Who owns AMPX (AMPX)
Which tracked institutional funds hold AMPX, how they are positioned, and who is buying versus exiting — from SEC Form 13F-HR filings. See AMPX company fundamentals →
Ownership as of the 2026-Q1 13F filings. 13F is disclosed up to 45 days after quarter-end, so the most recent quarter fills in over the following weeks.
How the tape is positioned
The tracked-fund tape on AMPX is one-sided between 2025-Q4 and 2026-Q1: 142 added or opened and 30 trimmed or exited — on balance accumulating.
A prompt to read the filings, not a verdict. 13F is a quarter-end snapshot disclosed up to 45 days late; a fund adds or exits for mandate, benchmark, and timing reasons that have nothing to do with a view on the stock. This is a starting question, not a signal to trade.
Conviction spread
AMPX’s largest tracked holder by dollar value, BlackRock, Inc., sizes it at 0.0% of its own reported 13F book, while the median holder sizes it at 0.0% of theirs — a 0.0pp gap the other way — the median holder sizes AMPX more heavily than its largest holder by dollar value does.
Book-share is each fund’s reported value in AMPX divided by its whole reported 13F book, so it is comparable across funds of different sizes and is unaffected by stock splits. A higher share means a fund has committed more of its book to the name — a starting question about conviction, not a verdict or a signal to trade.
Institutional & insider positioning
Between 2025-Q4 and 2026-Q1, across 254 tracked filers holding AMPX, 178 increased or opened the position and 101 reduced or closed it; over the same quarter, open-market insider Form 4 buying and selling roughly offset.
This fuses two public signals for the same quarter — how tracked institutions changed their positions and whether insiders bought or sold in the open market. It describes what was filed; it is a starting question, not a verdict or a signal to trade.
New buyers & exits
Funds opening or closing a position in AMPX between the 2025-Q4 and 2026-Q1 13F filings, and the largest changes among funds holding it in both. New buyers and exits are counted on fund presence (split-invariant); adds and trims are measured on reported value.
New buyers 40
- VANGUARD CAPITAL MANAGEMENT LLC$83M
- MASSACHUSETTS FINANCIAL SERVICES CO /MA/$34M
- MARSHALL WACE, LLP$21M
- VANGUARD PORTFOLIO MANAGEMENT LLC$18M
- HRT FINANCIAL LP$17M
- VANGUARD FIDUCIARY TRUST CO$15M
Full exits 18
- VANGUARD GROUP INC$48M
- NORGES BANK$10M
- JUPITER ASSET MANAGEMENT LTD$8M
- TWO SIGMA ADVISERS, LP$4M
- Artemis Investment Management LLP$4M
- OSTERWEIS CAPITAL MANAGEMENT INC$4M
Largest adds
- BlackRock, Inc.$86M
- JANE STREET GROUP, LLC$68M
- TWO SIGMA INVESTMENTS, LP$48M
- Driehaus Capital Management LLC$45M
- PRICE T ROWE ASSOCIATES INC /MD/$31M
- MORGAN STANLEY$31M
Largest trims
- SUSQUEHANNA INTERNATIONAL GROUP, LLP$12M
- Hudson Bay Capital Management LP$5M
- VOLORIDGE INVESTMENT MANAGEMENT, LLC$4M
- Point72 Asset Management, L.P.$3M
- Invesco Ltd.$3M
- Verition Fund Management LLC$2M
Institutional holders
One row per tracked fund, largest reported value first. “% of value” is the fund’s share of this security’s tracked institutional value — not of shares outstanding. Rows marked stale are from an earlier filing than the security’s latest quarter — that fund is absent from the newest snapshot (position exited, or reported under a different name).
| Fund | Shares | Reported value | % of value | Quarter |
|---|---|---|---|---|
| BlackRock, Inc. added | 9,225,611 | $156M | 10.5% | 2026-Q1 |
| VANGUARD CAPITAL MANAGEMENT LLC new | 4,908,875 | $83M | 5.6% | 2026-Q1 |
| JANE STREET GROUP, LLC added | 4,160,656 | $70M | 4.7% | 2026-Q1 |
| Driehaus Capital Management LLC added | 3,794,178 | $64M | 4.3% | 2026-Q1 |
| TWO SIGMA INVESTMENTS, LP added | 3,506,075 | $59M | 4.0% | 2026-Q1 |
| MORGAN STANLEY added | 3,162,167 | $53M | 3.6% | 2026-Q1 |
| GEODE CAPITAL MANAGEMENT, LLC added | 2,814,530 | $47M | 3.2% | 2026-Q1 |
| STATE STREET CORP added | 2,712,630 | $46M | 3.1% | 2026-Q1 |
| UBS Group AG added | 2,311,554 | $39M | 2.6% | 2026-Q1 |
| GOLDMAN SACHS GROUP INC added | 2,226,181 | $38M | 2.5% | 2026-Q1 |
| MASSACHUSETTS FINANCIAL SERVICES CO /MA/ new | 2,024,760 | $34M | 2.3% | 2026-Q1 |
| PRICE T ROWE ASSOCIATES INC /MD/ added | 1,897,420 | $32M | 2.2% | 2026-Q1 |
| LMR Partners LLP added | 4,489,842 | $31M | 2.1% | 2026-Q1 |
| Baird Financial Group, Inc. added | 1,585,098 | $27M | 1.8% | 2026-Q1 |
| CITADEL ADVISORS LLC added | 1,438,660 | $24M | 1.6% | 2026-Q1 |
| MARSHALL WACE, LLP added | 1,227,599 | $21M | 1.4% | 2026-Q1 |
| Qube Research & Technologies Ltd added | 1,227,570 | $21M | 1.4% | 2026-Q1 |
| WILLIAM BLAIR INVESTMENT MANAGEMENT, LLC added | 1,170,131 | $20M | 1.3% | 2026-Q1 |
| VANGUARD PORTFOLIO MANAGEMENT LLC new | 1,073,396 | $18M | 1.2% | 2026-Q1 |
| JPMORGAN CHASE & CO added | 1,216,185 | $18M | 1.2% | 2026-Q1 |
| BARCLAYS PLC added | 1,054,927 | $18M | 1.2% | 2026-Q1 |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC added | 1,039,394 | $18M | 1.2% | 2026-Q1 |
| MILLENNIUM MANAGEMENT LLC trimmed | 1,035,238 | $17M | 1.2% | 2026-Q1 |
| NORTHERN TRUST CORP added | 1,022,625 | $17M | 1.2% | 2026-Q1 |
| HRT FINANCIAL LP added | 1,002,658 | $17M | 1.1% | 2026-Q1 |
| Hood River Capital Management LLC added | 949,147 | $16M | 1.1% | 2026-Q1 |
| Stephens Investment Management Group LLC trimmed | 893,108 | $15M | 1.0% | 2026-Q1 |
| DEUTSCHE BANK AG\ trimmed | 875,031 | $15M | 1.0% | 2026-Q1 |
| VANGUARD FIDUCIARY TRUST CO new | 872,582 | $15M | 1.0% | 2026-Q1 |
| Wolf Hill Capital Management, LP new | 802,925 | $14M | 0.9% | 2026-Q1 |
| MYDA Advisors LLC new | 735,000 | $12M | 0.8% | 2026-Q1 |
| STIFEL FINANCIAL CORP trimmed | 733,172 | $12M | 0.8% | 2026-Q1 |
| Trexquant Investment LP added | 716,257 | $12M | 0.8% | 2026-Q1 |
| Science & Technology Partners, L.P. new | 635,106 | $11M | 0.7% | 2026-Q1 |
| OBERWEIS ASSET MANAGEMENT INC/ new | 585,000 | $10M | 0.7% | 2026-Q1 |
| SEI INVESTMENTS CO added | 579,161 | $10M | 0.7% | 2026-Q1 |
| Russell Investments Group, Ltd. added | 543,463 | $9M | 0.6% | 2026-Q1 |
| VOLORIDGE INVESTMENT MANAGEMENT, LLC trimmed | 531,998 | $9M | 0.6% | 2026-Q1 |
| THAMES CAPITAL MANAGEMENT LLC | 526,832 | $9M | 0.6% | 2026-Q1 |
| ARISTEIA CAPITAL, L.L.C. added | 1,215,397 | $8M | 0.6% | 2026-Q1 |
| MIRAE ASSET GLOBAL ETFS HOLDINGS Ltd. trimmed | 489,652 | $8M | 0.6% | 2026-Q1 |
| ESSEX INVESTMENT MANAGEMENT CO LLC trimmed | 445,441 | $8M | 0.5% | 2026-Q1 |
| Caption Management, LLC added | 1,084,367 | $7M | 0.5% | 2026-Q1 |
| Invesco Ltd. trimmed | 433,211 | $7M | 0.5% | 2026-Q1 |
| SG Americas Securities, LLC added | 423,037 | $7M | 0.5% | 2026-Q1 |
| POLEN CAPITAL MANAGEMENT LLC added | 422,145 | $7M | 0.5% | 2026-Q1 |
| TUDOR INVESTMENT CORP ET AL trimmed | 419,661 | $7M | 0.5% | 2026-Q1 |
| OPPENHEIMER & CO INC trimmed | 412,509 | $7M | 0.5% | 2026-Q1 |
| Allspring Global Investments Holdings, LLC added | 431,398 | $7M | 0.5% | 2026-Q1 |
| FIRST TRUST ADVISORS LP added | 394,569 | $7M | 0.4% | 2026-Q1 |
| Palisades Investment Partners, LLC new | 369,476 | $6M | 0.4% | 2026-Q1 |
| Calamos Advisors LLC added | 364,506 | $6M | 0.4% | 2026-Q1 |
| RENAISSANCE TECHNOLOGIES LLC added | 359,525 | $6M | 0.4% | 2026-Q1 |
| Lisanti Capital Growth, LLC added | 352,375 | $6M | 0.4% | 2026-Q1 |
| Public Sector Pension Investment Board new | 332,000 | $6M | 0.4% | 2026-Q1 |
| SILVERCREST ASSET MANAGEMENT GROUP LLC trimmed | 319,879 | $5M | 0.4% | 2026-Q1 |
| CSS LLC/IL added | 754,893 | $5M | 0.4% | 2026-Q1 |
| Hudson Bay Capital Management LP trimmed | 741,715 | $5M | 0.3% | 2026-Q1 |
| Bank of New York Mellon Corp trimmed | 298,865 | $5M | 0.3% | 2026-Q1 |
| Voleon Capital Management LP added | 298,354 | $5M | 0.3% | 2026-Q1 |
| BNP PARIBAS FINANCIAL MARKETS trimmed | 286,546 | $5M | 0.3% | 2026-Q1 |
| Aquatic Capital Management LLC added | 282,663 | $5M | 0.3% | 2026-Q1 |
| BANK OF AMERICA CORP /DE/ trimmed | 265,418 | $4M | 0.3% | 2026-Q1 |
| Informed Momentum Co LLC added | 262,036 | $4M | 0.3% | 2026-Q1 |
| Nuveen, LLC added | 243,895 | $4M | 0.3% | 2026-Q1 |
| ZEVENBERGEN CAPITAL INVESTMENTS LLC new | 236,875 | $4M | 0.3% | 2026-Q1 |
| Swiss National Bank added | 232,400 | $4M | 0.3% | 2026-Q1 |
| Squarepoint Ops LLC added | 232,109 | $4M | 0.3% | 2026-Q1 |
| Legato Capital Management LLC added | 228,498 | $4M | 0.3% | 2026-Q1 |
| ARROWSTREET CAPITAL, LIMITED PARTNERSHIP trimmed | 227,132 | $4M | 0.3% | 2026-Q1 |
| UBS AM, a distinct business unit of UBS ASSET MANAGEMENT AMERICAS LLC added | 225,224 | $4M | 0.3% | 2026-Q1 |
| ALGERT GLOBAL LLC added | 215,315 | $4M | 0.2% | 2026-Q1 |
| Sender Co & Partners, Inc. new | 179,243 | $3M | 0.2% | 2026-Q1 |
| FEDERATED HERMES, INC. trimmed | 169,753 | $3M | 0.2% | 2026-Q1 |
| OSAIC HOLDINGS, INC. added | 169,492 | $3M | 0.2% | 2026-Q1 |
| ALPS ADVISORS INC added | 167,420 | $3M | 0.2% | 2026-Q1 |
| NEW YORK STATE COMMON RETIREMENT FUND added | 165,627 | $3M | 0.2% | 2026-Q1 |
| Amundi added | 164,589 | $3M | 0.2% | 2026-Q1 |
| Y-Intercept (Hong Kong) Ltd new | 164,224 | $3M | 0.2% | 2026-Q1 |
| Huntleigh Advisors, Inc. added | 162,905 | $3M | 0.2% | 2026-Q1 |
| CALIFORNIA STATE TEACHERS RETIREMENT SYSTEM added | 159,903 | $3M | 0.2% | 2026-Q1 |
| DNB Asset Management AS new | 153,032 | $3M | 0.2% | 2026-Q1 |
| HUSSMAN STRATEGIC ADVISORS, INC. trimmed | 147,000 | $2M | 0.2% | 2026-Q1 |
| DRW Securities, LLC added | 335,173 | $2M | 0.2% | 2026-Q1 |
| AQR CAPITAL MANAGEMENT LLC trimmed | 135,985 | $2M | 0.2% | 2026-Q1 |
| Schonfeld Strategic Advisors LLC added | 135,774 | $2M | 0.2% | 2026-Q1 |
| LPL Financial LLC added | 134,781 | $2M | 0.2% | 2026-Q1 |
| RHUMBLINE ADVISERS added | 132,093 | $2M | 0.2% | 2026-Q1 |
| BLAIR WILLIAM & CO/IL added | 126,622 | $2M | 0.1% | 2026-Q1 |
| ARDSLEY ADVISORY PARTNERS LP new | 125,000 | $2M | 0.1% | 2026-Q1 |
| VANGUARD GROUP INC trimmed | 6,099,966 | $48M | 3.3% | 2025-Q4 stale |
| NORGES BANK new | 1,304,838 | $10M | 0.7% | 2025-Q4 stale |
| JUPITER ASSET MANAGEMENT LTD added | 960,912 | $8M | 0.5% | 2025-Q4 stale |
| Capitolis Liquid Global Markets LLC new | 680,600 | $7M | 0.5% | 2025-Q3 stale |
| Board of Trustees of The Leland Stanford Junior University trimmed | 1,146,636 | $5M | 0.3% | 2025-Q2 stale |
| TWO SIGMA ADVISERS, LP trimmed | 479,500 | $4M | 0.3% | 2025-Q4 stale |
| Artemis Investment Management LLP trimmed | 464,029 | $4M | 0.2% | 2025-Q4 stale |
| OSTERWEIS CAPITAL MANAGEMENT INC added | 454,830 | $4M | 0.2% | 2025-Q4 stale |
| NEXT CENTURY GROWTH INVESTORS LLC new | 228,628 | $2M | 0.2% | 2025-Q3 stale |
| Walleye Capital LLC added | 269,406 | $2M | 0.1% | 2025-Q4 stale |
Ownership over time
Tracked institutional holder count and total shares held by filing quarter (independent scales). The curated-era tail and any mid-ingest latest quarter are handled honestly — a partial quarter is not drawn as a collapse.
Reading this table
Funds hold the same stock for different reasons — an index fund “holds” almost everything, an active manager sizes a name to a mandate and a benchmark, and each fund entered at its own price and time. Because 13F is filed up to 45 days after quarter-end, every row is a backward-looking snapshot; a manager may have traded since. Share-class siblings (a company’s A and C shares) are rolled up to one line so a dual-class name is never double-counted. Compare like-for-like. A large holder is not an endorsement, and a fund exiting is not a warning — this is a starting question, not a verdict.
About 13F filings
A Form 13F is a quarterly disclosure that institutional investment managers with over $100 million in US-listed equities must file with the SEC. In plain English: it is a snapshot of the long stock positions a fund held at the end of a quarter. It covers long US-listed equities only — not short positions, options, cash, or private holdings — and the funds shown are the large sample we track, not the complete 13F universe.