MxV specification.
The MxV upgrade is not a minor refresh. It replaces the power supply transformer with the new 2,200 VA linear unit with the current winding pattern, giving 50% more current output. It replaces the input stage with the current bipolar-transistor front end delivering ten times the current and power of the originals. It replaces the driver stage with the fully complementary Relentless-derived design. It replaces the output-stage transistors with the current 26-piece, 69 MHz array. It re-optimizes thermal transfer to the copper heatsinks. Every electrical enhancement in the current M400 MxV is included. The chassis, metalwork, and copper heatsinks are retained. The one visible external change is a new “400 Watt” meter plate reflecting the increased output — a badge that also serves as easy verification of upgrade status.
Per Hi-Fi News, the M400 → M400 MxV upgrade requires return to the factory; UK pricing has been published at £29,000/pair, but D'Agostino does not publish a US upgrade price list. The Momentum Preamplifier → HD-spec upgrade was $15,000. Pricing for the M400 MxV upgrade and the newer C2/C4-level and Momentum Z retrofits is quoted per unit — contact the factory or an authorized US dealer for a current quote.
Consider a used Momentum M300 or M400 in good condition. On the secondary market, these often list well below the price of new M400 MxV. Add the factory upgrade cost, and the total delivered price is frequently lower than a comparable used M400 MxV — with the benefit that you get factory-fresh internals, a fresh warranty on the upgraded components, and a chassis you already know the history of. The upgrade path effectively removes generational obsolescence from Momentum ownership. A first-year 2011 buyer can, if they choose, still be listening to the same physical chassis in 2026 with 2026 electronics inside.
The MxV upgrade path is retrofittable to the Momentum S200, S250, M300, and M400 monoblocks per D’Agostino’s published guidance. The Momentum Stereo lineage is similarly upgradable to S250 MxV specification. The Momentum Preamplifier line has an equivalent path through HD and now C2/C4. Recent Momentum Z technology may be retrofittable to earlier MxV-generation units — this is worth confirming directly with the factory for any specific unit under consideration. Progression and Relentless owners have their own separate upgrade paths within their families; Progression Neo and Relentless Z retrofits are new enough that pricing and eligibility are still being finalized.
Look at the meter plate first. An MxV-status Momentum monoblock reads “400 Watt” on the meter plate; pre-MxV M400s do not. Original M300s show “300 Watt.” Serial numbers should cross-reference with factory records — DDMAS keeps them, and any authorized dealer can verify a specific serial number against the factory’s build and service history. Pay particular attention to the meter itself: post-upgrade meters glow the same signature green, but a poorly-serviced or non-factory unit may show inconsistent illumination or minor variations in the plate finish. The rear panel is a giveaway too: post-MxV units have the input impedance and current rear-panel labeling that changed with the upgrade.
Beyond the factory upgrade path, another under-appreciated part of the D’Agostino used market is authorized dealer demo inventory. These are units used for in-store demonstration or hi-fi show duty and are typically sold with approximately one year of remaining factory warranty. They’re often lightly used, come with all original packaging (including the D’Agostino Pelican flight cases, which are essential for units this heavy), and are typically discounted 30-45% from new retail. When a demo unit is available from an authorized dealer, it’s usually the strongest single value point in the D’Agostino used market.
When you evaluate a used Momentum listing on HFR, ask three questions: What is the current spec status (M300, M400, M400 MxV)? Has the unit been to the factory for upgrade or service, and if so, when? Is it eligible for the current MxV or Z upgrade if you want to invest in bringing it forward? A candid seller will have documentation for all of this — service records, factory correspondence, upgrade receipts. Buyers who understand the upgrade path have significant negotiating leverage; sellers who don’t understand it may be underselling a chassis whose upgrade-completed value substantially exceeds their asking price.
D’Agostino amplifiers don’t require the room-tuning discipline that a Wilson or Rockport speaker demands, but they carry their own installation considerations that matter for both new and used owners.
These are heavy amplifiers. The Momentum M400 MxV Monoblock weighs 95 lb. The Progression M550 Monoblock weighs 125 lb per side. The Relentless Epic 1600 Monoblock weighs 570 lb per chassis — for reference, that’s more than most modern refrigerators. Racks and shelves must be rated accordingly. Concrete floors are strongly preferred; suspended wood floors need reinforcement under the amplifier position for the flagship models. Two-person moves are the minimum for anything in the Momentum lineup and above; four people plus a mechanical assist is safer for Relentless.
Copper heatsinks are the primary thermal management — copper dissipates heat several times more efficiently than aluminum, which is why D’Agostino uses it throughout. D’Agostino amplifiers run warm — not “fry an egg” warm per Hi-Fi News, but noticeably warm to the touch after any significant listening session. This is normal and by design. Leave at least four to six inches of clearance above the top plate and behind the amplifier. Do not stack these amplifiers, and do not enclose them in cabinets without active ventilation. Owners who put Momentums or Relentless monoblocks in closed-cabinet installations should expect to invest in active cooling.
All current D’Agostino amplifiers ship with hard rubber feet as stock. Multiple reviewers, including Stereophile’s Jason Victor Serinus, have found audible improvements with aftermarket footers under D’Agostino amplifiers. Wilson Audio Pedestals are a commonly cited choice.
Higher lines (Momentum, Relentless) accept balanced XLR only. Single-ended sources require an RCA-to-XLR adapter, which D’Agostino ships in the box with the amplifier. The Pendulum and the Progression Integrated accept both balanced and single-ended. Binding posts across the line are heavy 5-way, accepting spade, banana, or bare wire. Remote on/off triggers are standard.
A rear-mounted three-way toggle switches meter illumination between always-on, signal-active (dims when idle), and off. Most owners run always-on because the meters are one of the defining aesthetic elements. Signal-active is the compromise for owners who want the meters as a functional indicator without them being a constant light source in the room.
As with most high-current solid-state amplifiers, D’Agostino gear benefits from a break-in period before it settles into its full performance — sound quality early on is not representative of how the amplifier will sound after extended use. Factor this into any used purchase: a well-broken-in used unit can be a genuine advantage over new.
D’Agostino amplifiers are among the most robustly built products in high-end audio, and they typically age well. Inspection is nonetheless important, and there are specific things to look for that go beyond generic amplifier due-diligence.
The copper heatsinks that define the D’Agostino aesthetic are also the single most delicate surface on the chassis. Finishing the copper is, in Dan D’Agostino’s own words, “pure hell” — early attempts oxidized at the slightest touch before he found a refiner who could seal the surface without reducing cooling performance. Copper is soft; it marks easily. Small scratches, fingerprints, and minor oxidation are common on used units and are largely cosmetic. Deep scratches, dents, or heavy oxidation warrant a discount and, on higher-value units, potential return to the factory for refinishing. Photograph the heatsinks from multiple angles under natural light before purchase.
The signature illuminated meter is the piece most buyers focus on visually. Check that the meter glows evenly across its face — no dark spots, no flickering. Confirm the meter needle moves smoothly with signal input. The meter plate itself should match the amplifier’s current spec: “400 Watt” for M400 or M400 MxV, “300 Watt” for M300, “250 Watt” for S250. A mismatched or replaced meter plate is a red flag warranting factory verification of the unit’s actual internal spec.
As covered in the Factory Upgrade Path section above: verify the unit’s current specification through both the meter plate and the serial number. Ask the seller for any factory service or upgrade documentation. Cross-reference the serial number with an authorized dealer or directly with the factory. Legitimate factory-upgraded units carry paperwork; buyers who care about upgrade status should demand it.
Every D’Agostino amplifier ships in a heavy-duty Pelican-style flight case with wheels. These cases are essential — you cannot ship or move a Momentum or Relentless safely without one. Confirm the case is included with any used purchase. If it isn’t, factor the replacement cost (from the factory, several hundred to over a thousand dollars depending on model) into your offer. Also confirm original packaging materials inside the case are intact.
D’Agostino remote controls are round, machined aluminum objects — reviewers have praised their finish and heft as exuding the same quality and luxury as the amplifiers themselves. They should always be included with any Momentum or Progression preamp or integrated purchase. A missing remote is a meaningful reduction in value — replacements from the factory are expensive.
D’Agostino transformers are custom-wound and normally operate silently. Any audible transformer hum or buzz coming from a D’Agostino amplifier’s chassis is not normal and warrants factory inspection before purchase. Ask the seller to power the amplifier up in your presence (or on a video call) with no signal and verify silence.
Because these amplifiers run warm by design, small discoloration on the top plate is normal. Discoloration that suggests localized hot spots, warping of the top plate, or discolored copper suggests the amplifier has been operated in poor ventilation or under fault conditions. This is uncommon but worth checking.
Factory warranties transfer with proper documentation but only through authorized channels. Ask the seller how they purchased the unit — from an authorized dealer or private party — and whether they have the original bill of sale. Authorized-dealer demo units typically carry residual factory warranty; private-party second-and-later-hand units typically do not.
Full original packaging and documentation add meaningfully to used value. Factory-fresh accessories (IEC power cable, XLR-to-RCA adapter, remote, meter-plate documentation) should all be present.
Small marks on copper, fingerprints on brushed aluminum, minor scuffs on the bottom of the chassis, and a slight warm smell after long listening sessions are all normal and expected. Do not let cosmetic minor imperfections drive you away from an otherwise well-cared-for and correctly-spec’d unit.
D’Agostino gear holds its value better than most high-end audio electronics in the same price band, for three specific reasons.
Small-batch manufacturing. DDMAS produces relatively few units per model per year. Every amplifier is hand-built and individually tested in Cave Creek. That constrains supply on the used market and supports pricing. Compare this to brands with larger production runs, where fresh used inventory drives asking prices down over time.
The factory upgrade path. As covered above, the upgrade path effectively removes generational obsolescence from Momentum and Progression ownership. A 2015 Momentum M400 that has been upgraded to current M400 MxV spec is functionally identical inside to a brand-new M400 MxV, at a total delivered cost typically lower than new. This creates active demand for used Momentum inventory from buyers who plan to upgrade — which supports asking prices for pre-upgrade units too, since they’re the raw material for that transaction.
Sonic and aesthetic longevity. D’Agostino amplifiers are widely regarded as generation-defining. Buyers who acquire one tend to keep it. Turnover in the used market is lower than in comparable price bands, which further constrains supply.
D’Agostino amplifiers are voiced to drive demanding loudspeakers with authority. They’re most often paired with a specific set of speaker brands and source components that experienced dealers and reviewers have consolidated over the past decade.
Wilson Audio. Dan D’Agostino uses a full Relentless system driving Wilson Audio Chronosonic XVX in his own listening room. Hi-fi+ has singled out the dCS-source, D’Agostino-amplification, Wilson-speaker combination as a turn-key top-tier system. The combination pairs Wilson’s dynamic-range capability and low-impedance handling with D’Agostino’s current delivery.
Rockport Technologies. Stereophile’s coverage of the dCS Vivaldi / D’Agostino Momentum / Rockport Cygnus / Transparent MM2 pairing at CES 2015 called it a “demonstration class” system. Rockport’s constrained-mode-damped MDF cabinets have a more damped presentation than Wilson’s proprietary compound cabinets; the pairing with D’Agostino tends toward openness and neutrality.
Magico. Positive Feedback’s review of the Momentum Integrated Amplifier explicitly confirmed it drives the Magico Q7 — a notoriously difficult 94 dB, low-sensitivity, low-impedance load — “with ease.” Momentum, Progression M550, and Relentless all pair naturally with Magico’s Q, A, S, and M lines.
Sonus Faber. Sonus Faber Stradivari with Progression and Momentum has been used by multiple reviewers as a reference pairing.
The Momentum M400 MxV delivers 400/800/1,600 watts into 8/4/2 ohms — the current doubles down cleanly at each impedance step. This is exactly what electrostatic panels (Martin Logan reference, Quad ESL), planar magnetics, and low-impedance dynamic loads need. If your speaker is difficult, D’Agostino electronics are among the safest choices.
dCS digital sources are the dominant partner across all levels of D’Agostino ownership — Vivaldi, Rossini, Bartok all appear regularly in professional review systems. Vinyl-focused owners tend toward VPI, TechDAS, and Kuzma turntables with high-quality moving-coil cartridges.
Nordost Odin 2, AudioQuest Dragon, Transparent, and Cardas Clear all appear in professional reviewer setups. There is no “official” cable partner, but XLR interconnects are essentially mandatory for higher-lineage components.
The Pendulum (120W/8Ω) is well-matched to reasonably efficient speakers in modest rooms. The Progression (200-500W/8Ω per unit) covers most demanding modern high-end speakers. The Momentum (250-400W/8Ω per unit) handles anything short of the most difficult electrostatic full-range panels. Relentless (1,600W+/8Ω) is genuinely no-compromise for any load.
DDMAS was founded in 2011 in Cave Creek, Arizona by Daniel D’Agostino, who had co-founded Krell Industries in 1980 and served as its CEO and chief engineer through 2009. Every DDMAS amplifier is hand-built and individually tested at the Cave Creek facility. The company is a separate entity from Krell.
Three tiers of the D’Agostino lineup arranged by scale and price. Progression is the entry, delivering roughly 200 watts into 8 ohms per unit. Momentum is the mid-flagship, delivering 400 watts into 8 ohms per monoblock. Relentless is the flagship, delivering over 1,600 watts into 8 ohms. Pendulum sits outside the tiers as an entry-level integrated.
Mass times Velocity — the physics equation for momentum. Applied to Momentum amplifiers, MxV designates the current generation of the family, introduced in 2021, incorporating technology developed for the Relentless line. Any pre-MxV Momentum monoblock (M300, M400, S200, S250) can be factory-upgraded to current MxV specification.
Yes. This is one of the defining features of D’Agostino ownership. Any Momentum monoblock ever built can be returned to the Cave Creek factory and brought to current M400 MxV specification. The upgrade replaces the power supply, input, driver, and output stages while retaining the original chassis and copper heatsinks. UK pricing has been published at £29,000/pair; D’Agostino does not publish a US upgrade price list, so contact the factory or an authorized US dealer for a current quote.
Yes. Every D’Agostino amplifier is hand-built and individually tested at the DDMAS facility at 5855 E Surrey Drive in Cave Creek, Arizona. Dan D’Agostino personally reviews production and design decisions. Factory tours are available to serious buyers through authorized dealers.
No formal program in the way some automotive-adjacent brands operate them. What D’Agostino has instead is the factory upgrade path, plus authorized dealer demo inventory that typically carries approximately one year of remaining factory warranty. Private-party used purchases do not carry manufacturer warranty; factory service is available regardless of ownership history.
Wilson Audio, Rockport Technologies, Magico, and Sonus Faber are the most common professional-review pairings. Dan D’Agostino himself uses Wilson Audio Chronosonic XVX in his personal listening room. D’Agostino electronics are voiced to drive demanding low-impedance loads, making them particularly suited to demanding modern high-end speakers.
The Pendulum, launched in 2025, is D’Agostino’s most compact and accessible integrated at a $15,000 US base price. It delivers 120 watts into 8 ohms. The Progression Integrated starts at $20,950 (base) and delivers 200 watts. Pendulum is single-chassis; Progression is more powerful, more feature-rich, and physically larger.
Yes. Dan D’Agostino co-founded Krell in 1980, ran the company as CEO and chief engineer for 29 years, and was pushed out in 2009 after new investors gained voting control of the company. He founded Dan D’Agostino Master Audio Systems in 2011. Krell and DDMAS are entirely separate companies with different ownership.
Krell Industries closed June 18, 2024 following the death of owner and CEO Rondi D’Agostino, Dan’s ex-wife. Krell service operations resumed March 19, 2025, and Krell has announced plans to resume manufacturing in 2026. This has no operational connection to Dan D’Agostino Master Audio Systems, which remains in continuous operation.
Momentum Z technology (the Momentum C2Z Preamplifier and Momentum MZ Monoblock) and the Relentless Z Series announced June 2026 at High End Vienna. The Progression Neo Series was announced at the same show. Z-topology components feature a new preamplifier-amplifier coupling architecture using FET circuitry that improves current delivery and dynamic contrast.
Very. D’Agostino uses through-hole circuit board construction (rather than surface-mount) for long-term durability, individual factory testing of every unit, and premium components throughout. The factory upgrade path further extends effective ownership lifespan. Reports of major mechanical or electrical failures on D’Agostino gear are rare in the professional review and enthusiast literature.
D’Agostino sells through a small, curated network of authorized dealers globally. Authorized-dealer status matters more with D’Agostino than with most brands because of the small production runs, the factory upgrade path (which requires proper documentation), and the high per-unit values.
Authorized dealers can facilitate factory service, verify unit specifications against DDMAS records, and often broker the return-to-factory process for upgrades. Dealer demo units are frequently the strongest single value point in the D’Agostino used market — lightly used, discounted 30-45% from new, and with approximately one year of remaining factory warranty.
Buyers considering a used D’Agostino purchase from a private party should still consider engaging with a local authorized dealer for a pre-purchase inspection or serial-number verification. Most authorized dealers are willing to do this as a courtesy for serious buyers, especially if the buyer intends to eventually engage the dealer for the factory upgrade or service.
When you see an “Authorized Dan D’Agostino Dealer” claim on any used listing on HFR, the badge is verified against DDMAS’s current dealer roster. Non-authorized sellers may still offer legitimate used gear, but the authorization badge does provide additional signal about the seller’s relationship to the manufacturer.
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Create a listing →A curated bibliography of the sources cited throughout this Buyer’s Guide chapter. All specialist reviews and manufacturer materials referenced in the sections above are indexed here.
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